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Sample records for cassini etude photometrique

  1. Folds and Etudes

    Science.gov (United States)

    Bean, Robert

    2007-01-01

    In this article, the author talks about "Folds" and "Etudes" which are images derived from anonymous typing exercises that he found in a used copy of "Touch Typing Made Simple". "Etudes" refers to the musical tradition of studies for a solo instrument, which is a typewriter. Typing exercises are repetitive attempts to type words and phrases…

  2. Cassini's Grand Finale

    Science.gov (United States)

    Spilker, L. J.; Edgington, S. G.; Altobelli, N.

    2016-12-01

    After more than 12 years in Saturn orbit, the Cassini-Huygens mission has entered its final year of data collection. Cassini will return its final bits of unique data on 15 September 2017 as it plunges into Saturn's atmosphere, vaporizing and satisfying planetary protection requirements. Since early 2016 Cassini's orbital inclination was slowly increased towards its final inclination. In November Cassini transitioned to a series of 20 orbits with peripases just outside Saturn's F ring that include some of the closest flybys of the tiny ring moons and excellent views of the F ring and outer A ring. Cassini's final close flyby of Titan will propel it across Saturn's main rings and into its final orbits. Cassini's Grand Finale begins in April 2017 and is comprised of 22 orbits at an inclination of 63 degrees. Cassini will repeatedly dive between the innermost ring and Saturn's upper atmosphere providing insights into fundamental questions unattainable during the rest of the mission. It will be the first spacecraft to explore this region. These close orbits provide the highest resolution observations of both the rings and Saturn, and direct in situ sampling of the ring particles' composition, plasma, Saturn's exosphere and the innermost radiation belts. Saturn's gravitational field will be measured to unprecedented accuracy, providing information on Saturn's interior structure and mass distribution in the rings. Probing the magnetic field will give insight into the nature of the magnetic dynamo and the true rotation rate of Saturn's interior. The ion and neutral mass spectrometer will sniff the exosphere and upper atmosphere and examine water-based molecules originating from the rings. The cosmic dust analyzer will sample particle composition from different parts of the main rings. Recent science highlights and science objectives from Cassini's final orbits will be discussed. This work was carried out in part at the Jet Propulsion Laboratory, California Institute of

  3. Cassini science planning process

    Science.gov (United States)

    Paczkowski, Brian G.; Ray, Trina L.

    2004-01-01

    The mission design for Cassini-Huygens calls for a four-year orbital survey of the Saturnian system and the descent into the Titan atmosphere and eventual soft-landing of the Huygens probe. The Cassini orbiter tour consists of 76 orbits around Saturn with 44 close Titan flybys and 8 targeted icy satellite flybys. The Cassini orbiter spacecraft carries twelve scientific instruments that will perform a wide range of observations on a multitude of designated targets. The science opportunities, frequency of encounters, the length of the Tour, and the use of distributed operations pose significant challenges for developing the science plan for the orbiter mission. The Cassini Science Planning Process is the process used to develop and integrate the science and engineering plan that incorporates an acceptable level of science required to meet the primary mission objectives far the orbiter. The bulk of the integrated science and engineering plan will be developed prior to Saturn Orbit Insertion (Sol). The Science Planning Process consists of three elements: 1) the creation of the Tour Atlas, which identifies the science opportunities in the tour, 2) the development of the Science Operations Plan (SOP), which is the conflict-free timeline of all science observations and engineering activities, a constraint-checked spacecraft pointing profile, and data volume allocations to the science instruments, and 3) an Aftermarket and SOP Update process, which is used to update the SOP while in tour with the latest information on spacecraft performance, science opportunities, and ephemerides. This paper will discuss the various elements of the Science Planning Process used on the Cassini Mission to integrate, implement, and adapt the science and engineering activity plans for Tour.

  4. Study of the fibrinogen - fibrin transformation kinetics and modifications caused to this reaction by irradiation (X rays) of the fibrinogen solution; Etude de la cinetique de la transformation fibrinogene-fibrine et modifications apportees dans cette reaction par irradiation (rayons X) de solution de fibrinogene

    Energy Technology Data Exchange (ETDEWEB)

    Hollard, D.; Suscillon, M.; Marcille, G.; Rambaud, F.; Baloyan, M. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1966-07-01

    The authors present a spectrophotometric method for studying the transformation fibrinogen - fibrin. This method has the advantage of drawing immediately in graph form the three, phases of this transformation: proteolysis or monomerization; polymerisation; clot stabilization. It is a simple, faithful and easily reproductive technic. Owing to this method, they studied modifications of this transformation due to irradiation of fibrinogen solution. Low doses (90 000 R/mn) prevent transverse polymerisation. To upper doses (180 000 R and more), the action of thrombin on fibrinogen does not give an organised clot but a lacteous and fragile gel. There is not here a coagulation in the physiological understanding. (author) [French] Les auteurs presentent une methode d'etude spectro-photometrique de la transformation fibrinogene - fibrine. Cette technique a l'avantage de visualiser instantanement-par le trace d'une courbe les 3 phases de cette transformation: proteolyse ou monomerisation; polymerisation; stabilisation du caillot. C'est une technique simple, fidele, reproductible; grace a cette methode les auteurs ont pu etudier les modifications apportees dans cette transformation par irradiation aux rayons X de la solution de fibrinogene. A faible dose (90 000 R) l'irradiation inhibe la polymerisation Transversale. A forte dose ( > 180 000 R) le fibrinogene n'est plus transforme par la thrombine en un caillot organise mais en un gel laiteux et fragile. Il ne s'agit plus alors de coagulation au sens physiologique du terme. (auteur)

  5. Cassini launch contingency effort

    Science.gov (United States)

    Chang, Yale; O'Neil, John M.; McGrath, Brian E.; Heyler, Gene A.; Brenza, Pete T.

    2002-01-01

    On 15 October 1997 at 4:43 AM EDT, the Cassini spacecraft was successfully launched on a Titan IVB/Centaur on a mission to explore the Saturnian system. It carried three Radioisotope Thermoelectric Generators (RTGs) and 117 Light Weight Radioisotope Heater Units (LWRHUs). As part of the joint National Aeronautics and Space Administration (NASA)/U.S. Department of Energy (DoE) safety effort, a contingency plan was prepared to address the unlikely events of an accidental suborbital reentry or out-of-orbital reentry. The objective of the plan was to develop procedures to predict, within hours, the Earth impact footprints (EIFs) for the nuclear heat sources released during the atmospheric reentry. The footprint predictions would be used in subsequent notification and recovery efforts. As part of a multi-agency team, The Johns Hopkins University Applied Physics Laboratory (JHU/APL) had the responsibility to predict the EIFs of the heat sources after a reentry, given the heat sources' release conditions from the main spacecraft. (No ablation burn-through of the heat sources' aeroshells was expected, as a result of earlier testing.) JHU/APL's other role was to predict the time of reentry from a potential orbital decay. The tools used were a three degree-of-freedom trajectory code, a database of aerodynamic coefficients for the heat sources, secure links to obtain tracking data, and a high fidelity special perturbation orbit integrator code to predict time of spacecraft reentry from orbital decay. In the weeks and days prior to launch, all the codes and procedures were exercised. Notional EIFs were derived from hypothetical reentry conditions. EIFs predicted by JHU/APL were compared to those by JPL and US SPACECOM, and were found to be in good agreement. The reentry time from orbital decay for a booster rocket for the Russian Progress M-36 freighter, a cargo ship for the Mir space station, was predicted to within 5 minutes more than two hours before reentry. For the

  6. Cassini at Saturn Huygens results

    CERN Document Server

    Harland, David M

    2007-01-01

    "Cassini At Saturn - Huygens Results" will bring the story of the Cassini-Huygens mission and their joint exploration of the Saturnian system right up to date. Cassini is due to enter orbit around Saturn on the 1 July 2004 and the author will have 8 months of scientific data available for review, including the most spectacular images of Saturn, its rings and satellites ever obtained by a space mission. As the Cassini spacecraft approached its destination in spring 2004, the quality of the images already being returned by the spacecraft clearly demonstrate the spectacular nature of the close-range views that will be obtained. The book will contain a 16-page colour section, comprising a carefully chosen selection of the most stunning images to be released during the spacecraft's initial period of operation. The Huygens craft will be released by Cassini in December 2004 and is due to parachute through the clouds of Saturn's largest moon, Titan, in January 2005.

  7. Exploration of the Saturn System by the Cassini Mission: Observations with the Cassini Infrared Spectrometer

    Science.gov (United States)

    Abbas, Mian M.

    2014-01-01

    Outline: Introduction to the Cassini mission, and Cassini mission Objectives; Cassini spacecraft, instruments, launch, and orbit insertion; Saturn, Rings, and Satellite, Titan; Composite Infrared Spectrometer (CIRS); and Infrared observations of Saturn and titan.

  8. Cassini Mission Sequence Subsystem (MSS)

    Science.gov (United States)

    Alland, Robert

    2011-01-01

    This paper describes my work with the Cassini Mission Sequence Subsystem (MSS) team during the summer of 2011. It gives some background on the motivation for this project and describes the expected benefit to the Cassini program. It then introduces the two tasks that I worked on - an automatic system auditing tool and a series of corrections to the Cassini Sequence Generator (SEQ_GEN) - and the specific objectives these tasks were to accomplish. Next, it details the approach I took to meet these objectives and the results of this approach, followed by a discussion of how the outcome of the project compares with my initial expectations. The paper concludes with a summary of my experience working on this project, lists what the next steps are, and acknowledges the help of my Cassini colleagues.

  9. NASA 3D Models: Cassini

    Data.gov (United States)

    National Aeronautics and Space Administration — Cassini spacecraft from SPACE rendering package, built by Michael Oberle under NASA contract at JPL. Includes orbiter only, Huygens probe detached. Accurate except...

  10. Titan from Cassini-Huygens

    CERN Document Server

    Brown, Robert H; Waite, J. Hunter

    2010-01-01

    This book reviews our current knowledge of Saturn's largest moon Titan featuring the latest results obtained by the Cassini-Huygens mission. A global author team addresses Titan’s origin and evolution, internal structure, surface geology, the atmosphere and ionosphere as well as magnetospheric interactions. The book closes with an outlook beyond the Cassini-Huygens mission. Colorfully illustrated, this book will serve as a reference to researchers as well as an introduction for students.

  11. Cassini Tour Atlas Automated Generation

    Science.gov (United States)

    Grazier, Kevin R.; Roumeliotis, Chris; Lange, Robert D.

    2011-01-01

    During the Cassini spacecraft s cruise phase and nominal mission, the Cassini Science Planning Team developed and maintained an online database of geometric and timing information called the Cassini Tour Atlas. The Tour Atlas consisted of several hundreds of megabytes of EVENTS mission planning software outputs, tables, plots, and images used by mission scientists for observation planning. Each time the nominal mission trajectory was altered or tweaked, a new Tour Atlas had to be regenerated manually. In the early phases of Cassini s Equinox Mission planning, an a priori estimate suggested that mission tour designers would develop approximately 30 candidate tours within a short period of time. So that Cassini scientists could properly analyze the science opportunities in each candidate tour quickly and thoroughly so that the optimal series of orbits for science return could be selected, a separate Tour Atlas was required for each trajectory. The task of manually generating the number of trajectory analyses in the allotted time would have been impossible, so the entire task was automated using code written in five different programming languages. This software automates the generation of the Cassini Tour Atlas database. It performs with one UNIX command what previously took a day or two of human labor.

  12. The Cassini-Huygens mission

    CERN Document Server

    The joint NASA-ESA Cassini-Huygens mission promises to return four (and possibly more) years of unparalleled scientific data from the solar system’s most exotic planet, the ringed, gas giant, Saturn. Larger than Galileo with a much greater communication bandwidth, Cassini can accomplish in a single flyby what Galileo returned in a series of passes. Cassini explores the Saturn environment in three dimensions, using gravity assists to climb out of the equatorial plane to look down on the rings from above, to image the aurora and to study polar magnetospheric processes such as field-aligned currents. Since the radiation belt particle fluxes are much more benign than those at Jupiter, Cassini can more safely explore the inner regions of the magnetosphere. The spacecraft approaches the planet closer than Galileo could, and explores the inner moons and the rings much more thoroughly than was possible at Jupiter. This book is the second volume, in a three volume set, that describes the Cassini/Huygens mission. Thi...

  13. Cassini data assessment report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-08-01

    On October 15, 1997, the Cassini spacecraft was launched from Cape Canaveral Air Station (CCAS) and is now on its way to the planet Saturn. The functional support provided to NASA by DOE included the Advance Launch Support Group (ALSG). If there had been a launch anomaly, the ALSG would have provided a level of radiological emergency response support adequate to transition into a Federal Radiological Monitoring and Assessment Center (FRMAC). Additional functional radiological emergency response support, as part of the ALSG, included the: (1) Aerial Measurement System (AMS); (2) Atmospheric Release Advisory Capability (ARAC); (3) Geographic Information System (GIS); (4) Emergency Response Data System (ERDS); (5) Radiation Emergency Assistance Center and Training Site (REAC/TS); (6) Field monitoring and sampling; (7) Radioanalysis via RASCAL; (8) Source recovery; and (9) Neutron dosimetry and communications support. This functional support provided the capability to rapidly measure and assess radiological impacts from a launch anomaly. The Radiological Control Officer (RCO) on KSC established a Radiological Control Center (RADCC) as the focal point for all on-site and off-site radiological data and information flow. Scientists and radiological response personnel located at the RADCC managed the field monitoring team on the KSC/CCAS federal properties. Off-site radiological emergency response activities for all public lands surrounding the KSC/CCAS complex were coordinated through the Off-site ALSG located at the National Guard Armory in Cocoa, Florida. All of the in situ measurement data of good quality gathered during the dry run, the first launch attempt and the launch day are listed in this document. The RASCAL analysis results of the air filters and impactor planchets are listed.

  14. Saturn from Cassini-Huygens

    CERN Document Server

    Dougherty, Michele K; Krimigis, Stamatios M

    2009-01-01

    This book reviews our current knowledge of Saturn featuring the latest results obtained by the Cassini-Huygens mission. A global author team addresses the planet’s origin and evolution, internal structure, composition and chemistry, the atmosphere and ionosphere, the magnetosphere, as well as its ring system. Furthermore, Saturn's icy satellites are discussed. The book closes with an outlook beyond the Cassini-Huygens mission. Colorfully illustrated, this book will serve as a reference to researchers as well as an introduction for students.

  15. CASSIUS: The Cassini Uplink Scheduler

    Science.gov (United States)

    Bellinger, Earl

    2012-01-01

    The Cassini Uplink Scheduler (CASSIUS) is cross-platform software used to generate a radiation sequence plan for commands being sent to the Cassini spacecraft. Because signals must travel through varying amounts of Earth's atmosphere, several different modes of constant telemetry rates have been devised. These modes guarantee that the spacecraft and the Deep Space Network agree with respect to the data transmission rate. However, the memory readout of a command will be lost if it occurs on a telemetry mode boundary. Given a list of spacecraft message files as well as the available telemetry modes, CASSIUS can find an uplink sequence that ensures safe transmission of each file. In addition, it can predict when the two on-board solid state recorders will swap. CASSIUS prevents data corruption by making sure that commands are not planned for memory readout during telemetry rate changes or a solid state recorder swap.

  16. Criticality studies; Etudes de criticite

    Energy Technology Data Exchange (ETDEWEB)

    Breton, D.; Lecorche, P.; Clouet d' Orval, Ch. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    Criticality studies made at the Commissariat a l'Energie atomique deal on the one hand with experiments on plutonium and uranium solutions, on the other hand with theoretical work on the development and use of computation, methods for the resolution of problems concerning the nuclear safety of chemical and metallurgical plants. I - Since 1958 the experimental studies have dealt with homogeneous media constituted by a fissile salt dissolved in light water. Developed using the reactor Proserpine, the experiments have been carried on at Saclay on the Alecto assemblies where solutions of plutonium or of 90 p.100 - enriched uranium can be made critical. The results already obtained relate to critical masses of cylindrical tanks of diameters from 20 to 50 cm. reflected in several ways (water, concrete, etc. . ) at concentrations up to 100 g/liter. Physical measurements (spectra, reactor noises) and interaction measurements complete the results. Other experiments relating to plutonium solutions were begun in 1963, at the Valduc Center. They deal with the study of critical masses of annular vessels of external diameter 50 cm and internal diameter varying from 10 to 30 cm. These vessels can be water reflected internally, externally, or both. Two of these vessels have been studied in interaction for various geometries. Slabs of various thicknesses were also studied. II - The studies thus undertaken allowed the development of methods of computation which have been tested on several experiments. Particular use has been made of the possibilities of calculations based on transport theory and on Monte Carlo methods. All these theoretical studies are applied to the design and control of industrial plants from the point of view of safety. (authors) [French] Les etudes de criticite effectuees au CEA comportent d'une part des experiences sur des solutions de plutonium et d'uranium enrichi, d'autre part des travaux theoriques portant sur la mise au point et l

  17. The Italian involvement in Cassini radar

    Science.gov (United States)

    Nirchio, F.; Pernice, B.; Borgarelli, L.; Dionisio, C.

    1991-12-01

    The Radio Frequency Electronic Subsystem (RFES) of the Cassini radar is described. The requirements of the Cassini radar are summarized. The design parameters taken into consideration in developing the RFES are described. The RFES interfaces with the High Gain Antenna (HGA) for signal transmission and reception. The operational parameters of the Cassini radar are presented. The front end electronics (FEE), microwave receiver (MR), high power amplifier (HPA), frequency generator (FG), digital chip generator (DCG), Chirp Up Converter and Amplifier (CUCA) and power supply of the RFES are described.

  18. Cassini UVIS Auroral Observations in 2016

    Science.gov (United States)

    Pryor, Wayne R.; Jouchoux, Alain; Esposito, Larry W.; Radioti, Aikaterini; Grodent, Denis; Gustin, Jacques; Gerard, Jean-Claude; Lamy, Laurent; Badman, Sarah; Bunce, Emma; Cecconi, Baptiste; Clarke, John T.; Crary, Frank; Dougherty, Michele; Dyudina, Ulyana A.; Kurth, William; Mitchell, Don; Nichols, Jonathan; Prange, Renee; Schippers, Patricia; Zarka, Philippe; Cassini UVIS Team

    2016-10-01

    In June of 2016, the Cassini Saturn orbiter began a series of high inclination orbits that will continue until September 2017 when the mission ends as Cassini enters the Saturn atmosphere. These orbits present excellent views of Saturn's polar regions suitable for auroral imaging at the closest distances to date, with the additional prospect of simultaneous particle and fields measurements within the sources of Saturn Kilometric Radiation (SKR) associated with ultraviolet auroral emissions and/or acceleration regions likely coinciding with them. We will present new Cassini Ultraviolet Imaging Spectrograph (UVIS) auroral images, spectra and movies obtained during the summer and fall of 2016 and put them in the context of auroral data collected since Cassini orbit insertion in 2004. Included in the new data will be UVIS south polar observations obtained simultaneously with Hubble Space Telescope observations of the north polar region on June 29, 2016 and August 19, 2016.

  19. Cassini: Mission to Saturn and Titan

    Science.gov (United States)

    Kerridge, Stuart J.; Flury, Walter; Horn, Linda J.; Lebreton, Jean-Pierre; Stetson, Douglas S.; Stoller, Richard L.; Tan, Grace H.

    1992-01-01

    The Cassini Mission to Saturn and Titan represents an important step into the exploration of the outerplanets. It will expand on the flyby encounters of Pioneer and Voyager and parallel the detailed exploration of the Jupiter system to be accomplished by the Galileo Mission. By continuing the study of the two giant planets and enabling detailed comparisons of their structure and behavior, Cassini will provide a tremendous insight into the formation and evolution of the solar system. In addition, by virtue of its focus on the Saturnian satellite Titan, Cassini will return detailed data on an environment whose atmospheric chemistry may resemble that of the primitive Earth. The scientific objectives can be divided into five categories: Titan, Saturn, rings, icy satellites, and magnetospheres. The key area of interest to exobiologists is Titan; the other four scientific categories will be discussed briefly to provide a comprehensive overview of the Cassini Mission.

  20. Cassini's Scientist for a Day program

    Science.gov (United States)

    Seal, David

    2009-11-01

    NASA's Cassini project has conducted a series of innovative "Scientist for a Day" outreach sessions with great success. Individual students and classrooms are presented, via the Cassini web site, with a selection of images that could be taken by the Cassini spacecraft in orbit around Saturn. Student essays are submitted indicating their preferred image, along with a detailed description of why that image was selected, often drawing heavily from material found elsewhere in the Cassini web resources. Winners from different age categories are chosen, and the selected images are sequenced. Very soon after the images reach the ground, winning classrooms are invited to participate via tele- and video-con with key Cassini scientists and engineers, where interactive discussions take place. This program has been very successful and is considered a key outreach highlight of Cassini and JPL in general. It reaches a significant number of students, involves them directly in image planning, and engages them in a highly interactive and inspirational environment requiring detailed study and creative thought.

  1. Cassini's Grand Finale: The Final Orbits

    Science.gov (United States)

    Spilker, Linda; Edgington, Scott

    2016-04-01

    The Cassini-Huygens mission, a joint collaboration between NASA, ESA and the Italian Space Agency, is approaching its last year of operations after nearly 12 years in orbit around Saturn. Cassini will send back its final bits of unique data on September 15th, 2017 as it plunges into Saturn's atmosphere, vaporizing and satisfying planetary protection requirements. Before that time Cassini will continue its legacy of exploration and discovery with 12 close flybys of Titan in 2016 and 2017 that will return new science data as well as sculpt the inclinations and periods of the final orbits. Even though all of our close icy satellite flybys, including those of Enceladus, are now completed, numerous Voyager-class flybys (summer solstice approaches. In November 2016 Cassini will transition to a series of orbits with peripases just outside Saturn's F ring. These 20 orbits will include close flybys of some tiny ring moons and excellent views of the F ring and outer A ring. The 126th and final close flyby of Titan will propel Cassini across Saturn's main rings and into its final orbits. Cassini's Grand Finale, starting in April 2017, is comprised of 22 orbits at an inclination of 63 degrees. Cassini will repeatedly dive between the innermost rings and the upper atmosphere of the planet providing insights into fundamental questions unattainable during the rest of the mission. Cassini will be the first spacecraft to explore this region. These close orbits provide the highest resolution observations of both the rings and Saturn, and direct in situ sampling of the ring particles, composition, plasma, Saturn's exosphere and the innermost radiation belts. Saturn's gravitational field will be measured to unprecedented accuracy, providing information on the interior structure of the planet, winds in the outer layers of Saturn's atmosphere, and the mass distribution in the rings. Probing the magnetic field will give insight into the nature of the magnetic dynamo, telling us: why the

  2. Etude Sedimentologique et Esquisse Paleoenvironnementale des ...

    African Journals Online (AJOL)

    Etude Sedimentologique et Esquisse Paleoenvironnementale des ... Les analyses sédimentologiques réalisées dans ce travail, sont un prélude d'un projet d'études pluridisciplinaires ... (Crétacé inférieur) à l'océanisation complète (fin.

  3. Cassini State Transitions with a Fossil Figure

    Science.gov (United States)

    Matsuyama, Isamu; Tuttle Keane, James

    2016-10-01

    The Moon has experienced large obliquity variations during Cassini state transitions which greatly impact tidal heating, and the long-term stability of polar volatiles. It has been known for centuries that the lunar rotational and tidal bulges are much larger than expected. The South Pole-Aitken basin can explain a large fraction of the excess deformation. Accounting for the contribution of this basin (and other large basins), the remaining excess deformation arises due to a fossil figure established when the Moon orbited much closer to Earth than it does today. Previous studies assume that the present, excess deformation is entirely preserved throughout Cassini state transitions. This ignores basin contributions to the excess deformation, and requires an interior with infinite rigidity. We consider Cassini state transition models that take into account basin contributions to the excess deformation, and the effect of finite rigidity on the fossil figure.

  4. Cassini Solstice Mission Maneuver Experience: Year Three

    Science.gov (United States)

    Wagner, Sean V.; Arrieta, Juan; Hahn, Yungsun; Stumpf, Paul W.; Valerino, Powtawche N.; Wong, Mau C.

    2013-01-01

    The Solstice Mission is the final extension of the Cassini spacecraft s tour of Saturn and its moons. To accommodate an end-of-mission in 2017, the maneuver decision process has been refined. For example, the Cassini Project now prioritizes saving propellant over minimizing maneuver cycles. This paper highlights 30 maneuvers planned from June 2012 through July 2013, targeted to nine Titan flybys and the final Rhea encounter in the mission. Of these maneuvers, 90% were performed to maintain the prescribed trajectory and preserve downstream delta V. Recent operational changes to maneuver executions based on execution-error modeling and analysis are also discussed.

  5. Cassini Solstice Mission Maneuver Experience: Year One

    Science.gov (United States)

    Wagner, Sean V.; Arrieta, Juan; Ballard, Christopher G.; Hahn, Yungsun; Stumpf, Paul W.; Valerino, Powtawche N.

    2011-01-01

    The Cassini-Huygens spacecraft began its four-year Prime Mission to study Saturn's system in July 2004. Two tour extensions followed: a two-year Equinox Mission beginning in July 2008 and a seven-year Solstice Mission starting in September 2010. This paper highlights Cassini maneuver activities from June 2010 through June 2011, covering the transition from the Equinox to Solstice Mission. This interval included 38 scheduled maneuvers, nine targeted Titan flybys, three targeted Enceladus flybys, and one close Rhea flyby. In addition, beyond the demanding nominal navigation schedule, numerous unforeseen challenges further complicated maneuver operations. These challenges will be discussed in detail.

  6. Les Etudes De Langues Aux Pays-Bas

    NARCIS (Netherlands)

    Zwarts, F.

    1995-01-01

    Les Etudes de Langues dans l'Enseignement Superieur en Europe: Des Rapports Nationaux Préparés pour une Conference sur les Etudes de Langues en Europe et Cooperation dans le Domaine de l'Enseignement Superieur à l'Univerité de Stockholm.

  7. Managing Cassini Safe Mode Attitude at Saturn

    Science.gov (United States)

    Burk, Thomas A.

    2010-01-01

    The Cassini spacecraft was launched on October 15, 1997 and arrived at Saturn on June 30, 2004. It has performed detailed observations and remote sensing of Saturn, its rings, and its satellites since that time. In the event safe mode interrupts normal orbital operations, Cassini has flight software fault protection algorithms to detect, isolate, and recover to a thermally safe and commandable attitude and then wait for further instructions from the ground. But the Saturn environment is complex, and safety hazards change depending on where Cassini is in its orbital trajectory around Saturn. Selecting an appropriate safe mode attitude that insures safe operation in the Saturn environment, including keeping the star tracker field of view clear of bright bodies, while maintaining a quiescent, commandable attitude, is a significant challenge. This paper discusses the Cassini safe table management strategy and the key criteria that must be considered, especially during low altitude flybys of Titan, in deciding what spacecraft attitude should be used in the event of safe mode.

  8. Modernization of the Cassini Ground System

    Science.gov (United States)

    Razo, Gus; Fujii, Tammy

    2014-01-01

    The Cassini Spacecraft and its ground system have been operational for over 16 years. Modernization presents several challenges due to the personnel, processes, and tools already invested and embedded into the current ground system structure. Every mission's ground system has its own unique complexities and challenges, involving various organizational units. As any mission from its inception to its execution, schedules are always tight. This forces GDS engineers to implement a working ground system that is not necessarily fully optimized. Ground system challenges increase as technology evolves and cyber threats become more sophisticated. Cassini's main challenges were due to its ground system existing before many security requirements were levied on the multi-mission tools and networks. This caused a domino effect on Cassini GDS tools that relied on outdated technological features. In the aerospace industry reliable and established technology is preferred over innovative yet less proven technology. Loss of data for a spacecraft mission can be catastrophic; therefore, there is a reluctance to make changes and updates to the ground system. Nevertheless, all missions and associated teams face the need to modernize their processes and tools. Systems development methods from well-known system analysis and design principles can be applied to many missions' ground systems. Modernization should always be considered, but should be done in such a way that it does not affect flexibility nor interfere with established practices. Cassini has accomplished a secure and efficient ground data system through periodic updates. The obstacles faced while performing the modernization of the Cassini ground system will be outlined, as well as the advantages and challenges that were encountered.

  9. Cassini's Grand Finale and Recent Science Highlights

    Science.gov (United States)

    Spilker, Linda J.

    2017-06-01

    After almost 13 years in Saturn orbit, the Cassini-Huygens mission has entered its final year of data collection. Cassini will return its final bits of unique data on 15 September 2017 as it plunges into Saturn’s atmosphere, vaporizing and satisfying planetary protection requirements.Since early 2016 Cassini’s orbital inclination was slowly increased towards its final inclination. In November Cassini transitioned to a series of 20 orbits with periapses just outside Saturn's F ring that included some of the closest flybys of the tiny ring moons and excellent views of the F ring and outer A ring.Cassini's final close flyby of Titan in April 2017 propelled it across Saturn’s main rings and into its final orbits. Cassini's Grand Finale began in April 2017 and is comprised of 22 orbits at an inclination of 63 degrees. Cassini is repeatedly diving between the innermost ring and Saturn's upper atmosphere providing insights into fundamental questions unattainable during the rest of the mission. It is the first spacecraft to explore this region.These close orbits provide the highest resolution observations of both the rings and Saturn, and direct in situ sampling of the ring particles' composition, plasma, Saturn's exosphere and the innermost radiation belts. Saturn's gravitational field will be measured to unprecedented accuracy, providing information on Saturn's interior structure and mass distribution in the rings. Probing the magnetic field will give insight into the nature of the magnetic dynamo and the true rotation rate of Saturn's interior. The ion and neutral mass spectrometer will sniff the exosphere and upper atmosphere and examine water-based molecules originating from the rings. The cosmic dust analyzer will sample particle composition from different parts of the main rings.Recent science highlights and science objectives from Cassini’s final orbits will be discussed.This work was carried out in part at the Jet Propulsion Laboratory, California

  10. Cassini states for black-hole binaries

    CERN Document Server

    Correia, Alexandre C M

    2016-01-01

    Cassini states correspond to equilibria of the spin axis of a celestial body when its orbit is perturbed. They were initially described for planetary satellites, but the spin axes of black-hole binaries also present this kind of equilibria. In previous works, Cassini states were reported as spin-orbit resonances, but actually the spin of black-hole binaries is in circulation and there is no resonant motion. Here we provide a general description of the spin dynamics of black-hole binary systems based on a Hamiltonian formalism. In absence of dissipation the problem is integrable and it is easy to identify all possible trajectories for the spin for a given value of the total angular momentum. As the system collapses due to radiation reaction, the Cassini states are shifted to different positions, which modifies the dynamics around them. This is why the final spin distribution may differ from the initial one. Our method provides a simple way of predicting the distribution of the spin of black-hole binaries at th...

  11. Composite Infrared Spectrometer (CIRS) on Cassini

    Science.gov (United States)

    Jennings, Donald E.; Flasar, F. M.; Kunde, V. G.; Nixon, C. A.; Segura, M. E.; Romani, P. N.; Gorius, N.; Albright, S.; Brasunas, J. C.; Carlson, R. C.; hide

    2017-01-01

    The Cassini spacecraft orbiting Saturn carries the composite infrared spectrometer (CIRS) designed to study thermal emission from Saturn and its rings and moons. CIRS, a Fourier transform spectrometer, is an indispensable part of the payload providing unique measurements and important synergies with the other instruments. It takes full advantage of Cassini's 13-year-long mission and surpasses the capabilities of previous spectrometers on Voyager 1 and 2. The instrument, consisting of two interferometers sharing a telescope and a scan mechanism, covers over a factor of 100 in wavelength in the mid and far infrared. It is used to study temperature, composition, structure, and dynamics of the atmospheres of Jupiter, Saturn, and Titan, the rings of Saturn, and surfaces of the icy moons. CIRS has returned a large volume of scientific results, the culmination of over 30 years of instrument development, operation, data calibration, and analysis. As Cassini and CIRS reach the end of their mission in 2017, we expect that archived spectra will be used by scientists for many years to come.

  12. Ensuring Cassini's End-of-Mission Propellant Margins

    Science.gov (United States)

    Sturm, Erick J., II; Barber, Todd J.; Roth, Duane

    2015-01-01

    The Cassini spacecraft is in its final years. On September 15, 2017, Cassini will plunge deep into Saturn's atmosphere never to reemerge; thus concluding its second extended mission and 13 years in orbit around the ringed planet. As of October 2014, the spacecraft is four years in to its seven-year, second extended mission, the Cassini Solstice Mission (CSM). With three years left and only 2.5% of its loaded bipropellant and 37% of its loaded monopropellant remaining, the Cassini project actively manages the predicted end-of-mission propellant margins to maintain a high confidence in the spacecraft's ability to complete the CSM as designed.

  13. Cassini Information Management System in Distributed Operations Collaboration and Cassini Science Planning

    Science.gov (United States)

    Equils, Douglas J.

    2008-01-01

    Launched on October 15, 1997, the Cassini-Huygens spacecraft began its ambitious journey to the Saturnian system with a complex suite of 12 scientific instruments, and another 6 instruments aboard the European Space Agencies Huygens Probe. Over the next 6 1/2 years, Cassini would continue its relatively simplistic cruise phase operations, flying past Venus, Earth, and Jupiter. However, following Saturn Orbit Insertion (SOI), Cassini would become involved in a complex series of tasks that required detailed resource management, distributed operations collaboration, and a data base for capturing science objectives. Collectively, these needs were met through a web-based software tool designed to help with the Cassini uplink process and ultimately used to generate more robust sequences for spacecraft operations. In 2001, in conjunction with the Southwest Research Institute (SwRI) and later Venustar Software and Engineering Inc., the Cassini Information Management System (CIMS) was released which enabled the Cassini spacecraft and science planning teams to perform complex information management and team collaboration between scientists and engineers in 17 countries. Originally tailored to help manage the science planning uplink process, CIMS has been actively evolving since its inception to meet the changing and growing needs of the Cassini uplink team and effectively reduce mission risk through a series of resource management validation algorithms. These algorithms have been implemented in the web-based software tool to identify potential sequence conflicts early in the science planning process. CIMS mitigates these sequence conflicts through identification of timing incongruities, pointing inconsistencies, flight rule violations, data volume issues, and by assisting in Deep Space Network (DSN) coverage analysis. In preparation for extended mission operations, CIMS has also evolved further to assist in the planning and coordination of the dual playback redundancy of

  14. The architecture of the Cassini division

    Science.gov (United States)

    Hedman, M.M.; Nicholson, P.D.; Baines, K.H.; Buratti, B.J.; Sotin, Christophe; Clark, R.N.; Brown, R.H.; French, R.G.; Marouf, E.A.

    2010-01-01

    The Cassini Division in Saturn's rings contains a series of eight named gaps, three of which contain dense ringlets. Observations of stellar occultations by the Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft have yielded 40 accurate and precise measurements of the radial position of the edges of all of these gaps and ringlets. These data reveal suggestive patterns in the shapes of many of the gap edges: the outer edges of the five gaps without ringlets are circular to within 1 km, while the inner edges of six of the gaps are eccentric, with apsidal precession rates consistent with those expected for eccentric orbits near each edge. Intriguingly, the pattern speeds of these eccentric inner gap edges, together with that of the eccentric Huygens Ringlet, form a series with a characteristic spacing of 006 day-1. The two gaps with non-eccentric inner edges lie near first-order inner Lindblad resonances (ILRs) with moons. One such edge is close to the 5:4 ILR with Prometheus, and the radial excursions of this edge do appear to have an m = 5 component aligned with that moon. The other resonantly confined edge is the outer edge of the B ring, which lies near the 2:1 Mimas ILR. Detailed investigation of the B-ring-edge data confirm the presence of an m = 2 perturbation on the B-ring edge, but also show that during the course of the Cassini Mission, this pattern has drifted backward relative to Mimas. Comparisons with earlier occultation measurements going back to Voyager suggest the possibility that the m = 2 pattern is actually librating relative to Mimas with a libration frequency L 006 day-1 (or possibly 012 day -1). In addition to the m = 2 pattern, the B-ring edge also has an m = 1 component that rotates around the planet at a rate close to the expected apsidal precession rate (?? ?? ?? B ??? 5.??06 day -1). Thus, the pattern speeds of the eccentric edges in the Cassini Division can be generated from various combinations of the pattern speeds

  15. Cassini, Jean-Dominique [known as Cassini IV] (1748-1845)

    Science.gov (United States)

    Murdin, P.

    2000-11-01

    Astronomer, born at the Paris Observatory, great-grandson of the first director, grandson of the second, son of the third and himself the fourth, assuming the responsibilities of the directorship during the decline of his father, and the directorship itself in 1784. Persuaded King Louis XVI to restore the observatory, but the French Revolution occurred and Cassini, a monarchist, bitterly opposed ...

  16. Thermal Infrared Spectroscopy of Saturn and Titan from Cassini

    Science.gov (United States)

    Jennings, Donald E.; Brasunas, J. C.; Carlson, R. C.; Flasar, F. M.; Kunde, V. G.; Mamoutkine, A. A.; Nixon, A.; Pearl, J. C.; Romani, P. N.; Simon-Miller, A. A.; Bjoraker, G. L.

    2009-01-01

    The Cassini spacecraft completed its nominal mission at Saturn in 2008 and began its extended mission. Cassini carries the Composite Infrared Spectrometer (CIRS); a Fourier transform spectrometer that measures the composition, thermal structure and dynamics of the atmospheres of Saturn and Titan, and also the temperatures of other moons and the rings.

  17. A Traveling Exhibit of Cassini Image Science

    Science.gov (United States)

    Burns, Joseph A.; Hedman, M. M.; Tiscareno, M. S.; Ebel, D.; Mac Low, M.; Lovett, L. E.; Burns, J. K.; Schaff, N.; Bilson, E. M.

    2007-10-01

    An exhibit of Cassini's images will open at NYC's American Museum of Natural History in March 2008 and then visit the Johnson Art Museum (Cornell) throughout fall 2008, including during next year's DPS. It is under consideration by several other venues in the States and overseas. The exhibit will feature 40-50 images, ranging from letter size to large posters, taken by remote-sensing instruments aboard Cassini and Huygens. Photos will be organized into a half-dozen thematic clusters (e.g., organized by celestial target or by physical process); a panel will introduce each grouping with individual images identified briefly. The Saturn system is a perfect vehicle to educate citizens about planetary science and origins. The images’ beauty should capture the public's attention, allowing us to then engage their curiosity about the relevant science. Among the Saturn system's broad suite of objects are Enceladus and Titan, two satellites of astrobiological interest; moreover, the rings display many processes active in other astrophysical disks. Several auxiliary ideas will be implemented. In Ithaca, we will project images at night against the museum's sand-colored exterior walls. A 10-12 minute musical composition has been commissioned from Roberto Sierra to open the show. We will encourage school children to participate in a human orrery circling the museum and will seek volunteers to participate in several Saturnalia. At Cornell we will involve the university and local communities, by taping their reactions to the images’ exquisite beauty as well as to their scientific content. Cassini will be the E/PO focus of next year's DPS meeting; those materials will be employed throughout the fall at New York schools and be available to travel with the show. We intend to work with NYC partners to offer teacher credits for associated weekend courses. We will produce classroom materials, including a DVD, for teacher use.

  18. Cassini Solstice Mission Maneuver Experience: Year Two

    Science.gov (United States)

    Arrieta, Juan; Ballard, Christopher G.; Hahn, Yungsun

    2012-01-01

    The Cassini Spacecraft was launched in October 1997 on a mission to observe Saturn and its moons; it entered orbit around Saturn in July 2004 for a nominal four-year Prime Mission, later augmented by two extensions: the Equinox Mission, from July 2008 through September 2010, and the Solstice Mission, from October 2010 through September 2017. This paper provides an overview of the maneuver activities from August 2011 through June 2012 which include the design of 38 Orbit Trim Maneuvers--OTM-288 through OTM-326-- for attaining 14 natural satellite encounters: seven with Titan, six with Enceladus, and one with Dione.

  19. An Overview of Cassini Radio Science

    Science.gov (United States)

    Kliore, A.; Rappaport, N.; Anabtawi, A.; Asmar, S.; Armstrong, J.; Barbinis, E.; Goltz, G.; Johnston, D.; Fleischman, D.; Rochblatt, D.; Anderson, J.; Marouf, E.; Wong, K.; Thomson, F.; Flasar, F. M.; Schinder, P.; French, R.; McGhee, C.; Mohammed, P.; Steffes, P.; Nagy, A.; Iess, L.; Tortora, P.; Ambrosini, R.; Flamini, E.

    2005-08-01

    The Cassini spacecraft, which has been in orbit about Saturn for over a year, is the first Radio Science platform to provide three downlink frequencies. In addition to the X-band telemetry link (3,56 cm w.l.), two other frequencies, S-band (13.04 cm), and Ka-band (0.94 cm) are available. This, plus the high SNR (>50 dBHz at X-band) afforded by the 4 m diameter s/c high gain antenna in combination with the excellent low noise receivers of the DSN, as well as overall system stabilities of 1 x 10-13 when referenced to the on-board ultra-stable oscillator (USO) in one-way operation, and 1 x 10-15 for a two-way link, make Cassini an unprecedented instrument of radio science. In addition to Gravitational Wave Search and Solar Conjunction experiments conducted during the cruise phase, the orbital tour phase of the mission has as its main radio science objectives: a) determination of the masses and gravity fields of Saturn's icy satellites, Titan, and Saturn through two-way tracking during fly-bys. To date, the masses of Phoebe, Iapetus, Dione and Enceladus have been measured, and will be reported here. b) Measurement of the structure and other properties of Saturn's rings through three-band occultation. Several near-diametric occultations at a high ring opening angle have been completed, and the results will be presented here. c) Measurement of the vertical structure of the atmosphere and ionosphere of Saturn. The same series of occultations have provided nearly equatorial occultations, and the results on the atmosphere structure, the ionosphere, and the abundances of microwave-absorbing gases in Saturn's atmosphere will be described here. In the remaining years of the Cassini mission, these results will be expanded to include the atmosphere, ionosphere, surface, and gravity field of Titan, the gravity field and masses of Saturn and the remaining icy satellites, and the completion of the Saturn objectives described above. The Cassini Radio Science Team wishes to express

  20. Enhancing Cassini Operations & Science Planning Tools

    Science.gov (United States)

    Castello, Jonathan

    2012-01-01

    The Cassini team uses a variety of software utilities as they manage and coordinate their mission to Saturn. Most of these tools have been unchanged for many years, and although stability is a virtue for long-lived space missions, there are some less-fragile tools that could greatly benefit from modern improvements. This report shall describe three such upgrades, including their architectural differences and their overall impact. Emphasis is placed on the motivation and rationale behind architectural choices rather than the final product, so as to illuminate the lessons learned and discoveries made.These three enhancements included developing a strategy for migrating Science Planning utilities to a new execution model, rewriting the team's internal portal for ease of use and maintenance, and developing a web-based agenda application for tracking the sequence of files being transmitted to the Cassini spacecraft. Of this set, the first two have been fully completed, while the agenda application is currently in the early prototype stage.

  1. The Architecture of the Cassini Division

    CERN Document Server

    Hedman, M M; Baines, K; Buratti, B; Sotin, C; Clark, R N; Brown, R H; French, R; Marouf, E

    2009-01-01

    The Cassini Division in Saturn's rings contains a series of eight named gaps, three of which contain dense ringlets. Observations of stellar occultations by the Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft have yielded ~40 accurate and precise measurements of the radial position of the edges of all of these gaps and ringlets. These data reveal suggestive patterns in the shapes of many of the gap edges: the outer edges of the 5 gaps without ringlets are circular to within 1 km, while the inner edges of 6 of the gaps are eccentric, with apsidal precession rates consistent with those expected for eccentric orbits near each edge. Intriguingly, the pattern speeds of these eccentric inner gap edges, together with that of the eccentric Huygens ringlet,form a series with a characteristic spacing of 0.06 degrees/day. The two gaps with non-eccentric inner edges lie near first-order Inner Lindblad Resonances (ILRs) with moons. One such edge is close to the 5:4 ILR with Prometheus. The other re...

  2. Cassini-Huygens results on Titan's surface

    Institute of Scientific and Technical Information of China (English)

    Athena Coustenis; Mathieu Hirtzig

    2009-01-01

    Our understanding of Titan, Saturn's largest satellite, has recently been consid-erably enhanced, thanks to the Cassini-Huygens mission. Since the Saturn Orbit Injection in July 2004, the probe has been harvesting new insights of the Kronian system. In par-ticular, this mission orchestrated a climax on January 14, 2005 with the descent of the Huygens probe into Titan's thick atmosphere. The orbiter and the lander have provided us with picturesque views of extraterrestrial landscapes, new in composition but reassuringly Earth-like in shape. Thus, Saturn's largest satellite displays chains of mountains, fields of dark and damp dunes, lakes and possibly geologic activity. As on Earth, landscapes on Titan are eroded and modeled by some alien hydrology: dendritic systems, hydrocarbon lakes, and methane clouds imply periods of heavy rainfalls, even though rain was never observed directly. Titan's surface also proved to be geologically active - today or in the recent past - given the small number of impact craters listed to date, as well as a few possible cryovolcanic features. We attempt hereafter a synthesis of the most significant results of the Cassini-Huygens endeavor, with emphasis on the surface.

  3. Cassini's remote sensing pallet is installed in the PHSF

    Science.gov (United States)

    1997-01-01

    Technicians from the Jet Propulsion Laboratory (JPL) of the California Institute of Technology lift the remote sensing pallet in the Payload Hazardous Servicing Facility at KSC in July prior to installation on the Cassini spacecraft. A four- year, close-up study of the Saturnian system, the Cassini mission is scheduled for launch from Cape Canaveral Air Station in October 1997. It will take seven years for the spacecraft to reach Saturn. Scientific instruments carried aboard the spacecraft will study Saturn's atmosphere, magnetic field, rings, and several moons. JPL is managing the Cassini project for NASA.

  4. Exploration of the Saturn System by the Cassini Mission: Observations with the Cassini Infrared Spectrometer

    Science.gov (United States)

    Abbas, Mian M.

    2014-01-01

    The Cassini mission is a joint NASA-ESA international mission, launched on October 17, 1997 with 12 instruments on board, for exploration of the Saturn system. A composite Infrared Spectrometers is one of the major instruments. Successful insertion of the spacecraft in Saturn's orbit for an extended orbital tour occurred on July 1, 2004. The French Huygens-Probe on board, with six instruments was programmed for a soft landing on Titan's surface occurred in January 2005. The broad range scientific objectives of the mission are: Exploration of the Saturn system for investigations of the origin, formation, & evolution of the solar system, with an extensive range of measurements and the analysis of the data for scientific interpretations. The focus of research dealing with the Cassini mission at NASA/MSFC in collaboration with the NASA/Goddard Space Flight Center, JPL, as well as the research teams at Oxford/UK and Meudon Observatory/France, involves the Infrared observations of Saturn and its satellites, for measurements of the thermal structure and global distributions of the atmospheric constituents. A brief description of the Cassini spacecraft, the instruments, the objectives, in particular with the infrared observations of the Saturn system will be given. The analytical techniques for infrared radiative transfer and spectral inversion programs, with some selected results for gas constituent distributions will be presented.

  5. How Mimas cleared the Cassini Division

    Science.gov (United States)

    Noyelles, Benoit; Baillie, Kevin; Lainey, Valery; Charnoz, Sebastien

    2016-10-01

    Recent measurements of the dissipation of Saturn (Lainey et al. 2016, Icarus, in press) combined with a theoretical study by Fuller et al. (2016, MNRAS) require to revisit the energy dissipation models in planetary systems and the way it affects their satellite system. In addition, the measurements of the large librations of Mimas (Tajeddine et al. 2014, Science) could point to a global ocean underneath the surface of the satellite. These results allowed us to refine the scenarios of the opening of the Cassini Division that we initially presented at the DPS 2012. Assuming a dissipation that is consistent with these latest results, we propose scenarios of combined evolutions of Mimas and the main rings of Saturn, that explain the current size and location of the Division, the excess of density in the outer B ring, a past episode of intense heating of Mimas required to create a global ocean, and its current eccentricity. For that, we show that a past resonance with Tethys increased the eccentricity of Mimas up to 0.2, possibly triggering the melting of Mimas and an episode of inward migration, which created the Cassini Division: the 2:1 resonance between Mimas and the rings pushed the ring material inner to accumulate in the B ring. Once its eccentricity is damped, Mimas resumes its outward migration, leading to a trapping into the current vertical resonance with Tethys. These results are supported by numerical simulations, in which Mimas is driven by the tides, and the rings are simulated with the 1-D hydrodynamical code Hydrorings (Charnoz et al., 2010, Nature). This study has been partially supported by the International Space Sciences Institute in Bern, Switzerland.

  6. Titan's Isotopic Menagerie: The Cassini CIRS Perspective

    Science.gov (United States)

    Nixon, Conor A.; Achterberg, R. K.; Bezard, B.; Bjoraker, G. L.; Coustenis, A.; de Kok, R.; Flasar, F. M.; Hewagama, T.; Irwin, P. G. J.; Jennings, D. E.; Jolly, A.; Romani, P. N.; Teanby, N. A.; Vinatier, S.; CIRS Team

    2008-09-01

    Saturn's long-mysterious moon Titan is gradually yielding up its secrets under the intense scrutiny of the Cassini spacecraft, which has just completed a 4-year prime mission including 45 close flybys of the giant satellite. We here focus on the isotopic composition of the stratosphere, which since Voyager 1 in 1980 has been known to comprise a surprisingly rich mixture of hydrocarbons, nitriles and several oxygen species. These molecules are now understood to originate in the upper atmosphere by chemical processes initiated by the dissociation of the most abundant native species - methane and nitrogen - with some oxygen added from externally-supplied water. Measurements of isotopic ratios in these compounds are important and can provide valuable information on the formation and evolution of Titan's atmosphere. E.g. Chemical processes can cause isotopic fractionation via the 'kinetic isotope effect' (KIE). Cassini's Composite Infrared Spectrometer (CIRS), which is sensitive to thermal infrared radiation from 10-1500 cm-1 (7-1000 micron), is an ideal tool for measuring molecular concentrations and can distinguish between isotopologues due to the shifts in the molecular bands. CIRS has now identified at least eleven isotopologue species in our spectra, with multiple new detections in the past year (13CO2, CO18O, HC13CCCN). CIRS has measured the ratios 12C/13C in a total of seven species, D/H in two species, and 14N/15N and 16O/18O each in one species - the best measurement so far of the important ratio 16O/18O on Titan (346±110). In this presentation we will summarize all our results to date on isotopic ratios, including comparison with Huygens GCMS and other determinations, a discussion of possible isotopic separation in hydrocarbon chains, and formation/evolution implications of these measurements for Titan.

  7. Cassini Radio Occultation by Enceladus Plume

    Science.gov (United States)

    Kliore, A.; Armstrong, J.; Flasar, F.; French, R.; Marouf, E.; Nagy, A.; Rappaport, N.; McGhee, C.; Schinder, P.; Anabtawi, A.; Asmar, S.; Barbinis, E.; Fleischman, D.; Goltz, G.; Aguilar, R.; Rochblatt, D.

    2006-12-01

    A fortuitous Cassini radio occultation by Enceladus plume occurs on September 15, 2006. The occultation track (the spacecraft trajectory in the plane of the sky as viewed from the Earth) has been designed to pass behind the plume (to pass above the south polar region of Enceladus) in a roughly symmetrical geometry centered on a minimum altitude above the surface of about 20 km. The minimum altitude was selected primarily to ensure probing much of the plume with good confidence given the uncertainty in the spacecraft trajectory. Three nearly-pure sinusoidal signals of 0.94, 3.6, and 13 cm-wavelength (Ka-, X-, and S-band, respectively) are simultaneously transmitted from Cassini and are monitored at two 34-m Earth receiving stations of the Deep Space Network (DSN) in Madrid, Spain (DSS-55 and DSS-65). The occultation of the visible plume is extremely fast, lasting less than about two minutes. The actual observation time extends over a much longer time interval, however, to provide a good reference baseline for potential detection of signal perturbations introduced by the tenuous neutral and ionized plume environment. Given the likely very small fraction of optical depth due to neutral particles of sizes larger than about 1 mm, detectable changes in signal intensity is perhaps unlikely. Detection of plume plasma along the radio path as perturbations in the signals frequency/phase is more likely and the magnitude will depend on the electron columnar density probed. The occultation time occurs not far from solar conjunction time (Sun-Earth-probe angle of about 33 degrees), causing phase scintillations due to the solar wind to be the primary limiting noise source. We estimate a delectability limit of about 1 to 3E16 electrons per square meter columnar density assuming about 100 seconds integration time. Potential measurement of the profile of electron columnar density along the occultation track is an exciting prospect at this time.

  8. Precision Pointing Reconstruction and Geometric Metadata Generation for Cassini Images

    Science.gov (United States)

    French, R. S.; Showalter, M. R.; Gordon, M. K.

    2017-06-01

    We are reconstructing accurate pointing for 400,000 images taken by Cassini at Saturn. The results will be provided to the public along with per-pixel metadata describing precise image contents such as geographical location and viewing geometry.

  9. Cassini Discovers a Kinematic Spiral Ring around Saturn

    National Research Council Canada - National Science Library

    S. Charnoz; C. C. Porco; E. Déau; A. Brahic; J. N. Spitale; C. Bacques; K. Baillie

    2005-01-01

    .... New Cassini observations show that these strands, initially interpreted as concentric ring segments, are in fact connected and form a single one-arm trailing spiral winding at least three times around Saturn...

  10. Technical and harmonic analysis of Carl Czerny op. 299 number 34 etude

    Directory of Open Access Journals (Sweden)

    Mehmet Serkan Umuzdas

    2012-11-01

    Full Text Available In this study, the 34th etude of the book Czerny Op. 299 that is one of the commonly employed books in the piano training was analysed in terms of technique and harmony. The etude was examined in terms of its technical features and contributions to technical development. If an etude is analysed before it is played, time and effort can be amanged much more efficiently. In turn, it may contribute to play the etude or work in accordance with its objectives and to produce outcomes. The aims of this study are to make the students aware of the goals and methods of etudes and to provide them with the suggestions for studying. It is suggested that any etude written with the 2/4 rhythm pattern should be played very vividly and energytically. Any etude written in the octave width of 5.5 is made up of 43 scales in two section. The etude is composed of two sections, each with four sentences and two periods. It also involves 43 scales. Of them, 16 scales are in the first section and the remaining 27 scales are in the second section. The etude has very regular system in terms of harmonic continuity and motives. It has a homogenious pattern in terms of the order of the sentences with half-decsion and those with full-decision.

  11. The Saturn System Through the Eyes of Cassini

    Science.gov (United States)

    Green, James

    2017-01-01

    More than 400 years ago, Galileo Galilei trained his homemade telescope on the night sky and observed that Saturn had two objects closely related to the planet extending on either side. At the time, in 1610, Galileo declared them to be moons. A few decades later, Saturn moon science accelerated at a dizzying pace. Christiaan Huygens first observed Saturn's largest moon Titan in 1655 and was the first to describe the extended moon-like features at Saturn as a disk of material sounding the planet. From 1671 to 1674, Giovanni Cassini discovered the moons lapetus, Rhea, Dione and Tethys. In 1675, Cassini discovered the gap in Saturn's rings that we now know as the Cassini Division. In the space age, before the Cassini-Huygens mission, we had only hints of the discoveries awaiting us at Saturn. Pioneer 11 and Voyagers 1 and 2 conducted flybys decades ago. But these quick encounters didn't allow time for more extensive research. NASA and the European Space Agency created a partnership to orbit a Saturn orbiter (Cassini) and a lander (Huygens) on Titan. Like its namesakes, the Cassini-Huygens mission not only discovered previously unknown moons, but it also helped us understand the science behind their formation, their interactions with the rings, and how truly diverse they are. The Cassini-Huygens mission revolutionized what we know about the Saturn system. The rings of Saturn, the moons, and the planet itself offer irresistible and inexhaustible subjects for intense study, and Cassini-Huygens did not disappoint. The Saturnian system proved to be a rich ground for science exploration and discoveries, and Cassini has been nothing short of a discovery machine. At the time Cassini plunged into Saturn at the end of its mission, it had observed the planet for a little less than half of a Saturn year. But it also orbited the gas giant 293 times, forever changing our understanding of the Saturn system and yielding tremendous insight for understanding the entire Solar System.

  12. Ten Years of ENA Imaging from Cassini

    Science.gov (United States)

    Brandt, Pontus; Mitchell, Donald; Westlake, Joseph; Carbary, James; Paranicas, Christopher; Mauk, Barry; Krimigis, Stamatios

    2014-05-01

    In this presentation we will provide a detailed review of the science highlights of the ENA observations obtained by The Ion Neutral Camera (INCA) on board Cassini. Since the launch of Cassini, INCA has unveiled an invisible world of hot plasma and neutral gas of the two biggest objects of our solar system: the giant magnetosphere of Jupiter and Saturn. Although more than ten years ago, INCA captured the first ENA images of the Jovian system revealing magnetospheric dynamics and an asymmetric Europa neutral gas torus. Approaching Saturn, INCA observed variability of Saturn's magnetospheric activity in response to changes in solar wind dynamic pressure, which was contrary to expectations and current theories. In orbit around Saturn, INCA continued the surprises including the first imaging and global characterization of Titan's exosphere extended out to its gravitational Hill sphere; recurring injections correlating with periodic Saturn Kilometric Radiation (SKR) bursts and magnetic field perturbations; and the discovery of energetic ionospheric outflow. Perhaps most significant, and the focal point of this presentation, is INCA's contribution to the understanding of global magnetospheric particle acceleration and transport, where the combination between ENA imaging and in-situ measurements have demonstrated that transport and acceleration of plasma is likely to occur in a two-step process. First, large-scale injections in the post-midnight sector accelerate and transport plasma in to about 12 RS up to energies of several hundreds of keV. Second, centrifugal interchange acts on the plasma inside of this region and provides further heating and transport in to about 6RS. We discuss this finding in the context of the two fundamental types of injections (or ENA intensifications) that INCA has revealed during its ten years of imaging. The first type is large-scale injections appearing beyond 12 RS in the post-midnight sector that have in many cases had an inward component

  13. PENULISAN ETUDE-ETUDE MUSIK TALEMPONG UNGGAN (Sebuah Usaha Pembelajaran Musik Tradisi Berbasis Literatur

    Directory of Open Access Journals (Sweden)

    Asri MK

    2014-12-01

    Full Text Available “Talempong unggan”, a traditional music from Minangkabau community particularly in Unggan, Sumpur Kudus, Sijunjung Regency, West Sumatera Indonesia is classified into genre of “talempong duduak” (rea. Due to its special musical concept and the playing technics, this traditional music is selected as a practising course in the Karawitan Department of Indonesian Institute of Art (ISI Padang Panjang since 1993 till now. In a system of class learning with many students, Talempong Unggan definitely needs supporting methods and learning technics suitable for the course where the students can reach their maximum skills. All the melody of “talempong unggan” that has been made as a material of practice is transcribed to the system of numeric notation and rhythm motive of “gendang” and “aguang” which is written into signs and special notation. All of qualitative data is formulated into finding methods, technics and etude of learning ensamble of Talempong Unggan the traditional music that learned in Karawitan Department of ISI Padang Panjang. Key words: Talempong Unggan, Methods, Technics, Etude

  14. Dimming titan revealed by the Cassini observations.

    Science.gov (United States)

    Li, Liming

    2015-02-04

    Here we report the temporal variation of Titan's emitted energy with the Cassini/CIRS observations. In the northern hemisphere, the hemispheric-average emitted power decreased from 2007 to 2009 and increased from 2009 to 2012-13, which make the net change insignificant (0.1 ± 0.2%) during the period 2007-2013. The decrease from 2007 to 2009 is mainly due to the cooling around the stratospause, and the increase from 2009 to 2012-13 is probably related to temporal variation of atmospheric temperature around the tropopuase in the northern hemisphere. In the southern hemisphere, the emitted power continuously decreased by 5.0 ± 0.6% from 2.40 ± 0.01 W/m(2) in 2007 to 2.28 ± 0.01 in 2012-13, which is mainly related to Titan's seasonal variation. The asymmetry in the temporal variation between the two hemispheres results in the global-average emitted power decreasing by 2.5 ± 0.6% from 2.41 ± 0.01 W/m(2) in 2007 to 2.35 ± 0.01 W/m(2) in 2012-13. The solar constant at Titan decreased by ~13.0% in the same period 2007-2013, which is much stronger than the temporal variation of emitted power. The measurements of Titan's absorbed solar power are needed to determine the temporal variation of the global energy budget.

  15. Adding "Missed" Science to Cassini's Ops Plan

    Science.gov (United States)

    Roy, Mou; Burton, Marcia E.; Edgington, Scott; Pitesky, Jo E.; Steadman, Kimberly B.; Ray, Trina L.; Evans, Mike

    2014-01-01

    The phenomenal success of the Cassini Mission at Saturn is largely due to flagship instruments, in a target rich environment, for a long period of time, executing almost error free complex mission operations. A smooth transition from cruise operations through the prime science mission and extended science (Equinox) mission culminating in the currently executing Solstice mission has folded in necessary procedural alterations due to improved understanding of the spacecraft, instruments, uplink and planning systems as well as additional science objectives. These have come with the maturation of the mission along with management of workforce reductions. One important set of operational changes has been initiated due to scientific findings highlighting "missed" science opportunities. This is the case for the Titan Meteorology Campaigns and Saturn Storm Watch Campaigns. These observations involve long term monitoring of the atmospheres of Titan and Saturn while the spacecraft and science teams are focused on other high priority targets of opportunity (like Enceladus). Our objective in this paper is to emphasize how a non-invasive strategy to get additional remarkable science was conceived and implemented in a mission with an already well defined operational plan. To illustrate this we will detail Titan Meteorology Campaign and Saturn Storm Watch Campaign integration and implementation strategies as well as the scientific goals and achievements of both.

  16. Cassini observation of Jovian anomalous continuum radiation

    Science.gov (United States)

    Ye, Sheng-Yi; Gurnett, D. A.; Menietti, J. D.; Kurth, W. S.; Fischer, G.; Schippers, P.; Hospodarsky, G. B.

    2012-04-01

    Jovian anomalous continuum is a narrowband electromagnetic radiation near 10 kHz that can escape from Jupiter's magnetosphere to interplanetary space. One possible source mechanism is the magnetosheath re-radiation of the Jovian low frequency radio emissions such as the quasiperiodic (QP) radio emissions, broadband kilometric radiation (bKOM) and non-thermal continuum. Jovian anomalous continuum was consistently observed by the Cassini Radio and Plasma Wave Science instrument from 2000 to 2004, right before the Saturn orbit insertion, which means the radiation can be detected as far as 8 AU away from Jupiter. An analysis of intensity versus radial distance shows that the Jovian anomalous continuum has a line source rather than a point source, consistent with the theory that the emission is radiated by the whole length of the magnetotail. The emissions are modulated at the system III period of Jupiter and are unpolarized. Since the lower cutoff frequency of the anomalous continuum is related to the plasma frequency in the magnetosheath of Jupiter, which is a function of solar wind density, the recurrent variations of the lower cutoff frequency can be used as a remote diagnostic of the solar wind condition at Jupiter. We propose that the frequency dispersion, a unique characteristic of the anomalous continuum, is likely a comprehensive effect of both the slow group velocity near the local plasma frequency and the refraction/scattering of the waves by density structures as they propagate in the magnetosheath.

  17. Saturn's Exploration Beyond Cassini-Huygens

    CERN Document Server

    Guillot, Tristan; Charnoz, Sébastien; Dougherty, Michele K; Read, Peter

    2009-01-01

    For its beautiful rings, active atmosphere and mysterious magnetic field, Saturn is a fascinating planet. It also holds some of the keys to understanding the formation of our Solar System and the evolution of giant planets in general. While the exploration by the Cassini-Huygens mission has led to great advances in our understanding of the planet and its moons, it has left us with puzzling questions: What is the bulk composition of the planet? Does it have a helium core? Is it enriched in noble gases like Jupiter? What powers and controls its gigantic storms? We have learned that we can measure an outer magnetic field that is filtered from its non-axisymmetric components, but what is Saturn's inner magnetic field? What are the rings made of and when were they formed? These questions are crucial in several ways: a detailed comparison of the compositions of Jupiter and Saturn is necessary to understand processes at work during the formation of these two planets and of the Solar System. This calls for the contin...

  18. The Cassini project: Lessons learned through operations

    Science.gov (United States)

    McCormick, Egan D.

    1998-01-01

    The Cassini space probe requires 180 238Pu Light-weight Radioisotopic Heater Units (LWRHU) and 216 238Pu General Purpose Heat Source (GPHS) pellets. Additional LWRHU and GPHS pellets required for non-destructive (NDA) and destructive assay purposes were fabricated bringing the original pellet requirement to 224 LWRHU and 252 GPHS. Due to rejection of pellets resulting from chemical impurities in the fuel and/or failure to meet dimensional specifications a total of 320 GPHS pellets were fabricated for the mission. Initial plans called for LANL to process a total of 30 kg of oxide powder for pressing into monolithic ceramic pellets. The original 30 kg commitment was processed within the time frame allotted; an additional 8 kg were required to replace fuel lost due to failure to meet Quality Assurance specifications for impurities and dimensions. During the time frame allotted for pellet production, operations were impacted by equipment failure, unacceptable fuel impurities levels, and periods of extended down time, >30 working days during which little or no processing occurred. Throughout the production process, the reality of operations requirements varied from the theory upon which production schedules were based.

  19. Man with a Mission: Jean-Dominique Cassini

    Science.gov (United States)

    Belkora, Leila

    2004-03-01

    Jean-Dominique Cassini, for whom the Cassini mission to Saturn is named, is best known for his early understanding of that planet's rings. This article is an overview of his influential career in astronomy and other scientific fields.= Born in Italy in1625 and formally educated at an early age, he was a professor of astronomy at the University of Bologna, a leading center of learning in Europe of the time. He was an early observer of Jupiter, Mars, and Venus. He is best known for constructing a giant pinhole camera in a cathedral that he used with a meridian line on the floor to track the Sun's image through the year, thus providing the Catholic Church with a reliable calendar. Cassini also used the pinhole camera observations to calculate the variation in the distance between the Sun and Earth, thus lending support to the Copernican (Sun-centered) view of the solar system. Cassini moved to Paris at the request of King Louis XIV, originally to oversee the surveying needed for a new map system of France, but ultimately he took over as the director of the Paris Observatory. Cassini's descendants ran the observatory there for the following century.

  20. Titan's interior from Cassini-Huygens

    Science.gov (United States)

    Tobie, G.; Baland, R.-M.; Lefevre, A.; Monteux, J.; Cadek, O.; Choblet, G.; Mitri, G.

    2013-09-01

    The Cassini-Huygens mission has brought many informations about Titan that can be used to infer its interior structure: the gravity field coefficients (up to degree 3, [1]), the surface shape (up to degree 6, [2]), the tidal Love number [1], the electric field [3], and the orientation of its rotation axis [4]. The measured obliquity and gravity perturbation due to tides, as well as the electric field, are lines of evidence for the presence of an internal global ocean beneath the ice surface of Titan [5,1,3]. The observed surface shape and gravity can be used to further constrain the structure of the ice shell above the internal ocean. The presence of a significant topography associated with weak gravity anomalies indicates that deflections of internal interface or lateral density variations may exist to compensate the topography. To assess the sources of compensation, we consider interior models including interface deflections and/or density variations, which reproduces simultaneously the surface gravity and long-wavelength topography data [6]. Furthermore, in order to test the long-term mechanical stability of the internal mass anomalies, we compute the relaxation rate of each internal interface in response to surface mass load. We show that the topography can be explained either by defections of the ocean/ice interface or by density variations in an upper crust [6]. For non-perfectly compensated models of the outer ice shell, the present-day structure is stable only for a conductive layer above a relatively cold ocean (for bottom viscosity > 1016 Pa.s, T Love number and the obliquity. To derive the possible density profile, the obliquity is computed from a Cassini state model for a satellite with an internal liquid layer, each layer having an ellipsoidal shape consistent with the measured surface shape and gravity field [7]. We show that, once the observed surface flattening is taken into account, the measured obliquity can be reproduced only for internal models

  1. Cassini's Cameras Catch Delightful Dynamics Surrounding Saturn

    Science.gov (United States)

    Burns, J. A.; Cassini Imaging Team

    2005-05-01

    Saturn's rings and satellites delight DDA members because of the baroque variety of their extant features and the pivotal role played by resonances. I will review some of the highlights imaged by Cassini during the first nine months of its mission. Numerous density waves, mainly in the outer A ring, were identified with unprecedented accuracy from high-resolution approach images. These include waves initiated by the classically known perturbing satellites, but also by tiny (though nearby) Atlas and Pan, the latter embedded within the A ring. Wavelet analyses have eased identification of waves, allowing estimates of the ring's areal mass density and viscosity, and the perturber's mass. The latter, when combined with satellite images, indicate that low satellite densities (ρ ˜ 0.5 g-cm-3) are the norm. Pan pries open the Encke gap, producing edge waves and imposing numerous (kinematic) gravity wakes. A narrow ringlet within that gap, coincident with Pan's orbit, shows clumps and wiggles that march along relative to Pan, presumably horseshoeing particles. All aspects of the narrow Keeler gap still await explanation. Several previously unknown structures may result from collective effects or non-linear instabilities as particles are driven together. The F ring's structure is beautifully complex but can be mostly understood as resulting from Prometheus's tugs. A few isolated narrow ringlets have been found, occasionally sharing the paths of known satellites. Some parts of the rings show time variability already. We eagerly await the switch of co-orbital Janus/Epimetheus in 2006, and again in 2010, and the plunge of Prometheus into the F ring in 2010. To date, three new satellites have been discovered: two orbit between the classical moons Mimas and Enceladus, while the third is a trailing Lagrangian of Dione. Several other objects, probably temporary clumps of material, were sighted near the F ring.

  2. The Saturn System's Icy Satellites: New Results from Cassini

    Science.gov (United States)

    Lopes-Gautier, Rosaly M.; Buratti, Bonnie; Hendrix, A. R.

    2008-01-01

    Cassini-Huygens is a multidisciplinary, international planetary mission consisting of an orbiting spacecraft and a probe. The Huygens probe successfully landed on Titan's surface on January 14, 2005, while the orbiter has performed observations of Saturn, its rings, satellites, and magnetosphere since it entered orbit around Saturn on July 1, 2004. The Cassini mission has been prolific in its scientific discoveries about the Saturn system. In this special section, we present new mission results with a focus on the 'icy satellites,' which we define as all Saturn's moons with the exception of Titan. The results included in this section have come out of the Cassini SOST--Satellites Orbiter Science Team--a multi-instrument and multidiscipline group that works together to better understand the icy satellites and their interactions with Saturn and its rings. Other papers included in this issue present ground-based observations and interior modeling of these icy moons.

  3. Automation of Cassini Support Imaging Uplink Command Development

    Science.gov (United States)

    Ly-Hollins, Lisa; Breneman, Herbert H.; Brooks, Robert

    2010-01-01

    "Support imaging" is imagery requested by other Cassini science teams to aid in the interpretation of their data. The generation of the spacecraft command sequences for these images is performed by the Cassini Instrument Operations Team. The process initially established for doing this was very labor-intensive, tedious and prone to human error. Team management recognized this process as one that could easily benefit from automation. Team members were tasked to document the existing manual process, develop a plan and strategy to automate the process, implement the plan and strategy, test and validate the new automated process, and deliver the new software tools and documentation to Flight Operations for use during the Cassini extended mission. In addition to the goals of higher efficiency and lower risk in the processing of support imaging requests, an effort was made to maximize adaptability of the process to accommodate uplink procedure changes and the potential addition of new capabilities outside the scope of the initial effort.

  4. Cassini detection of Enceladus' cold water-group plume ionosphere

    Science.gov (United States)

    Tokar, R. L.; Johnson, R. E.; Thomsen, M. F.; Wilson, R. J.; Young, D. T.; Crary, F. J.; Coates, A. J.; Jones, G. H.; Paty, C. S.

    2009-07-01

    This study reports direct detection by the Cassini plasma spectrometer of freshly-produced water-group ions (O+, OH+, H2O+, H3O+) and heavier water dimer ions (HxO2)+ very close to Enceladus where the plasma begins to emerge from the plume. The data were obtained during two close (52 and 25 km) flybys of Enceladus in 2008 and are similar to ion data in cometary comas. The ions are observed in detectors looking in the Cassini ram direction exhibiting energies consistent with the Cassini speed, indicative of a nearly stagnant plasma flow in the plume. North of Enceladus the plasma slowing commences about 4 to 6 Enceladus radii away, while south of Enceladus signatures of the plasma interaction with the plume are detected 22 Enceladus radii away.

  5. Updating the Reference Trajectory for the Cassini Solstice Mission

    Science.gov (United States)

    Valerino, Powtawche N.

    2014-01-01

    The Cassini-Huygens deep-space probe has successfully completed a four-year prime tour and a two-year extended tour of the Saturnian system. Now in a second extended phase called the Solstice Mission, the Cassini spacecraft will continue to gather data as directed by the reference trajectory until 2017. This paper will describe the process of how a reference trajectory update is prepared and delivered to the project by the navigation team during Solstice Mission flight operations. This paper will also document the timeline of products released and utilized, as well as the study to include an Enceladus occultation observation that occurs in 2016.

  6. Cassini-Huygens Ion Neutral Mass Spectrometer and the Future

    Science.gov (United States)

    Waite, J. Hunter

    2014-05-01

    The Cassini-Huygens Ion Neutral Mass Spectrometer (Cassini INMS) designed and built by Hasso Niemann has revolutionized our understanding of the Saturn system and demonstrated the importance of mass spectrometry as a tool for understanding formation, evolution, and chemical processes. In this talk that honors the accomplishments of Hasso I will discuss: 1) the major discoveries of INMS at Titan, Enceladus, and the other icy moons of Saturn, 2) the new perspective this has given us on understanding the formation and evolution of the outer solar system, and 3) the implications for future studies in the outer solar system using mass spectrometry.

  7. Going Out in a Blaze of Glory: Cassini's Grand Finale

    Science.gov (United States)

    Spilker, Linda; Edgington, Scott G.; Altobelli, Nicolas

    2016-10-01

    The Cassini-Huygens mission, a joint collaboration between NASA, ESA and the Italian Space Agency, is approaching its final year of operations after more than 12 years in Saturn orbit. Cassini will send back its final bits of unique data on 15 September 2017 as it plunges into Saturn's atmosphere, vaporizing and satisfying planetary protection requirements.Since early 2016 Cassini's orbital inclination has been slowly increasing. In November Cassini will transition to a series of 20 orbits with peripases just outside Saturn's F ring that include some of the closest flybys of the tiny ring moons and excellent views of the F ring and outer A ring. Cassini's final close flyby of Titan will propel it across Saturn's main rings and into its final orbits.Cassini's Grand Finale begins in April 2017 and is comprised of 22 orbits at an inclination of 63 degrees. Cassini will repeatedly dive between the innermost ring and Saturn's upper atmosphere providing insights into fundamental questions unattainable during the rest of the mission. It will be the first spacecraft to explore this region.These close orbits provide the highest resolution observations of both the rings and Saturn, and direct in situ sampling of the ring particles' composition, plasma, Saturn's exosphere and the innermost radiation belts. Saturn's gravitational field will be measured to unprecedented accuracy, providing information on Saturn's interior structure and mass distribution in the rings. Probing the magnetic field will give insight into the nature of the magnetic dynamo and the true rotation rate of Saturn's interior. The ion and neutral mass spectrometer will sniff the exosphere and upper atmosphere and examine water-based molecules originating from the rings. The cosmic dust analyzer will sample particle composition from different parts of the main rings.New science highlights and science objectives from Cassini's final orbits will be discussed.This work was carried out in part at the Jet

  8. Modelling the non-gravitational acceleration during Cassini's gravitation experiments

    CERN Document Server

    Bertolami, O; Gil, P J S; Páramos, J

    2014-01-01

    In this work we present a computation of the thermally generated acceleration on the Cassini probe during its solar conjunction experiment, obtained from a model of the spacecraft. We use a point-like source method to build a thermal model of the vehicle and find that the results are in close agreement with the estimates of this effect performed through Doppler data analysis.

  9. Automated Scheduling of Science Activities for Titan Encounters by Cassini

    Science.gov (United States)

    Ray, Trina L.; Knight, Russel L.; Mohr, Dave

    2014-01-01

    In an effort to demonstrate the efficacy of automated planning and scheduling techniques for large missions, we have adapted ASPEN (Activity Scheduling and Planning Environment) [1] and CLASP (Compressed Large-scale Activity Scheduling and Planning) [2] to the domain of scheduling high-level science goals into conflict-free operations plans for Titan encounters by the Cassini spacecraft.

  10. Cassini's Compositae genera: A nomenclatural and taxonomic assessment

    NARCIS (Netherlands)

    Flann, C.M.; Greuter, W.; Hind, D.J.N.

    2010-01-01

    Work on the Global Compositae Checklist has highlighted uncertainties and errors in the nomenclatural parameters of many genera and subgenera described by Henri Cassini. Problems concern rank (subgenus vs. genus); type designation; correct place of valid publication; alternative names; and other

  11. Observational Constraints on Planet Nine: Cassini Range Observations

    CERN Document Server

    Holman, Matthew J

    2016-01-01

    We significantly constrain the sky position, distance, and mass of a possible additional, distant planet in the solar system by examining its influence on the distance between Earth and the Cassini Spacecraft. Our preferred region is approximately centered on (RA, Dec) = ($40\\arcdeg$, $-15\\arcdeg$), extending approximately 20 degrees in all directions.

  12. In Situ Cassini Spacecraft Observations of Turbulence in Saturn's Magnetosheath

    Science.gov (United States)

    Hadid, L.; Sahraoui, F.; Retino, A.; Modolo, R.; Canu, P.; Jackman, C.; Masters, A.; Dougherty, M. K.; Gurnett, D. A.

    2013-09-01

    Throughout this work we investigate, the properties of turbulence in the Magnetosheath of Saturn. To do so, we computed Power Spectral Densities (PSD) based on Cassini interplanetary magnetic field data between 2004 and 2007. As a preliminary result, we show the absence of the Kolmogorov scale ~ f-5/3 in the inertial range whereas only the f-1 scale is present.

  13. Watch Cassini-Huygens setting off for Saturn and Titan

    Science.gov (United States)

    1997-10-01

    NASA's Cassini spacecraft, to which the Italian Space Agency ASI has made an important contribution, is crammed with instruments prepared by American and European scientists. It will spend four busy years in orbit around Saturn, and explore its famous rings and eighteen known moons. On its arrival at Saturn in 2004, the Cassini orbiter will release the European Space Agency's probe Huygens towards the largest moon, Titan.Also equipped by multinational scientific teams, Huygens will parachute through Titan's atmosphere to accomplish the most distant landing ever made, on the surface of another world. Television coverage of the launch for viewers in Europe On Monday 13 October the launch window for Cassini-Huygens opens at 4.55 a.m. Florida time (EDT). Starting at 4.00 a.m. Florida time (10.00 a.m. in most of western Europe and 9.00 a.m. in Great Britain and Ireland) ESA will provide a live TV transmission via satellite for European news organizations and other organizations wishing to receive it. Views of the launch will be accompanied by interviews with scientists and engineers of the Cassini-Huygens joint mission. A short news package will be transmitted near the end of transmission, and details will be announced on air. If the launch occurs promptly, ESA's TV operation will last until about 60 minutes after launch (i.e. about noon, European time). Technical details for TV reception Two satellites links are available, both carrying English on audio channel 1 and French on audio channel 2. Broadcasters and others with digital receivers will favour Intelsat K, while those with analogue receivers can use Eutelsat 2. Full information on transponders etc. is contained in an appendix to this press release. Paris press centre At ESA Headquarters in Paris, journalists will be able to view the TV transmission and to obtain news and background information about the Cassini-Huygens mission. The press centre will open at 10.00 a.m. on 13 October. If you wish to attend, please

  14. Nuclear study of Melusine; Etude nucleaire de Melusine

    Energy Technology Data Exchange (ETDEWEB)

    Cherot, J. [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    In this report are reviewed - with respect to starting of experiments - the main nuclear characteristics of a 20 per cent enriched uranium lattice, with light water as moderator and reflector. The reactor is to operate at 1 MW. 1) Study of various critical masses. 2) Control. Effectiveness of cadmium. Control rods and of a stainless steel regulating rod. 3) Study of the effect on reactivity of disturbances in the core center. 4) Study of xenon and samarium poisoning. 5) Temperature factor. 6) Heat exchanges in a fuel element. (author) [French] On etudie, dans ce rapport, les principales proprietes nucleaires d'un reseau a uranium enrichi (20 pour cent), dont le moderateur et le reflecteur sont l'eau legere en vue des experiences de demarrage. Ce reacteur devra fonctionner a 1 MW. 1) Etude de diverses masses critiques. 2) Controle. Efficacite des barres de controle en cadmium et d'une barre de reglage en acier inoxydable. 3) Etude de l'effet sur la reactivite de perturbation au centre du coeur. 4) Etude de l'empoisonnement xenon et samarium. 5) Coefficient de temperature. 6) Echanges thermiques dans un element. (auteur)

  15. Cassini Science Highlights: Surprises in the Saturn System

    Science.gov (United States)

    Spilker, Linda J.

    2012-10-01

    Cassini’s exploration of the Saturn system has generated a treasure trove of scientific data on Saturn, Titan, Enceladus, and other diverse icy satellites, the rings, and magnetosphere. After eight years of close study of this exceptionally complex and dynamic environment, Cassini is still unveiling new scientific discoveries that continue to amaze us. Standout recent highlights include aftereffects from Saturn’s huge storm, a possible subsurface ocean on Titan, close flybys of icy satellites, migrating ring “propellers”, and unexpected variations in Saturn kilometric radiation periodicities. Current observations show seasonal changes including the formation of a polar vortex at Titan’s south pole. To date, Cassini has observed Saturn from just after northern winter solstice through northern spring equinox and now is observing the Saturn system in the previously unobserved period leading up to northern summer solstice. In the remaining five years of the on-going Solstice Mission, Cassini will continue to study seasonally and temporally dependent processes. Given the long Saturnian year ( 30 years) the longevity of Cassini is essential for elucidating seasonal change in the Saturn system. The grand finale of the mission occurs in 2017, when a series of inclined orbits brings Cassini between the innermost D ring and the upper regions of Saturn’s atmosphere. This geometry will offer unique opportunities for new discoveries and ground-breaking science, including Saturn interior structure science from otherwise unobtainable gravity and magnetic field measurements and unprecedented determination of the ring mass, currently uncertain by an order of magnitude. This Proximal orbit phase is similar to Juno’s mission at Jupiter. Comparing Jupiter and Saturn is the first step toward the next great leap in solar system origins research. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA

  16. The Cassini Imaging Science Subsystem: Science Today and in Cassini's Final Three Years

    Science.gov (United States)

    West, R. A.

    2014-12-01

    The Cassini Imaging Science Subsystem (ISS) instrument was designed for long-range, high resolution imaging of Saturn and its system of rings and moons. It consists of two cameras, a Narrow Angle Camera (NAC, 2000 mm focal length) and a Wide Angle Camera (WAC, 200 mm focal length). The NAC has sensitivity from 200 nm to 1100 nm. The WAC is sensitive from 350 nm to 1100 nm. Among the mission highlights thus far for ISS have been discoveries of particulate plumes from Enceladus, details of surface topography along the 'tiger stripes', the discovery of an equatorial ridge on Iapetus, detailed images of small inner moons and distant moons Phoebe and Hyperion, features in Saturn's rings including perturbed edges near embedded moons, 'propellers', ephemeral clumps, and evidence for impacts in the rings and free-oscillation modes in Saturn's interior. The camera documented the aftermath of a methane/ethane 'rain' storm on Titan as well as seasonal behavior in the detached haze and visible airglow generated by magnetospheric plasma. The cameras documented the formation and evolution of a giant storm on Saturn, lightning from storms on Saturn, and determined that eddies are powering Saturn's zonal jets. In the F-ring and Proximal orbits ISS will obtain even better resolution on the rings, planet and inner moons.

  17. Cassini Scientist for a Day: a tactile experience

    Science.gov (United States)

    Canas, L.; Altobelli, N.

    2012-09-01

    In September 2011, the Cassini spacecraft took images of three targets and a challenge was launched to all students: to choose the one target they thought would provide the best science and to write an essay explaining their reasons (more information on the "Cassini Scientist for a Day" essay contest official webpage in: http://saturn.jpl.nasa.gov/education/scientistforaday10thedition/, run by NASA/JPL) The three targets presented were: Hyperion, Rhea and Titan, and Saturn. The idea behind "Cassini Scientist for a Day: a tactile experience" was to transform each of these images into schematic tactile images, highlighting relevant features apprehended through a tactile key, accompanied by a small text in Braille with some additional information. This initial approach would allow reach a broader community of students, more specifically those with visual impairment disabilities. Through proper implementation and careful study cases the adapted images associated with an explanatory key provide more resources in tactile astronomy. As the 2012 edition approaches a new set of targeted objet images will be once again transformed and adapted to visually impaired students and will aim to reach more students into participate in this international competition and to engage them in a quest to expand their knowledge in the amazing Cassini discoveries and the wonders of Saturn and its moons. As the winning essays will be published on the Cassini website and contest winners invited to participate in a dedicated teleconference with Cassini scientists from NASA's Jet Propulsion Laboratory, this initiative presents a great chance to all visually impaired students and teachers to participate in an exciting experience. These initiatives must be complemented with further information to strengthen the learning experience. However they stand as a good starting point to tackle further astronomical concepts in the classroom, especially this field that sometimes lacks the resources. Although

  18. Ongoing Analysis of Jupiter's Equatorial Hotspots and Plumes from Cassini

    Science.gov (United States)

    Choi, D. S.; Showmwn, A. P.; Vasavada, A. R.; Simon-Miller, A. A.

    2012-01-01

    We present updated results from our ongoing analysis of Cassini observations of Jupiter's equatorial meteorology. For two months preceding the spacecraft's closest approach of the planet, the ISS instrument onboard Cassini regularly imaged the atmosphere of Jupiter. We created time-lapse movies from this period that show the complex activity and interactions of the equatorial atmosphere. During this period, hot spots exhibited significant variations in size and shape over timescales of days and weeks. Some of these changes appear to be a result of interactions with passing vortex systems in adjacent latitudes. Strong anticyclonic gyres to the southeast of the dark areas converge with flow from the west and appear to circulate into a hot spot at its southwestern corner.

  19. Cassini Orbit Determination Performance (July 2008 - December 2011)

    Science.gov (United States)

    Pelletier, Frederic J.; Antreasian, Peter; Ardalan, Shadan; Buffington, Brent; Criddle, Kevin; Ionasescu, Rodica; Jacobson, Robert; Jones, Jeremy; Nandi, Sumita; Nolet, Simon; hide

    2012-01-01

    This paper reports on the orbit determination performance for the Cassini spacecraft from July 2008 to December 2011. During this period, Cassini made 85 revolutions around Saturn and had 52 close satellite encounters. 35 of those were with the massive Titan, 13 with the small, yet interesting, Enceladus as well as 2 with Rhea and 2 with Dione. The period also includes 4 double encounters, where engineers had to plan the trajectory for two close satellite encounters within days of each other at once. Navigation performance is characterized by ephemeris errors relative to in-flight predictions. Most Titan encounters 3-dimensional results are within a 1.5 formal sigma, with a few exceptions, mostly attributable to larger maneuver execution errors. Results for almost all other satellite encounter reconstructions are less than 3 sigma from their predictions. The errors are attributable to satellite ephemerides errors and in some cases to maneuver execution errors.

  20. Cassini/CAPS Observations of Tail Dynamics at Saturn

    Science.gov (United States)

    Thomsen, M. F.; Tokar, R. L.; Wilson, R. J.; Jackman, C. M.

    2013-12-01

    Following up a recent study of the density and flow direction of plasmas in Saturn's premidnight tail, we apply the same methodology to examine Cassini's near- and post-midnight tail passes as well. Specifically, we focus on intervals when CAPS was able to view both inward and outward plasma flows, and we examine the spatial distribution and other properties of such flows. We compare our results with those found by McAndrews et al. [Plasma in Saturn's nightside magnetosphere and the implications for global circulation, Plan. Sp. Sci. (2009)], using a different approach to the analysis of Cassini/CAPS data. These observations provide important clues to Saturn's tail structure and dynamics.

  1. The rotational dynamics of Titan from Cassini RADAR images

    Science.gov (United States)

    Meriggiola, Rachele; Iess, Luciano; Stiles, Bryan. W.; Lunine, Jonathan. I.; Mitri, Giuseppe

    2016-09-01

    Between 2004 and 2009 the RADAR instrument of the Cassini mission provided 31 SAR images of Titan. We tracked the position of 160 surface landmarks as a function of time in order to monitor the rotational dynamics of Titan. We generated and processed RADAR observables using a least squares fit to determine the updated values of the rotational parameters. We provide a new rotational model of Titan, which includes updated values for spin pole location, spin rate, precession and nutation terms. The estimated pole location is compatible with the occupancy of a Cassini state 1. We found a synchronous value of the spin rate (22.57693 deg/day), compatible at a 3-σ level with IAU predictions. The estimated obliquity is equal to 0.31°, incompatible with the assumption of a rigid body with fully-damped pole and a moment of inertia factor of 0.34, as determined by gravity measurements.

  2. The formation of the Cassini division in Saturn's rings

    Science.gov (United States)

    Goldreich, P.; Tremaine, S.

    1978-01-01

    An explanation for the size and location of the Cassini division in Saturn's rings is proposed. The explanation is based on the collective response of the particles in the ring to the resonant forcing by Mimas. An upper limit is calculated for the width of the gap that could be opened at a resonance. In addition, an estimate is obtained regarding the damping of the density waves by viscous and nonlinear effects. A picture is presented of the development of a gap. The results are compared with the observed properties of the divisions in Saturn's rings. The exact position of the inner edge of the Cassini division is difficult to predict, because the 2:1 resonance lies very near several weaker resonances (4:2 and 6:3 with Mimas, 4:1 with Tethys). However, the edge should lie near 17 seconds, and this is consistent with ground based observations.

  3. Improving the Planetary Ephemeris with Astrometric Observations of Cassini

    Science.gov (United States)

    Jones, Dayton L.; Fomalont, E.; Dhawan, V.; Romney, J.; Lanyi, G.; Border, J.; Folkner, B.; Jacobson, B.

    2009-05-01

    During the past three years we have carried out a series of astrometric VLBA observations of the Cassini spacecraft. At each epoch, we used phase referencing to obtain high precision relative positions between Cassini and an angularly nearby calibration source. The calibration sources were separately tied to nearby defining sources of the International Celestial Reference Frame (ICRF) through additional phase-referenced VLBA experiments. By combining our position measurements of Cassini with a model of Cassini's orbit around Saturn (from Doppler measurements by the Deep Space Network), we are able to determine the ICRF position of Saturn at each epoch to about 0.3 mas. This is about 2 km at the average distance of Saturn. These results will improve the Saturn ephemeris, particularly in ecliptic latitude (the plane of Saturn's orbit). The error in latitude decreases dramatically as the total time span of VLBA data approaches 1/4 of Saturn's orbital period in 2011-2012. Saturn is the first outer planet whose ephemeris can be improved and more closely tied to the ICRF and the inner solar system through long-term observations of an orbiter. The planned Juno mission to Jupiter will allow this technique to be applied there also. The planetary ephemeris is an essential tool for studies of solar system dynamics, interplanetary spacecraft navigation, and test of general relativity. It requires continuous maintenance and improvement. This research has been carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration, and has relied on observations by the Very Long Baseline Array, a facility of the National Science Foundation operated by the National Radio Astronomy Observatory under a cooperative agreement with Associated Universities, Inc.

  4. Design and Analysis of RTGs for CRAF and Cassini Missions

    Energy Technology Data Exchange (ETDEWEB)

    Schock, Alfred; Noravian, Heros; Or, Chuen; Sankarankandath, Kumar

    1991-01-01

    The design and analysis of Radioisotope Thermoelectric Generators integrated with JPL's CRAF and Cassini spacecraft are described. The principal purposed of the CRAF mission are the study of asteroids and comets, and the principal purposes of the Cassini mission are the study of asteroids, Saturn, and its moons (particularly Titan). Both missions will employ the Mariner/Mark-2 spacecraft, and each will be powered by two GPHS-RTGs. JPL's spacecraft designers wish to locate the two RTGs in close proximity to each other, resulting in mutual and unsymmetrical obstruction of their heat rejection paths. To support JPL's design studies, the U.S. Department of Energy asked Fairchild to determine the effect of the RTGs' proximity on their power output. This required the development of novel analysis methods and computer codes, described in this report, for the coupled thermal and electrical analysis of obstructed RTGs with axial and circumferential temperature, voltage, and current variations. The code was validated against measured data of unobstructed RTG tests, and was used for the detailed analysis of the obstructed CRAF/Cassini RTGs. Also described is a new method for predicting the combined effect of fuel decay and thermoelectric degradation on the output of obstructed RTGs, which accounts for the effect of diminishing temperatures on degradation rates. The computed results indicate that for the 24-degree separation angle of JPL's baseline design, the mutually obstructed standard GPHS/RTGs show adequate power margins for the CRAF mission, but slightly negative margins for the Cassini mission.

  5. Rpws Science Today and in Cassini's Final Three Year

    Science.gov (United States)

    Kurth, W. S.; Lamy, L.

    2014-12-01

    Ten years of Cassini/RPWS remote and in situ observations of Saturn and its environment have provided a rich return feeding numerous studies of the various types of kronian radio emissions (such as Saturn's kilometric radiation [SKR], auroral hiss, narrowband [NB] and drifting burst emissions, and Saturn's electrostatic discharges [SED]), local plasma waves (such as chorus, upper hybrid bands and electron cyclotron harmonic emissions) and dusty plasmas. Nonetheless, several major objectives for RPWS science remain for the last three years of the Cassini mission, and will culminate with the detailed study of Saturn's auroral regions, where SKR and possibly other types of radio waves are produced and large-scale plasma acceleration is suspected to take place. During the F-ring and proximal orbital sequences, Cassini is expected to pass through northern and southern auroral regions tens of times around noon local time. These passes can be accurately predicted through the modeling of SKR sources and in turn help to trigger combined observations with other Cassini instruments and Earth-based observatories such as Hubble. Altogether, these observations will provide crucial complementary insights to understand kronian auroral processes. RPWS will also continue to measure the rotational modulation of various radio emissions (SKR, NB and hiss), pushing forward the study of magnetospheric periodicities long after equinox, pursue the monitoring of SEDs and lightning whistlers, whose occurrence probes the activity of atmospheric storms, or probe in detail the dusty environment of the D ring and wave-particle interactions taking place in the very inner magnetosphere where the magnetic field links the planet to the rings.

  6. Cassini at Saturn Proximal Orbits - Attitude Control Challenges

    Science.gov (United States)

    Burk, Thomas A.

    2013-01-01

    The Cassini mission at Saturn will come to an end in the spring and summer of 2017 with a series of 22 orbits that will dip inside the rings of Saturn. These are called proximal orbits and will conclude with spacecraft disposal into the atmosphere of the ringed world on September 15, 2017. These unique orbits that cross the ring plane only a few thousand kilometers above the cloud tops of the planet present new attitude control challenges for the Cassini operations team. Crossing the ring plane so close to the inner edge of the rings means that the Cassini orientation during the crossing will be tailored to protect the sensitive electronics bus of the spacecraft. This orientation will put the sun sensors at some extra risk so this paper discusses how the team prepares for dust hazards. Periapsis is so close to the planet that spacecraft controllability with RCS thrusters needs to be evaluated because of the predicted atmospheric torque near closest approach to Saturn. Radiation during the ring plane crossings will likely trigger single event transients in some attitude control sensors. This paper discusses how the attitude control team deals with radiation hazards. The angular size and unique geometry of the rings and Saturn near periapsis means that star identification will be interrupted and this paper discusses how the safe mode attitude is selected to best deal with these large bright bodies during the proximal orbits.

  7. Cassini at Saturn Proximal Orbits - Attitude Control Challenges

    Science.gov (United States)

    Burk, Thomas A.

    2013-01-01

    The Cassini mission at Saturn will come to an end in the spring and summer of 2017 with a series of 22 orbits that will dip inside the rings of Saturn. These are called proximal orbits and will conclude with spacecraft disposal into the atmosphere of the ringed world on September 15, 2017. These unique orbits that cross the ring plane only a few thousand kilometers above the cloud tops of the planet present new attitude control challenges for the Cassini operations team. Crossing the ring plane so close to the inner edge of the rings means that the Cassini orientation during the crossing will be tailored to protect the sensitive electronics bus of the spacecraft. This orientation will put the sun sensors at some extra risk so this paper discusses how the team prepares for dust hazards. Periapsis is so close to the planet that spacecraft controllability with RCS thrusters needs to be evaluated because of the predicted atmospheric torque near closest approach to Saturn. Radiation during the ring plane crossings will likely trigger single event transients in some attitude control sensors. This paper discusses how the attitude control team deals with radiation hazards. The angular size and unique geometry of the rings and Saturn near periapsis means that star identification will be interrupted and this paper discusses how the safe mode attitude is selected to best deal with these large bright bodies during the proximal orbits.

  8. Avoiding Human Error in Mission Operations: Cassini Flight Experience

    Science.gov (United States)

    Burk, Thomas A.

    2012-01-01

    Operating spacecraft is a never-ending challenge and the risk of human error is ever- present. Many missions have been significantly affected by human error on the part of ground controllers. The Cassini mission at Saturn has not been immune to human error, but Cassini operations engineers use tools and follow processes that find and correct most human errors before they reach the spacecraft. What is needed are skilled engineers with good technical knowledge, good interpersonal communications, quality ground software, regular peer reviews, up-to-date procedures, as well as careful attention to detail and the discipline to test and verify all commands that will be sent to the spacecraft. Two areas of special concern are changes to flight software and response to in-flight anomalies. The Cassini team has a lot of practical experience in all these areas and they have found that well-trained engineers with good tools who follow clear procedures can catch most errors before they get into command sequences to be sent to the spacecraft. Finally, having a robust and fault-tolerant spacecraft that allows ground controllers excellent visibility of its condition is the most important way to ensure human error does not compromise the mission.

  9. A Change Of Seasons On Titan Observed By Cassini

    Science.gov (United States)

    Teanby, Nicholas; Irwin, P.; Nixon, C.; de Kok, R.; Vinatier, S.; Coustenis, A.; Sefton-Nash, E.; Calcutt, S.; Flasar, M.

    2012-10-01

    Cassini's tour of the Saturn system now spans over eight years, equivalent to more than a quarter of a Titan year. This provides us with an excellent opportunity to study atmospheric seasonal behaviour. Here we use infrared spectra measured by Cassini's CIRS instrument to determine variations in temperature and composition throughout the mission - covering northern fall to northern spring - and use these quantities as tracers to probe changes in atmospheric circulation. Our results focus on the middle atmosphere (stratosphere-mesosphere at 100-500km altitude), where the majority of atmospheric super-rotation occurs and where high altitude photochemical production is linked to the lower atmosphere and surface. Our observations show significant changes in the distribution of trace chemical species with season - indicating changes in large-scale circulation patterns around the 2009 equinox. The timing and behaviour of the transition between different seasonal regimes will be discussed, in addition to implications for atmospheric general circulation models. Cassini has allowed us to study these phenomenon for the first time and is providing fresh insight into planetary atmospheric processes.

  10. Abundances of Jupiter's Trace Hydrocarbons from Voyager and Cassini

    Science.gov (United States)

    Nixon, C. A.; Achterberg, R. K.; Romani, P. N.; Allen, M.; Zhang, X.; Teanby, N. A.; Irwin, P. G. J.; Flasar, F. M.

    2010-01-01

    The flybys of Jupiter by the Voyager spacecraft in 1979, and over two decades later by Cassini in 2000, have provided us with unique datasets from two different epochs, allowing the investigation of seasonal change in the atmosphere. In this paper we model zonal averages of thermal infrared spectra from the two instruments, Voyager 1 IRIS and Cassini CIRS, to retrieve the vertical and meridional profiles of temperature, and the abundances of the two minor hydrocarbons, acetylene (C2H2) and ethane (C2H6). The spatial variation of these gases is controlled by both chemistry and dynamics, and therefore their observed distribution gives us an insight into both processes, We find that the two gases paint quite different pictures of seasonal change. Whilst the 2-D cross-section of C2H6 abundance is slightly increased and more symmetric in 2000 (northern summer solstice) compared to 1979 (northern fall equinox), the major trend of equator to pole increase remains. For C2H2 on tile other hand, the Voyager epoch exhibits almost no latitudinal variation, whilst the Cassini era shows a marked decrease polewards in both hemispheres. At the present time, these experimental findings are in advance of interpretation, as there are no published models of 2-D Jovian seasonal chemical variation available for comparison.

  11. Abundances of Jupiter's Trace Hydrocarbons from Voyager and Cassini

    Science.gov (United States)

    Nixon, C. A.; Achterberg, R. K.; Romani, P. N.; Allen, M.; Zhang, X.; Teanby, N. A.; Irwin, P. G. J.; Flasar, F. M.

    2010-01-01

    The flybys of Jupiter by the Voyager spacecraft in 1979, and over two decades later by Cassini in 2000, have provided us with unique datasets from two different epochs, allowing the investigation of seasonal change in the atmosphere. In this paper we model zonal averages of thermal infrared spectra from the two instruments, Voyager 1 IRIS and Cassini CIRS, to retrieve the vertical and meridional profiles of temperature, and the abundances of the two minor hydrocarbons, acetylene (C2H2) and ethane (C2H6). The spatial variation of these gases is controlled by both chemistry and dynamics, and therefore their observed distribution gives us an insight into both processes, We find that the two gases paint quite different pictures of seasonal change. Whilst the 2-D cross-section of C2H6 abundance is slightly increased and more symmetric in 2000 (northern summer solstice) compared to 1979 (northern fall equinox), the major trend of equator to pole increase remains. For C2H2 on tile other hand, the Voyager epoch exhibits almost no latitudinal variation, whilst the Cassini era shows a marked decrease polewards in both hemispheres. At the present time, these experimental findings are in advance of interpretation, as there are no published models of 2-D Jovian seasonal chemical variation available for comparison.

  12. User Guide to the PDS Dataset for the Cassini Composite Infrared Spectrometer (CIRS)

    Science.gov (United States)

    Nixon, Conor A.; Kaelberer, Monte S.; Gorius, Nicolas

    2012-01-01

    This User Guide to the Cassini Composite Infrared Spectrometer (CIRS) has been written with two communities in mind. First and foremost, scientists external to the Cassini Project who seek to use the CIRS data as archived in the Planetary Data System (PDS). In addition, it is intended to be a comprehensive reference guide for those internal to the CIRS team.

  13. E ring dust sources: Implications from Cassini's dust measurements

    Science.gov (United States)

    Spahn, Frank; Albers, Nicole; Hörning, Marcel; Kempf, Sascha; Krivov, Alexander V.; Makuch, Martin; Schmidt, Jürgen; Seiß, Martin; Miodrag Sremčević

    2006-08-01

    The Enceladus flybys of the Cassini spacecraft are changing our understanding of the origin and sustainment of Saturn's E ring. Surprisingly, beyond the widely accepted dust production caused by micrometeoroid impacts onto the atmosphereless satellites (the impactor-ejecta process), geophysical activities have been detected at the south pole of Enceladus, providing an additional, efficient dust source. The dust detector data obtained during the flyby E11 are used to identify the amount of dust produced in the impactor-ejecta process and to improve related modeling [Spahn, F., Schmidt, J., Albers, N., Hörning, M., Makuch, M., Seiß, M., Kempf, S., Srama, R., Dikarev, V.V., Helfert, S., Moragas-Klostermeyer, G., Krivov, A.V., Sremčević, M., Tuzzolino, A., Economou, T., Grün, E., 2006. Cassini dust measurements at Enceladus: implications for Saturn's E ring. Science, in press]. With this, we estimate the impact-generated dust contributions of the other E ring satellites and find significant differences in the dust ejection efficiency by two projectile families - the E ring particles (ERPs) and the interplanetary dust particles (IDPs). Together with the Enceladus south-pole source, the ERP impacts play a crucial role in the inner region, whereas the IDP impacts dominate the particle production in the outer E ring, possibly accounting for its large radial extent. Our results can be verified in future Cassini flybys of the E ring satellites. In this way poorly known parameters of the dust particle production in hypervelocity impacts can be constrained by comparison of the data and theory.

  14. The Saturnian satellite Rhea as seen by Cassini VIMS

    Science.gov (United States)

    Stephan, K.; Jaumann, R.; Wagner, R.; Clark, R.N.; Cruikshank, D.P.; Giese, B.; Hibbitts, C.A.; Roatsch, T.; Matz, K.-D.; Brown, R.H.; Filacchione, G.; Cappacioni, F.; Scholten, F.; Buratti, B.J.; Hansen, G.B.; Nicholson, P.D.; Baines, K.H.; Nelson, R.M.; Matson, D.L.

    2012-01-01

    Since the arrival of the Cassini spacecraft at Saturn in June 2004, the Visual and Infrared Mapping Spectrometer has obtained new spectral data of the icy satellites of Saturn in the spectral range from 0.35 to 5.2 ??m. Numerous flybys were performed at Saturn's second largest satellite Rhea, providing a nearly complete coverage with pixel-ground resolutions sufficient to analyze variations of spectral properties across Rhea's surface in detail. We present an overview of the VIMS observations obtained so far, as well as the analysis of the spectral properties identified in the VIMS spectra and their variations across its surface compared with spatially highly resolved Cassini ISS images and digital elevation models. Spectral variations measured across Rhea's surface are similar to the variations observed in the VIMS observations of its neighbor Dione, implying similar processes causing or at least inducing their occurrence. Thus, magnetospheric particles and dust impacting onto the trailing hemisphere appear to be responsible for the concentration of dark rocky/organic material and minor amounts of CO 2 in the cratered terrain on the trailing hemisphere. Despite the prominent spectral signatures of Rhea's fresh impact crater Inktomi, radiation effects were identified that also affect the H 2O ice-rich cratered terrain of the leading hemisphere. The concentration of H 2O ice in the vicinity of steep tectonic scarps near 270??W and geologically fresh impact craters implies that Rhea exhibits an icy crust at least in the upper few kilometers. Despite the evidence for past tectonic events, no indications of recent endogenically powered processes could be identified in the Cassini data. ?? 2011 Elsevier Ltd. All rights reserved.

  15. The Cassini Solstice Mission: Streamlining Operations by Sequencing with PIEs

    Science.gov (United States)

    Vandermey, Nancy; Alonge, Eleanor K.; Magee, Kari; Heventhal, William

    2014-01-01

    The Cassini Solstice Mission (CSM) is the second extended mission phase of the highly successful Cassini/Huygens mission to Saturn. Conducted at a much-reduced funding level, operations for the CSM have been streamlined and simplified significantly. Integration of the science timeline, which involves allocating observation time in a balanced manner to each of the five different science disciplines (with representatives from the twelve different science instruments), has long been a labor-intensive endeavor. Lessons learned from the prime mission (2004-2008) and first extended mission (Equinox mission, 2008-2010) were utilized to design a new process involving PIEs (Pre-Integrated Events) to ensure the highest priority observations for each discipline could be accomplished despite reduced work force and overall simplification of processes. Discipline-level PIE lists were managed by the Science Planning team and graphically mapped to aid timeline deconfliction meetings prior to assigning discrete segments of time to the various disciplines. Periapse segments are generally discipline-focused, with the exception of a handful of PIEs. In addition to all PIEs being documented in a spreadsheet, allocated out-of-discipline PIEs were entered into the Cassini Information Management System (CIMS) well in advance of timeline integration. The disciplines were then free to work the rest of the timeline internally, without the need for frequent interaction, debate, and negotiation with representatives from other disciplines. As a result, the number of integration meetings has been cut back extensively, freeing up workforce. The sequence implementation process was streamlined as well, combining two previous processes (and teams) into one. The new Sequence Implementation Process (SIP) schedules 22 weeks to build each 10-week-long sequence, and only 3 sequence processes overlap. This differs significantly from prime mission during which 5-week-long sequences were built in 24 weeks

  16. The Cassini Solstice Mission: Streamlining Operations by Sequencing with PIEs

    Science.gov (United States)

    Vandermey, Nancy; Alonge, Eleanor K.; Magee, Kari; Heventhal, William

    2014-01-01

    The Cassini Solstice Mission (CSM) is the second extended mission phase of the highly successful Cassini/Huygens mission to Saturn. Conducted at a much-reduced funding level, operations for the CSM have been streamlined and simplified significantly. Integration of the science timeline, which involves allocating observation time in a balanced manner to each of the five different science disciplines (with representatives from the twelve different science instruments), has long been a labor-intensive endeavor. Lessons learned from the prime mission (2004-2008) and first extended mission (Equinox mission, 2008-2010) were utilized to design a new process involving PIEs (Pre-Integrated Events) to ensure the highest priority observations for each discipline could be accomplished despite reduced work force and overall simplification of processes. Discipline-level PIE lists were managed by the Science Planning team and graphically mapped to aid timeline deconfliction meetings prior to assigning discrete segments of time to the various disciplines. Periapse segments are generally discipline-focused, with the exception of a handful of PIEs. In addition to all PIEs being documented in a spreadsheet, allocated out-of-discipline PIEs were entered into the Cassini Information Management System (CIMS) well in advance of timeline integration. The disciplines were then free to work the rest of the timeline internally, without the need for frequent interaction, debate, and negotiation with representatives from other disciplines. As a result, the number of integration meetings has been cut back extensively, freeing up workforce. The sequence implementation process was streamlined as well, combining two previous processes (and teams) into one. The new Sequence Implementation Process (SIP) schedules 22 weeks to build each 10-week-long sequence, and only 3 sequence processes overlap. This differs significantly from prime mission during which 5-week-long sequences were built in 24 weeks

  17. The determination of Dione's gravity field after four Cassini flybys

    Science.gov (United States)

    Zannoni, Marco; Tortora, Paolo; Iess, Luciano; Jacobson, Robert A.; Armstrong, John W.; Asmar, Sami W.

    2015-04-01

    We present the expected accuracy in the determination of Dione's gravity field obtained through numerical simulations of all radio science flybys currently planned in the entire Cassini mission. During its tour of the Saturn system, Cassini already performed two flybys of Dione dedicated to the determination of its mass and gravity field, in October 2005 and December 2011, respectively. Two additional radio science flybys are planned in June 2015 and August 2015. The analysis of the Doppler data acquired during the closest approach of the second flyby allowed the first estimation of Dione's J2 and C22 but, given the limited amount of data, their estimation has a large correlation and cannot be considered fully reliable. Here we infer the expected final accuracy in the determination of Dione's J2 and C22 by combining the available results from the already performed experiments with numerical simulations of future flybys. The main observables considered in the analysis are two-way and three-way Doppler data obtained from the frequency shift of a highly stable microwave carrier between the spacecraft and the stations of NASA's Deep Space Network. White Gaussian noise was added to the simulated data, with a constant standard deviation for each tracking pass, obtained from an accurate noise budget of the Cassini mission. For the two flybys to be carried out in 2015, we consider a continuous coverage during +/-18 hours around the closest approach, plus one tracking pass 36 hours before and after it. The data analysis is carried out using a global, multi-arc fit, and comparing the independent solutions obtained from each flyby and different multi-arc solutions. The analysis of all four flybys is expected to provide the best, unconstrained, reliable estimation of the full quadrupole gravity field of Dione.

  18. Microwave absorptivity in the Saturn atmosphere from Cassini Radio Science

    Science.gov (United States)

    Kliore, A. J.; Marouf, E. A.; Flasar, F. M.

    2011-12-01

    Since 2005, the Cassini spacecraft has collected data from numerous radio occultations by the atmosphere of Saturn. These occultations probed a wide range of latitudes, ranging from equatorial to near-polar. The radio system of Cassini transmits three coherent downlinks to Earth at S-Band (13.04 cm), X-Band (3.56 cm), and Ka-Band (0.94 cm) wavelengths. With the Deep Space Net 70 m receiving stations, The signal-to-noise ratio (SNR) is approximately 48 dB at X-Band, and 38 dB at S-band. At Ka-band, 34 m DSN stations are used, resulting in an SNR of about 41 dB. These SNRs are quite adequate to follow the signals through the top of the microwave-absorbing regions before the noise-floor is reached. By subtracting the refractive defocusing attenuation in the atmosphere (derived from the phase data) from the total attenuation, one obtains the attenuation due to absorption (dB0, which can then be inverted to obtain vertical profiles of absorptivity (dB km-1 ) at each of the three wavelengths. Preliminary results show the expected large effect of wavelength on the absorptivity profiles, with the shorter wavelength signals being absorbed higher in the atmosphere. These profiles can be used to estimate the vertical density profiles of known microwave absorbers, such as NH3 and PH3, examples of which are presented .This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, San Jose State University, and NASA Goddard Space Flight Center with support from the Cassini program.

  19. Optical navigation planning process for the Cassini Solstice Mission

    Science.gov (United States)

    Nolet, Simon; Gillam, Stephen D.; Jones, Jeremy B.

    2011-01-01

    During the Cassini Equinox Mission, the Optical Navigation strategy has gradually evolved toward maintenance of an acceptable level of uncertainty on the positions of the bodies to be observed. By counteracting the runoff of the uncertainty over time, this strategy helps satisfy the spacecraft pointing requirements throughout the Solstice Mission, while considerably reducing the required imaging frequency. Requirements for planning observations were established, and the planning process itself was largely automated to facilitate re-planning if it becomes necessary. This paper summarizes the process leading to the optical navigation schedule for the seven years of the Solstice Mission.

  20. Health physics innovations developed during Cassini for future space applications

    Science.gov (United States)

    Nickell, Rod; Rutherford, Theresa; Marmaro, George

    1999-01-01

    There has been a long history of space missions involving Space Nuclear Auxiliary Power (SNAP) devices starting with the Transit 4A Spacecraft (1961), on through the Apollo, Pioneer, Viking, Voyager, Galileo, Ulysses, Mars Pathfinder, and most recently, Cassini (1997). All of these Major Radiological Source (MRS) missions were processed at the Kennedy Space Center/Cape Canaveral Air Station (KSC/CCAS) Launch Site in full compliance with program and regulatory requirements. The cumulative experience gained supporting these past missions has led to significant innovations which will be useful for bench-marking future MRS ground processing.

  1. Optical navigation planning process for the Cassini Solstice Mission

    Science.gov (United States)

    Nolet, Simon; Gillam, Stephen D.; Jones, Jeremy B.

    2011-01-01

    During the Cassini Equinox Mission, the Optical Navigation strategy has gradually evolved toward maintenance of an acceptable level of uncertainty on the positions of the bodies to be observed. By counteracting the runoff of the uncertainty over time, this strategy helps satisfy the spacecraft pointing requirements throughout the Solstice Mission, while considerably reducing the required imaging frequency. Requirements for planning observations were established, and the planning process itself was largely automated to facilitate re-planning if it becomes necessary. This paper summarizes the process leading to the optical navigation schedule for the seven years of the Solstice Mission.

  2. Lightweight Radioisotope Heater Unit (LWRHU) production for the Cassini mission

    Energy Technology Data Exchange (ETDEWEB)

    Rinehart, G.H.

    1996-06-01

    The Lightweight Radioisotope Heater Unit (LWRHU) is a {sup 238}PuO{sub 2} fueled heat source designed to provide a thermal watt of power for space missions. The LWRHU will be used to maintain the temperature of various components on the spacecraft at the required level. The heat source consists of a {sup 238}PuO{sub 2} fuel pellet, a Pt-30Rh capsule, a pyrolytic graphite insulator, and a woven graphite aeroshell assembly. Los Alamos has fabricated 180 heater units, which will be used on the Cassini mission. This report summarizes the specifications, fabrication processes, and production data for the heat sources fabricated at Los Alamos.

  3. Titan's Complex Neutral Composition as Measured by Cassini INMS

    Science.gov (United States)

    Waite, J. H.; Magee, B. A.; Gell, D. A.; Kasprzak, W. T.; Cravens, T.; Vuitton, V. S.; Yelle, R. V.

    2006-12-01

    The composition of Titan's complex neutral atmosphere above 1000 km as observed by the Cassini Ion Neutral Mass Spectrometer on recent flybys of Titan are presented. A rich mixture of hydrocarbons and nitriles are found with mixing ratios that vary from 10-4 to 10-7: acetylene, ethylene, ethane, benzene, toluene, cyanogen, propyne, propene, propane, and various nitriles. The calibration and mass deconvolution processes are presented in order to establish clear boundaries on the systematic errors that can occur in the mass deconvolution process. The role of ion neutral chemistry in forming these compounds will also be discussed.

  4. Flight Path Control Design for the Cassini Solstice Mission

    Science.gov (United States)

    Ballard, Christopher G.; Ionasescu, Rodica

    2011-01-01

    The Cassini spacecraft has been in orbit around Saturn for just over 7 years, with a planned 7-year extension, called the Solstice Mission, which started on September 27, 2010. The Solstice Mission includes 205 maneuvers and 70 flybys which consist of the moons Titan, Enceladus, Dione, and Rhea. This mission is designed to use all available propellant with a statistical margin averaging 0.6 m/s per encounter, and the work done to prove and ensure the viability of this margin is highlighted in this paper.

  5. Analysis of Cassini UVIS Image Cube Vectors of Enceladus

    Science.gov (United States)

    Shemansky, D. E.; Yoshii, J.; Hansen, Candice; Hendrix, Amanda R.; Liu, X.; Yung, Yuk

    2016-10-01

    Cassini UVIS image cubes of Enceladus from a spacecraft range of image cube matrix discussed here is a virtual 20 X 20 RE structure centered on the satellite body with pixel size 0.2 X 0.2 RE. The pixels are composed of FUV spectral vectors accumulated from multiple exposures by the Cassini experiments in the years 2005 - 2015. In spite of the multiple year exposure, the matrix structure is significantly non-uniform in brightness and spectral content. The features that can be presented at this time are: 1) The pixels at the center of the body show a strong solar reflection that over the 1500 – 1900 A region indicates a spectrally structureless albedo. 2) The central pixels show no discrete emissions other than a weak optically thick atomic hydrogen resonance line (HLya) at 1216 A. 3) Above the limb the solar reflection spectrum appears at irregular locations. One of these is recognized as the south polar plume. The plume solar reflection albedo shows a multiply scattered spectrum dominantly composed of hydrocarbon absorbers, primarily C2H4. 4) Above the limb, the HLya line shows spatially irregular structure with emission peaks in the north 50X brighter than the signal from body center. No discrete emissions other than HLya are observed in the < 2RE region above the limb. The neutral torus at the Enceladus orbit shows only the OI 1304 A line emission. Limits on the presence of other species, H2 in particular, will be presented.

  6. Cassini Thruster Calibration Algorithm Using Reaction Wheel Biasing Data

    Science.gov (United States)

    Rizvi, Farheen

    2012-01-01

    Thrust force estimates for the reaction control thrusters on-board Cassini spacecraft are presented in this paper. Cassini consists of two thruster branches (A and B) each with eight thrusters. The four Z-thrusters control the X and Y-axes, while the four Y-thrusters control the Z-axis. It is important to track the thrust force estimates in order to detect any thruster degradation and for supporting various activities in spacecraft operations (Titan flyby, spacecraft maneuvers). The Euler equation, which describes the rotational motion of the spacecraft during a reaction wheel bias event, is used to develop the algorithm. The thrust estimates are obtained from the pseudo inverse solution using flight telemetry during the bias. Results show that the A-branch Z3A and Z4A thrusters exhibited degraded thrust in November 2008. Due to the degraded thrust performance of Z3A and Z4A, A-branch usage was discontinued and prime branch was swapped to B-branch in March 2009. The thrust estimates from the B-branch do not show any degradation to date. The algorithm is used to trend the B-branch thrust force estimates as the mission continues.

  7. Estimation of Enceladus Plume Density Using Cassini Flight Data

    Science.gov (United States)

    Wang, Eric K.; Lee, Allan Y.

    2011-01-01

    The Cassini spacecraft was launched on October 15, 1997 by a Titan 4B launch vehicle. After an interplanetary cruise of almost seven years, it arrived at Saturn on June 30, 2004. In 2005, Cassini completed three flybys of Enceladus, a small, icy satellite of Saturn. Observations made during these flybys confirmed the existence of water vapor plumes in the south polar region of Enceladus. Five additional low-altitude flybys of Enceladus were successfully executed in 2008-9 to better characterize these watery plumes. During some of these Enceladus flybys, the spacecraft attitude was controlled by a set of three reaction wheels. When the disturbance torque imparted on the spacecraft was predicted to exceed the control authority of the reaction wheels, thrusters were used to control the spacecraft attitude. Using telemetry data of reaction wheel rates or thruster on-times collected from four low-altitude Enceladus flybys (in 2008-10), one can reconstruct the time histories of the Enceladus plume jet density. The 1 sigma uncertainty of the estimated density is 5.9-6.7% (depending on the density estimation methodology employed). These plume density estimates could be used to confirm measurements made by other onboard science instruments and to support the modeling of Enceladus plume jets.

  8. Dust occultation at Titan measured by CDA onboard Cassini

    Science.gov (United States)

    Srama, Ralf; CDA science Team

    2016-10-01

    The Cosmic Dust Analyzer (CDA) onboard Cassini characterized successfully the dust environment at Saturn since 2004. The instrument measures the primary charge, speed, mass and composition of individual submicron and micron sized dust grains. The detection threshold scales with speed^3.5 such that the detection of fast nanograins (~100 km/s) is possible. Saturn's nanodust environment (streams) is studied many years. However, a special geometric condition of Saturn, Cassini and Titan during a Titan flyby in 2014 (DOY 65) provided a special dust occultation opportunity. Titan and its atmosphere blocked the stream of fast nanoparticles such that CDA registered a clear drop in impact rate around closest approach. An analysis of the data allows to constrain the source region of the nanograins, which is compatible with a source region in the ring plane at distances from Saturn between 4 and 8 Saturn radii. Backward and forward modeling was performed leading to dust grain sizes between 3 and 9 nm and speeds between 80 and 150 km/s. The new modeling results also show that Enceladus acts a direct source for nanodust streams leading to the observation of periodic impact rates in the outer Saturn system. Such periodicities were observed recently by CDA and showed a clear signature of the Enceladus orbital period. A second dust occultation opportunity using Titan is planned august 2016.

  9. Cassini observations of carbon-based anions in Titan's ionosphere

    Science.gov (United States)

    Desai, Ravindra; Lewis, Gethyn; Waite, J. Hunter; Kataria, Dhiren; Wellbrock, Anne; Jones, Geraint; Coates, Andrew

    2016-07-01

    Cassini observations of Titan's ionosphere revealed an atmosphere rich in positively and negatively charged ions and organic molecules. The detection of large quantities of negatively charged ions was particularly surprising and adds Titan to the growing list of locations where anion chemistry has been observed to play an important role. In this study we present updated analysis on these negatively charged ions through an enhanced understanding of the Cassini CAPS Electron Spectrometer (CAPS-ELS) instrument response. The ionisation of Titan's dominant atmospheric constituent, N2, by the HeII Solar line, results in an observable photoelectron population at 24.1eV which we use to correct for differential spacecraft charging. Correcting for further energy-angle signatures within this dataset, we use an updated fitting procedure to show how the ELS mass spectrum, previously grouped into broad mass ranges, can be resolved into specific peaks at multiples of carbon-based anion species up to over 100amu/q. These peaks are shown to be ubiquitous within Titan's upper atmosphere and reminiscent of carbon-based anions identified in dense molecular clouds beyond our Solar System. It is thus shown how the moon Titan in the Outer Solar System can be used as an analogue to study these even more remote and exotic astrophysical environments.

  10. Planetary turbulence: survey of Cassini data in the Saturn's magnetosheath

    Science.gov (United States)

    Hadid, Lina; Sahraoui, Fouad; Kiyani, Khurom; Modolo, Ronan; Retino, Alessandro; Canu, Patrick; Masters, Adam; Dougherty, Michele K.; Gurnett, Donald A.

    2015-04-01

    Turbulence is one of the most important yet not fully understood topics of modern physics. Understanding turbulence is collisionless plasmas, where kinetic effects mediate interactions between fields and charged particles play, is crucial to apprehend many dynamical processes such as particle heating and acceleration. Among others, one key open issue of plasma turbulence is how the energy associated to magnetic and electric fields is converted, and eventually dissipated, into kinetic and internal energy of the plasma. The planets' magnetosheath present a high level of turbulence that involves both nonlinear stochastic processes and a rich variety of wave phenomena. In comparison with turbulence in the solar wind and in the terrestrial magnetosheath, turbulence around other planets is far less explored. Here, we expand our knowledge in plasma turbulence by exploring the properties of turbulence in the Kronian magnetosheath using the Cassini spacecraft data. These properties include the magnetic field energy spectra, the magnetic compressibility and intermittency at both MHD and kinetic scales. The analysis is based on in-situ data provided by the Fluxgate Magnetometer of the MAG instrument, which measures the magnetic field data with 32ms time resolution and the plasma data from the CAPS/IMS (Cassini Plasma Spectrometer) and the Electron Spectrometer (ELS), during 39 shock-crossings between 2004 and 2005. Similarities and differences with the solar wind were found, in particular about the nature of the turbulence and its scaling laws, as well as the dependence of those properties on the topology of the bow shock.

  11. Exploring Plasma Turbulence in the Kronian Magnetosheath Using Cassini Data

    Science.gov (United States)

    Hadid, L.; Sahraoui, F.; Kiyani, K. H.; Modolo, R.; Retino, A.; Canu, P.; Masters, A.; Dougherty, M. K.

    2014-12-01

    The shocked solar wind plasma upstream of the bowshock forms the magnetosheath. Through this region energy, mass and momentum are transported from the solar wind into the planet's magnetosphere, playing a crucial role in the solar-planet interactions. Hence, the planets' magnetosheath present a high level of turbulence, with a rich variety of wave and stochastic phenomena. While the magnetic turbulence of the terrestrial magnetosheath has been extensively studied, not so much work has been done regarding the planets magnetosheaths. Therefore, and in order to expand our knowledge on plasma turbulence, we investigate here the main properties of the plasma turbulence in the magnetosheath of Saturn using the Cassini spacecraft data and compare it with the well-explored terrestrial solar wind turbulence. These properties include the magnetic field energy spectra, the magnetic compressibility and intermittency, at both MHD and kinetic scales. The analysis is based on in-situ data provided by the Fluxgate Magnetometer of the MAG instrument, which measures the magnetic field data with 32ms time resolution and the plasma data from the CAPS/IMS (Cassini Plasma Spectrometer) and the Electron Spectrometer (ELS), during 39 shock-crossings between 2004 and 2005. Similarities and differences were found between the different media, in particular about the nature of the turbulence and its scaling laws. These finding will be discussed along with theoretical implications on the modeling of space plasma.

  12. Cassini RPWS Observation of Saturn's Radio Rotation Rates After Equinox

    Science.gov (United States)

    Ye, S.; Fischer, G.; Kurth, W. S.; Gurnett, D. A.

    2015-12-01

    Saturn's radio rotation rate, originally thought to be constant, was found to vary with time by comparing the Voyager and Ulysses observation of Saturn kilometric radiation (SKR). Later on, Cassini RPWS observation of SKR revealed that the two hemispheres of Saturn are rotating at two different rotational periods, and it was proposed that the two periods are subject to seasonal change. The topic we would like to focus on resolving is whether the north and south rotational periods actually crossed after equinox. The almost continuous observation of SKR, Saturn narrowband emission, and auroral hiss by RPWS provide a good method of tracking the radio rotation periods of the planet. SKR power from the northern and southern hemispheres can be separated by the polarization of the radiation. Based on the evolution of SKR phase in the northern and southern hemispheres, we show that the rotation rate of the northern SKR is slower than that of the southern SKR starting from late 2014. Auroral hiss provides another unambiguous method of isolating the rotation signals from one hemisphere because the whistler mode plasma wave cannot cross the equator. Rotational modulation rates of auroral hiss are shown to agree with those of SKR during Cassini's high inclination orbits. Hemispherical origins of the narrowband emission are not distinguishable due to its unique generation mechanism. However, Lomb-Scargle periodogram of the 5 kHz narrowband emissions indicates that the two separate radio rotation periods of Saturn's magnetosphere reappeared after a long break since equinox.

  13. The shape of Saturn's Huygens ringlet viewed by Cassini ISS

    Science.gov (United States)

    Spitale, J. N.; Hahn, J. M.

    2016-11-01

    A new model for the shape of the prominent eccentric ringlet in the gap exterior to Saturn's B ring is developed based on Cassini imaging observations taken over about 8 years. Unlike previous analyses, the new model treats each edge of the ringlet separately. The Keplerian component of the model is consistent with results derived from Voyager observations, and m = 2 modes forced by the nearby Mimas 2:1 Lindblad resonance are seen. Additionally, a free m = 2 mode is seen on the outer edge of the ringlet. Significant irregular structure that cannot be described using normal-mode analysis is seen on the ringlet edges as well. Particularly on the inner edge, that structure remains coherent over multi-year intervals, moving at the local Keplerian rate. We interpret the irregular structure as the signature of embedded massive bodies. The long coherence time suggests the responsible bodies are concentrated near the edge of the ringlet. Long wake-like structures originate from two locations on the inner edge of the ringlet, revealing the locations of the two most massive embedded bodies in that region. As with the Voyager observations, the Cassini data sets showed no correlation between the width and the radius of the ringlet as would be expected for a self-gravitating configuration, except for a brief interval during late 2006, when the width-radius relation was similar to those seen in most other narrow eccentric ringlets in the Solar System.

  14. Characterization of Cassini GPHS Fueled-Clad Production Girth Welds

    Energy Technology Data Exchange (ETDEWEB)

    Franco-Ferreira, E.A.

    2000-03-23

    Fueled clads for radioisotope power systems are produced by encapsulating {sup 238}PuO{sub 2} in iridium alloy cups, which are joined at their equators by gas tungsten arc welding. Cracking problems at the girth weld tie-in area during production of the Galileo/Ulysses GPHS capsules led to the development of a first-generation ultrasonic test for girth weld inspection at the Savannah River Plant. A second-generation test and equipment with significantly improved sensitivity and accuracy were jointly developed by the Oak Ridge Y-12 Plant and Westinghouse Savannah River Company for use during the production of Cassini GPHS capsules by the Los Alamos National Laboratory. The test consisted of Lamb wave ultrasonic scanning of the entire girth weld from each end of the capsule combined with a time-of-flight evaluation to aid in characterizing nonrelevant indications. Tangential radiography was also used as a supplementary test for further evaluation of reflector geometry. Each of the 317 fueled GPHS capsules, which were girth welded for the Cassini Program, was subjected to a series of nondestructive tests that included visual, dimensional, helium leak rate, and ultrasonic testing. Thirty-three capsules were rejected prior to ultrasonic testing. Of the 44 capsules rejected by the standard ultrasonic test, 22 were upgraded to flight quality through supplementary testing for an overall process acceptance rate of 82.6%. No confirmed instances of weld cracking were found.

  15. Io Plasma Torus Ion Composition: Voyager, Galileo, Cassini

    Science.gov (United States)

    Bagenal, Fran; Nerney, Edward; Steffl, Andrew Joseph

    2016-10-01

    With JAXA's Hisaki spacecraft in orbit around Earth gathering information on the Io plasma torus and NASA's Juno mission measuring plasma conditions in the jovian magnetosphere, the time is ripe for a re-evaluation of earlier observations of the plasma torus to assess evidence for temporal variations. In particular, we are interested in exploring the ion composition of the torus and whether there is evidence of the ultimate source – the volcanic gases from Io – have deviated from SO2. We use the latest CHIANTI 8.0 atomic database to analyze UV spectra of the torus from Voyager, Galileo and Cassini as well as with the physical chemistry model of Delamere, Steffl and Bagenal (2005). We find that contrary to earlier analyses of Voyager data (e.g. Shemansky 1987; 1988) that produced a composition requiring a neutral source of O/S~4, we find an ion composition that is consistent with the Cassini UVIS data (Steffl et al. 2004) and a neutral O/S~2, consistent with SO2.

  16. Abundances of Jupiter's Trace Hydrocarbons From Voyager and Cassini

    CERN Document Server

    Nixon, Conor A; Romani, Paul N; Allen, Mark; Zhang, Xi; Teanby, Nicholas A; Irwin, Patrick G J; Flasar, F Michael; 10.1016/j.pss2010.05.08

    2010-01-01

    The flybys of Jupiter by the Voyager spacecraft in 1979, and over two decades later by Cassini in 2000, have provided us with unique datasets from two different epochs, allowing the investigation of seasonal change in the atmosphere. In this paper we model zonal averages of thermal infrared spectra from the two instruments, Voyager 1 IRIS and Cassini CIRS, to retrieve the vertical and meridional profiles of temperature, and the abundances of the two minor hydrocarbons, acetylene (C2H2) and ethane (C2H6). The spatial variation of these gases is controlled by both chemistry and dynamics, and therefore their observed distribution gives us an insight into both processes. We find that the two gases paint quite different pictures of seasonal change. Whilst the 2-D cross-section of C2H6 abundance is slightly increased and more symmetric in 2000 (northern summer solstice) compared to 1979 (northern fall equinox), the major trend of equator to pole increase remains. For C2H2 on the other hand, the Voyager epoch exhibi...

  17. A close look at Saturn's rings with Cassini VIMS

    Science.gov (United States)

    Nicholson, P.D.; Hedman, M.M.; Clark, R.N.; Showalter, M.R.; Cruikshank, D.P.; Cuzzi, J.N.; Filacchione, G.; Capaccioni, F.; Cerroni, P.; Hansen, G.B.; Sicardy, B.; Drossart, P.; Brown, R.H.; Buratti, B.J.; Baines, K.H.; Coradini, A.

    2008-01-01

    Soon after the Cassini-Huygens spacecraft entered orbit about Saturn on 1 July 2004, its Visual and Infrared Mapping Spectrometer obtained two continuous spectral scans across the rings, covering the wavelength range 0.35-5.1 ??m, at a spatial resolution of 15-25 km. The first scan covers the outer C and inner B rings, while the second covers the Cassini Division and the entire A ring. Comparisons of the VIMS radial reflectance profile at 1.08 ??m with similar profiles at a wavelength of 0.45 ??m assembled from Voyager images show very little change in ring structure over the intervening 24 years, with the exception of a few features already known to be noncircular. A model for single-scattering by a classical, many-particle-thick slab of material with normal optical depths derived from the Voyager photopolarimeter stellar occultation is found to provide an excellent fit to the observed VIMS reflectance profiles for the C ring and Cassini Division, and an acceptable fit for the inner B ring. The A ring deviates significantly from such a model, consistent with previous suggestions that this region may be closer to a monolayer. An additional complication here is the azimuthally-variable average optical depth associated with "self-gravity wakes" in this region and the fact that much of the A ring may be a mixture of almost opaque wakes and relatively transparent interwake zones. Consistently with previous studies, we find that the near-infrared spectra of all main ring regions are dominated by water ice, with a typical regolith grain radius of 5-20 ??m, while the steep decrease in visual reflectance shortward of 0.6 ??m is suggestive of an organic contaminant, perhaps tholin-like. Although no materials other than H2O ice have been identified with any certainty in the VIMS spectra of the rings, significant radial variations are seen in the strength of the water-ice absorption bands. Across the boundary between the C and B rings, over a radial range of ???7000 km, the

  18. Enceladus Plume Density Modeling and Reconstruction for Cassini Attitude Control System

    Science.gov (United States)

    Sarani, Siamak

    2010-01-01

    In 2005, Cassini detected jets composed mostly of water, spouting from a set of nearly parallel rifts in the crust of Enceladus, an icy moon of Saturn. During an Enceladus flyby, either reaction wheels or attitude control thrusters on the Cassini spacecraft are used to overcome the external torque imparted on Cassini due to Enceladus plume or jets, as well as to slew the spacecraft in order to meet the pointing needs of the on-board science instruments. If the estimated imparted torque is larger than it can be controlled by the reaction wheel control system, thrusters are used to control the spacecraft. Having an engineering model that can predict and simulate the external torque imparted on Cassini spacecraft due to the plume density during all projected low-altitude Enceladus flybys is important. Equally important is being able to reconstruct the plume density after each flyby in order to calibrate the model. This paper describes an engineering model of the Enceladus plume density, as a function of the flyby altitude, developed for the Cassini Attitude and Articulation Control Subsystem, and novel methodologies that use guidance, navigation, and control data to estimate the external torque imparted on the spacecraft due to the Enceladus plume and jets. The plume density is determined accordingly. The methodologies described have already been used to reconstruct the plume density for three low-altitude Enceladus flybys of Cassini in 2008 and will continue to be used on all remaining low-altitude Enceladus flybys in Cassini's extended missions.

  19. Enceladus Plume Density Modeling and Reconstruction for Cassini Attitude Control System

    Science.gov (United States)

    Sarani, Siamak

    2010-01-01

    In 2005, Cassini detected jets composed mostly of water, spouting from a set of nearly parallel rifts in the crust of Enceladus, an icy moon of Saturn. During an Enceladus flyby, either reaction wheels or attitude control thrusters on the Cassini spacecraft are used to overcome the external torque imparted on Cassini due to Enceladus plume or jets, as well as to slew the spacecraft in order to meet the pointing needs of the on-board science instruments. If the estimated imparted torque is larger than it can be controlled by the reaction wheel control system, thrusters are used to control the spacecraft. Having an engineering model that can predict and simulate the external torque imparted on Cassini spacecraft due to the plume density during all projected low-altitude Enceladus flybys is important. Equally important is being able to reconstruct the plume density after each flyby in order to calibrate the model. This paper describes an engineering model of the Enceladus plume density, as a function of the flyby altitude, developed for the Cassini Attitude and Articulation Control Subsystem, and novel methodologies that use guidance, navigation, and control data to estimate the external torque imparted on the spacecraft due to the Enceladus plume and jets. The plume density is determined accordingly. The methodologies described have already been used to reconstruct the plume density for three low-altitude Enceladus flybys of Cassini in 2008 and will continue to be used on all remaining low-altitude Enceladus flybys in Cassini's extended missions.

  20. Birotor dipole for Saturn's inner magnetic field from Cassini observations

    Science.gov (United States)

    Galopeau, Patrick

    2017-04-01

    The radio and plasma wave science (RPWS) experiment on board the Cassini spacecraft, orbiting around Saturn since July 2004, revealed the presence of two distinct and variable rotation periods in the Saturnian kilometric radiation (SKR). These two periods were attributed to the northern and southern hemispheres respectively. We suppose that the periodic time modulations present in the SKR are mainly due to the rotation of Saturn's inner magnetic field. The existence of a double period implies that the inner field is not only limited to a simple rotation dipole but displays more complex structures having the same time periodicities than the radio emission. In order to build a model of this complex magnetic field, it is absolutely necessary to know the accurate phases of rotation linked with the two periods. The radio observations from the RPWS experiment allow a continuous and accurate follow-up of these rotation phases, since the SKR emission is permanently observable and produced very close to the planetary surface. A continuous wavelet transform analysis of the intensity of the SKR signal received at 290 kHz between July 2004 and June 2012 was performed in order to calculate in the same time the different periodicities and phases. A dipole model was proposed for Saturn's inner magnetic field: this dipole presents the particularity to have North and South poles rotating around Saturn's axis at two different angular velocities; this dipole is tilted and not centered. 57 Cassini's revolutions, the periapsis of which is less than 5 Saturnian radii, have been selected for this study. For each of these chosen orbits, it is possible to fit with high precision the measurements of the MAG data experiment given by the magnetometers embarked on board Cassini. A nonrotating external magnetic field completes the model. This study suggests that Saturn's inner magnetic field is neither stationary nor fully axisymmetric. These results can be used as a boundary condition for

  1. Tidal Control of Jet Eruptions Observed by Cassini ISS

    Science.gov (United States)

    Hurford, T. A.; Helfenstein, P.; Spitale, J. N.

    2012-01-01

    Observations by Cassini's Imaging Science Subsystem (ISS) of Enceladus' south polar region at high phase angles has revealed jets of material venting into space. Observations by Cassini's Composite Infrared Spectrometer (CIRS) have also shown that the south polar region is anomalously warm with hotspots associated with geological features called the Tiger Stripes. The Tiger Stripes are large rifts near the south pole of Enceladus, which are typically about 130 km in length, 2 km wide, with a trough 500 m deep, and are l1anked on each side by 100m tall ridges. Preliminary triangulation of jets as viewed at different times and with different viewing geometries in Cassini ISS images taken between 2005 and 2007 have constrained the locations of eight major eruptions of material and found all of them associated with the south polar fractures unofficially the 'Tiger Stripes', and found four of them coincident with the hotspots reported in 2006 by CIRS. While published ISS observations of jet activity suggest that individual eruption sites stay active on the timescale of years, any shorter temporal variability (on timescales of an orbital period, or 1.3 Earth days, for example) is more difficult to establish because of the spotty temporal coverage and the difficulty of visually isolating one jet from the forest of many seen in a typical image. Consequently, it is not known whether individual jets are continuously active, randomly active, or if they erupt on a predictable, periodic schedule. One mechanism that may control the timing of eruptions is diurnal tidal stress, which oscillates between compression/tension as well as right and left lateral shear at any given location throughout Enceladus' orbit and may allow the cracks to open and close regularly. We examine the stresses on the Tiger Stripe regions to see how well diurnal tidal stress caused by Enceladus' orbital eccentricity may possibly correlate with and thus control the observed eruptions. We then identify

  2. Cassini-plasma interactions in the Enceladus torus

    Science.gov (United States)

    Yaroshenko, V. V.; Miloch, W. J.; Morfill, G. E.

    2012-04-01

    This study reports the results of the first simulations of spacecraft-plasma interactions within the proposed Enceladus torus, a radially narrow toroidal region surrounding Saturn that contains a high density of water-group neutrals. Charge exchange collisions scatter these neutrals and replace a fraction of the co-rotating ions with a new and slower-moving ion population. The newly-created ions are moving near the local Keplerian speed, slower than the co-rotation speed, and are ''picked-up'' by Saturn's magnetic field. These water-group ions are detected throughout the Enceladus torus including regions far from Enceladus [1,2]. Three-dimensional particle-in-cell self-consistent code is applied to find the potential and plasma distributions around the spherical model of Cassini in a complicated plasma environment of the Enceladus torus. The modeling includes two types of water group ions (co-rotating, and non-thermalized pick-up ions), plasma flows, photoemission due to solar UV radiation, and flyby geometry. As input data the parameters derived from the Cassini plasma spectrometer measurements obtained in 2005 on Oct. 11, and 29, Nov. 27, and Dec. 24 [1] are employed. The numerical simulations show that the pick-up ions significantly modify the spatial structure of the plasma perturbations, arising in the vicinity of the orbiter in comparison to that obtained for only co-rotating ions [3]. The plasma species produce a specific strongly inhomogeneous configuration with a self-consistent charge separation between the different plasma components in the electric field of the orbiter. The highly energetic co-rotating water group ions are mainly responsible for the configuration of the plasma wake. The region extending up to a few electron Debye lengths downstream of the spacecraft reveals negative potentials that are a significant fraction of the thermal electron energy. Arising wake electric fields capture the cold, pick-up ions and lead to a strong enhancement of

  3. Constraints on Titan's rotation from Cassini mission radar data

    Science.gov (United States)

    Bills, Bruce; Stiles, Bryan W.; Hayes, Alexander

    2015-05-01

    We present results of a new analysis of the rotational kinematics of Titan, as constrained by Cassini radar data, extending over the entire currently available set of flyby encounters. Our analysis provides a good constraint on the current orientation of the spin pole, but does not have sufficient accuracy and duration to clearly see the expected spin pole precession. In contrast, we do clearly see temporal variations in the spin rate, which are driven by gravitational torques which attempt to keep the prime meridian oriented toward Saturn.Titan is a synchronous rotator. At lowest order, that means that the rotational and orbital motions are synchronized. At the level of accuracy required to fit the Cassini radar data, we can see that synchronous rotation and uniform rotation are not quite the same thing. Our best fitting model has a fixed pole, and a rotation rate which varies with time, so as to keep Titan's prime meridian oriented towards Saturn, as the orbit varies.A gravitational torque on the tri-axial figure of Titan attempts to keep the axis of least inertia oriented toward Saturn. The main effect is to synchronize the orbit and rotation periods, as seen in inertial space. The response of the rotation angle, to periodic changes in orbital mean longitude, is modeled as a damped, forced harmonic oscillator. This acts as a low-pass filter. The rotation angle accurately tracks orbital variations at periods longer than the free libration period, but is unable to follow higher frequency variations.The mean longitude of Titan's orbit varies on a wide range of time scales. The largest variations are at Saturn's orbital period (29.46 years), and are due to solar torques. There are also variations at periods of 640 and 5800 days, due to resonant interaction with Hyperion.For a rigid body, with moments of inertia estimated from observed gravity, the free libration period for Titan would be 850 days. The best fit to the radar data is obtained with a libration period of

  4. The Attraction of Gravity (Jean Dominique Cassini Medal Lecture)

    Science.gov (United States)

    Iess, Luciano

    2017-04-01

    The motion of planetary bodies, their interior structure, their shape, and ultimately their landscape, are all determined, more or less directly, by gravity. It is therefore not surprising that by measuring the orbital motion and the gravity field of planets and satellites we have been able to gather crucial information on the interior structure and evolution of those bodies, and at the same time to put the laws of gravity to the test. Planetary geodesy is now a fully developed discipline that uses methods and observable quantities adopted also in other fields, such as space navigation and telecommunications. Thanks to this winning synergy between science and engineering, we can now measure spacecraft velocities to 10-6 m/s and accelerations to 10-9 m/s2 over time scales as short as 1000 s, everywhere in the solar system. The past ten years have seen outstanding results in the scientific exploration of the deep space, with gravity investigations contributing to the success of many missions. Thanks to gravity measurements, MESSENGER was able to unveil the main features of Mercury's interior structure. GRAIL, the first planetary mission entirely devoted to gravity, recovered the structure of the lunar gravity anomalies to a spatial resolution and accuracy unmatched even for the Earth. The discovery and characterization of habitable environments in the Saturnian system, on Enceladus and Titan, were possible also by the radio science investigations of the mission Cassini. Thanks to a carefully designed orbit, with a pericenter just 3000 km above the cloud level, the spacecraft Juno is now carrying out precise gravity measurements at Jupiter to unveil the interior structure of the planet and the depth of its winds. With Cassini providing similar information at Saturn in the Grand Finale orbits, just before the final plunge into the planet, we will soon be able to reveal how similar or different the two gas giants are. But the interior structure of many planetary bodies

  5. Maneuver Performance Assessment of the Cassini Spacecraft Through Execution-Error Modeling and Analysis

    Science.gov (United States)

    Wagner, Sean

    2014-01-01

    The Cassini spacecraft has executed nearly 300 maneuvers since 1997, providing ample data for execution-error model updates. With maneuvers through 2017, opportunities remain to improve on the models and remove biases identified in maneuver executions. This manuscript focuses on how execution-error models can be used to judge maneuver performance, while providing a means for detecting performance degradation. Additionally, this paper describes Cassini's execution-error model updates in August 2012. An assessment of Cassini's maneuver performance through OTM-368 on January 5, 2014 is also presented.

  6. Cassini's remote sensing pallet is mated to the spacecraft in the PHSF

    Science.gov (United States)

    1997-01-01

    The complete remote sensing pallet is lowered by technicians from the Jet Propulsion Laboratory (JPL) of the California Institute of Technology and mated at the interface with the Cassini spacecraft in the Payload Hazardous Servicing Facility at KSC in July. A four-year, close-up study of the Saturnian system, the Cassini mission is scheduled for launch from Cape Canaveral Air Station in October 1997. It will take seven years for the spacecraft to reach Saturn. Scientific instruments carried aboard the spacecraft will study Saturn's atmosphere, magnetic field, rings, and several moons. JPL is managing the Cassini project for NASA.

  7. Cassini's remote sensing pallet is prepared for installation in the PHSF

    Science.gov (United States)

    1997-01-01

    The complete remote sensing pallet is lowered by technicians from the Jet Propulsion Laboratory (JPL) of the California Institute of Technology to mate with the Cassini spacecraft in the Payload Hazardous Servicing Facility at KSC in July. A four-year, close- up study of the Saturnian system, the Cassini mission is scheduled for launch from Cape Canaveral Air Station in October 1997. It will take seven years for the spacecraft to reach Saturn. Scientific instruments carried aboard the spacecraft will study Saturn's atmosphere, magnetic field, rings, and several moons. JPL is managing the Cassini project for NASA.

  8. Maneuver Performance Assessment of the Cassini Spacecraft Through Execution-Error Modeling and Analysis

    Science.gov (United States)

    Wagner, Sean

    2014-01-01

    The Cassini spacecraft has executed nearly 300 maneuvers since 1997, providing ample data for execution-error model updates. With maneuvers through 2017, opportunities remain to improve on the models and remove biases identified in maneuver executions. This manuscript focuses on how execution-error models can be used to judge maneuver performance, while providing a means for detecting performance degradation. Additionally, this paper describes Cassini's execution-error model updates in August 2012. An assessment of Cassini's maneuver performance through OTM-368 on January 5, 2014 is also presented.

  9. Cassini Attitude Control Fault Protection Design: Launch to End of Prime Mission Performance

    Science.gov (United States)

    Meakin, Peter C.

    2008-01-01

    The Cassini Attitude and Articulation Control Subsystem (AACS) Fault Protection (FP) has been successfully supporting operations for over 10 years from launch through the end of the prime mission. Cassini's AACS FP is complex, containing hundreds of error monitors and thousands of tunable parameters. Since launch there have been environmental, hardware, personnel and mission event driven changes which have required AACS FP to adapt and be robust to a variety of scenarios. This paper will discuss the process of monitoring, maintaining and updating the AACS FP during Cassini's lengthy prime mission as well as provide some insight into lessons learned during tour operations.

  10. Cassini Attitude Control Fault Protection Design: Launch to End of Prime Mission Performance

    Science.gov (United States)

    Meakin, Peter C.

    2008-01-01

    The Cassini Attitude and Articulation Control Subsystem (AACS) Fault Protection (FP) has been successfully supporting operations for over 10 years from launch through the end of the prime mission. Cassini's AACS FP is complex, containing hundreds of error monitors and thousands of tunable parameters. Since launch there have been environmental, hardware, personnel and mission event driven changes which have required AACS FP to adapt and be robust to a variety of scenarios. This paper will discuss the process of monitoring, maintaining and updating the AACS FP during Cassini's lengthy prime mission as well as provide some insight into lessons learned during tour operations.

  11. Exploration of Kronian Magnetosheath Turbulence Using Cassini Data.

    Science.gov (United States)

    Hadid, L.; Sahraoui, F.; Retino, A.; Kiyani, K.; Modolo, R.; Canu, P.; Masters, A.; Dougherty, M. K.

    2014-04-01

    The power density spectra and the magnetic compressibility in Saturn's magnetosheath are investigated using in-situ measurements of the fields and particles from Cassini spacecraft mission. Two major results are found. 1) The absence of the f-5/3 Kolmogorov-like inertial range: the averaged magnetic power spectral densities indicate that the spectra jump from a 1/f scaling at the large scales (typical for solar wind spectra, Leamon et al. 1999) directly into the ion scales with a slope of - 2.5 ,without forming any 5/3 inertial range. Furthermore 2) computing the magnetic compressibility we show the dominance of the compressible magnetosonic modes at the kinetic scales compared with Kinetic Alfven Waves (KAW) reported in the solar wind (Sahraoui et al 2009 )

  12. Cassini Main Engine Assembly Cover Flight Management and Performance

    Science.gov (United States)

    Somawardhana, Ruwan P.; Millard, Jerry M.

    2010-01-01

    The Cassini spacecraft has performed its four year Prime Mission at Saturn and is currently in orbit at Saturn performing a two year extended mission. 12Its main engine nozzles are susceptible to impact damage from micrometeoroids and on-orbit dust. The spacecraft has an articulating device known as the Main Engine Assembly (MEA) cover which can close and shield the main engines from these threats. The cover opens to allow for main engine burns that are necessary to maintain the trajectory. Periodically updated analyses of potential on-orbit dust hazard threats have resulted in the need to continue to use the MEA cover beyond its intended use and beyond its design life. This paper provides a detailed Systems-level overview of the flight management of the MEA cover device and its flight performance to date.

  13. The Gravity Field of Enceladus from the three Cassini Flybys

    Science.gov (United States)

    Iess, L.; Parisi, M.; Ducci, M.; Jacobson, R. A.; Armstrong, J. W.; Asmar, S. W.; Lunine, J. I.; Stevenson, D. J.; Tortora, P.

    2013-12-01

    The Cassini spacecraft carried out gravity measurements of the small Saturnian moon Enceladus during three close flybys on April 28, 2010, November 30, 2010 and May 2, 2012 (designated E9, E12 and E19), at the low altitudes of 100, 48 and 70 km to maximize the accelerations exerted by the moon on the spacecraft. The goals of these observations were the determination of the gravitational quadrupole and the search for a North-South asymmetry in the gravity field, controlled primarily by the spherical harmonic coefficient C30. The estimation of Enceladus' gravity field is especially complex because of the small surface gravity (0.11 m/s2), the short duration of the gravitational interaction and the small number of available flybys. In addition to the gravitational accelerations, the spacecraft was also subject to small but non-negligible drag when it flew through the plume emitted from the south pole of the satellite. This effect occurred during the two south polar flybys E9 and E19. The inclusion of these non-gravitational accelerations proved to be crucial to attain a stable solution for the gravity field. Our estimation relied entirely on precise range rate measurements enabled by a coherent, two-way, microwave link at X-band (7.2-8.4 GHz). Measurement accuracies of 10 micron/s at 60 s integration times were attained under favorable conditions, thanks also to an advanced tropospheric calibration system. The data were fitted using the MONTE orbit determination code, recently developed by JPL for deep space navigation. In addition to the satellite degree 2 gravity field and C30, the solution included the state vector of the spacecraft (one for each flyby) and corrections to the mass and the initial orbital elements of Enceladus. The effect of the drag in E9 and E19 was modeled either as an unknown, impulsive, vectorial delta-V at closest approach, or by using density profiles from models of the plume and solving for the aerodynamic coefficient of the spacecraft. Both

  14. Cassini observations of ion cyclotron waves and ions anisotropy

    Science.gov (United States)

    Crary, F. J.; Dols, V. J.; Cassidy, T. A.; Tokar, R. L.

    2013-12-01

    In Saturn's equatorial, inner magnetosphere, the production of fresh ions in a pick-up distribution generates ion cyclotron waves. These waves are a sensitive indicator of fresh plasma production, but the quantitative relation between wave properties and ionization rates is nontrivial. We present a combined analysis of Cassini MAG and CAPS data, from a variety of equatorial orbits between 2005 and 2012. Using the MAG data, we determine the amplitude and peak frequency of ion cyclotron waves. From the CAPS data we extract the parallel and perpendicular velocity distribution of water group ions. We compare these results with hybrid simulations of the ion cyclotron instability and relate the observed wave amplitudes and ion velocity distributions to the production rate of pickup ions. The resulting relation between wave and plasma properties will allow us to infer ion production rates even at times when no direct ion measurements are available.

  15. Cassini discovers a kinematic spiral ring around Saturn.

    Science.gov (United States)

    Charnoz, S; Porco, C C; Déau, E; Brahic, A; Spitale, J N; Bacques, G; Baillie, K

    2005-11-25

    Since the time of the Voyager flybys of Saturn in 1980-1981, Saturn's eccentric F ring has been known to be accompanied on either side by faint strands of material. New Cassini observations show that these strands, initially interpreted as concentric ring segments, are in fact connected and form a single one-arm trailing spiral winding at least three times around Saturn. The spiral rotates around Saturn with the orbital motion of its constituent particles. This structure is likely the result of differential orbital motion stretching an initial cloud of particles scattered from the dense core of the F ring. Different scenarios of formation, implying ringlet-satellite interactions, are explored. A recently discovered moon candidate, S/2004 S6, is on an orbit that crosses the F-ring core at the intersection of the spiral with the ring, which suggests a dynamical connection between S/2004 S6 and the spiral.

  16. Meteorology of Jupiter's Equatorial Hot Spots and Plumes from Cassini

    CERN Document Server

    Choi, David S; Vasavada, Ashwin R; Simon-Miller, Amy A

    2013-01-01

    We present an updated analysis of Jupiter's equatorial meteorology from Cassini observations. For two months preceding the spacecraft's closest approach, the Imaging Science Subsystem (ISS) onboard regularly imaged the atmosphere. We created time-lapse movies from this period in order to analyze the dynamics of equatorial hot spots and their interactions with adjacent latitudes. Hot spots are quasi-stable, rectangular dark areas on visible-wavelength images, with defined eastern edges that sharply contrast with surrounding clouds, but diffuse western edges serving as nebulous boundaries with adjacent equatorial plumes. Hot spots exhibit significant variations in size and shape over timescales of days and weeks. Some of these changes correspond with passing vortex systems from adjacent latitudes interacting with hot spots. Strong anticyclonic gyres present to the south and southeast of the dark areas appear to circulate into hot spots. Impressive, bright white plumes occupy spaces in between hot spots. Compact...

  17. Enceladus Plume Structure and Time Variability: Comparison of Cassini Observations.

    Science.gov (United States)

    Teolis, Ben D; Perry, Mark E; Hansen, Candice J; Waite, J Hunter; Porco, Carolyn C; Spencer, John R; Howett, Carly J A

    2017-09-05

    During three low-altitude (99, 66, 66 km) flybys through the Enceladus' plume in 2010 and 2011, Cassini's ion neutral mass spectrometer (INMS) made its first high spatial resolution measurements of the plume's gas density and distribution, detecting in situ the individual gas jets within the broad plume. Since those flybys, more detailed Imaging Science Subsystem (ISS) imaging observations of the plume's icy component have been reported, which constrain the locations and orientations of the numerous gas/grain jets. In the present study, we used these ISS imaging results, together with ultraviolet imaging spectrograph stellar and solar occultation measurements and modeling of the three-dimensional structure of the vapor cloud, to constrain the magnitudes, velocities, and time variability of the plume gas sources from the INMS data. Our results confirm a mixture of both low and high Mach gas emission from Enceladus' surface tiger stripes, with gas accelerated as fast as Mach 10 before escaping the surface. The vapor source fluxes and jet intensities/densities vary dramatically and stochastically, up to a factor 10, both spatially along the tiger stripes, and over time between flyby observations. This complex spatial variability and dynamics may result from time-variable tidal stress fields interacting with subsurface fissure geometry and tortuosity beyond detectability, including changing gas pathways to the surface, and fluid flow and boiling in response evolving lithostatic stress conditions. The total plume gas source has 30% uncertainty depending on the contributions assumed for adiabatic and nonadiabatic gas expansion/acceleration to the high Mach emission. The overall vapor plume source rate exhibits stochastic time variability up to a factor ∼5 between observations, reflecting that found in the individual gas sources/jets. Key Words: Cassini at saturn-Geysers-Enceladus-Gas dynamics-Icy satellites. Astrobiology 17, xxx-xxx.

  18. Saturn's equatorial jet structure from Cassini/ISS

    Science.gov (United States)

    García-Melendo, Enrique; Legarreta, Jon; Sánchez-Lavega, Agustín.; Pérez-Hoyos, Santiago; Hueso, Ricardo

    2010-05-01

    Detailed wind observations of the equatorial regions of the gaseous giant planets, Jupiter and Saturn, are crucial for understanding the basic problem of the global circulation and obtaining new detailed information on atmospheric phenomena. In this work we present high resolution data of Saturn's equatorial region wind profile from Cassini/ISS images. To retrieve wind measurements we applied an automatic cross correlator to image pairs taken by Cassini/ISS with the MT1, MT2, MT3 filters centred at the respective three methane absorbing bands of 619nm, 727nm, and 889nm, and with the adjacent continuum CB1, CB2, and CB3 filters. We obtained a complete high resolution coverage of Saturn's wind profile in the equatorial region. The equatorial jet displays an overall symmetric structure similar to that shown the by same region in Jupiter. This result suggests that, in accordance to some of the latest compressible atmosphere computer models, probably global winds in gaseous giants are deeply rooted in the molecular hydrogen layer. Wind profiles in the methane absorbing bands show the effect of strong vertical shear, ~40m/s per scale height, confirming previous results and an important decay in the wind intensity since the Voyager era (~100 m/s in the continuum and ~200 m/s in the methane absorbing band). We also report the discovery of a new feature, a very strong and narrow jet on the equator, about only 5 degrees wide, that despite the vertical shear maintains its intensity (~420 m/s) in both, the continuum and methane absorbing band filters. Acknowledgements: Work supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07.

  19. Tidally modulated eruptions on Enceladus: Cassini ISS observations and models

    Energy Technology Data Exchange (ETDEWEB)

    Nimmo, Francis [Department of Earth and Planetary Sciences, University of California, Santa Cruz, CA 95064 (United States); Porco, Carolyn; Mitchell, Colin, E-mail: carolyn@ciclops.org [CICLOPS, Space Science Institute, Boulder, CO 80304 (United States)

    2014-09-01

    We use images acquired by the Cassini Imaging Science Subsystem (ISS) to investigate the temporal variation of the brightness and height of the south polar plume of Enceladus. The plume's brightness peaks around the moon's apoapse, but with no systematic variation in scale height with either plume brightness or Enceladus' orbital position. We compare our results, both alone and supplemented with Cassini near-infrared observations, with predictions obtained from models in which tidal stresses are the principal control of the eruptive behavior. There are three main ways of explaining the observations: (1) the activity is controlled by right-lateral strike slip motion; (2) the activity is driven by eccentricity tides with an apparent time delay of about 5 hr; (3) the activity is driven by eccentricity tides plus a 1:1 physical libration with an amplitude of about 0.°8 (3.5 km). The second hypothesis might imply either a delayed eruptive response, or a dissipative, viscoelastic interior. The third hypothesis requires a libration amplitude an order of magnitude larger than predicted for a solid Enceladus. While we cannot currently exclude any of these hypotheses, the third, which is plausible for an Enceladus with a subsurface ocean, is testable by using repeat imaging of the moon's surface. A dissipative interior suggests that a regional background heat source should be detectable. The lack of a systematic variation in plume scale height, despite the large variations in plume brightness, is plausibly the result of supersonic flow; the details of the eruption process are yet to be understood.

  20. Analyzing Bleriot's propeller gaps in Cassini NAC images

    Science.gov (United States)

    Hoffmann, Holger; Chen, Cheng; Seiß, Martin; Albers, Nicole; Spahn, Frank; Nic

    2016-10-01

    Among the great discoveries of the Cassini mission are the propeller-shaped structures created by small moonlets embedded in Saturn's dense rings. These moonlets are not massive enough to counteract the viscous ring diffusion to open and maintain circumferential gaps, distinguishing them from ring-moons like Pan and Daphnis.Although one of the defining features of propeller structures, well-formed partial gaps have been resolved by the Imaging Science Subsystem Narrow Angle Camera onboard the Cassini spacecraft only for the largest known propeller named Bleriot. We analyze images of the sunlit side of Saturn's outer A ring showing the propeller Bleriot with clearly visible gaps. By fitting a Gaussian to radial brightness profiles at different azimuthal locations, we obtain the evolution of gap minimum and gap width downstream of the moonlet.We report two findings:1) Numerical simulations indicate that the radial separation of the partial propeller gaps is expected to be 4 Hill radii (Spahn and Sremcevic, 2000, A&A). We infer Bleriot's Hill radius to be a few hundred meters, consistent with values given by Sremcevic et al. (2014, DPS) and Hoffmann et al. (2015, Icarus).2) In order to estimate the ring viscosity in the region of Saturn's outer A ring, where Bleriot orbits, we fit several model functions (one example being the analytic solution derived by Sremcevic, Spahn and Duschl, 2002, MNRAS) describing the azimuthal evolution of the surface density in the propeller gap region to the data obtained from the image analysis. We find viscosity values consistent with the parameterization of ring viscosity by Daisaka et al. (2001, Icarus), but significantly lower than the upper limit given by Esposito et al. (1983, Icarus)

  1. ARAC's operational support of the Cassini Launch

    Energy Technology Data Exchange (ETDEWEB)

    Baskett, R L; Pace, J C

    1998-10-01

    The Atmospheric Release Advisory Capability (ARAC) program at the Lawrence Livermore National Laboratory (LLNL) was the U.S. Department of Energy atmospheric modeling resource used for the contingency of potential radiological releases during the launch of the Cassini mission. The ARAC Center at LLNL forecasted detailed weather conditions and delivered consequence assessments for potential accident scenarios to NASA before and during launch operations. A key aspect of ARAC's support was to acquire a variety of meteorological data for use in both forecast and real-time model calculations. ARAC acquired electronically two types of real-time observed meteorological data: 1) the full set of on-site towers and profilers via the Cape Canaveral Air Station (CCAS) Meteorological Interactive Data Display System (MIDDS), and 2) routine regional airport observations (delivered to the ARAC Center from the Air Force Weather Agency). We also used two forecasted data sources: 1) the U.S. Air Force 45th Weather Squadron at CCAS forecasted soundings for launch time, and 2) the Navy Operational Regional Atmospheric Prediction System (NORAPS) prognostic model which ARAC ran over the Cape. The NORAPS runs produced detailed 24-hr forecasts of 3-D wind fields. ARAC used default radiological accident source terms involving the potential destruction of Cassini's Radioisotope Thermoelectric Generators (RTGs) during 3 phases: 1) before the launch, 2) during the first S set after ignition, and 3) from 5 to 143 set after ignition. ARAC successfully developed and delivered dose and deposition plots at 24 hours, 3 hours, and 30 minutes before each of the lau

  2. ARAC's radiological support of the Cassini Launch

    Energy Technology Data Exchange (ETDEWEB)

    Baskett, R L; Pace, J C

    1998-10-01

    The Atmospheric Release Advisory Capability (ARAC) program at the Lawrence Livermore National Laboratory (LLNL) was the U.S. Department of Energy atmospheric modeling resource used for the contingency of potential radiological releases during the launch of the Cassini mission. Having the ARAC system up and running was one of the launch criteria during the countdown. The ARAC Center at LLNL forecasted detailed weather conditions and delivered consequence assessments for potential accident scenarios to NASA before and during launch operations. A key aspect of ARAC's support was to acquire a variety of meteorological data for use in both forecast and real-time model calculations. ARAC acquired electronically two types of real-time observed meteorological data: 1) the set of on-site tower and profiler data via the Cape Canaveral Air Station (CCAS) Meteorological Interactive Data Display System (MIDDS), and 2) routine regional airport observations delivered to the ARAC Center from the Air Force Weather Agency. We also used two forecasted data sources: 1) the U.S. Air Force 45th Weather Squadron at CCAS forecasted soundings for launch time, and 2) the Navy Operational Regional Atmospheric Prediction System (NORAPS) prognostic model which ARAC ran over the Cape. The NORAPS runs produced detailed 24-hr forecasts of 3-D wind fields. ARAC used default radiological accident source terms involving the potential destruction of Cassini's Radioisotope Thermoelectric Generators (RTGs) during 3 phases: 1) before the launch, 2) during the first 5 sec after ignition, and 3) from 5 to 143 sec after ignition. ARAC successfully developed and delivered dose and deposition plots at 24 hours, 3 hours, and 30 minutes before each of the launch windows.

  3. Rhea gravity field and interior modeling from Cassini data analysis

    Science.gov (United States)

    Tortora, Paolo; Zannoni, Marco; Hemingway, Doug; Nimmo, Francis; Jacobson, Robert A.; Iess, Luciano; Parisi, Marzia

    2016-01-01

    During its tour of the Saturn system, Cassini performed two close flybys of Rhea dedicated to gravity investigations, the first in November 2005 and the second in March 2013. This paper presents an estimation of Rhea's fully unconstrained quadrupole gravity field obtained from a joint multi-arc analysis of the two Cassini flybys. Our best estimates of the main gravity quadrupole unnormalized coefficients are J2 × 106 = 946.0 ± 13.9, C22 × 106 = 242.1 ± 4.0 (uncertainties are 1-σ). Their resulting ratio is J2/C22 = 3.91 ± 0.10, statistically not compatible (at a 5-σ level) with the theoretical value of 10/3, predicted for a hydrostatic satellite in slow, synchronous rotation around a planet. Therefore, it is not possible to infer the moment of inertia factor directly using the Radau-Darwin approximation. The observed excess J2 (gravity oblateness) was investigated using a combined analysis of gravity and topography, under different plausible geophysical assumptions. The observed gravity is consistent with that generated by the observed shape for an undifferentiated (uniform density) body. However, because the surface is more likely to be water ice, a two-layer model may be a better approximation. In this case, and assuming a mantle density of 920 kg/m3, some 1-3 km of excess core oblateness is consistent with the observed gravity. A wide range of moments of inertia is allowed, but models with low moments of inertia (i.e., more differentiation) require greater magnitudes of excess core topography to satisfy the observations.

  4. Cassini Radio and Plasma Wave Observations at Saturn

    Science.gov (United States)

    Gurnett, D. A.; Kurth, W. S.; Hospodarsky, G. B.; Persoon, A. M.; Averkamp, T. F.; Ceccni, B.; Lecacheux, A.; Zarka, P.; Canu, P.; Cornilleau-Wehrlin, N.

    2005-01-01

    Results are presented from the Cassini radio and plasma wave instrument during the approach and first few orbits around Saturn. During the approach the intensity modulation of Saturn Kilometric Radiation (SKR) showed that the radio rotation period of Saturn has increased to 10 hr 45 min plus or minus 36 sec, about 6 min longer than measured by Voyager in 1980-81. Also, many intense impulsive radio signals called Saturn Electrostatic Discharges (SEDs) were detected from saturnian lightning, starting as far as 1.08 AU from Saturn, much farther than terrestrial lightning can be detected from Earth. Some of the SED episodes have been linked to cloud systems observed in Saturn s atmosphere by the Cassini imaging system. Within the magnetosphere plasma wave emissions have been used to construct an electron density profile through the inner region of the magnetosphere. With decreasing radial distance the electron density increases gradually to a peak of about 100 per cubic centimeter near the outer edge of the A ring, and then drops precipitously to values as low as .03 per cubic centimeter over the rings. Numerous nearly monochromatic whistler-mode emissions were observed as the spacecraft passed over the rings that are believed to be produced by meteoroid impacts on the rings. Whistlermode emissions, similar to terrestrial auroral hiss were also observed over the rings, indicating that an electrodynamic interaction, similar to auroral particle acceleration, may be occurring in or near the rings. During the Titan flybys Langmuir probe and plasma wave measurements provided observations of the density and temperature in Titan's ionosphere.

  5. Io plasma torus ion composition: Voyager, Galileo, and Cassini

    Science.gov (United States)

    Nerney, Edward G.; Bagenal, Fran; Steffl, Andrew J.

    2017-01-01

    The Io torus produces ultraviolet emissions diagnostic of plasma conditions. We revisit data sets obtained by the Voyager 1, Galileo, and Cassini missions at Jupiter. With the latest version (8.0) of the CHIANTI atomic database we analyze UV spectra to determine ion composition. We compare ion composition obtained from observations from these three missions with a theoretical model of the physical chemistry of the torus by Delamere et al. (2005). We find ion abundances from the Voyager data similar to the Cassini epoch, consistent with the dissociation and ionization of SO2, but with a slightly higher average ionization state for sulfur, consistent with the higher electron temperature measured by Voyager. This reanalysis of the Voyager data produces a much lower oxygen:sulfur ratio than earlier analysis by Shemansky (1988), which was also reported by Bagenal (1994). We derive fractional ion compositions in the center of the torus to be S+/Ne 5%, S++/Ne 20%, S+++/Ne 5%, O+/Ne 20%, O++/Ne 3%, and Σ(On+)/Σ(Sn+) 0.8, leaving about 10-15% of the charge as protons. The radial profile of ion composition indicates a slightly higher average ionization state, a modest loss of sulfur relative to oxygen, and Σ(On+)/Σ(Sn+) 1.2 at about 8 RJ, beyond which the composition is basically frozen in. The Galileo observations of UV emissions from the torus suggest that the composition in June 1996 may have comprised a lower abundance of oxygen than usual, consistent with observations made at the same time by the EUVE satellite.

  6. Cassini RSS occultation observations of density waves in Saturn's rings

    Science.gov (United States)

    McGhee, C. A.; French, R. G.; Marouf, E. A.; Rappaport, N. J.; Schinder, P. J.; Anabtawi, A.; Asmar, S.; Barbinis, E.; Fleischman, D.; Goltz, G.; Johnston, D.; Rochblatt, D.

    2005-08-01

    On May 3, 2005, the first of a series of eight nearly diametric occultations by Saturn's rings and atmosphere took place, observed by the Cassini Radio Science (RSS) team. Simultaneous high SNR measurements at the Deep Space Network (DSN) at S, X, and Ka bands (λ = 13, 3.6, and 0.9 cm) have provided a remarkably detailed look at the radial structure and particle scattering behavior of the rings. By virtue of the relatively large ring opening angle (B=-23.6o), the slant path optical depth of the rings was much lower than during the Voyager epoch (B=5.9o), making it possible to detect many density waves and other ring features in the Cassini RSS data that were lost in the noise in the Voyager RSS experiment. Ultimately, diffraction correction of the ring optical depth profiles will yield radial resolution as small as tens of meters for the highest SNR data. At Ka band, the Fresnel scale is only 1--1.5 km, and thus even without diffraction correction, the ring profiles show a stunning array of density waves. The A ring is replete with dozens of Pandora and Prometheus inner Lindblad resonance features, and the Janus 2:1 density wave in the B ring is revealed with exceptional clarity for the first time at radio wavelengths. Weaker waves are abundant as well, and multiple occultation chords sample a variety of wave phases. We estimate the surface mass density of the rings from linear density wave models of the weaker waves. For stronger waves, non-linear models are required, providing more accurate estimates of the wave dispersion relation, the ring surface mass density, and the angular momentum exchange between the rings and satellite. We thank the DSN staff for their superb support of these complex observations.

  7. Inflight Characterization of the Cassini Spacecraft Propellant Slosh and Structural Frequencies

    Science.gov (United States)

    Lee, Allan Y.; Stupik, Joan

    2015-01-01

    While there has been extensive theoretical and analytical research regarding the characterization of spacecraft propellant slosh and structural frequencies, there have been limited studies to compare the analytical predictions with measured flight data. This paper uses flight telemetry from the Cassini spacecraft to get estimates of high-g propellant slosh frequencies and the magnetometer boom frequency characteristics, and compares these values with those predicted by theoretical works. Most Cassini attitude control data are available at a telemetry frequency of 0.5 Hz. Moreover, liquid sloshing is attenuated by propellant management device and attitude controllers. Identification of slosh and structural frequency are made on a best-effort basis. This paper reviews the analytical approaches that were used to predict the Cassini propellant slosh frequencies. The predicted frequencies are then compared with those estimated using telemetry from selected Cassini burns where propellant sloshing was observed (such as the Saturn Orbit Insertion burn).

  8. The Geodesy of the Main Saturnian Satellites from Range Rate Measurements of the Cassini Spacecraft

    Science.gov (United States)

    Ducci, M.; Iess, L.; Armstrong, J. W.; Asmar, S. W.; Jacobson, R. A.; Lunine, J. I.; Racioppa, P.; Rappaport, N. J.; Stevenson, D. J.; Tortora, P.

    2012-03-01

    During Cassini's eight-year tour in the saturnian system, the gravity field of the main satellites was inferred from range rate measurements of the spacecraft. Here we present our latest results and an overview of our analysis methods.

  9. Revised Full-Disk Spectra by Cassini-VIMS of the Saturnian Minor Icy Moons

    Science.gov (United States)

    Filacchione, G.; Cuzzi, J. N.; Clark, R. N.; Buratti, B. J.; Capaccioni, F.; Tosi, F.; Coradini, A.; Cerroni, P.; Adriani, A.; Cruikshank, D. P.; Jaumann, R.; Stephan, K.; Brown, R. H.; Nicholson, P. D.; Baines, K. H.; Nelson, R. M.; McCord, T. B.

    2009-03-01

    This abstract concern with a detailed re-analysis of the disk-integrated spectra of the minor moons of Saturn (Atlas, Prometheus, Pandora, Janus, Epimetheus, Calypso and Telesto) obtained by Cassini-VIMS.

  10. Cassini Mission. (Latest citations from the EI Compendex*Plus database)

    Science.gov (United States)

    1996-01-01

    The bibliography contains citations concerning the Cassini mission to the Saturnian system. Topics include radar instrumentation, altimetry, and model testing, and reference the Voyager and Galileo missions. The interplanetary trajectory design process is discussed.

  11. Precise Pointing for Radio Science Occultations and Radar Mapping During the Cassini Mission at Saturn

    Science.gov (United States)

    Burk, Thomas A.

    2015-01-01

    This paper discusses the implementation challenges and lessons learned from radar and radio science pointing observations during the Cassini mission at Saturn. Implementation of the precise desired pointing reveals key issues in the ground system, the flight system, and the pointing paradigm itself. To achieve accurate pointing on some observations, specific workarounds had to be implemented and folded into the sequence development process. Underlying Cassini's pointing system is a remarkable construct known as Inertial Vector Propagation.

  12. Exploring inner structure of Titan's dunes from Cassini Radar observations

    Science.gov (United States)

    Sharma, P.; Heggy, E.; Farr, T. G.

    2013-12-01

    Linear dunes discovered in the equatorial regions of Titan by the Cassini-Huygens mission are morphologically very similar to many terrestrial linear dune fields. These features have been compared with terrestrial longitudinal dune fields like the ones in Namib desert in western Africa. This comparison is based on the overall parallel orientation of Titan's dunes to the predominant wind direction on Titan, their superposition on other geomorphological features and the way they wrap around topographic obstacles. Studying the internal layering of dunes has strong implications in understanding the hypothesis for their origin and evolution. In Titan's case, although the morphology of the dunes has been studied from Cassini Synthetic Aperture Radar (SAR) images, it has not been possible to investigate their internal structure in detail as of yet. Since no radar sounding data is available for studying Titan's subsurface yet, we have developed another technique to examine the inner layering of the dunes. In this study, we utilize multiple complementary radar datasets, including radar imaging data for Titan's and Earth's dunes and Ground Penetrating Radar (GPR)/radar sounding data for terrestrial dunes. Based on dielectric mixing models, we suggest that the Cassini Ku-band microwaves should be able to penetrate up to ~ 3 m through Titan's dunes, indicating that the returned radar backscatter signal would include contributions from both surface and shallow subsurface echoes. This implies that the shallow subsurface properties can be retrieved from the observed radar backscatter (σ0). In our analysis, the variation of the radar backscatter as a function of dune height is used to provide an insight into the layering in Titan's dunes. We compare the variation of radar backscatter with elevation over individual dunes on Titan and analogous terrestrial dunes in three sites (Great Sand Sea, Siwa dunes and Qattaniya dunes) in the Egyptian Sahara. We observe a strong, positive

  13. Cassini atmospheric chemistry mapper. Volume 1. Investigation and technical plan

    Science.gov (United States)

    Smith, William Hayden; Baines, Kevin Hays; Drossart, Pierre; Fegley, Bruce; Orton, Glenn; Noll, Keith; Reitsema, Harold; Bjoraker, Gordon L.

    1990-01-01

    The Cassini Atmospheric Chemistry Mapper (ACM) enables a broad range of atmospheric science investigations for Saturn and Titan by providing high spectral and spatial resolution mapping and occultation capabilities at 3 and 5 microns. ACM can directly address the major atmospheric science objectives for Saturn and for Titan, as defined by the Announcement of Opportunity, with pivotal diagnostic measurements not accessible to any other proposed Cassini instrument. ACM determines mixing ratios for atmospheric molecules from spectral line profiles for an important and extensive volume of the atmosphere of Saturn (and Jupiter). Spatial and vertical profiles of disequilibrium species abundances define Saturn's deep atmosphere, its chemistry, and its vertical transport phenomena. ACM spectral maps provide a unique means to interpret atmospheric conditions in the deep (approximately 1000 bar) atmosphere of Saturn. Deep chemistry and vertical transport is inferred from the vertical and horizontal distribution of a series of disequilibrium species. Solar occultations provide a method to bridge the altitude range in Saturn's (and Titan's) atmosphere that is not accessible to radio science, thermal infrared, and UV spectroscopy with temperature measurements to plus or minus 2K from the analysis of molecular line ratios and to attain an high sensitivity for low-abundance chemical species in the very large column densities that may be achieved during occultations for Saturn. For Titan, ACM solar occultations yield very well resolved (1/6 scale height) vertical mixing ratios column abundances for atmospheric molecular constituents. Occultations also provide for detecting abundant species very high in the upper atmosphere, while at greater depths, detecting the isotopes of C and O, constraining the production mechanisms, and/or sources for the above species. ACM measures the vertical and horizontal distribution of aerosols via their opacity at 3 microns and, particularly, at 5

  14. Gruusia loeb kokku venelaste jäetud pomme ja sõjaohvreid / Liisi Poll

    Index Scriptorium Estoniae

    Poll, Liisi, 1980-

    2008-01-01

    Vene vägede lahkumist ootavas Gruusias loetakse kokku sõjakaotusi, milleks on inimkaotused, katkenud kaubandus, purustatud infrastruktuur, mahajäetud lõhkekehad. Punase Risti hinnangust sõjapõgenike kohta. Vt. samas: Vene väed lahkuvad endiselt vaid teoreetiliselt

  15. Profil de l'etudiant du premier cycle des etudes medicales de Lome ...

    African Journals Online (AJOL)

    Profil de l'etudiant du premier cycle des etudes medicales de Lome et sa perception de l'enseignement de l'anatomie. ... Journal de la Recherche Scientifique de l'Universite de Lome ... aux différentes questions des paramètres étudiés.

  16. Radio Telescopes Will Add to Cassini-Huygens Discoveries

    Science.gov (United States)

    2004-12-01

    When the European Space Agency's Huygens spacecraft makes its plunge into the atmosphere of Saturn's moon Titan on January 14, radio telescopes of the National Science Foundation's National Radio Astronomy Observatory (NRAO) will help international teams of scientists extract the maximum possible amount of irreplaceable information from an experiment unique in human history. Huygens is the 700-pound probe that has accompanied the larger Cassini spacecraft on a mission to thoroughly explore Saturn, its rings and its numerous moons. The Green Bank Telescope The Robert C. Byrd Green Bank Telescope CREDIT: NRAO/AUI/NSF (Click on image for GBT gallery) The Robert C. Byrd Green Bank Telescope (GBT) in West Virginia and eight of the ten telescopes of the continent-wide Very Long Baseline Array (VLBA), located at Pie Town and Los Alamos, NM, Fort Davis, TX, North Liberty, IA, Kitt Peak, AZ, Brewster, WA, Owens Valley, CA, and Mauna Kea, HI, will directly receive the faint signal from Huygens during its descent. Along with other radio telescopes in Australia, Japan, and China, the NRAO facilities will add significantly to the information about Titan and its atmosphere that will be gained from the Huygens mission. A European-led team will use the radio telescopes to make extremely precise measurements of the probe's position during its descent, while a U.S.-led team will concentrate on gathering measurements of the probe's descent speed and the direction of its motion. The radio-telescope measurements will provide data vital to gaining a full understanding of the winds that Huygens encounters in Titan's atmosphere. Currently, scientists know little about Titan's winds. Data from the Voyager I spacecraft's 1980 flyby indicated that east-west winds may reach 225 mph or more. North-south winds and possible vertical winds, while probably much weaker, may still be significant. There are competing theoretical models of Titan's winds, and the overall picture is best summarized as

  17. Cassini/MIMI Measurements in Saturn's Magnetosphere and their Implications for Magnetospheric Dynamics

    Science.gov (United States)

    Mitchell, D. G.

    2016-12-01

    The Cassini spacecraft has been in orbit about Saturn since early July, 2004. In less than a year, on September 15, 2017, Cassini will plunge into Saturn's atmosphere, ending what has been a highly successful and interesting mission. As befitting a Planetary Division Flagship Mission, Cassini's science payload included instrumentation designed for a multitude of science objectives, from surfaces of moons to rings to atmospheres to Saturn's vast, fast-rotating magnetosphere. Saturn's magnetosphere exhibits considerable variability, both from inner magnetosphere to outer, and over time. Characterizing the dynamics of the magnetosphere has required the full range of energetic particles (measured by the magnetospheric imaging instrument, MIMI - https://saturn.jpl.nasa.gov/magnetospheric-imaging-instrument/), plasma (provided by the Cassini plasma spectrometer, CAPS), gas (ion and neutral mass spectrometer, INMS), magnetic fields (Cassini magnetometer, MAG), radio and plasma waves (radio and plasma wave science, RPWS), dust (Cassini Dust Analyzer, CDA), as well as ultraviolet, visible and infrared imaging (ultraviolet imaging spectrograph, UVIS; Cassini imaging subsystem ISS; visible and infrared mapping spectrometer, VIMS; Cassini composite infrared spectrometer, CIRS) and ionospheric sounding by the Cassini radio science subsystem (RSS). It has also required the full range of orbital geometries from equatorial to high inclination and all local times, as well as the full range of solar wind conditions, seasonal sun-Saturn configurations. In this talk we focus on the contributions of the MIMI instrument suite (CHEMS, LEMMS, and INCA) to our understanding of the dynamics of Saturn's magnetosphere. We will both review past work, and present recent observations from the high inclination orbits that precede the final stages of the Cassini mission, the sets of high inclination orbits that cross the equator just beyond the edge of the main ring system, and later cross between

  18. Cassini observations of ionospheric plasma in Saturn's magnetotail lobes.

    Science.gov (United States)

    Felici, M; Arridge, C S; Coates, A J; Badman, S V; Dougherty, M K; Jackman, C M; Kurth, W S; Melin, H; Mitchell, D G; Reisenfeld, D B; Sergis, N

    2016-01-01

    Studies of Saturn's magnetosphere with the Cassini mission have established the importance of Enceladus as the dominant mass source for Saturn's magnetosphere. It is well known that the ionosphere is an important mass source at Earth during periods of intense geomagnetic activity, but lesser attention has been dedicated to study the ionospheric mass source at Saturn. In this paper we describe a case study of data from Saturn's magnetotail, when Cassini was located at ≃ 2200 h Saturn local time at 36 RS from Saturn. During several entries into the magnetotail lobe, tailward flowing cold electrons and a cold ion beam were observed directly adjacent to the plasma sheet and extending deeper into the lobe. The electrons and ions appear to be dispersed, dropping to lower energies with time. The composition of both the plasma sheet and lobe ions show very low fluxes (sometimes zero within measurement error) of water group ions. The magnetic field has a swept-forward configuration which is atypical for this region, and the total magnetic field strength is larger than expected at this distance from the planet. Ultraviolet auroral observations show a dawn brightening, and upstream heliospheric models suggest that the magnetosphere is being compressed by a region of high solar wind ram pressure. We interpret this event as the observation of ionospheric outflow in Saturn's magnetotail. We estimate a number flux between (2.95 ± 0.43) × 10(9) and (1.43 ± 0.21) × 10(10) cm(-2) s(-1), 1 or about 2 orders of magnitude larger than suggested by steady state MHD models, with a mass source between 1.4 ×10(2) and 1.1 ×10(3) kg/s. After considering several configurations for the active atmospheric regions, we consider as most probable the main auroral oval, with associated mass source between 49.7 ±13.4 and 239.8 ±64.8 kg/s for an average auroral oval, and 10 ±4 and 49 ±23 kg/s for the specific auroral oval morphology found during this event. It is not clear how

  19. Saturn Ring Radiation Environment for the Cassini Grand Finale Orbits

    Science.gov (United States)

    Cooper, John F.; Kollmann, Peter; Johnson, Robert E.; Roussos, Elias; Sittler, Edward C.; Sturner, Steven J.

    2016-10-01

    Grand Finale (proximal) orbits of Cassini from April to September 2017 will provide an unprecedented opportunity for further in-situ exploration of the energetic radiation environment primarily arising from galactic cosmic ray interactions with the main rings. Improved modeling of these interactions contributes to ring mass properties, radiation chemistry, and source modeling for trapped radiation within and beyond the rings. Our new GEANT simulations show that these interactions produce very substantial fluxes of secondary gamma rays, neutrons, electrons, protons, and more short-lived particles. Cosmic ray albedo neutron decay from ring neutron emissions provides the primary source of trapped protons near and above 10 MeV in the radiation belts extending from beyond the F ring to the orbit of Tethys. Fluxes of these high-energy trapped protons increased as expected with declining solar activity from 2004 through 2009, consistent with decreasing modulation of the galactic cosmic ray protons and heavier ions by the solar wind. In 2017 solar activity and modulation will again be declining from earlier maximum levels in 2012 - 2014, while solar illumination of the rings will be near solstice levels. There may then be similarities in the ring radiation and plasma environment to conditions in 2004. In comparison, the 1979 traversal of the main rings by Pioneer 11 occurred during peak solar activity but declining cosmic ray flux. The questions are then what radiation environment we might expect to find during the Grand Finale orbits, how would the Cassini MIMI LEMMS sensor respond to this environment, and how might these new measurements change our understanding of the rings? During SOI flyover of the rings, LEMMS nominal data showed intensities higher than those from Pioneer 11 to an extent that cannot be explained by the updated interaction model. LEMMS more likely responded to penetrating high-energy radiation at energies outside its nominal ranges for electrons and

  20. Cassini observations of ionospheric plasma in Saturn's magnetotail lobes

    Science.gov (United States)

    Felici, M.; Arridge, C. S.; Coates, A. J.; Badman, S. V.; Dougherty, M. K.; Jackman, C. M.; Kurth, W. S.; Melin, H.; Mitchell, D. G.; Reisenfeld, D. B.; Sergis, N.

    2016-01-01

    Studies of Saturn's magnetosphere with the Cassini mission have established the importance of Enceladus as the dominant mass source for Saturn's magnetosphere. It is well known that the ionosphere is an important mass source at Earth during periods of intense geomagnetic activity, but lesser attention has been dedicated to study the ionospheric mass source at Saturn. In this paper we describe a case study of data from Saturn's magnetotail, when Cassini was located at ≃ 2200 h Saturn local time at 36 RS from Saturn. During several entries into the magnetotail lobe, tailward flowing cold electrons and a cold ion beam were observed directly adjacent to the plasma sheet and extending deeper into the lobe. The electrons and ions appear to be dispersed, dropping to lower energies with time. The composition of both the plasma sheet and lobe ions show very low fluxes (sometimes zero within measurement error) of water group ions. The magnetic field has a swept-forward configuration which is atypical for this region, and the total magnetic field strength is larger than expected at this distance from the planet. Ultraviolet auroral observations show a dawn brightening, and upstream heliospheric models suggest that the magnetosphere is being compressed by a region of high solar wind ram pressure. We interpret this event as the observation of ionospheric outflow in Saturn's magnetotail. We estimate a number flux between (2.95 ± 0.43) × 109 and (1.43 ± 0.21) × 1010 cm-2 s-1, 1 or about 2 orders of magnitude larger than suggested by steady state MHD models, with a mass source between 1.4 ×102 and 1.1 ×103 kg/s. After considering several configurations for the active atmospheric regions, we consider as most probable the main auroral oval, with associated mass source between 49.7 ±13.4 and 239.8 ±64.8 kg/s for an average auroral oval, and 10 ±4 and 49 ±23 kg/s for the specific auroral oval morphology found during this event. It is not clear how much of this mass is

  1. Pickup ions at Dione and Enceladus: Cassini Plasma Spectrometer simulations

    Science.gov (United States)

    Sittler, Ed C.; Johnson, R. E.; Jurac, S.; Richardson, J. D.; McGrath, M.; Crary, F.; Young, D. T.; Nordholt, J. E.

    2004-01-01

    Voyager images of the icy satellites of Saturn, Dione and Enceladus, suggest that they may have been geologically active and are not only composed of ice. Recent observations by the Hubble Space Telescope have shown the presence of ozone at both Dione and Rhea, which also implies the presence of molecular oxygen at these bodies. Observations of Ariel, Europa, Ganymede, and Callisto indicate the presence of CO2, so its presence on the Saturnian satellites is also expected. The Cassini Plasma Spectrometer (CAPS) will provide the capability to determine the global composition of these bodies by measuring the pickup ions produced by the ionization of their sputter-produced atmospheres. We will present a model of these atmospheres and associated pickup ions and demonstrate CAPS ability to distinguish the freshly produced picked up ions from the ambient plasma. Such ions are expected to form a ring distribution that will have a uniquely different energy-angle dependence than the ambient plasma ions. In the case of Dione we expect the potential for a moderate strength interaction for which both Voyager 1 and Pioneer 11 spacecraft measured ion cyclotron waves centered on the Dione L shell and near the equatorial plane. SKR radio emissions also displayed emissions occurring at the orbital period of Dione which could indicate some intrinsic activity due to Dione. So again, something interesting may be going on at Dione. Since Enceladus, or material in orbit near Enceladus, may be the source of the E-ring, some surprises may be encountered during its close encounter with the Cassini spacecraft. In the case of Dione we will show that a wake pass at 500 km altitude is more than an order of magnitude better than an upstream pass at 500 km altitude. Pickup ion detection for minor ion species such as NH3+ is possible for 500 km altitude wake pass but not for ≈500 km altitude upstream pass at closest approach. For navigation reasons a 100 km pass is not allowed. Therefore it is

  2. Titan Extinction Profiles Observed by Cassini Radio Occultations and Implications

    Science.gov (United States)

    Marouf, Essam; French, Richard; Flasar, F. Michael; Schinder, Paul J.; Rappaport, Nicole J.

    Three monochromatic and phase-coherent radio signals of wavelength = 0.9, 3.6, and 13 cm (Ka-, X-, and S-bands), were propagated by Cassini through the neutral atmosphere of Titan and the refracted signals were observed on the Earth. Abel inversion of observed changes in the signal frequency is used to recover the refractivity profile of the atmosphere, hence estimate the expected loss in signal strength due to defocusing of the radio signal by differential refraction. The refractive defocusing component (wavelength independent, in principle) is then removed from the actual measured signal strength profiles yielding the "true" signal extinction due to absorption and scattering integrated along the propagation path. Abel inversion of the integrated intensity profiles, tempered to combat noise contribution, yields localized estimates of the extinction coefficient (absorbtivity) as a function of altitude, or the extinction profiles. The initial radio measurements are diffraction-limited. We extend Fresnel transform based diffraction reconstruction procedures developed for radio occultation observations of planetary rings to remove diffraction effects from the initial radio measurements. The procedures are tested using idealized models of simple isothermal atmospheric profile extending above a hard-limb (knife-edge) model. Reconstruction of the simulated "observed" diffraction-limited data shows good agreement with the assumed atmospheric profile and the location of the hard-limb for a range of model parameters. We then apply a similar approach to the actual measured data. Strong wavelength-dependent extinction coefficient profile behavior is observed. Its large-scale structure appears well modeled by predictions based on N2-N2 collision-induced gaseous absorption for Titan's physical conditions. Interesting localized features of yet unexplained origin are also observed. Because the spatial scales of the extinction profile features are relatively large compared with

  3. Analysis and interpretation of Cassini Titan radar altimeter echoes

    Science.gov (United States)

    Zebker, Howard A.; Gim, Yonggyu; Callahan, Philip; Hensley, Scott; Lorenz, Ralph; Cassini Radar Team

    2009-03-01

    The Cassini spacecraft has acquired 25 radar altimeter elevation profiles along Titan's surface as of April 2008, and we have analyzed 18 of these for which there are currently reconstructed ephemeris data. Altimeter measurements were collected at spatial footprint sizes from 6-60 km along ground tracks of length 400-3600 km. The elevation profiles yield topographic information at this resolution with a statistical height accuracy of 35-50 m and kilometer-scale errors several times greater. The data exhibit significant variations in terrain, from flat regions with little topographic expression to very rugged Titanscapes. The bandwidth of the transmitted waveform admits vertical resolution of the terrain height to 35 m at each observed location on the surface. Variations in antenna pointing and changes in surface statistics cause the range-compressed radar echoes to exhibit strong systematic and time-variable biases of hundreds of meters in delay. It is necessary to correct the received echoes for these changes, and we have derived correction algorithms such that the derived echo profiles are accurate at the 100 m level for off-nadir pointing errors of 0.3° and 0.6°, for leading edge and echo centroid estimators, respectively. The leading edge of the echo yields the elevation of the highest points on the surface, which we take to be the peaks of any terrain variation. The mean value of the echo delay is more representative of the mean elevation, so that the difference of these values gives an estimate of any local mountain heights. Finding locations where these values diverge indicates higher-relief terrain. Elevation features are readily seen in the height profiles. Several of the passes show mountains of several hundred m altitude, spread over 10's or even 100's of km in spatial extent, so that slopes are very small. Large expanses of sub-100 m topography are commonplace on Titan, so it is rather smooth in many locations. Other areas exhibit more relief

  4. New constraints on Saturn's interior from Cassini astrometric data

    CERN Document Server

    Lainey, Valéry; Tajeddine, Radwan; Cooper, Nicholas J; Murray, Carl; Robert, Vincent; Tobie, Gabriel; Guillot, Tristan; Mathis, Stéphane; Remus, Françoise; Desmars, Josselin; Arlot, Jean-Eudes; De Cuyper, Jean-Pierre; Dehant, Véronique; Pascu, Dan; Thuillot, William; Poncin-Lafitte, Christophe Le; Zahn, Jean-Paul

    2015-01-01

    Using astrometric observations spanning more than a century and including a large set of Cassini data, we determine Saturn's tidal parameters through their current effects on the orbits of the eight main and four coorbital moons. We have used the latter to make the first determination of Saturn's Love number, $k_2=0.390 \\pm 0.024$, a value larger than the commonly used theoretical value of 0.341 (Gavrilov & Zharkov, 1977), but compatible with more recent models (Helled & Guillot, 2013) for which $k_2$ ranges from 0.355 to 0.382. Depending on the assumed spin for Saturn's interior, the new constraint can lead to a reduction of up to 80% in the number of potential models, offering great opportunities to probe the planet's interior. In addition, significant tidal dissipation within Saturn is confirmed (Lainey et al., 2012) corresponding to a high present-day tidal ratio $k_2/Q=(1.59 \\pm 0.74) \\times 10^{-4}$ and implying fast orbital expansions of the moons. This high dissipation, with no obvious variati...

  5. Determining Titan surface topography from Cassini SAR data

    Science.gov (United States)

    Stiles, Bryan W.; Hensley, Scott; Gim, Yonggyu; Bates, David M.; Kirk, Randolph L.; Hayes, Alex; Radebaugh, Jani; Lorenz, Ralph D.; Mitchell, Karl L.; Callahan, Philip S.; Zebker, Howard; Johnson, William T.K.; Wall, Stephen D.; Lunine, Jonathan I.; Wood, Charles A.; Janssen, Michael; Pelletier, Frederic; West, Richard D.; Veeramacheneni, Chandini

    2009-01-01

    A technique, referred to as SARTopo, has been developed for obtaining surface height estimates with 10 km horizontal resolution and 75 m vertical resolution of the surface of Titan along each Cassini Synthetic Aperture Radar (SAR) swath. We describe the technique and present maps of the co-located data sets. A global map and regional maps of Xanadu and the northern hemisphere hydrocarbon lakes district are included in the results. A strength of the technique is that it provides topographic information co-located with SAR imagery. Having a topographic context vastly improves the interpretability of the SAR imagery and is essential for understanding Titan. SARTopo is capable of estimating surface heights for most of the SAR-imaged surface of Titan. Currently nearly 30% of the surface is within 100 km of a SARTopo height profile. Other competing techniques provide orders of magnitude less coverage. We validate the SARTopo technique through comparison with known geomorphological features such as mountain ranges and craters, and by comparison with co-located nadir altimetry, including a 3000 km strip that had been observed by SAR a month earlier. In this area, the SARTopo and nadir altimetry data sets are co-located tightly (within 5-10 km for one 500 km section), have similar resolution, and as expected agree closely in surface height. Furthermore the region contains prominent high spatial resolution topography, so it provides an excellent test of the resolution and precision of both techniques.

  6. Determining titan's spin state from cassini radar images

    Science.gov (United States)

    Stiles, B.W.; Kirk, R.L.; Lorenz, R.D.; Hensley, S.; Lee, E.; Ostro, S.J.; Allison, M.D.; Callahan, P.S.; Gim, Y.; Iess, L.; Del Marmo, P.P.; Hamilton, G.; Johnson, W.T.K.; West, R.D.

    2008-01-01

    For some 19 areas of Titan's surface, the Cassini RADAR instrument has obtained synthetic aperture radar (SAR) images during two different flybys. The time interval between flybys varies from several weeks to two years. We have used the apparent misregistration (by 10-30 km) of features between separate flybys to construct a refined model of Titan's spin state, estimating six parameters: north pole right ascension and declination, spin rate, and these quantities' first time derivatives We determine a pole location with right ascension of 39.48 degrees and declination of 83.43 degrees corresponding to a 0.3 degree obliquity. We determine the spin rate to be 22.5781 deg day -1 or 0.001 deg day-1 faster than the synchronous spin rate. Our estimated corrections to the pole and spin rate exceed their corresponding standard errors by factors of 80 and 8, respectively. We also found that the rate of change in the pole right ascension is -30 deg century-1, ten times faster than right ascension rate of change for the orbit normal. The spin rate is increasing at a rate of 0.05 deg day -1 per century. We observed no significant change in pole declination over the period for which we have data. Applying our pole correction reduces the feature misregistration from tens of km to 3 km. Applying the spin rate and derivative corrections further reduces the misregistration to 1.2 km. ?? 2008. The American Astronomical Society. All rights reserved.

  7. Constraints on Mimas' interior from Cassini ISS libration measurements.

    Science.gov (United States)

    Tajeddine, R; Rambaux, N; Lainey, V; Charnoz, S; Richard, A; Rivoldini, A; Noyelles, B

    2014-10-17

    Like our Moon, the majority of the solar system's satellites are locked in a 1:1 spin-orbit resonance; on average, these satellites show the same face toward the planet at a constant rotation rate equal to the satellite's orbital rate. In addition to the uniform rotational motion, physical librations (oscillations about an equilibrium) also occur. The librations may contain signatures of the satellite's internal properties. Using stereophotogrammetry on Cassini Image Science Subsystem (ISS) images, we measured longitudinal physical forced librations of Saturn's moon Mimas. Our measurements confirm all the libration amplitudes calculated from the orbital dynamics, with one exception. This amplitude depends mainly on Mimas' internal structure and has an observed value of twice the predicted one, assuming hydrostatic equilibrium. After considering various possible interior models of Mimas, we argue that the satellite has either a large nonhydrostatic interior, or a hydrostatic one with an internal ocean beneath a thick icy shell. Copyright © 2014, American Association for the Advancement of Science.

  8. On Cas A, Cassini, Comets and King Charles

    CERN Document Server

    Soria, Roberto; Ohtsuka, Yasuyo

    2013-01-01

    We re-examine the long-standing problem of the date of the Cassiopeia A supernova (SN), in view of recent claims that it might be the 1630 "noon-star" seen at the birth of King Charles II. We do not support this identification, based on the expected brightness of a Type-IIb SN (too faint to be seen in daylight), the extrapolated motion of the ejecta (inconsistent with a date earlier than 1650), the lack of any scientific follow-up observations, the lack of any mention of it in Asian archives. The origin of the 1630 noon-star event (if real) remains a mystery; there was a bright comet in 1630 June but no evidence to determine whether or not it was visible in daylight. Instead, we present French reports about a 4th-magnitude star discovered by Cassini in Cassiopeia in or shortly before 1671, which was not seen before or since. The brightness is consistent with what we expect for the Cas A SN; the date is consistent with the extrapolated motion of the ejecta. We argue that this source could be the long-sought SN...

  9. Fluvial channels on Titan: Initial Cassini RADAR observations

    Science.gov (United States)

    Lorenz, R.D.; Lopes, R.M.; Paganelli, F.; Lunine, J.I.; Kirk, R.L.; Mitchell, K.L.; Soderblom, L.A.; Stofan, E.R.; Ori, G.; Myers, M.; Miyamoto, H.; Radebaugh, J.; Stiles, B.; Wall, S.D.; Wood, C.A.

    2008-01-01

    Cassini radar images show a variety of fluvial channels on Titan's surface, often several hundreds of kilometers in length. Some (predominantly at low- and mid-latitude) are radar-bright and braided, resembling desert washes where fines have been removed by energetic surface liquid flow, presumably from methane rainstorms. Others (predominantly at high latitudes) are radar-dark and meandering and drain into or connect polar lakes, suggesting slower-moving flow depositing fine-grained sediments. A third type, seen predominantly at mid- and high latitudes, have radar brightness patterns indicating topographic incision, with valley widths of up to 3 km across and depth of several hundred meters. These observations show that fluvial activity occurs at least occasionally at all latitudes, not only at the Huygens landing site, and can produce channels much larger in scale than those observed there. The areas in which channels are prominent so far amount to about 1% of Titan's surface, of which only a fraction is actually occupied by channels. The corresponding global sediment volume inferred is not enough to account for the extensive sand seas. Channels observed so far have a consistent large-scale flow pattern, tending to flow polewards and eastwards. ?? 2008.

  10. Probing Saturn's tropospheric cloud with Cassini/VIMS

    CERN Document Server

    Barstow, Joanna K; Fletcher, Leigh N; Giles, Rohini S; Merlet, Cecile

    2016-01-01

    In its decade of operation the Cassini mission has allowed us to look deep into Saturn's atmosphere and investigate the processes occurring below its enshrouding haze. We use Visual and Infrared Mapping Spectrometer (VIMS) 4.6-5.2 micron data from early in the mission to investigate the location and properties of Saturn's cloud structure between 0.6 and 5 bars. We average nightside spectra from 2006 over latitude circles and model the spectral limb darkening using the NEMESIS radiative transfer and retrieval tool. We present our best-fit deep cloud model for latitudes between -40 and 50 degrees, along with retrieved abundances for NH3, PH3 and AsH3. We find an increase in NH3 abundance at the equator, a cloud base at ~2.3 bar and no evidence for cloud particles with strong absorption features in the 4.6-5.2 micron wavelength range, all of which are consistent with previous work. Non-scattering cloud models assuming a composition of either NH3 or NH4SH, with a scattering haze overlying, fit limb darkening curv...

  11. Trajectory Dispersion Control for the Cassini Grand Finale Mission

    Science.gov (United States)

    Wong, Mau; Hahn, Yungsun; Roth, Duane; Vaquero, Mar

    2015-01-01

    The Cassini Grand Finale Mission, which consists of 22 ballistic orbits, will begin on April 22, 2017 after the last targeted Titan flyby. It will end on September 15, 2017 when the spacecraft dives into Saturn's atmosphere and be permanently captured. High volumes of unique science data from various onboard instruments are expected from the mission. To ensure its success and facilitate science planning, the trajectory dispersion needs to be controlled below 250 km (root-mean-square spatial deviation at the 68th percentile level) for a few segments of trajectory in the mission. This paper reports the formulation and solution of this dispersion control problem. We consider various sources of uncertainties including flyby error, orbit determination error, maneuver execution error, thruster firing control error, and uncertainty in Saturn's atmospheric model. A non-linear Monte Carlo Trajectory Dispersion tool is developed and employed for the analysis. It is found that a total of three Orbit Trim Maneuvers with a 99% (Delta)V usage of less than 2 m/s will adequately control the trajectory.

  12. SOLAR OCCULTATION BY TITAN MEASURED BY CASSINI/UVIS

    Energy Technology Data Exchange (ETDEWEB)

    Capalbo, Fernando J.; Benilan, Yves [Laboratoire Interuniversitaire des Systemes Atmospheriques (LISA), UMR 7583 du CNRS, Universites Paris Est Creteil (UPEC) and Paris Diderot - UPD, 61 avenue du General de Gaulle, 94010 Creteil Cedex (France); Yelle, Roger V.; Koskinen, Tommi T.; Sandel, Bill R. [Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721 (United States); Holsclaw, Gregory M.; McClintock, William E., E-mail: fernando.capalbo@lisa.u-pec.fr [Laboratory for Atmospheric and Space Physics, University of Colorado, 3665 Discovery Drive, Boulder, CO 80303 (United States)

    2013-04-01

    We present the first published analysis of a solar occultation by Titan's atmosphere measured by the Ultraviolet Imaging Spectrograph on board Cassini. The data were measured during flyby T53 in 2009 April and correspond to latitudes between 21 Degree-Sign and 28 Degree-Sign south. The analysis utilizes the absorption of two solar emission lines (584 A and 630 A) in the ionization continuum of the N{sub 2} absorption cross section and solar emission lines around 1085 A where absorption is due to CH{sub 4}. The measured transmission at these wavelengths provides a direct estimate of the N{sub 2} and CH{sub 4} column densities along the line of sight from the spacecraft to the Sun, which we inverted to obtain the number densities. The high signal-to-noise ratio of the data allowed us to retrieve density profiles in the altitude range 1120-1400 km for nitrogen and 850-1300 km for methane. We find an N{sub 2} scale height of {approx}76 km and a temperature of {approx}153 K. Our results are in general agreement with those from previous work, although there are some differences. Particularly, our profiles agree, considering uncertainties, with the density profiles derived from the Voyager 1 Ultraviolet Spectrograph data, and with in situ measurements by the Ion Neutral Mass Spectrometer with revised calibration.

  13. Silicates on Iapetus from Cassini's Composite Infrared Spectrometer

    CERN Document Server

    Young, Cindy L; Clark, Roger N; Spencer, John R; Jennings, Donald E; Hand, Kevin P; Poston, Michael J; Carlson, Robert W

    2015-01-01

    We present the first spectral features obtained from Cassini's Composite Infrared Spectrometer (CIRS) for any icy moon. The spectral region covered by CIRS focal planes (FP) 3 and 4 is rich in emissivity features, but previous studies at these wavelengths have been limited by low signal to noise ratios (S/Rs) for individual spectra. Our approach is to average CIRS FP3 spectra to increase the S/R and use emissivity spectra to constrain the composition of the dark material on Iapetus. We find an emissivity feature at ~855 cm-1 and a possible doublet at 660 and 690 cm-1 that do not correspond to any known instrument artifacts. We attribute the 855 cm-1 feature to fine-grained silicates, similar to those found in dust on Mars and in meteorites, which are nearly featureless at shorter wavelengths. Silicates on the dark terrains of Saturn's icy moons have been suspected for decades, but there have been no definitive detections until now. Serpentines reported in the literature at ambient temperature and pressure hav...

  14. (abstract) Cassini MLI Balnkets High-Temperature Exposure Tests

    Science.gov (United States)

    Lin, Edward I.; Stultz, James W.

    1995-01-01

    The trajectory required for the Cassini spacecraft to reach Saturn will subject the spacecraft to a 0.61 AU temperature environment at perihelion. Temperatures on some sunlit blanket surfaces at 0.61 AU can reach levels that are beyond the service capability of the conventional Mylar/Dacron net MLI. The majority of the blanket surfaces, however, will experience temperatures with an upper bound of 250(deg) C. The maximum allowable temperature for Mylar/Dacron net is determined to be 220(deg)C. Kapton can withstand temperatures in excess of 400(deg) C; however, the high cost of embossed Kapton relative to Mylar/Dacron net requires a baseline design which includes a standard layup and a high-temperature layup. The high-temperature layup is utilized at a limited number of locations, while at least 90% of the blankets are of the standard layup. The verification of both layups' capability to meet all temperature requirements has been accomplished by a comprehensive test program which addressed their high-temperature survivability, effective emittance, and optical and electrical properties. This paper focuses on the high-temperature exposure tests which helped define the hybrid standard layup, and which demonstrated the adequacy of both layups in withstanding their respective thermal environments.

  15. On Cas A, Cassini, Comets, and King Charles

    Science.gov (United States)

    Soria, Roberto; Balestrieri, Riccardo; Ohtsuka, Yasuyo

    2013-03-01

    We re-examine the long-standing problem of the date of the Cassiopeia A supernova (SN), in view of recent claims that it might be the 1630 'noon-star' seen at the birth of King Charles II. We do not support this identification, based on the expected brightness of a Type-IIb SN (too faint to be seen in daylight), the extrapolated motion of the ejecta (inconsistent with a date earlier than 1650), the lack of any scientific follow-up observations, the lack of any mention of it in Asian archives. The origin of the 1630 noon-star event (if real) remains a mystery; there was a bright comet in 1630 June but no evidence to determine whether or not it was visible in daylight. Instead, we present French reports about a fourth-magnitude star discovered by Cassini in Cassiopeia in or shortly before 1671, which was not seen before or since. The brightness is consistent with what we expect for the Cas A SN; the date is consistent with the extrapolated motion of the ejecta. We argue that this source could be the long-sought SN.

  16. Coherent dust cloud observed by three Cassini instruments

    CERN Document Server

    Khalisi, Emil

    2015-01-01

    We revisit the evidence for a "dust cloud" observed by the Cassini spacecraft at Saturn in 2006. The simultaneous data of 3 instruments are compared to interpret the signatures of a coherent swarm of dust that could have remained floating near the equatorial plane. The conspicuous pattern, as seen in the dust counters of the Cosmic Dust Analyser (CDA) and in the magnetic field (MAG), clearly repeats on three consecutive revolutions of the spacecraft. The data of the Radio Plasma and Wave Science (RPWS) appear less decisive but do back our conclusions. The results support the idea of a "magnetic bubble" as reported from both Voyager flybys in the early 1980ies. That particular cloud, which we firstly discovered in the CDA data, is estimated to about 1.36 Saturnian radii in size, and probably broadening. Both the bulk of dust particles and the peak of the magnetic depression seem to drift apart, but this can also be an effect of hitting the cloud at different parts during the traverse.

  17. The Shape of Saturn's Huygens Ringlet Viewed by Cassini ISS

    CERN Document Server

    Spitale, Joseph N

    2015-01-01

    A new model for the shape of the prominent eccentric ringlet in the gap exterior to Saturn's B-ring is developed based on Cassini observations taken over about 8 years. Unlike previous treatments, the new model treats each edge of the ringlet separately. The Keplerian component of the model is consistent with results derived from Voyager observations, and $m=2$ modes forced by the nearby Mimas 2:1 Lindblad resonance are seen. Additionally, a free $m=2$ mode is seen on the outer edge of the ringlet. Significant irregular structure that cannot be described using normal-mode analysis is seen on the ringlet edges as well. Particularly on the inner edge, that structure remains coherent over multi-year intervals, moving at the local Keplerian rate. We interpret the irregular structure as the signature of embedded massive bodies. The long coherence time suggests the responsible bodies are concentrated near the edge of the ringlet. Long wake-like structures originate from two locations on the inner edge of the ringle...

  18. Saturn's aurora observed by the Cassini camera at visible wavelengths

    CERN Document Server

    Dyudina, Ulyana A; Ewald, Shawn P; Wellington, Danika

    2015-01-01

    The first observations of Saturn's visible-wavelength aurora were made by the Cassini camera. The aurora was observed between 2006 and 2013 in the northern and southern hemispheres. The color of the aurora changes from pink at a few hundred km above the horizon to purple at 1000-1500 km above the horizon. The spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with laboratory simulated auroras. Auroras in both hemispheres vary dramatically with longitude. Auroras form bright arcs between 70 and 80 degree latitude north and between 65 and 80 degree latitude south, which sometimes spiral around the pole, and sometimes form double arcs. A large 10,000-km-scale longitudinal brightness structure persists for more than 100 hours. This structure rotates approximately together with Saturn. On top of the large steady structure, the auroras brighten suddenly on the timescales of a few minutes. These brightenings repeat with a period of about 1 hour....

  19. The Structure of Enceladus' Plume from Cassini Occultation Observations

    Science.gov (United States)

    Hansen, C. J.; Esposito, L. W.; Buffington, B. B.; Colwell, J.; Hendrix, A. R.; Meinke, B. K.; Shemansky, D. E.; Stewart, I.; West, R. A.

    2011-12-01

    Cassini's Ultraviolet Imaging Spectrograph (UVIS) has observed 2 stellar and one solar occultation by Enceladus' water vapor plume. These observations have established that water is the primary constituent of the plume, allowed us to calculate the flux of water coming from the plume, and detected super-sonic jets of gas imbedded within the plume [1]. On 19 October 2011 two stars (epsilon and zeta Orionis) will simultaneously be occulted by the plume, and the signal of the two will be in separate pixels on the detector. This is a tangential occultation that will provide a horizontal cut through the plume at two altitudes. The two stars are separated by 24 mrad, or ~20 km, with the lower altitude star 18 km above the limb at its closest point. The groundtrack is similar to the 2010 solar occultation, but viewed from the other side of the plume. Results from this new data set with implications for the vertical structure of the plume and jets will be presented.

  20. Cassini CAPS Measurements of Thermal Ion Properties: An Update

    Science.gov (United States)

    Wilson, R. J.; Bagenal, F.; Delamere, P. A.

    2010-12-01

    Since the Wilson et al. [2008] paper on thermal ion properties in Saturn's inner equatorial magnetosphere there have been several advances in forward model techniques and instrument knowledge. These include: a) Improved CAPS (SNG) calibration values since 2008. While the previous fits to data are still valid, this efficiency adjustment has the effect of reducing the density values calculated from that fit. Compared to the previous calibration values, nOH+ and nH+ are ≈30% and ≈9% lower respectively. b) Robust error analysis on the forward model process to produce standard deviations for the fitted parameters. This also shows the expected dependences between various fitted parameters, such as Vφ and OH+ T⊥, inherent in the model. c) Utilization of real magnetic field data to forward model T⊥ and T\\par. Previously assumed magnetic field was in the -z direction. In addition, these improvements allow us to remove the constraint that Vz = 0, and the use of real magnetic field data allows us to analyze data farther from the equator. References Wilson, R. J., R. L. Tokar, M. G. Henderson, T. W. Hill, M. F. Thomsen, and D. H. Pontius (2008), Cassini plasma spectrometer thermal ion measurements in Saturn's inner magnetosphere,

  1. Cassini in Titan's tail: CAPS observations of plasma escape

    Science.gov (United States)

    Coates, A. J.; Wellbrock, A.; Lewis, G. R.; Arridge, C. S.; Crary, F. J.; Young, D. T.; Thomsen, M. F.; Reisenfeld, D. B.; Sittler, E. C., Jr.; Johnson, R. E.; Szego, K.; Bebesi, Z.; Jones, G. H.

    2012-05-01

    We present observations of CAPS electron and ion spectra during Titan distant tail crossings at 5,000-10,000 km altitude by the Cassini spacecraft. In common with closer tail encounters, we identify ionospheric plasma in the tail. Some of the electron spectra indicate a direct magnetic connection to Titan's dayside ionosphere due to the presence of ionospheric photoelectrons. Ion observations reveal heavy (m/q˜ 16 and 28) and light (m/q = 1-2) ion populations streaming into the tail. Using the distant tail encounters T9, T75 and T63, we estimate total plasma loss rates from Titan via this process of (4.2, 0.96 and 2.3) × 1024 ions s-1 respectively for the three encounters, values which are in agreement with some simulations but slightly lower than earlier estimates based on non-differential techniques. Using the mass-separated data, this corresponds to mass loss rates of (8.9, 1.6, 4.0) × 1025 amu s-1 for T9, T75 and T63 respectively, an average loss rate of ˜7 tonnes per Earth day. Remarkably, all of the tail encounters studied here indicate a split tail feature, indicating that this may be a common feature in Titan's interaction with Saturn's magnetosphere.

  2. Cassini Attitude Control Operations Flight Rules and How They are Enforced

    Science.gov (United States)

    Burk, Thomas; Bates, David

    2008-01-01

    The Cassini spacecraft was launched on October 15, 1997 and arrived at Saturn on June 30, 2004. It has performed detailed observations and remote sensing of Saturn, its rings, and its satellites since that time. Cassini deployed the European-built Huygens probe which descended through the Titan atmosphere and landed on its surface on January 14, 2005. Operating the Cassini spacecraft is a complex scientific, engineering, and management job. In order to safely operate the spacecraft, a large number of flight rules were developed. These flight rules must be enforced throughout the lifetime of the Cassini spacecraft. Flight rules are defined as any operational limitation imposed by the spacecraft system design, hardware, and software, violation of which would result in spacecraft damage, loss of consumables, loss of mission objectives, loss and/or degradation of science, and less than optimal performance. Flight rules require clear description and rationale. Detailed automated methods have been developed to insure the spacecraft is continuously operated within these flight rules. An overview of all the flight rules allocated to the Cassini Attitude Control and Articulation Subsystem and how they are enforced is presented in this paper.

  3. Cassini Attitude Control Operations Flight Rules and How They are Enforced

    Science.gov (United States)

    Burk, Thomas; Bates, David

    2008-01-01

    The Cassini spacecraft was launched on October 15, 1997 and arrived at Saturn on June 30, 2004. It has performed detailed observations and remote sensing of Saturn, its rings, and its satellites since that time. Cassini deployed the European-built Huygens probe which descended through the Titan atmosphere and landed on its surface on January 14, 2005. Operating the Cassini spacecraft is a complex scientific, engineering, and management job. In order to safely operate the spacecraft, a large number of flight rules were developed. These flight rules must be enforced throughout the lifetime of the Cassini spacecraft. Flight rules are defined as any operational limitation imposed by the spacecraft system design, hardware, and software, violation of which would result in spacecraft damage, loss of consumables, loss of mission objectives, loss and/or degradation of science, and less than optimal performance. Flight rules require clear description and rationale. Detailed automated methods have been developed to insure the spacecraft is continuously operated within these flight rules. An overview of all the flight rules allocated to the Cassini Attitude Control and Articulation Subsystem and how they are enforced is presented in this paper.

  4. Etude aerodynamique d'un jet turbulent impactant une paroi concave

    Science.gov (United States)

    LeBlanc, Benoit

    Etant donne la demande croissante de temperatures elevees dans des chambres de combustion de systemes de propulsions en aerospatiale (turbomoteurs, moteur a reaction, etc.), l'interet dans le refroidissement par jets impactant s'est vu croitre. Le refroidissement des aubes de turbine permet une augmentation de temperature de combustion, ce qui se traduit en une augmentation de l'efficacite de combustion et donc une meilleure economie de carburant. Le transfert de chaleur dans les au bages est influence par les aspects aerodynamiques du refroidissement a jet, particulierement dans le cas d'ecoulements turbulents. Un manque de comprehension de l'aerodynamique a l'interieur de ces espaces confinees peut mener a des changements de transfert thermique qui sont inattendus, ce qui augmente le risque de fluage. Il est donc d'interet pour l'industrie aerospatiale et l'academie de poursuivre la recherche dans l'aerodynamique des jets turbulents impactant les parois courbes. Les jets impactant les surfaces courbes ont deja fait l'objet de nombreuses etudes. Par contre des conditions oscillatoires observees en laboratoire se sont averees difficiles a reproduire en numerique, puisque les structures d'ecoulements impactants des parois concaves sont fortement dependantes de la turbulence et des effets instationnaires. Une etude experimentale fut realisee a l'institut PPRIME a l'Universite de Poitiers afin d'observer le phenomene d'oscillation dans le jet. Une serie d'essais ont verifie les conditions d'ecoulement laminaires et turbulentes, toutefois le cout des essais experimentaux a seulement permis d'avoir un apercu du phenomene global. Une deuxieme serie d'essais fut realisee numeriquement a l'Universite de Moncton avec l'outil OpenFOAM pour des conditions d'ecoulement laminaire et bidimensionnel. Cette etude a donc comme but de poursuivre l'enquete de l'aerodynamique oscillatoire des jets impactant des parois courbes, mais pour un regime d'ecoulement transitoire, turbulent

  5. Cassini Imaging of Auroral Emissions on the Galilean Satellites

    Science.gov (United States)

    Geissler, P.; McEwen, A.; Porco, C.

    2001-05-01

    Cassini captured several sequences of images showing Io, Europa and Ganymede while the moons were eclipsed by Jupiter. Io was the best studied of the satellites, with 4 eclipses successfully recorded. Earlier eclipse imaging by Galileo (Geissler et al., Science 295, 870-874) had shown colorful atmospheric emissions from Io and raised questions concerning their temporal variability and the identity of the emitting species. With its high data rate and numerous filter combinations, Cassini was able to fill some of the gaps in our knowledge of Io's visible aurorae. Io's bright equatorial glows were detected at previously unknown wavelengths and were also seen in motion. One eclipse took place on 12/29/2000 while Io was far from the plasma torus center. The pair of equatorial glows near the sub-Jupiter and anti-Jupiter points appeared about equal in brightness and changed little in location or intensity over a two hour period. Io crossed the plasma torus center during the next eclipse on 1/01/2001, as it passed through System III magnetic longitudes from 250 to 303 degrees. The equatorial glows were seen to shift in latitude during this eclipse, tracking the tangent points of the jovian magnetic field lines. This behaviour is similar to that observed for ultraviolet and other atomic emissions, and confirms that these visible glows are powered by Birkeland currents connecting Io and Jupiter. The eclipse on 1/05/2001 provided the best spectral measurements of the aurorae. The equatorial glows were detected at near ultraviolet wavelengths, consistent with their interpretation as molecular SO2 emissions. More than 100 kR were recorded in the ISS UV3 filter (300-380 nm) along with a similar intensity in BL1 (290-500 nm), comparable to Galileo estimates. At least 50 kR were detected in UV2 images (265-330 nm). No detection was made in UV1 (235-280 nm), allowing us to place an upper limit of about 100 kR. A new detection of the equatorial glows was made in the IR1 band (670

  6. Constraining the Enceladus plume using numerical simulation and Cassini data

    Science.gov (United States)

    Yeoh, Seng Keat; Li, Zheng; Goldstein, David B.; Varghese, Philip L.; Levin, Deborah A.; Trafton, Laurence M.

    2017-01-01

    Since its discovery, the Enceladus plume has been subjected to intense study due to the major effects that it has on the Saturnian system and the window that it provides into the interior of Enceladus. However, several questions remain and we attempt to answer some of them in this work. In particular, we aim to constrain the H2O production rate from the plume, evaluate the relative importance of the jets and the distributed sources along the Tiger Stripes, and make inferences about the source of the plume by accurately modeling the plume and constraining the model using the Cassini INMS and UVIS data. This is an extension of a previous work (Yeoh, S.K., et al. [2015] Icarus, 253, 205-222) in which we only modeled the collisional part of the Enceladus plume and studied its important physical processes. In this work, we propagate the plume farther into space where the flow has become free-molecular and the Cassini INMS and UVIS data were sampled. Then, we fit this part of the plume to the INMS H2O density distributions sampled along the E3, E5 and E7 trajectories and also compare some of the fit results with the UVIS measurements of the plume optical depth collected during the solar occultation observation on 18 May 2010. We consider several vent conditions and source configurations for the plume. By constraining our model using the INMS and UVIS data, we estimate H2O production rates of several hundred kgs-1: 400-500 kg/s during the E3 and E7 flybys and ∼900 kg/s during the E5 flyby. These values agree with other estimates and are consistent with the observed temporal variability of the plume over the orbital period of Enceladus (Hedman, M.M., et al. [2013] Nature, 500, 182-184). In addition, we determine that one of the Tiger Stripes, Cairo, exhibits a local temporal variability consistent with the observed overall temporal variability of the plume. We also find that the distributed sources along the Tiger Stripes are likely dominant while the jets provide a

  7. Transient surface liquid in Titan's south polar region from Cassini

    Science.gov (United States)

    Hayes, A.G.; Aharonson, O.; Lunine, J.I.; Kirk, R.L.; Zebker, H.A.; Wye, L.C.; Lorenz, R.D.; Turtle, E.P.; Paillou, P.; Mitri, Giuseppe; Wall, S.D.; Stofan, E.R.; Mitchell, K.L.; Elachi, C.

    2011-01-01

    Cassini RADAR images of Titan's south polar region acquired during southern summer contain lake features which disappear between observations. These features show a tenfold increases in backscatter cross-section between images acquired one year apart, which is inconsistent with common scattering models without invoking temporal variability. The morphologic boundaries are transient, further supporting changes in lake level. These observations are consistent with the exposure of diffusely scattering lakebeds that were previously hidden by an attenuating liquid medium. We use a two-layer model to explain backscatter variations and estimate a drop in liquid depth of approximately 1-m-per-year. On larger scales, we observe shoreline recession between ISS and RADAR images of Ontario Lacus, the largest lake in Titan's south polar region. The recession, occurring between June 2005 and July 2009, is inversely proportional to slopes estimated from altimetric profiles and the exponential decay of near-shore backscatter, consistent with a uniform reduction of 4 ± 1.3 m in lake depth. Of the potential explanations for observed surface changes, we favor evaporation and infiltration. The disappearance of dark features and the recession of Ontario's shoreline represents volatile transport in an active methane-based hydrologic cycle. Observed loss rates are compared and shown to be consistent with available global circulation models. To date, no unambiguous changes in lake level have been observed between repeat images in the north polar region, although further investigation is warranted. These observations constrain volatile flux rates in Titan's hydrologic system and demonstrate that the surface plays an active role in its evolution. Constraining these seasonal changes represents the first step toward our understanding of longer climate cycles that may determine liquid distribution on Titan over orbital time periods.

  8. Meteorology of Jupiter's Equatorial Hot Spots and Plumes from Cassini

    Science.gov (United States)

    Choi, David Sanghun; Showman, Adam P.; Vasavada, Ashwin R.; Simon-Miller, Amy A.

    2013-01-01

    We present an updated analysis of Jupiter's equatorial meteorology from Cassini observations. For two months preceding the spacecraft's closest approach, the Imaging Science Subsystem (ISS) onboard regularly imaged the atmosphere. We created time-lapse movies from this period in order to analyze the dynamics of equatorial hot spots and their interactions with adjacent latitudes. Hot spots are relatively cloud-free regions that emit strongly at 5 lm; improved knowledge of these features is crucial for fully understanding Galileo probe measurements taken during its descent through one. Hot spots are quasistable, rectangular dark areas on visible-wavelength images, with defined eastern edges that sharply contrast with surrounding clouds, but diffuse western edges serving as nebulous boundaries with adjacent equatorial plumes. Hot spots exhibit significant variations in size and shape over timescales of days and weeks. Some of these changes correspond with passing vortex systems from adjacent latitudes interacting with hot spots. Strong anticyclonic gyres present to the south and southeast of the dark areas appear to circulate into hot spots. Impressive, bright white plumes occupy spaces in between hot spots. Compact cirrus-like 'scooter' clouds flow rapidly through the plumes before disappearing within the dark areas. These clouds travel at 150-200 m/s, much faster than the 100 m/s hot spot and plume drift speed. This raises the possibility that the scooter clouds may be more illustrative of the actual jet stream speed at these latitudes. Most previously published zonal wind profiles represent the drift speed of the hot spots at their latitude from pattern matching of the entire longitudinal image strip. If a downward branch of an equatorially-trapped Rossby wave controls the overall appearance of hot spots, however, the westward phase velocity of the wave leads to underestimates of the true jet stream speed.

  9. Dielectric Property Measurements to Support Interpretation of Cassini Radar Data

    Science.gov (United States)

    Jamieson, Corey; Barmatz, M.

    2012-10-01

    Radar observations are useful for constraining surface and near-surface compositions and illuminating geologic processes on Solar System bodies. The interpretation of Cassini radiometric and radar data at 13.78 GHz (2.2 cm) of Titan and other Saturnian icy satellites is aided by laboratory measurements of the dielectric properties of relevant materials. However, existing dielectric measurements of candidate surface materials at microwave frequencies and low temperatures is sparse. We have set up a microwave cavity and cryogenic system to measure the complex dielectric properties of liquid hydrocarbons relevant to Titan, specifically methane, ethane and their mixtures to support the interpretation of spacecraft instrument and telescope radar observations. To perform these measurements, we excite and detect the TM020 mode in a custom-built cavity with small metal loop antennas powered by a Vector Network Analyzer. The hydrocarbon samples are condensed into a cylindrical quartz tube that is axially oriented in the cavity. Frequency sweeps through a resonance are performed with an empty cavity, an empty quartz tube inserted into the cavity, and with a sample-filled quartz tube in the cavity. These sweeps are fit by a Lorentzian line shape, from which we obtain the resonant frequency, f, and quality factor, Q, for each experimental arrangement. We then derive dielectric constants and loss tangents for our samples near 13.78 GHz using a new technique ideally suited for measuring liquid samples. We will present temperature-dependent, dielectric property measurements for liquid methane and ethane. The full interpretation of the radar and radiometry observations of Saturn’s icy satellites depends critically on understanding the dielectric properties of potential surface materials. By investigating relevant liquids and solids we will improve constrains on lake depths, volumes and compositions, which are important to understand Titan’s carbon/organic cycle and inevitably

  10. Design and Analysis of RTGs for CRAF and Cassini Missions

    Energy Technology Data Exchange (ETDEWEB)

    Schock, Alfred; Noravian, Heros; Sankarankandath

    1990-11-30

    This report consists of two parts. Part 1 describes the development of novel analytical methods needed to predict the BOM performance and the subsequent performance degradation of the mutually obstructed RTGs for the CRAF and Cassini missions. Part II applies those methods to the two missions, presents the resultant predictions, and discusses their programmatic implications. The results indicate that JPL's original power demand goals could have been met with two standard GPHS RTGs for each mission. But subsequently JPL significantly increased both the power level and the mission duration for both missions, so that they can no longer by met by two standard RTGs. The resultant power gap must be closed either by reducing JPL's power demand (e.g., by decreasing contingency reserves) and/or by increasing the power system's output. One way under active consideration which more than meets the system power goal would be the addition of a third RTG for each mission. However, the author concluded that it may be possible to meet or closely approach the CRAF power demand goals with just two RTGs by relatively modest modification of their design and/or operating conditions. To explore that possibility, the effect of various modifications - either singly or in combination - was analyzed by Fairchild. The results indicate that modest modifications can meet or come very close to meeting the CRAF power goals with just two RTGs. Elimination of the third RTG would yield substantial cost and schedule savings. There are three copies in the file.

  11. The Global Geology of Titan from Cassini RADAR data

    Science.gov (United States)

    Lopes, Rosaly; Malaska, Michael J.

    The variety of geological processes on Titan is rivaled in our Solar System only on Earth. Results from the Cassini-Huygens mission obtained so far have revealed a wide range of geologic and climatological processes. We use data obtained by Cassini’s Titan Radar Mapper (13.78 GHz, lambda=2.17 cm) to analyze the distribution of different types of geologic processes occurring on Titan’s surface, both endogenic and exogenic, and to derive temporal relationships between these processes, at least at local scales. The distribution and interplay of geologic processes is important to provide constraints on models of the interior and of surface-atmosphere interactions. We mapped the SAR images in terms of characteristic morphology of geological features and their radar backscatter in order to determine possible emplacement sequences and the overall distribution of geologic processes. All the major planetary geologic processes - volcanism, tectonism, impact cratering and erosion - appear to have played a role in shaping Titan’s complex surface. This paper will review the distribution and relative ages of different geomorphologic units. While some units (craters, dunes, mountains, channels, lakes and seas) are well established in the literature, the presence of cryovolcanic features is still somewhat controversial, and the origin of undifferentiated plains (known as blandlands) is still mysterious. We now have over half of Titan’s surface imaged by SAR and the interpretation of these and other terrains is better constrained. The results from our latest analyses suggest that a sedimentary origin for the undifferentiated plains is the most likely. Cryovolcanism appears to have occurred on Titan, but it is not ubiquitous, and the major cryovolcanic area appears to be old, now partly covered by dunes. Titan’s surface shows a complex interaction between the surface and atmosphere, with erosional processes being driven by wind, liquids and dissolution.

  12. Cassini Radar at Titan : Evolving Studies of an Evolving World

    Science.gov (United States)

    Lorenz, Ralph D.

    2013-04-01

    The Cassini RADAR investigation continues to explore Titan : here I summarize some recent and ongoing developments. Geological interpretation of SAR imaging engages a wide community, in particular addressing Titan's dunes, lakes, seas and fluvial systems, impact craters and possible cryovolcanic features. Mapping of these features continues to suggest a dynamic world, with geologically-recent surface change due to tectonic, hydrological and aeolian processes. Mapping of fluvial channels and shoreline features suggests some tectonic controls and spatially-variable land/sea level changes. A despeckle filter applied to the images has proven popular for image interpretation, for example in resolving what may be star- and barchanoid dune morphologies which contrast with the dominant linear type. New observations in 2012 (T83, T84 and T86) place bounds on liquid accumulation in the northern polar regions - not expected to be substantial for another couple of years - and have highlighted a possibly cryomagma-inflated 'hot cross bun' feature and anomalous midlatitude ridges that may be paleodunes from a different climate epoch. The accumulating body of topographic data from altimetry and SARtopo has permitted the assembly of a global topographic map (albeit substantially interpolated) and an estimate of the spherical harmonic shape out to degree ~12. These datasets will be of substantial value in interpreting Titan's structure and geology, and as a boundary condition on global circulation models and fluvial studies. The growing number of overlap regions also permits stereo topography on smaller scales (e.g. of impact structures Ksa and Soi) which helps to understand the processes obliterating craters on Titan.

  13. Saturn's aurora observed by the Cassini camera at visible wavelengths

    Science.gov (United States)

    Dyudina, Ulyana A.; Ingersoll, Andrew P.; Ewald, Shawn P.; Wellington, Danika

    2016-01-01

    The first observations of Saturn's visible-wavelength aurora were made by the Cassini camera. The aurora was observed between 2006 and 2013 in the northern and southern hemispheres. The color of the aurora changes from pink at a few hundred km above the horizon to purple at 1000-1500 km above the horizon. The spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with laboratory simulated auroras. Auroras in both hemispheres vary dramatically with longitude. Auroras form bright arcs between 70° and 80° latitude north and between 65° and 80° latitude south, which sometimes spiral around the pole, and sometimes form double arcs. A large 10,000-km-scale longitudinal brightness structure persists for more than 100 h. This structure rotates approximately together with Saturn. On top of the large steady structure, the auroras brighten suddenly on the timescales of a few minutes. These brightenings repeat with a period of ∼1 h. Smaller, 1000-km-scale structures may move faster or lag behind Saturn's rotation on timescales of tens of minutes. The persistence of nearly-corotating large bright longitudinal structure in the auroral oval seen in two movies spanning 8 and 11 rotations gives an estimate on the period of 10.65 ± 0.15 h for 2009 in the northern oval and 10.8 ± 0.1 h for 2012 in the southern oval. The 2009 north aurora period is close to the north branch of Saturn Kilometric Radiation (SKR) detected at that time.

  14. Retrievals of Jovian Tropospheric Phosphine from Cassini/CIRS

    Science.gov (United States)

    Irwin, P. G. J.; Parrish, P.; Fouchet, T.; Calcutt, S. B.; Taylor, F. W.; Simon-Miller, A. A.; Nixon, C. A.

    2004-01-01

    On December 30th 2000, the Cassini-Huygens spacecraft reached the perijove milestone on its continuing journey to the Saturnian system. During an extended six-month encounter, the Composite Infrared Spectrometer (CIRS) returned spectra of the Jovian atmosphere, rings and satellites from 10-1400 cm(exp -1) (1000-7 microns) at a programmable spectral resolution of 0.5 to 15 cm(exp -1). The improved spectral resolution of CIRS over previous IR instrument-missions to Jupiter, the extended spectral range, and higher signal-to-noise performance provide significant advantages over previous data sets. CIRS global observations of the mid-infrared spectrum of Jupiter at medium resolution (2.5 cm(exp -1)) have been analysed both with a radiance differencing scheme and an optimal estimation retrieval model to retrieve the spatial variation of phosphine and ammonia fractional scale height in the troposphere between 60 deg S and 60 deg N at a spatial resolution of 6 deg. The ammonia fractional scale height appears to be high over the Equatorial Zone (EZ) but low over the North Equatorial Belt (NEB) and South Equatorial Belt (SEB) indicating rapid uplift or strong vertical mixing in the EZ. The abundance of phosphine shows a similar strong latitudinal variation which generally matches that of the ammonia fractional scale height. However while the ammonia fractional scale height distribution is to a first order symmetric in latitude, the phosphine distribution shows a North/South asymmetry at mid latitudes with higher amounts detected at 40 deg N than 40 deg S. In addition the data show that while the ammonia fractional scale height at this spatial resolution appears to be low over the Great Red Spot (GRS), indicating reduced vertical mixing above the approx. 500 mb level, the abundance of phosphine at deeper levels may be enhanced at the northern edge of the GRS indicating upwelling.

  15. Saturn's Aurora Observed by Cassini Camera in Visible Wavelengths

    Science.gov (United States)

    Dyudina, U.; Ingersoll, A. P.; Ewald, S.; Wellington, D. F.

    2014-12-01

    Cassini camera's movies in 2009-2013 show Saturn's aurora in both the northern and southern hemispheres. The color of the aurora changes from pink at a few hundreds of km above the cloud tops to purple at 1000-1500 km above the cloud tops. The spectrum observed in 9 lters spanning wavelengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with the laboratory simulated auroras [1]. Auroras in both hemispheres vary dramatically with longitude. Auroras form bright arcs, sometimes a spiral around the pole, and sometimes double arcs at 70-75 both north and south latitude. 10,000-km-scale longitudinal brightness structures can persist for more than 100 hours. This structures rotate together with Saturn. Besides the steady structure, the auroras brighten suddenly on the timescales of few minutes. 1000-km-scale disturbances may move faster or lag behind Saturn's rotation on timescales of tens of minutes. The persistence of the longitudinal structure of the aurora in two long observations in 2009 and 2012 allowed us to estimate its period of rotation of 10.65±0.15 h for 2009 and 10.8±0.1 h for 2012. The 2009 north aurora period is close to the north branch of Saturn Kilometric Radiation (SKR) detected at that time. The 2012 south aurora period is longer than the SKR periods detected at the time. These periods are also close to the rotation period of the lightning storms on Saturn. We discuss those periodicities and their relevance to Saturn's internal rotation. [1] Aguilar, A. et al. The Electron-Excited Mid-Ultraviolet to Near-Infrared Spectrum of H2:Cross Sections and Transition Probabilities. Astrophys. J. Supp. Ser. 177, 388-407 (2008).

  16. New constraints on Saturn's interior from Cassini astrometric data

    Science.gov (United States)

    Lainey, Valéry; Jacobson, Robert A.; Tajeddine, Radwan; Cooper, Nicholas J.; Murray, Carl; Robert, Vincent; Tobie, Gabriel; Guillot, Tristan; Mathis, Stéphane; Remus, Françoise; Desmars, Josselin; Arlot, Jean-Eudes; De Cuyper, Jean-Pierre; Dehant, Véronique; Pascu, Dan; Thuillot, William; Le Poncin-Lafitte, Christophe; Zahn, Jean-Paul

    2017-01-01

    Using astrometric observations spanning more than a century and including a large set of Cassini data, we determine Saturn's tidal parameters through their current effects on the orbits of the eight main and four coorbital Moons. We have used the latter to make the first determination of Saturn's Love number from observations, k2=0.390 ± 0.024, a value larger than the commonly used theoretical value of 0.341 (Gavrilov & Zharkov, 1977), but compatible with more recent models (Helled & Guillot, 2013) for which the static k2 ranges from 0.355 to 0.382. Depending on the assumed spin for Saturn's interior, the new constraint can lead to a significant reduction in the number of potential models, offering great opportunities to probe the planet's interior. In addition, significant tidal dissipation within Saturn is confirmed (Lainey et al., 2012) corresponding to a high present-day tidal ratio k2/Q=(1.59 ± 0.74) × 10-4 and implying fast orbital expansions of the Moons. This high dissipation, with no obvious variations for tidal frequencies corresponding to those of Enceladus and Dione, may be explained by viscous friction in a solid core, implying a core viscosity typically ranging between 1014 and 1016 Pa.s (Remus et al., 2012). However, a dissipation increase by one order of magnitude at Rhea's frequency could suggest the existence of an additional, frequency-dependent, dissipation process, possibly from turbulent friction acting on tidal waves in the fluid envelope of Saturn (Ogilvie & Lin, 2004; Fuller et al. 2016).

  17. Cassini Attitude and Articulation Control Subsystem Fault Protection Challenges During Saturn Proximal Orbits

    Science.gov (United States)

    Bates, David M.

    2015-01-01

    NASA's Cassini Spacecraft, launched on October 15th, 1997 arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. As the first spacecraft to achieve orbit at Saturn, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended mission through 2017. As part of the final extended mission, Cassini will begin an aggressive and exciting campaign of high inclination low altitude flybys within the inner most rings of Saturn, skimming Saturn's outer atmosphere, until the spacecraft is finally disposed of via planned impact with the planet. This final campaign, known as the proximal orbits, presents unique fault protection related challenges, the details of which are discussed in this paper.

  18. Cassini's Maneuver Automation Software (MAS) Process: How to Successfully Command 200 Navigation Maneuvers

    Science.gov (United States)

    Yang, Genevie Velarde; Mohr, David; Kirby, Charles E.

    2008-01-01

    To keep Cassini on its complex trajectory, more than 200 orbit trim maneuvers (OTMs) have been planned from July 2004 to July 2010. With only a few days between many of these OTMs, the operations process of planning and executing the necessary commands had to be automated. The resulting Maneuver Automation Software (MAS) process minimizes the workforce required for, and maximizes the efficiency of, the maneuver design and uplink activities. The MAS process is a well-organized and logically constructed interface between Cassini's Navigation (NAV), Spacecraft Operations (SCO), and Ground Software teams. Upon delivery of an orbit determination (OD) from NAV, the MAS process can generate a maneuver design and all related uplink and verification products within 30 minutes. To date, all 112 OTMs executed by the Cassini spacecraft have been successful. MAS was even used to successfully design and execute a maneuver while the spacecraft was in safe mode.

  19. The Double Flybys of the Cassini Mission: Navigation Challenges and Lessons Learned

    Science.gov (United States)

    Wagner, Sean; Buffington, Brent

    2014-01-01

    Since 2004, the Cassini spacecraft has flown by Titan and other Saturn moons numerous times, successfully accomplishing its 100th targeted encounter of Titan in March 2014. The navigation of Cassini is challenging, even more so with "double flybys," two encounters separated by at most a few days. Because of this tight spacing, there is not enough time for a maneuver in between. Additionally, maneuvers prior to a double flyby only target one of the two encounters. This paper discusses the challenges faced by the Cassini Navigation Team with each double flyby, as well as lessons learned during operational support of each dual encounter. The strengths and weaknesses of the targeting strategies considered for each double flyby are also detailed, by comparing downstream ?V costs and changes to the non-targeted flyby conditions.

  20. CDA in-situ measurements during Cassini's F-ring plane crossings in 2017

    Science.gov (United States)

    Srama, Ralf; Moragas-Klostermeyer, Georg; Albin, Thomas; Economou, Thanasis; Hsu, Sean; Horanyi, Mihaly; Kempf, Sascha; Li, Yanwei; Postberg, Frank; Simolka, Jonas; Soja, Rachel; Strack, Heiko; Altobelli, Nicolas

    2017-04-01

    The Cosmic Dust Analyzer (CDA) onboard Cassini characterized successfully the dust environment at Saturn since 2004. The instrument measures the primary charge, speed, mass and composition of individual submicron and micron sized dust grains. Starting in December 2016 Cassini performed ring plane crossings at radial distances of 2.48 Saturn radii. For the first time, an in-situ dust detector explored this F-ring region of Saturn. CDA performed density, mass and compositional measurements. Furthermore, the High Rate Detector was activated using a high time and spatial resolution. The spatial resolution on January 2nd (2017) was as low as 2000 meters. Here, we do report preliminary results of the in-situ measurements of three F-ring orbit crossings. The relative encounter speed between Cassini and F-ring particles was approximately 20 km per second.

  1. Cassini Operational Sun Sensor Risk Management During Proximal Orbit Saturn Ring Plane Crossings

    Science.gov (United States)

    Bates, David M.

    2016-01-01

    NASA's Cassini Spacecraft, launched on October 15th, 1997 which arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. As the first spacecraft to achieve orbit at Saturn, Cassini has collected science data throughout its four-year prime mission (2004–08), and has since been approved for a first and second extended mission through 2017. As part of the final extended missions, Cassini will begin an aggressive and exciting campaign of high inclination, low altitude flybys within the inner most rings of Saturn, skimming Saturn’s outer atmosphere, until the spacecraft is finally disposed of via planned impact with the planet. This final campaign, known as the proximal orbits, requires a strategy for managing the Sun Sensor Assembly (SSA) health, the details of which are presented in this paper.

  2. Cassini Attitude and Articulation Control Subsystem Fault Protection Challenges During Saturn Proximal Orbits

    Science.gov (United States)

    Bates, David M.

    2015-01-01

    NASA's Cassini Spacecraft, launched on October 15th, 1997 arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. As the first spacecraft to achieve orbit at Saturn, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended mission through 2017. As part of the final extended mission, Cassini will begin an aggressive and exciting campaign of high inclination low altitude flybys within the inner most rings of Saturn, skimming Saturn's outer atmosphere, until the spacecraft is finally disposed of via planned impact with the planet. This final campaign, known as the proximal orbits, presents unique fault protection related challenges, the details of which are discussed in this paper.

  3. Cassini's Maneuver Automation Software (MAS) Process: How to Successfully Command 200 Navigation Maneuvers

    Science.gov (United States)

    Yang, Genevie Velarde; Mohr, David; Kirby, Charles E.

    2008-01-01

    To keep Cassini on its complex trajectory, more than 200 orbit trim maneuvers (OTMs) have been planned from July 2004 to July 2010. With only a few days between many of these OTMs, the operations process of planning and executing the necessary commands had to be automated. The resulting Maneuver Automation Software (MAS) process minimizes the workforce required for, and maximizes the efficiency of, the maneuver design and uplink activities. The MAS process is a well-organized and logically constructed interface between Cassini's Navigation (NAV), Spacecraft Operations (SCO), and Ground Software teams. Upon delivery of an orbit determination (OD) from NAV, the MAS process can generate a maneuver design and all related uplink and verification products within 30 minutes. To date, all 112 OTMs executed by the Cassini spacecraft have been successful. MAS was even used to successfully design and execute a maneuver while the spacecraft was in safe mode.

  4. Discovering habitable environments and life in the Saturn System (Jean Dominique Cassini Medal Lecture)

    Science.gov (United States)

    Lunine, Jonathan I.

    2015-04-01

    One of the most notable scientific adventures of our time is being conducted jointly by Europe and the United States around the solar system's great ringed planet, Saturn. The Cassini-Huygens mission arrived in orbit in 2004, and the Huygens probe descended through Titan's atmosphere in January 2005. Titan's surface has been found to host a rich and still-enigmatic methane cycle, complete with lakes, seas, rivers and rain. Enceladus is jetting its interior volatiles into space, where the Cassini Orbiter detected and measured a number of species within the resulting plume. These include water, organic molecules, nitrogen compounds, and salts. Cassini radio science detected the presence within both Enceladus and Titan of internal water oceans. Variability with orbital phase of the Enceladus plume, also discovered by the Cassini Orbiter, makes a convincing case for the jets themselves being derived from the deep interior and controlled by tidal forces. Both Enceladus and Titan host potentially habitable environments, and they represent unique opportunities for testing whether either or both of these bodies harbor life. Titan's interior will be difficult to access, but its large surface hydrocarbon seas can be explored in situ with Huygens-like vehicles. The Cassini Orbiter determined the liquid in Titan's seas to be methane and ethane, which raises the question of whether simple chemistry can evolve into autocatalysis and self-replication in a non-aqueous liquid environment. In effect, is there an exotic kind of "life" in the Titan seas? Enceladus is perhaps more straightforward: given that the interior water ocean as expressed through the plume appears to satisfy the formal requirements for habitability, is biological activity occurring there? Answering these questions will require a new generation of robotic vehicles beyond Cassini-Huygens -- and new opportunities for international collaborations in planetary exploration.

  5. The Orbits of Saturn's Small Satellites Derived from Combined Historic and Cassini Imaging Observations

    Science.gov (United States)

    Spitale, J. N.; Jacobson, R. A.; Porco, C. C.; Owen, W. M., Jr.

    2006-08-01

    We report on the orbits of the small, inner Saturnian satellites, either recovered or newly discovered in recent Cassini imaging observations. The orbits presented here reflect improvements over our previously published values in that the time base of Cassini observations has been extended, and numerical orbital integrations have been performed in those cases in which simple precessing elliptical, inclined orbit solutions were found to be inadequate. Using combined Cassini and Voyager observations, we obtain an eccentricity for Pan 7 times smaller than previously reported because of the predominance of higher quality Cassini data in the fit. The orbit of the small satellite (S/2005 S1 [Daphnis]) discovered by Cassini in the Keeler gap in the outer A ring appears to be circular and coplanar; no external perturbations are apparent. Refined orbits of Atlas, Prometheus, Pandora, Janus, and Epimetheus are based on Cassini , Voyager, Hubble Space Telescope, and Earth-based data and a numerical integration perturbed by all the massive satellites and each other. Atlas is significantly perturbed by Prometheus, and to a lesser extent by Pandora, through high-wavenumber mean-motion resonances. Orbital integrations involving Atlas yield a mass of GMAtlas=(0.44+/-0.04)×10-3 km3 s -2, 3 times larger than reported previously (GM is the product of the Newtonian constant of gravitation G and the satellite mass M). Orbital integrations show that Methone is perturbed by Mimas, Pallene is perturbed by Enceladus, and Polydeuces librates around Dione's L5 point with a period of about 791 days. We report on the nature and orbits of bodies sighted in the F ring, two of which may have persisted for a year or more.

  6. Cassini Dust Measurements at Enceladus and Implications for the Origin of the E Ring

    Science.gov (United States)

    Spahn, Frank; Schmidt, Jürgen; Albers, Nicole; Hörning, Marcel; Makuch, Martin; Seiß, Martin; Kempf, Sascha; Srama, Ralf; Dikarev, Valeri; Helfert, Stefan; Moragas-Klostermeyer, Georg; Krivov, Alexander V.; Sremčević, Miodrag; Tuzzolino, Anthony J.; Economou, Thanasis; Grün, Eberhard

    2006-03-01

    During Cassini's close flyby of Enceladus on 14 July 2005, the High Rate Detector of the Cosmic Dust Analyzer registered micron-sized dust particles enveloping this satellite. The dust impact rate peaked about 1 minute before the closest approach of the spacecraft to the moon. This asymmetric signature is consistent with a locally enhanced dust production in the south polar region of Enceladus. Other Cassini experiments revealed evidence for geophysical activities near Enceladus' south pole: a high surface temperature and a release of water gas. Production or release of dust particles related to these processes may provide the dominant source of Saturn's E ring.

  7. VIMS spectral mapping observations of Titan during the Cassini prime mission

    Science.gov (United States)

    Barnes, J.W.; Soderblom, J.M.; Brown, R.H.; Buratti, B.J.; Sotin, Christophe; Baines, K.H.; Clark, R.N.; Jaumann, R.; McCord, T.B.; Nelson, R.; Le, Mouelic S.; Rodriguez, S.; Griffith, C.; Penteado, P.; Tosi, F.; Pitman, K.M.; Soderblom, L.; Stephan, K.; Hayne, P.; Vixie, G.; Bibring, J.-P.; Bellucci, G.; Capaccioni, F.; Cerroni, P.; Coradini, A.; Cruikshank, D.P.; Drossart, P.; Formisano, V.; Langevin, Y.; Matson, D.L.; Nicholson, P.D.; Sicardy, B.

    2009-01-01

    This is a data paper designed to facilitate the use of and comparisons to Cassini/visual and infrared mapping spectrometer (VIMS) spectral mapping data of Saturn's moon Titan. We present thumbnail orthographic projections of flyby mosaics from each Titan encounter during the Cassini prime mission, 2004 July 1 through 2008 June 30. For each flyby we also describe the encounter geometry, and we discuss the studies that have previously been published using the VIMS dataset. The resulting compliation of metadata provides a complementary big-picture overview of the VIMS data in the public archive, and should be a useful reference for future Titan studies. ?? 2009 Elsevier Ltd.

  8. Constraints on MOND theory from radio tracking data of the Cassini spacecraft

    CERN Document Server

    Hees, A; Jacobson, R A; Park, R S

    2014-01-01

    The MOdified Newtonian Dynamics (MOND) is an attempt to modify the gravitation theory to solve the Dark Matter problem. This phenomenology is very successful at the galactic level. The main effect produced by MOND in the Solar System is called the External Field Effect parametrized by the parameter $Q_2$. We have used 9 years of Cassini range and Doppler measurements to constrain $Q_2$. Our estimate of this parameter based on Cassini data is given by $Q_2=(3 \\pm 3)\\times 10^{-27} \\ \\rm{s^{-2}}$ which shows no deviation from General Relativity and excludes a large part of the relativistic MOND theories.

  9. Twenty Years of Systems Engineering on the Cassini-Huygens Mission

    Science.gov (United States)

    Manor-Chapman, Emily

    2013-01-01

    Over the past twenty years, the Cassini-Huygens Mission has successfully utilized systems engineering to develop and execute a challenging prime mission and two mission extensions. Systems engineering was not only essential in designing the mission, but as knowledge of the system was gained during cruise and science operations, it was critical in evolving operational strategies and processes. This paper discusses systems engineering successes, challenges, and lessons learned on the Cassini-Huygens Mission gathered from a thorough study of mission plans and developed scenarios, and interviews with key project leaders across its twenty-year history.

  10. Temperature Variations of Saturn Rings with Viewing Geometries from Prime to Equinox Cassini Missions

    Science.gov (United States)

    Deau, E. A.; Spilker, L. J.; Morishima, R.; Brooks, S.; Pilorz, S.; Altobelli, N.

    2011-01-01

    After more than six years in orbit around Saturn, the Cassini Composite Infrared Spectrometer (CIRS) has acquired an extensive set of measurements of Saturn's main rings (A, B, C and Cassini Division) in the thermal infrared. Temperatures were retrieved for the lit and unlit rings over a variety of ring geometries that include phase angle, solar and spacecraft elevations and local time. We show that some of these parameters (solar and spacecraft elevations, phase angle) play a role in the temperature variations in the first order, while the others (ring and particle local time) produced second order effects. The results of this comparison will be presented.

  11. Classification of conics and Cassini curves in Minkowski space-time plane

    Directory of Open Access Journals (Sweden)

    Emad N. Shonoda

    2016-04-01

    Full Text Available In this paper we use the Apollonius definition of conics to generate algebraic curves in the Minkowski space-time plane M2, which turn out to be different from classical conic sections. We extend and classify this sort of “M-conics”. We discuss the cases of the singularity points of these M-conics, coming from the transition from timelike world to spacelike world through the lightlike one. Finally, we translate the classical concept of Cassini curves with two foci and that of (multifocal Cassini curves to Minkowski planes M2.

  12. Cassini Attitude Control Flight Software: from Development to In-Flight Operation

    Science.gov (United States)

    Brown, Jay

    2008-01-01

    The Cassini Attitude and Articulation Control Subsystem (AACS) Flight Software (FSW) has achieved its intended design goals by successfully guiding and controlling the Cassini-Huygens planetary mission to Saturn and its moons. This paper describes an overview of AACS FSW details from early design, development, implementation, and test to its fruition of operating and maintaining spacecraft control over an eleven year prime mission. Starting from phases of FSW development, topics expand to FSW development methodology, achievements utilizing in-flight autonomy, and summarize lessons learned during flight operations which can be useful to FSW in current and future spacecraft missions.

  13. Cassini Attitude Control Flight Software: from Development to In-Flight Operation

    Science.gov (United States)

    Brown, Jay

    2008-01-01

    The Cassini Attitude and Articulation Control Subsystem (AACS) Flight Software (FSW) has achieved its intended design goals by successfully guiding and controlling the Cassini-Huygens planetary mission to Saturn and its moons. This paper describes an overview of AACS FSW details from early design, development, implementation, and test to its fruition of operating and maintaining spacecraft control over an eleven year prime mission. Starting from phases of FSW development, topics expand to FSW development methodology, achievements utilizing in-flight autonomy, and summarize lessons learned during flight operations which can be useful to FSW in current and future spacecraft missions.

  14. Cassini's Ring Grazing and Grand Finale Orbits: Topping Off an Awesome Mission

    Science.gov (United States)

    Edgington, Scott; Spilker, Linda; Coustenis, Athena

    2017-04-01

    The Cassini-Huygens mission, a joint collaboration between NASA, ESA, and the Italian Space Agency, is in its last year of operations after nearly 13 years in orbit around Saturn. Cassini will send back its final bits of unique data on September 15th, 2017 as it plunges into Saturn's atmosphere, vaporizing and satisfying planetary protection requirements. Before that time Cassini will continue its legacy of exploration and discovery in 2017 and return unique science data provided by orbits taking the spacecraft into unexplored regions near Saturn and its rings. From the new vantage points, Cassini will continue to study seasonal and temporal changes in the system as northern summer solstice approaches. With the exception of one remaining targeted Titan flyby, all of Cassini's close icy satellite flybys, including those of Enceladus, are now completed. In November 2016, Cassini transitioned to a series of orbits with peripases just outside Saturn's F ring. These 20 orbits include close flybys of some tiny ring moons and excellent views of the F ring and Saturn's outer A ring. The 126th and final close flyby of Titan will propel Cassini across Saturn's main rings and into its Grand Finale series of orbits. Cassini's Grand Finale, starting in April 2017, is comprised of 22 orbits at an inclination of 63 degrees. Cassini will repeatedly dive between Saturn's innermost rings and upper atmosphere providing insights into fundamental questions unattainable during the rest of the mission. Cassini will be the first spacecraft to explore this region. These close orbits provide the highest resolution observations of both the rings and Saturn, and direct in-situ sampling of the ring particles, composition, plasma, Saturn's exosphere and the innermost radiation belts. Saturn's gravitational field will be measured to unprecedented accuracy, providing information on the interior structure of the planet, winds in the outer layers of Saturn's atmosphere, and the mass distribution in

  15. Etude sur les tendons en materiaux composites et leur application aux ancrages postcontraints

    Science.gov (United States)

    Chennouf, Adil

    L'objectif general de la presente these est d'evaluer le comportement a l'arrachement et au fluage d'ancrages injectes constitues de tendons en materiaux composites afin d'etablir des recommandations plus appropriees et realistes pour le dimensionnement et la conception. Quatre types de tendons en materiaux composites, deux a base de fibres d'aramide et deux a base de fibres de carbone, ont ete utilises dans l'etude. Les travaux de recherche de cette these ont porte notamment sur: (I) Une caracterisation physique et mecanique des tendons en materiaux composites utilises dans l'etude. (II) Une etude en laboratoire sur les coulis de scellement. La premiere etape de cette etude a concerne le developpement d'un coulis de scellement performant adapte aux tendons en materiaux composites et a differentes situations d'injection. La seconde etape a traite des essais de caracterisations physique et mecanique du coulis de scellement developpe comparativement a trois coulis de scellement usuels d'un meme rapport E/L de 0,4. (III) Une etude sur des modeles reduits d'ancrages injectes. (IV) Une etude sur des modeles d'ancrages a grande echelle. La synthese de ces etudes a permis d'enoncer les principales conclusions suivantes: (1) Les valeurs moyennes des charges de rupture des tendons en materiaux composites ont ete de 1% a 29% superieures a celles specifiees par les manufacturiers. (2) L'etude sur les coulis de scellement a permis le developpement de coulis de ciment repondant aux criteres fixes, soient une grande stabilite, une bonne fluidite, une legere expansion et de bonnes caracteristiques mecaniques. (3) Les tendons en materiaux composites ont montre des contraintes d'adherence maximum superieures a celles des tendons en acier. (4) Le type de fibre, la configuration et le fini de surface des tendons en materiaux composites gouvernent leur resistance a l'adherence. (5) L'introduction de sable et d'autres ajouts comme les fines de silice et la poudre d'aluminium au coulis

  16. Magnetic resonance studies of solid polymers; Etude des polymeres solides par resonance magnetique

    Energy Technology Data Exchange (ETDEWEB)

    Lenk, R. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1969-07-01

    This paper is a review of the application of nuclear magnetic resonance (NMR) to solid polymers. In the first, theoretical part, the elements of the theory of NMR, which are necessary for the study of the properties of solid polymers are discussed: the moments method, nuclear relaxation and the distribution of correlation times. In the second part the experimental results are presented. (author) [French] Cette etude est une recherche bibliographique sur l'application de la resonance magnetique nucleaire (RMN) aux polymeres solides. Dans la premiere partie theorique on discute les elements de la theorie de RMN, necessaires pour l'etude des proprietes des polymeres solides: la methode des moments, la relaxation nucleaire et la distribution des temps de correlation. La deuxieme partie presente les resultats des experiences. (auteur)

  17. Temporal variations of Titan's surface with Cassini/VIMS

    Science.gov (United States)

    Solomonidou, Anezina; Coustenis, A.; Hirtzig, M.; Rodriguez, S.; Stephan, K.; Lopes, R. M. C.; Drossart, P.; Sotin, C.; Le Mouélic, S.; Lawrence, K.; Bratsolis, E.; Jaumann, R.; Brown, R. H.

    2016-05-01

    We analyze Cassini VIMS data of several areas on Titan's surface looking for variations with time. Three of these locations are near the equator (10-30°S), namely Hotei Regio, Tui Regio and Sotra Patera; in some cases changes in brightness and/or in appearance were reported therein. We also investigate a portion of the undifferentiated plains, areas relatively homogeneous and dark in radar observations, located near 20-25°N. This is a follow-up on a previous paper in which we had inferred surface albedos for some distinct regions of interest (RoIs) identified within the Hotei, Tui and Sotra areas through a Principal Component Analysis (PCA) and radiative transfer (RT) modeling (Solomonidou [2014]. J. Geophys. Res. 119, 1729-1747). We apply the same methods here to a larger dataset looking for variations of the surface albedo with time and using the Huygens landing site as the 'ground truth' for calibration purposes. As expected, the undifferentiated plains remain unchanged from January 2010 to June 2012. Our analysis of Hotei Regio data from March 2005 to March 2009 also does not show any significant surface albedo variations within uncertainties. We note however that our RT retrievals are not optimal in this case because of the use of a plane-parallel code and the unfavorable geometry of the associated datasets. Conversely, Tui Regio and Sotra Patera show surface albedo fluctuations with time with pronounced trends for darkening and for brightening respectively. The Tui Regio spectrum exhibits a surface albedo decrease from March 2005 to February 2009, at 0.94, 1.08, 2.03, and 5 μm wavelengths, while the spectrum shape remains the same over that time. On the contrary, the Sotra Patera area became at least two times brighter within a year (April 2005-February 2006), at 1.58 μm, 2.03 μm, and 5 μm. We also retrieved surface albedo spectra for three reference regions surrounding Hotei, Tui and Sotra and for three additional regions we use as 'test cases' that

  18. Constraints on Saturn's Tropospheric General Circulation from Cassini ISS Images

    Science.gov (United States)

    DelGenio, Anthony D.; Barbara, John M.

    2013-01-01

    An automated cloud tracking algorithm is applied to Cassini Imaging Science Subsystem high-resolution apoapsis images of Saturn from 2005 and 2007 and moderate resolution images from 2011 and 2012 to define the near-global distribution of zonal winds and eddy momentum fluxes at the middle troposphere cloud level and in the upper troposphere haze. Improvements in the tracking algorithm combined with the greater feature contrast in the northern hemisphere during the approach to spring equinox allow for better rejection of erroneous wind vectors, a more objective assessment at any latitude of the quality of the mean zonal wind, and a population of winds comparable in size to that available for the much higher contrast atmosphere of Jupiter. Zonal winds at cloud level changed little between 2005 and 2007 at all latitudes sampled. Upper troposphere zonal winds derived from methane band images are approx. 10 m/s weaker than cloud level winds in the cores of eastward jets and approx. 5 m/s stronger on either side of the jet core, i.e., eastward jets appear to broaden with increasing altitude. In westward jet regions winds are approximately the same at both altitudes. Lateral eddy momentum fluxes are directed into eastward jet cores, including the strong equatorial jet, and away from westward jet cores and weaken with increasing altitude on the flanks of the eastward jets, consistent with the upward broadening of these jets. The conversion rate of eddy to mean zonal kinetic energy at the visible cloud level is larger in eastward jet regions (5.2x10(exp -5) sq m/s) and smaller in westward jet regions (1.6x10(exp -5) sqm/s) than the global mean value (4.1x10(ep -5) sq m/s). Overall the results are consistent with theories that suggest that the jets and the overturning meridional circulation at cloud level on Saturn are maintained at least in part by eddies due to instabilities of the large-scale flow near and/or below the cloud level.

  19. The cosmic dust analyser onboard cassini: ten years of discoveries

    Science.gov (United States)

    Srama, R.; Kempf, S.; Moragas-Klostermeyer, G.; Altobelli, N.; Auer, S.; Beckmann, U.; Bugiel, S.; Burton, M.; Economomou, T.; Fechtig, H.; Fiege, K.; Green, S. F.; Grande, M.; Havnes, O.; Hillier, J. K.; Helfert, S.; Horanyi, M.; Hsu, S.; Igenbergs, E.; Jessberger, E. K.; Johnson, T. V.; Khalisi, E.; Krüger, H.; Matt, G.; Mocker, A.; Lamy, P.; Linkert, G.; Lura, F.; Möhlmann, D.; Morfill, G. E.; Otto, K.; Postberg, F.; Roy, M.; Schmidt, J.; Schwehm, G. H.; Spahn, F.; Sterken, V.; Svestka, J.; Tschernjawski, V.; Grün, E.; Röser, H.-P.

    2011-12-01

    The interplanetary space probe Cassini/Huygens reached Saturn in July 2004 after 7 years of cruise phase. The German cosmic dust analyser (CDA) was developed under the leadership of the Max Planck Institute for Nuclear Physics in Heidelberg under the support of the DLR e.V. This instrument measures the interplanetary, interstellar and planetary dust in our solar system since 1999 and provided unique discoveries. In 1999, CDA detected interstellar dust in the inner solar system followed by the detection of electrical charges of interplanetary dust grains during the cruise phase between Earth and Jupiter. The instrument determined the composition of interplanetary dust and the nanometre-sized dust streams originating from Jupiter's moon Io. During the approach to Saturn in 2004, similar streams of submicron grains with speeds in the order of 100 km/s were detected from Saturn's inner and outer ring system and are released to the interplanetary magnetic field. Since 2004 CDA measured more than one million dust impacts characterising the dust environment of Saturn. The instrument is one of the three experiments which discovered the active ice geysers located at the south pole of Saturn's moon Enceladus in 2005. Later, a detailed compositional analysis of the water ice grains in Saturn's E ring system led to the discovery of large reservoirs of liquid water (oceans) below the icy crust of Enceladus. Finally, the determination of the dust-magnetosphere interaction and the discovery of the extended E ring (at least twice as large as predicted) allowed the definition of a dynamical dust model of Saturn's E ring describing the observed properties. This paper summarizes the discoveries of a 10-year story of success based on reliable measurements with the most advanced dust detector flown in space until today. This paper focuses on cruise results and findings achieved at Saturn with a focus on flux and density measurements. CDA discoveries related to the detailed dust stream

  20. Icy Satellite Science Today and in Cassini's Final Three Years

    Science.gov (United States)

    Buratti, B. J.

    2014-12-01

    The Cassini Mission has turned our view of Saturn's icy moons from scientific sketches to fully realized worlds. Among the major discoveries are: Activity on Enceladus and associated plumes that originate in small hot spots on its south pole and that appear to be modulated by tidal forces; a liquid subsurface water ocean on Enceladus that is a habitable environment; several new moons; debris rings associated with moons; a unique equatorial ridge on Iapetus; the identity of new constituents on the moons including carbon dioxide ice on most of them and polycyclic aromatic hydrocarbons (PAHs)on Iapetus; differentiated or partially differentiated interiors; nano-iron on the surfaces of the moons and in the rings; volatile segregation on Iapetus and Hyperion; and a bewildering array of geologic processes on the small moons. But our new view of these icy worlds has spawned new questions. Among these unanswered questions are: How variable are the plumes? Have any other moons had activity similar to that on Enceladus and did it continue up to the recent past? How much dust do the moons contribute to the region around Saturn? What caused the ridge on Iapetus? What are the interiors of the moons like? How differentiated and compensated are they? Five additional targeted flybys, two of Dione and three of Enceladus, have been designed to answer these questions and will be implemented during the remainder of the Solstice Mission. The Dione flybys both include gravity passes to determine its state of differentiation. One of the flybys is optimized to measure the fields and particle environment around Dione. One of the two remote-sensing flybys of Enceladus will scrutinize the south polar region to further understand the size, temperature, and variability of the emitting areas, while the other will observe the north pole to determine why it is so different from the south. The third Enceladus flyby involves an unprecedented pass less than 50 km above the surface into the midst of

  1. Methane Band and Continuum Band Imaging of Titan's Atmosphere Using Cassini ISS Narrow Angle Camera Pictures from the CURE/Cassini Imaging Project

    Science.gov (United States)

    Shitanishi, Jennifer; Gillam, S. D.

    2009-05-01

    The study of Titan's atmosphere, which bears resemblance to early Earth's, may help us understand more of our own. Constructing a Monte Carlo model of Titan's atmosphere is helpful to achieve this goal. Methane (MT) and continuum band (CB) images of Titan taken by the CURE/Cassini Imaging Project, using the Cassini Narrow Angle Camera (NAC) were analyzed. They were scheduled by Cassini Optical Navigation. Images were obtained at phase 53°, 112°, 161°, and 165°. They include 22 total MT1(center wavelength at 619nm), MT2(727nm), MT3(889nm), CB1(635nm), CB2(751nm), and CB3(938nm) images. They were reduced with previously written scripts using the National Optical Astronomy Observatory Image Reduction and Analysis Facility scientific analysis suite. Correction for horizontal and vertical banding and cosmic ray hits were made. The MT images were registered with corresponding CB images to ensure that subsequently measured fluxes ratios came from the same parts of the atmosphere. Preliminary DN limb-to-limb scans and loci of the haze layers will be presented. Accurate estimates of the sub-spacecraft points on each picture will be presented. Flux ratios (FMT/FCB=Q0) along the scans and total absorption coefficients along the lines of sight from the spacecraft through the pixels (and into Titan) will also be presented.

  2. FMT (Flight Software Memory Tracker) For Cassini Spacecraft-Software Engineering Using JAVA

    Science.gov (United States)

    Kan, Edwin P.; Uffelman, Hal; Wax, Allan H.

    1997-01-01

    The software engineering design of the Flight Software Memory Tracker (FMT) Tool is discussed in this paper. FMT is a ground analysis software set, consisting of utilities and procedures, designed to track the flight software, i.e., images of memory load and updatable parameters of the computers on-board Cassini spacecraft. FMT is implemented in Java.

  3. Using AUTORAD for Cassini File Uplinks: Incorporating Automated Commanding into Mission Operations

    Science.gov (United States)

    Goo, Sherwin

    2014-01-01

    As the Cassini spacecraft embarked on the Solstice Mission in October 2010, the flight operations team faced a significant challenge in planning and executing the continuing tour of the Saturnian system. Faced with budget cuts that reduced the science and engineering staff by over a third in size, new and streamlined processes had to be developed to allow the Cassini mission to maintain a high level of science data return with a lower amount of available resources while still minimizing the risk. Automation was deemed an important key in enabling mission operations with reduced workforce and the Cassini flight team has made this goal a priority for the Solstice Mission. The operations team learned about a utility called AUTORAD which would give the flight operations team the ability to program selected command files for radiation up to seven days in advance and help minimize the need for off-shift support that could deplete available staffing during the prime shift hours. This paper will describe how AUTORAD is being utilized by the Cassini flight operations team and the processes that were developed or modified to ensure that proper oversight and verification is maintained in the generation and execution of radiated command files.

  4. In-Flight Position Calibration of the Cassini Articulated Reaction Wheel Assembly

    Science.gov (United States)

    Brown, Todd S.

    2012-01-01

    NASA's long-lived Cassini-Huygens spacecraft is currently in its 14th year of flight and in the midst of its second, and final, extended mission. Cassini is a massive interplanetary spacecraft that is three axis stabilized and can maintain attitude control using either its reaction control system thrusters or using reaction wheel control. Cassini has four identical reaction wheels, of which three are mutually orthogonal and have a fixed orientation. The fourth reaction wheel has an articulation motor that allows this reaction wheel to be aligned with the momentum direction of any of the other three fixed reaction wheels. The articulation motor allows this reaction wheel to be used as a replacement for any of the other three wheels without any performance degradation. However, due to limitations in the design of this backup system, there are few telemetric indications of the orientation of this reaction wheel following an articulation. This investigation serves to outline the procedures that have been developed by the Cassini Attitude and Articulation Control Subsystem to calibrate the position of the articulated reaction wheel assembly in the event that the momentum direction of this reaction wheel must be reoriented.

  5. Peeling the Onion: The Upper Surface of Mimas from Cassini VIMS

    Science.gov (United States)

    Buratti, Bonnie J.; Brown, R. H.; Clark, R. N.; Mosher, J. A.; Cruikshank, D. P.; Filacchione, G.; Baines, K. H.; Nicholson, P. D.

    2010-10-01

    Cloaked in light from Saturn and its rings, the medium-sized Saturnian satellite Mimas is difficult to observe form Earth, and it was the only major satellite not to have a close encounter by the Cassini spacecraft. Observations of the moon during Ring Plane Crossing in 1995 and by the Hubble Space Telescope established that the moon has a visual geometric albedo of greater than unity (Verbiscer et al. 2007, Science 315, 815) and a brighter trailing side (Buratti et al. 1998, Icarus 136, 223), suggesting it is being coated by the E-ring. Observations at opposition obtained by the Cassini Visual Infrared Mapping Spectrometer (VIMS) instrument between 0.4 and 5.2 microns show the moon has a surge similar to that seen on other icy bodies, increasing in brightness by over 30% in the last five degrees. During the closest nontargeted flyby by Cassini on February 13, 2010, when the Cassini spacecraft approached within 9500 km of Mimas, maps of the moon were obtained by VIMS. Water ice absorption bands in the central peak and crater rim of Herschel are deeper than those in the surrounding regions. Preliminary results indicate the water ice grain size decreases as the distance from the apex of motion increases. No constituents other than water ice have yet been identified. Funded by NASA.

  6. Galileo SSI and Cassini ISS Observations of Io's Pele Hotspot: Temperatures, Areas, and Variation with Time

    Science.gov (United States)

    Radebaugh, J.; McEwen, A. S.; Milazzo, M.; Davies, A. G.; Keszthelyi, L. P.; Geissler, P.

    2002-01-01

    Temperatures of Io's Pele hotspot were found using dual-filter observations from Galileo and Cassini. Temperatures average 1375 K, but vary widely over tens of minutes. Dropoff in emission with rotation consistent with lava fountaining at a lava lake. Additional information is contained in the original extended abstract.

  7. Cassini Radio Science Experiments on Saturn and Titan Preserved Because of Lewis Analysis

    Science.gov (United States)

    Wilson, Jeffrey D.

    1999-01-01

    The Cassini mission to Saturn is an international venture with participation from NASA, the European Space Agency, and the Italian Space Agency. The Cassini spacecraft was launched from Cape Canaveral in October 1997 and is scheduled to arrive at Saturn in July 2004. After arrival, the spacecraft will orbit Saturn about 60 times over a period of 4 years. During this time, the Cassini Radio Science Subsystem will be used to investigate the atmosphere and rings of Saturn and the atmosphere of its largest moon, Titan--which is larger than Mercury and is the only moon in our solar system with a dense atmosphere. A critical component in Cassini s Radio Science Subsystem is a traveling-wave tube (TWT) that was designed at the NASA Lewis Research Center and built by Hughes Electronic Dynamics Division (ref. 1). This TWT will amplify downlink microwave signals at a frequency of 32 GHz for the Deep Space Network and will be involved in a number of experiments. These include occultation experiments in which the microwave signal will be beamed through rings and atmospheres toward Earth. Researchers will analyze the received signals to determine the sizes and distributions of the particles in the rings and the structure and composition of the atmospheres. The Radio Science Subsystem also will also be used to more accurately determine the mass and size of Saturn and its moons, to investigate the solar corona, and to search for gravity waves from outside the solar system.

  8. Galileo SSI and Cassini ISS Observations of Io's Pele Hotspot: Temperatures, Areas, and Variation with Time

    Science.gov (United States)

    Radebaugh, J.; McEwen, A. S.; Milazzo, M.; Davies, A. G.; Keszthelyi, L. P.; Geissler, P.

    2002-01-01

    Temperatures of Io's Pele hotspot were found using dual-filter observations from Galileo and Cassini. Temperatures average 1375 K, but vary widely over tens of minutes. Dropoff in emission with rotation consistent with lava fountaining at a lava lake. Additional information is contained in the original extended abstract.

  9. Cassini Radio Science Experiments on Saturn and Titan Preserved Because of Lewis Analysis

    Science.gov (United States)

    Wilson, Jeffrey D.

    1999-01-01

    The Cassini mission to Saturn is an international venture with participation from NASA, the European Space Agency, and the Italian Space Agency. The Cassini spacecraft was launched from Cape Canaveral in October 1997 and is scheduled to arrive at Saturn in July 2004. After arrival, the spacecraft will orbit Saturn about 60 times over a period of 4 years. During this time, the Cassini Radio Science Subsystem will be used to investigate the atmosphere and rings of Saturn and the atmosphere of its largest moon, Titan--which is larger than Mercury and is the only moon in our solar system with a dense atmosphere. A critical component in Cassini s Radio Science Subsystem is a traveling-wave tube (TWT) that was designed at the NASA Lewis Research Center and built by Hughes Electronic Dynamics Division (ref. 1). This TWT will amplify downlink microwave signals at a frequency of 32 GHz for the Deep Space Network and will be involved in a number of experiments. These include occultation experiments in which the microwave signal will be beamed through rings and atmospheres toward Earth. Researchers will analyze the received signals to determine the sizes and distributions of the particles in the rings and the structure and composition of the atmospheres. The Radio Science Subsystem also will also be used to more accurately determine the mass and size of Saturn and its moons, to investigate the solar corona, and to search for gravity waves from outside the solar system.

  10. Clumping in the Cassini Division and C Ring: Constraints from Stellar Occultations

    Science.gov (United States)

    Colwell, J. E.; Jerousek, R. G.; Esposito, L. W.

    2014-12-01

    Particles in Saturn's rings are engaged in a constant tug-of-war between interparticle gravitational and adhesive forces that lead to clumping, on the one hand, and Keplerian shear that inhibits accretion on the other. Depending on the surface mass density of the rings and the local orbital velocity, ephemeral clumps or self-gravity wakes can form, giving the rings granularity on the scale of the most-unstable length scale against gravitational collapse. The A ring and many regions of the B ring are dominated by self-gravity wakes with a typical radial wavelength of ~50-100 m. A characteristic of self-gravity wakes is that they can effectively shadow the relatively empty spaces in between them, depending on viewing geometry. This leads to geometry-dependent measurements of optical depth in occultations of the rings. The C ring and Cassini Division have significantly lower surface mass densities than the A and B ring such that in most of these regions the most-unstable wavelength is comparable to the size of the ring particles (~1 m) so that self-gravity wake formation is not expected nor have its characteristics in various measurements been observed. Here we present measurements of the optical depth of the C ring and Cassini Division with the Cassini Ultraviolet Imaging Spectrograph (UVIS) showing variations with viewing geometry in the "ramp" regions and the Cassini Division "triple band". These variations are characteristic of self-gravity wakes. We place limits on clumping in other regions of the C ring and Cassini Division.

  11. Etude theorique des fluctuations structurales dans les composes organiques a dimensionnalite reduite

    Science.gov (United States)

    Dumoulin, Benoit

    Les systemes a dimensionnalite reduite constituent maintenant une branche entiere de la physique de la matiere condensee. Cette derniere s'est developpee rapidement au cours des dernieres annees, avec la decouverte des materiaux organiques qui presentent, justement, des proprietes physiques fortement anisotropes. Cette these presente une etude en trois parties de plusieurs composes organiques qui, bien que tres differents du point de vue de leurs compositions chimiques et de leurs proprietes physiques a haute temperature, subissent tous une instabilite structurale a tres basse temperature. De plus, dans chacun des cas, l'instabilite structurale est precedee d'un important regime fluctuatif a partir duquel les proprietes physiques changent de maniere significative. Notre etude suit un ordre chronologique inverse puisque nous nous attardons en premier lieu au cas de composes recemment decouverts: les composes de la famille des (BCPTTF)2X (X = PF6 , AsF6). Ces derniers sont des isolants magnetiques a la temperature ambiante et subissent une instabilite structurale de type spin-Peierls a une temperature appelee TSP. En particulier, nous nous interessons a l'etude des proprietes physiques de ces systemes dans le regime fluctuatif, qui precede cette instabilite. Notre etude theorique nous permet de comprendre en detail comment ces systemes s'approchent de l'instabilite struturale. Dans la seconde partie de cette these, nous etudions le regime fluctuatif (pre-transitionnel) observe experimentalement dans le compose de (TMTTF)2PF6. Ce compose organique, dont la structure s'apparente aux sels de Bechgaard, subit une instabilite de type spin-Peierls a une temperature T SP = 19K. Bien que ce compose possede la particularite d'etre un bon conducteur a la temperature ambiante, il subit une transition de type Mott-Hubbard a une temperature Trho ≈ 220K et devient alors un isolant magnetique, analogue aux composes de la famille des (BCPTTF)2X. Le regime fluctuatif precedant l

  12. SATURNʼS INNER SATELLITES: ORBITS, MASSES, AND THE CHAOTIC MOTION OF ATLAS FROM NEW CASSINI IMAGING OBSERVATIONS

    National Research Council Canada - National Science Library

    Cooper, Nicholas J; Renner, Stéfan; Murray, Carl D; Evans, Michael W

    2015-01-01

    We present numerically derived orbits and mass estimates for the inner Saturnian satellites, Atlas, Prometheus, Pandora, Janus, and Epimetheus from a fit to 2580 new Cassini Imaging Science Subsystem...

  13. Cassini Scientist for a Day: Encouraging Science Research and Writing for Students on National and International Scales

    Science.gov (United States)

    Zimmerman Brachman, R.; Wessen, A.; Piazza, E.

    2011-10-01

    The outreach team for the Cassini mission to Saturn at NASA's Jet Propulsion Laboratory (JPL) runs an international essay contest called "Cassini Scientist for a Day." Students write essays about Saturn and its rings and moons. The program has been run nine times, increasing in scope with each contest. Students in grades 5 to 12 (ages 10 to 18) gain skills in critical thinking, decision-making, researching, asking good questions, and communicating their ideas to scientists. Winners and their classes participate in teleconferencing question-and-answer sessions with Cassini scientists so students can ask questions to professional scientists. Videos of young Cassini scientists are included in the contest reference materials to provide role models for the students. Thousands of students in 50 countries on 6 continents have participated in the essay contest. Volunteers run the international contests outside of the United States, with their own rules, languages, and prizes.

  14. Lightning on Saturn observed by Cassini ISS and RPWS during 2006-2009

    Science.gov (United States)

    Dyudina, U.; Ingersoll, A. P.; Ewald, S. P.; Porco, C.; Fischer, G.

    2009-12-01

    Throughout the Cassini mission thousands of images had been taken on the night side of saturn in search for optical lightning flashes. No flashes were unambiguously detected so far. The reasons for that may be the lightning located too deep and covered by the thick clouds, and thus faint as seen from the orbit, cosmic rays hitting the detector that could be confused with lightning, and the ringshine compromising the observations both by potential saturation of the images and by illuminating small convective clouds whose shape in reflected light can be confused with lightning flash. The only time of nearly zero ringshine in the 30-year-long Saturnian year is during the equinox, which happened on August 11, 2009. Cassini ISS took 211 lightning search images within ten days from the equinox. We will report on possible lightning detections in those images and also in the previous Cassini ISS lightning searches. We also report on Cassini Imaging Science Subsystem (ISS) and Radio and Plasma Wave Science (RPWS) observations that indicate lightning on Saturn. A lightning storm that began in 2007 lasted for 7.5 months. Another storm started in mid-January 2009 and was still active in August of 2009. We will compare these recent storms with those studied by Cassini in 2004 and 2006. In all cases, radio emissions (Saturn Electrostatic Discharges, or SEDs) occur when a rare bright cloud erupts at a unique latitude ˜ 35 degrees South (planetocentric).The cloud typically lasts for several weeks to months, and then both the cloud and the SEDs disappear.The cloud and SED's reappear synchronously after being inactive for several months. The SEDs are periodic with roughly Saturn's rotation rate, and show correlated phase relative to the times when the clouds are seen on the spacecraft-facing side of the planet. The storm clouds erupt to unusually high altitudes and then slowly descend and spread.The eruption lasts for less than a day during which time the SEDs reach their maximum

  15. Cratering on Titan: A Pre-Cassini Perspective

    Science.gov (United States)

    Lorenz, R. D.

    1997-01-01

    The NASA-ESA Cassini mission, comprising a formidably instrumented orbiter and parachute-borne probe to be launched this October, promises to reveal a crater population on Titan that has been heretofore hidden by atmospheric haze. This population on the largest remaining unexplored surface in the solar system will be invaluable in comparative planetological studies, since it introduces evidence of the atmospheric effects of cratering on an icy satellite. Here, I highlight some impact features we may hope to find and could devote some modeling effort toward. Titan in a Nutshell: Radius= 2575 km. Density= 1880 kg/cubic m consistent with rock-ice composition. Surface pressure = 1.5 bar. Surface gravity = 1.35 m/square s Atmosphere -94% N2 6% CH, Surface temperature = 94K Tropopause temperature = 70K at 40 km alt. Probable liquid hydrocarbon deposits exist on or near the surface.Titan in a Nutshell: Radius= 2575 km. Density= 1880 kg/cubic m consistent with rock-ice composition. Surface pressure = 1.5 bar. Surface gravity = 1.35 m/square s; Atmosphere about 94% N2 6% CH, Surface temperature = 94K Tropopause temperature = 70K at 40 km alt. Probable liquid hydrocarbon deposits exist on or near the surface. Titan is comparable to Callisto and Ganymede for strength/gravity, Mars/Earth/Venus for atmospheric interaction, and Hyperion, Rhea, and Iapetus for impactor distribution. The leading/trailing asymmetry of crater density from heliocentric impactors is expected to be about 5-6, in the absence of resurfacing. Any Saturnocentric impactor population is likely to alter this. In particular the impact disruption of Hyperion is noted; because of the 3:4 orbital resonance with Titan, fragments from the proto-Hyperion breakup would have rapidly accreted onto Titan. Titan's resurfacing history is of course unknown. The disruption of impactors into fragments that individually create small craters is expected to occur. A crude estimate suggests a maximum separation of about 2 km

  16. Cratering on Titan: A Pre-Cassini Perspective

    Science.gov (United States)

    Lorenz, R. D.

    1997-01-01

    The NASA-ESA Cassini mission, comprising a formidably instrumented orbiter and parachute-borne probe to be launched this October, promises to reveal a crater population on Titan that has been heretofore hidden by atmospheric haze. This population on the largest remaining unexplored surface in the solar system will be invaluable in comparative planetological studies, since it introduces evidence of the atmospheric effects of cratering on an icy satellite. Here, I highlight some impact features we may hope to find and could devote some modeling effort toward. Titan in a Nutshell: Radius= 2575 km. Density= 1880 kg/cubic m consistent with rock-ice composition. Surface pressure = 1.5 bar. Surface gravity = 1.35 m/square s Atmosphere -94% N2 6% CH, Surface temperature = 94K Tropopause temperature = 70K at 40 km alt. Probable liquid hydrocarbon deposits exist on or near the surface.Titan in a Nutshell: Radius= 2575 km. Density= 1880 kg/cubic m consistent with rock-ice composition. Surface pressure = 1.5 bar. Surface gravity = 1.35 m/square s; Atmosphere about 94% N2 6% CH, Surface temperature = 94K Tropopause temperature = 70K at 40 km alt. Probable liquid hydrocarbon deposits exist on or near the surface. Titan is comparable to Callisto and Ganymede for strength/gravity, Mars/Earth/Venus for atmospheric interaction, and Hyperion, Rhea, and Iapetus for impactor distribution. The leading/trailing asymmetry of crater density from heliocentric impactors is expected to be about 5-6, in the absence of resurfacing. Any Saturnocentric impactor population is likely to alter this. In particular the impact disruption of Hyperion is noted; because of the 3:4 orbital resonance with Titan, fragments from the proto-Hyperion breakup would have rapidly accreted onto Titan. Titan's resurfacing history is of course unknown. The disruption of impactors into fragments that individually create small craters is expected to occur. A crude estimate suggests a maximum separation of about 2 km

  17. On what we have learned about the system of Saturn thanks to Cassini

    Science.gov (United States)

    El Moutamid, Maryame; Hedman, Matthew M.; Nicholson, Philip D.; Tiscareno, Matthew S.; Tajeddine, Radwan; Burns, Joseph A.

    2017-06-01

    This is the end; Cassini will crash into Saturn’s atmosphere within few months, providing unique data and results thanks to the last orbits. After losing contact with us, it will become part of the planet itself.By September 2017, Cassini will have spent 13 years in orbit around Saturn, during this period, scientists from the world have collected data from many instruments and have learned a great deal about the planet itself, its rings and satellites, and the connection between them. I will present some of the results on what we have learned about the evolution of the moons, on the main rings of Saturn and their dynamical connection with the interior of the planet.

  18. Skirting Saturn's Rings and Skimming Its Cloud Tops: Planning Cassini's End of Mission

    Science.gov (United States)

    Manor-Chapman, Emily; Magee, Kari; Brooks, Shawn; Edgington, Scott; Heventhal, William; Sturm, Erick

    2014-01-01

    In October 2010, the Cassini spacecraft embarked on the seven-year Solstice Mission. The mission will culminate with a spectacular series of orbits that bring Cassini between Saturn's innermost ring, the D ring, and the cloud tops of the planet. The spacecraft will make its closest passages ever to the planet allowing for unprecedented science to be collected on Saturn and its rings. These final orbits will expose the spacecraft to new environments, which presents a number of challenges to planning the final mission phase. While these challenges will require adaptations to planning processes and operations, they are not insurmountable. This paper describes the challenges identified and the steps taken to mitigate them to enable collection of unique Saturn system science.

  19. Fast forward modeling of Titan's infrared spectra to invert VIMS/Cassini hyperspectral images

    Science.gov (United States)

    Rodriguez, S.; Le Mouélic, Stéphane; Rannou, P.; Combe, J.-P.; Corre, L.L.; Tobie, G.; Barnes, J.W.; Sotin, Christophe; Brown, R.H.; Baines, K.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.

    2009-01-01

    The surface of Titan, the largest icy moon of Saturn, is veiled by a very thick and hazy atmosphere. The Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft, in orbit around Saturn since July 2004, conduct an intensive survey of Titan with the objective to understand the complex nature of the atmosphere and surface of the mysterious moon and the way they interact. Accurate radiative transfer modeling is necessary to analyze Titan's infrared spectra, but are often very computer resources demanding. As Cassini has gathered hitherto millions of spectra of Titan and will still observe it until at least 2010, we report here on the development of a new rapid, simple and versatile radiative transfer model specially designed to invert VIMS datacubes. ?? 2009 IEEE.

  20. Cassini UVIS Observations of the Io Plasma Torus. IV. Modeling Temporal and Azimuthal Variability

    CERN Document Server

    Steffl, A J; Bagenal, F

    2007-01-01

    In this fourth paper in a series, we present the results of our efforts to model the remarkable temporal and azimuthal variability of the Io plasma torus during the Cassini encounter with Jupiter. The long-term (months) temporal variation in the average torus composition observed by the Cassini Ultraviolet Imaging Spectrograph (UVIS) can be modeled by supposing a factor of ~4 increase in the amount of material supplied to the extended neutral clouds that are the source of torus plasma, followed by a gradual decay to more "typical" values. On shorter timescales, the observed 10.07-hour torus periodicity and azimuthal variation in plasma composition, including its surprising modulation with System III longitude, is reproduced by our model using the superposition of two azimuthal variations of suprathermal electrons: a primary hot electron variation that slips 12.5 degrees/day relative to the Jovian magnetic field and a secondary variation that remains fixed in System III longitude.

  1. Cassini Returns to Saturn's Poles: Seasonal Change in the Polar Vortices

    Science.gov (United States)

    Fletcher, Leigh N.; Orton, G. S.; Irwin, P. G. J.; Sinclair, J. A.; Hesman, B. E.; Hurley, J.; Bjoraker, G. L.; Simon-Miller, A. A.

    2013-01-01

    High inclination orbits during Cassini's solstice mission (2012) are providing us with our first observations of Saturn's high latitudes since the prime mission (2007). Since that time, the northern spring pole has emerged into sunlight and the southern autumn pole has disappeared into winter darkness, allowing us to study the seasonal changes occurring within the polar vortices in response to these dramatic insolation changes. Observations from the Cassini Composite Infrared Spectrometer] have revealed (i) the continued presence of small, cyclonic polar hotspots at both spring and autumn poles; and (ii) the emergence of an infrared-bright polar vortex at the north pole, consistent with the historical record of Saturn observations from the 1980s (previous northern spring).

  2. METER-SIZED MOONLET POPULATION IN SATURN'S C RING AND CASSINI DIVISION

    Energy Technology Data Exchange (ETDEWEB)

    Baillie, Kevin; Colwell, Joshua E. [Department of Physics, University of Central Florida, Orlando, FL 32816-2385 (United States); Esposito, Larry W. [Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, 392 UCB, Boulder, CO 80309-0392 (United States); Lewis, Mark C., E-mail: kevin.baillie@cea.fr [Department of Computer Science, Trinity University, One Trinity Place, San Antonio, TX 78212-7200 (United States)

    2013-06-01

    Stellar occultations observed by the Cassini Ultraviolet Imaging Spectrograph reveal the presence of transparent holes a few meters to a few tens of meters in radial extent in otherwise optically thick regions of the C ring and the Cassini Division. We attribute the holes to gravitational disturbances generated by a population of {approx}10 m boulders in the rings that is intermediate in size between the background ring particle size distribution and the previously observed {approx}100 m propeller moonlets in the A ring. The size distribution of these boulders is described by a shallower power-law than the one that describes the ring particle size distribution. The number and size distribution of these boulders could be explained by limited accretion processes deep within Saturn's Roche zone.

  3. Cassini Spacecraft In-Flight Swap to Backup Attitude Control Thrusters

    Science.gov (United States)

    Bates, David M.

    2010-01-01

    NASA's Cassini Spacecraft, launched on October 15th, 1997 and arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. In order to meet the challenging attitude control and navigation requirements of the orbit profile at Saturn, Cassini is equipped with a monopropellant thruster based Reaction Control System (RCS), a bipropellant Main Engine Assembly (MEA) and a Reaction Wheel Assembly (RWA). In 2008, after 11 years of reliable service, several RCS thrusters began to show signs of end of life degradation, which led the operations team to successfully perform the swap to the backup RCS system, the details and challenges of which are described in this paper. With some modifications, it is hoped that similar techniques and design strategies could be used to benefit other spacecraft.

  4. Cassini Orbit Trim Maneuvers at Saturn - Overview of Attitude Control Flight Operations

    Science.gov (United States)

    Burk, Thomas A.

    2011-01-01

    The Cassini spacecraft has been in orbit around Saturn since July 1, 2004. To remain on the planned trajectory which maximizes science data return, Cassini must perform orbit trim maneuvers using either its main engine or its reaction control system thrusters. Over 200 maneuvers have been executed on the spacecraft since arrival at Saturn. To improve performance and maintain spacecraft health, changes have been made in maneuver design command placement, in accelerometer scale factor, and in the pre-aim vector used to align the engine gimbal actuator prior to main engine burn ignition. These and other changes have improved maneuver performance execution errors significantly since 2004. A strategy has been developed to decide whether a main engine maneuver should be performed, or whether the maneuver can be executed using the reaction control system.

  5. Cassini Spacecraft In-Flight Swap to Backup Attitude Control Thrusters

    Science.gov (United States)

    Bates, David M.

    2010-01-01

    NASA's Cassini Spacecraft, launched on October 15th, 1997 and arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. In order to meet the challenging attitude control and navigation requirements of the orbit profile at Saturn, Cassini is equipped with a monopropellant thruster based Reaction Control System (RCS), a bipropellant Main Engine Assembly (MEA) and a Reaction Wheel Assembly (RWA). In 2008, after 11 years of reliable service, several RCS thrusters began to show signs of end of life degradation, which led the operations team to successfully perform the swap to the backup RCS system, the details and challenges of which are described in this paper. With some modifications, it is hoped that similar techniques and design strategies could be used to benefit other spacecraft.

  6. Cusp observation at Saturn's high-latitude magnetosphere by the Cassini spacecraft

    Science.gov (United States)

    Jasinski, J. M.; Arridge, C. S.; Lamy, L.; Leisner, J. S.; Thomsen, M. F.; Mitchell, D. G.; Coates, A. J.; Radioti, A.; Jones, G. H.; Roussos, E.; Krupp, N.; Grodent, D.; Dougherty, M. K.; Waite, J. H.

    2014-03-01

    We report on the first analysis of magnetospheric cusp observations at Saturn by multiple in situ instruments onboard the Cassini spacecraft. Using this we infer the process of reconnection was occurring at Saturn's magnetopause. This agrees with remote observations that showed the associated auroral signatures of reconnection. Cassini crossed the northern cusp around noon local time along a poleward trajectory. The spacecraft observed ion energy-latitude dispersions—a characteristic signature of the terrestrial cusp. This ion dispersion is "stepped," which shows that the reconnection is pulsed. The ion energy-pitch angle dispersions suggest that the field-aligned distance from the cusp to the reconnection site varies between ˜27 and 51 RS. An intensification of lower frequencies of the Saturn kilometric radiation emissions suggests the prior arrival of a solar wind shock front, compressing the magnetosphere and providing more favorable conditions for magnetopause reconnection.

  7. High Angular Resolution Stellar Imaging with Occultations from the Cassini Spacecraft I: Observational Technique

    CERN Document Server

    Stewart, Paul N; Hedman, Matthew M; Nicholson, Philip D; Lloyd, James P

    2013-01-01

    We present novel observations utilising the Cassini spacecraft to conduct an observing campaign for stellar astronomy from a vantage point in the outer solar system. By exploiting occultation events in which Mira passed behind the Saturnian ring plane as viewed by Cassini, parametric imaging data were recovered spanning the near-infrared. From this, spatial information at extremely high angular resolution was recovered enabling a study of the stellar atmospheric extension across a spectral bandpass spanning the 1 - 5 {\\mu}m spectral region in the near-infrared. The resulting measurements of the angular diameter of Mira were found to be consistent with existing observations of its variation in size with wavelength. The present study illustrates the validity of the technique; more detailed exploration of the stellar physics obtained by this novel experiment will be the subject of forthcoming papers.

  8. Upper limits for PH3 and H2S in Titan's Atmosphere from Cassini CIRS

    CERN Document Server

    Nixon, Conor A; Irwin, Patrick G J; Horst, Sarah M; 10.1016/j.icarus.2013.02.024

    2013-01-01

    We have searched for the presence of simple P and S-bearing molecules in Titan's atmosphere, by looking for the characteristic signatures of phosphine and hydrogen sulfide in infrared spectra obtained by Cassini CIRS. As a result we have placed the first upper limits on the stratospheric abundances, which are 1 ppb (PH3) and 330 ppb (H2S), at the 2-sigma significance level.

  9. Inflight Performance of Cassini Reaction Wheel Bearing Drag in 1997-2013

    Science.gov (United States)

    Lee, Allan Y.; Wang, Eric K.

    2013-01-01

    As the first spacecraft to achieve orbit at Saturn in 2004, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended missions through September 2017. Cassini is a three-axis stabilized spacecraft. It uses reaction wheels to achieve high level of spacecraft pointing stability that is needed during imaging operations of several science instruments. The Cassini flight software makes in-flight estimates of reaction wheel bearing drag torque and made them available to the mission operations team. These telemetry data are being trended for the purpose of monitoring the long-term health of the reaction wheel bearings. Anomalous drag torque signatures observed over the past 15 years are described in this paper. One of these anomalous drag conditions is bearing cage instability that appeared (and disappeared) spontaneously and unpredictably. Cage instability is an uncontrolled vibratory motion of the bearing cage that can produce high-impact forces internal to the bearing that will cause intermittent and erratic torque transients. Characteristics of the observed cage instabilities and other drag torque "spikes" are described in this paper. In day-to-day operations, the reaction wheels' rates must be neither too high nor too low. To protect against operating the wheels in any undesirable conditions (such as prolonged low spin rate operations), a ground software tool named Reaction Wheel Bias Optimization Tool (RBOT) was developed for the management of the wheels. Disciplined and long-term use of this ground software has led to significant reduction in the daily consumption rate of the wheels' low spin rate dwell time. Flight experience on the use of this ground software tool as well as other lessons learned on the management of Cassini reaction wheels is given in this paper.

  10. Impact of aerosols present in Titan's atmosphere on the CASSINI radar experiment

    Science.gov (United States)

    Rodriguez, S.; Paillou, P.; Dobrijevic, M.; Ruffié, G.; Coll, P.; Bernard, J. M.; Encrenaz, P.

    2003-07-01

    Simulations of Titan's atmospheric transmission and surface reflectivity have been developed in order to estimate how Titan's atmosphere and surface properties could affect performances of the Cassini radar experiment. In this paper we present a selection of models for Titan's haze, vertical rain distribution, and surface composition implemented in our simulations. We collected dielectric constant values for the Cassini radar wavelength (˜2.2 cm) for materials of interest for Titan: liquid methane, liquid mixture of methane-ethane, water ice, and light hydrocarbon ices. Due to the lack of permittivity values for Titan's haze particles in the microwave range, we performed dielectric constant ( ɛr) measurements around 2.2 cm on tholins synthesized in laboratory. We obtained a real part of ɛr in the range of 2-2.5 and a loss tangent between 10 -3 and 5×10 -2. By combining aerosol distribution models (with hypothetical condensation at low altitudes) to surface models, we find the following results: (1) Aerosol-only atmospheres should cause no loss and are essentially transparent for Cassini radar, as expected by former analysis. (2) However, if clouds are present, some atmospheric models generate significant attenuation that can reach -50 dB, well below the sensitivity threshold of the receiver. In such cases, a 13.78 GHz radar would not be able to measure echoes coming from the surface. We thus warn about possible risks of misinterpretation if a "wet atmosphere" is not taken into account. (3) Rough surface scattering leads to a typical response of ˜-17 dB. These results will have important implications on future Cassini radar data analysis.

  11. Cassini RTG program. Monthly technical progress report, September 29, 1997--October 26, 1997

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-11-24

    This report describes work on the contract to provide Radioisotope Thermoelectric Generators (RTG) and Ancillary Activities in support of the Cassini Spacecraft launch. The craft was successfully launched on October 15, 1997. Early telemetry results show excellent performance from the three launched RTG modules. A major share of this report describes safety analyses for contamination radii in the event of launch failures and generator destruction, as well as launch related activities.

  12. Irregular-Moons Science Today and in Cassini's Final Three Years

    Science.gov (United States)

    Denk, T.; Mottola, S.

    2014-12-01

    The outer or irregular moons belong to the by far most numerous, but least investigated group of moons in the Saturnian system. The group is comprised of at least 38, mainly small objects which orbit at quite large distances to the planet, the rings, the inner regular moon system, and the Cassini spacecraft. As seen from Earth, their apparent visual magnitudes mainly range from ~20 to >25, the phase angles from 0 to 6°. From Cassini, some irregular moons can reach pole-axis directions, convex-hull shapes, and sidereal periods. So far, lightcurve inversion of Ymir revealed a convex shape reminiscent to a triangular prism and a spin-axis direction close to the South Ecliptic pole. The figure shows the lightcurve at 64° phase (bottom left panel), and four equatorial and two polar views of the derived shape model are shown at bottom right. Within Cassini's final three years in Saturn orbit, further observations offer the potential of pole and shape determinations for up to 15 irregular moons and up to 30 rotational periods total. These data may reveal (or already do so) hemispherical color variations, limits for object densities and sizes, pole-direction patterns, correlations of spin frequencies to orbit parameters, and hints for contact binaries or binary natures of the moons. Such information, besides its value per se, provides constraints for the investigation on the formation and evolutionary processes within the Saturnian satellite system.

  13. Estimation of Gravitation Parameters of Saturnian Moons Using Cassini Attitude Control Flight Data

    Science.gov (United States)

    Krening, Samantha C.

    2013-01-01

    A major science objective of the Cassini mission is to study Saturnian satellites. The gravitational properties of each Saturnian moon is of interest not only to scientists but also to attitude control engineers. When the Cassini spacecraft flies close to a moon, a gravity gradient torque is exerted on the spacecraft due to the mass of the moon. The gravity gradient torque will alter the spin rates of the reaction wheels (RWA). The change of each reaction wheel's spin rate might lead to overspeed issues or operating the wheel bearings in an undesirable boundary lubrication condition. Hence, it is imperative to understand how the gravity gradient torque caused by a moon will affect the reaction wheels in order to protect the health of the hardware. The attitude control telemetry from low-altitude flybys of Saturn's moons can be used to estimate the gravitational parameter of the moon or the distance between the centers of mass of Cassini and the moon. Flight data from several low altitude flybys of three Saturnian moons, Dione, Rhea, and Enceladus, were used to estimate the gravitational parameters of these moons. Results are compared with values given in the literature.

  14. Estimation of Gravitation Parameters of Saturnian Moons Using Cassini Attitude Control Flight Data

    Science.gov (United States)

    Krening, Samantha C.

    2013-01-01

    A major science objective of the Cassini mission is to study Saturnian satellites. The gravitational properties of each Saturnian moon is of interest not only to scientists but also to attitude control engineers. When the Cassini spacecraft flies close to a moon, a gravity gradient torque is exerted on the spacecraft due to the mass of the moon. The gravity gradient torque will alter the spin rates of the reaction wheels (RWA). The change of each reaction wheel's spin rate might lead to overspeed issues or operating the wheel bearings in an undesirable boundary lubrication condition. Hence, it is imperative to understand how the gravity gradient torque caused by a moon will affect the reaction wheels in order to protect the health of the hardware. The attitude control telemetry from low-altitude flybys of Saturn's moons can be used to estimate the gravitational parameter of the moon or the distance between the centers of mass of Cassini and the moon. Flight data from several low altitude flybys of three Saturnian moons, Dione, Rhea, and Enceladus, were used to estimate the gravitational parameters of these moons. Results are compared with values given in the literature.

  15. Analysis of Clumps in Saturn's F Ring from Voyager and Cassini

    CERN Document Server

    French, Robert S; Showalter, Mark R; Antonsen, Adrienne K; Packard, Douglas R

    2014-01-01

    Saturn's F ring is subject to dynamic structural changes over short periods. Among the observed phenomena are diffuse extended bright clumps (ECs) ~ 3-40 degrees in longitudinal extent. These ECs appear, evolve, and disappear over a span of days to months. ECs have been seen by the two Voyager spacecraft, the Cassini orbiter, and various ground- and space-based telescopes. Showalter (2004, Icarus, 171, 356-371) analyzed all Voyager images of the F ring and found that there were 2-3 major and 20-40 minor ECs present in the ring at any given time. We expand upon these results by comparing the ECs seen by Voyager to those seen by Cassini in 2004-2010. We find that the number of minor ECs has stayed roughly constant and the ECs have similar distributions of angular width, absolute brightness, and semimajor axis. However, the common exceptionally bright ECs seen by Voyager are now exceedingly rare, with only two instances seen by Cassini in the six years, and they are now also much dimmer relative to the mean ring...

  16. A Decade of Cassini Radio Science so Far, and Three Spectacular Years Ahead

    Science.gov (United States)

    French, R. G.; Armstrong, J. W.; Flasar, F. M.; Iess, L.; Kliore, A. J.; Marouf, E. A.; McGhee-French, C.; Nagy, A. F.; Rappaport, N. J.; Schinder, P. J.; Tortora, P.; Anabtawi, A.; Asmar, S. W.; Barbinis, E.; Fleischman, D. U.; Kahan, D. S.

    2014-12-01

    Over the past decade, the Cassini RSS (Radio Science Subsystem) instrument has provided fundamental new insights into many aspects of the Saturn system. Taking advantage of the capability to use up to three simultaneous wavelengths (Ka, X, and S bands), a series of occultation experiments of Titan and Saturn have provided detailed vertical profiles of the atmospheric and ionospheric structure, exhibiting seasonal and regional variability. Gravity experiments, conducted during close flybys of Saturn's moons, have yielded information about their internal structure, including evidence of sub-surface oceans on Titan and Enceladus. From dozens of ring occultation experiements, the radial structure, scattering properties, and particle sizes of the rings have been measured to high precision, enabling detailed comparative studies of ring dynamics and orbital characteristics. Recent bistatic observations of Titan, in which the transmitted signal reflects off of the specular point and is received on Earth, have traversed the northern polar regions, crossing the boundaries between seas and land, showing that the surface of the seas is remarkably smooth, and providing information about the dielectric properties of the liquids and surface materials. The best is yet to come, during the final three years of the Cassini mission, when the RSS instrument will observe the rings in a series of occultation measurements at their most favorable geometry of the entire Cassini mission, and a companion set of close fly-bys of Saturn will provide the first detailed determination of Saturn's gravitational field.

  17. Cassini capturing of freshly-produced water-group ions in the Enceladus torus

    Science.gov (United States)

    Yaroshenko, V. V.; Miloch, W. J.; Thomas, H. M.; Morfill, G. E.

    2012-09-01

    The water vapor plume on the geological-active south-polar region of the moon Enceladus is recognized as the main source of Saturn's neutral torus centered on the Enceladus orbit. The composition of the torus is dominated by water group species. Recent in situ Cassini plasma spectrometer measurements indicate the existence of freshly produced, slow and non-thermalized water group ions throughout the Enceladus torus including regions far from the moon. We report the results of modeling spacecraft-plasma interactions in the environment relevant for the Enceladus torus to show that new-born non-thermalized ions will inevitably be captured by the electric fields arising around the charged spacecraft. The associated plasma configuration can directly impact the plasma measurements and thus is important for reliable interpretation of data obtained by Cassini instruments in the Enceladus torus. The simulation results appear to be partially supported by Cassini observations and can provide new insights into intricate process of Enceladus-plasma interactions.

  18. Cassini Observations During the Saturn Auroral Campaign of Spring 2013 (Invited)

    Science.gov (United States)

    Kurth, W. S.; Lamy, L.; Gurnett, D. A.; Mitchell, D. G.; Dougherty, M. K.; Bunce, E. J.; Badman, S. V.; Burton, M. E.; Crary, F. J.; Pryor, W. R.; Baines, K. H.; Dyudina, U.; Nichols, J. D.; Stallard, T.; Luhmann, J. G.; Zheng, Y.; Hansen, K. C.

    2013-12-01

    During April and May 2013, a concerted effort to study Saturn's auroras was mounted using multi-wavelength observations from Cassini and a number of Earth-based observations. This paper will focus on the Cassini observations acquired during the campaign with an emphasis on the fields and particle observations and Saturn Kilometric Radiation, in particular. It has been shown that the integrated power of Saturn Kilometric Radiation (SKR) provides a good proxy for auroral activity and there is at least a qualitative correlation between auroral brightness and SKR intensity. While the SKR observations can be complicated by beaming issues, they provide a reasonable, continuous context within which to place other observations. We compare the time history of SKR intensity with models of the solar wind input based on models which propagate 1 AU observations to the distance of Saturn. Further, direction-finding measurements of the SKR reveal the source of the SKR and these can be related to Earth-based and Cassini-based observations of the auroras. In this paper we will use the SKR observations to construct the evolution of auroral activity and place other in situ and remote sensing observations within this context.

  19. Production of 238PuO2 heat sources for the Cassini mission

    Science.gov (United States)

    George, Timothy G.; Foltyn, Elizabeth M.

    1998-01-01

    NASA's Cassini mission to Saturn, scheduled to launch in October, 1997, is perhaps the most ambitious interplanetary explorer ever constructed. Electric power for the spacecraft's science instruments and on-board computers will be provided by three radioisotope thermoelectric generators (RTGs) powered by 216 238PuO2-fueled General-Purpose Heat Source (GPHS) capsules. In addition, critical equipment and instruments on the spacecraft and Huygens probe will be warmed by 128 Light-Weight Radioisotope Heater Units (LWRHUs). Fabrication and assembly of the GPHS capsules and LWRHU heat sources was performed at Los Alamos National Laboratory (LANL) between January 1994 and September 1996. During this production campaign, LANL pressed and sintered 315 GPHS fuel pellets and 181 LWRHU pellets. By October 1996, NMT-9 had delivered a total of 235 GPHS capsules to EG&G Mound Applied Technologies (EG&G MAT) in Miamisburg, Ohio. EG&G MAT conditioned the capsules for use, loaded the capsules into the Cassini RTGs, tested the RTGs, and coordinated transportation to Kennedy Space Center (KSC). LANL also fabricated and assembled a total of 180 LWRHUs. The LWRHUs required for the Cassini spacecraft were shipped to KSC in mid-1997.

  20. Contributions a L'etude de Dispositifs D'optique Integree

    Science.gov (United States)

    Touam, Tahar

    Cette these contient des contributions a l'etude de deux champs du vaste domaine de l'optique integree. A cet effet, nous avons divise notre travail en deux grandes parties:. Dans une premiere partie, nous traitons le probleme de la realisation d'une nouvelle classe de guides d'onde planaires utilisables dans le domaine de longueur d'onde de l'infrarouge moyen (infrarouge thermique), domaine ou l'apparition anticipee de fibres optiques a pertes extremement faibles rendraient fort interessante l'existence de tels guides d'onde planaires. Dans un premier temps, nous presentons une etude analytique originale d'une structure planaire a profil d'indice gradue, suivie d'une analyse d'un guide canal base sur cette structure. Dans un deuxieme temps, nous decrivons le procede de fabrication par pulverisation atomique d'un guide planaire forme d'arseniure de gallium (AsGa) sur du dioxyde de silicium (SiO_2 ), combinaison de materiau compatible avec l'infrarouge moyen. Finalement, nous presentons une etude de conception d'un reseau de surface destine a coupler la lumiere dans un tel guide, les autres methodes traditionnelles de couplage semblant peu appropriees aux environs de lambda = 10 mum. Dans une deuxieme partie, nous traitons le probleme de la jonction Y en optique integree, jonction qui soufre de pertes tres importantes des que l'angle d'ouverture devient interessant pour le concepteur de circuits integres optiques. L'analyse est basee sur la methode numerique dite BPM (Beam Propagation Method; methode de propagation du faisceau) qui fait l'objet d'un bref rappel. Nous poursuivons avec l'etude et l'optimisation d'une nouvelle jonction Y dont l'essence est l'utilisation du phenomene de diffraction a travers trois fentes de phase. Nous obtenons ainsi une tres bonne jonction, separant proprement le faisceau, a une ouverture de 10 degres. Finalement, nous faisons un rappel d'un profil d'indice dit "ideal" pour guides courbes et nous proposons l'utilisation de tels guides

  1. Bio-metric study of pig karyotype; Etude biometrique du caryotype du porc

    Energy Technology Data Exchange (ETDEWEB)

    Haag, J.; Lacourly, N.; Nizza, P. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    This study has a twofold purpose, the former is to determine the swine karyotype as accurately as possible, the latter is to try and develop a method of automatic classification and to show its possibilities and limits. (authors) [French] Cette etude a un double objet: d'une part, de definir de la facon aussi precise que possible le caryotype du porc et d'autre part, de tenter une methode de classification automatique et d'en montrer les possibilites ainsi que les limites. (auteurs)

  2. The mass of Saturn's B-ring from Cassini's Grand Finale orbits

    Science.gov (United States)

    Racioppa, Paolo; Durante, Daniele; Iess, Luciano

    2017-04-01

    Cassini is one of the most successful space missions of all times. Arrived at Saturn in 2004, it collected an enormous amount of scientific data on the atmosphere and the magnetosphere of the gas giant, its icy moons, and its rings. In the final part of journey, ending in a deliberate plunge into Saturn's atmosphere, the spacecraft will collect gravity and magnetic data from a distance as close as 3000 km from the cloud level. Those data are crucial to build interior models of the planet and to determine the depth of zonal winds. The Cassini radio science investigation will measure Saturn gravity field and the ring mass by means of range rate measurements enabled by the onboard X band (7.2-8.4 GHz) radio system and the antennas of NASA's Deep Space Network and ESA's tracking network. The gravity determination is obtained by fitting the radial velocity of the spacecraft at accuracies of about 0.05 mm/s (at a time scale of 60 s) through predictions obtained from a model of the orbital dynamics. Cassini orbital geometry is crucial for the gravity experiment. The highly eccentric 6-day orbit has a pericenter close to Saturn's clouds, within the inner edge of the rings. With Cassini passing between the rings and the planet, there is an excellent prospect to disentangle the strong acceleration due to Saturn's oblateness from that due to tiny pull of the rings. The mass of the rings (concentrated mostly in the B ring) remains uncertain. Its value, generally expressed in terms of Mimas masses, bears crucial information on how and when the rings formed, and their relation with Saturn and its moons. This work presents the final round of simulations of the gravity experiment in Cassini's Grand Finale orbits, using the latest trajectory, spacecraft configuration, and tracking coverage from ground. In particular, we will provide our current best estimate of the accuracy in the ring mass determination, just a few months prior to the actual measurements taking place in six orbits

  3. Expression of cassini, a murine gamma-satellite sequence conserved in evolution, is regulated in normal and malignant hematopoietic cells

    Directory of Open Access Journals (Sweden)

    Arutyunyan Anna

    2012-08-01

    Full Text Available Abstract Background Acute lymphoblastic leukemia (ALL cells treated with drugs can become drug-tolerant if co-cultured with protective stromal mouse embryonic fibroblasts (MEFs. Results We performed transcriptional profiling on these stromal fibroblasts to investigate if they were affected by the presence of drug-treated ALL cells. These mitotically inactivated MEFs showed few changes in gene expression, but a family of sequences of which transcription is significantly increased was identified. A sequence related to this family, which we named cassini, was selected for further characterization. We found that cassini was highly upregulated in drug-treated ALL cells. Analysis of RNAs from different normal mouse tissues showed that cassini expression is highest in spleen and thymus, and can be further enhanced in these organs by exposure of mice to bacterial endotoxin. Heat shock, but not other types of stress, significantly induced the transcription of this locus in ALL cells. Transient overexpression of cassini in human 293 embryonic kidney cells did not increase the cytotoxic or cytostatic effects of chemotherapeutic drugs but provided some protection. Database searches revealed that sequences highly homologous to cassini are present in rodents, apicomplexans, flatworms and primates, indicating that they are conserved in evolution. Moreover, CASSINI RNA was induced in human ALL cells treated with vincristine. Surprisingly, cassini belongs to the previously reported murine family of γ-satellite/major satellite DNA sequences, which were not known to be present in other species. Conclusions Our results show that the transcription of at least one member of these sequences is regulated, suggesting that this has a function in normal and transformed immune cells. Expression of these sequences may protect cells when they are exposed to specific stress stimuli.

  4. Expression of cassini, a murine gamma-satellite sequence conserved in evolution, is regulated in normal and malignant hematopoietic cells.

    Science.gov (United States)

    Arutyunyan, Anna; Stoddart, Sonia; Yi, Sun-ju; Fei, Fei; Lim, Min; Groffen, Paula; Feldhahn, Niklas; Groffen, John; Heisterkamp, Nora

    2012-08-23

    Acute lymphoblastic leukemia (ALL) cells treated with drugs can become drug-tolerant if co-cultured with protective stromal mouse embryonic fibroblasts (MEFs). We performed transcriptional profiling on these stromal fibroblasts to investigate if they were affected by the presence of drug-treated ALL cells. These mitotically inactivated MEFs showed few changes in gene expression, but a family of sequences of which transcription is significantly increased was identified. A sequence related to this family, which we named cassini, was selected for further characterization. We found that cassini was highly upregulated in drug-treated ALL cells. Analysis of RNAs from different normal mouse tissues showed that cassini expression is highest in spleen and thymus, and can be further enhanced in these organs by exposure of mice to bacterial endotoxin. Heat shock, but not other types of stress, significantly induced the transcription of this locus in ALL cells. Transient overexpression of cassini in human 293 embryonic kidney cells did not increase the cytotoxic or cytostatic effects of chemotherapeutic drugs but provided some protection. Database searches revealed that sequences highly homologous to cassini are present in rodents, apicomplexans, flatworms and primates, indicating that they are conserved in evolution. Moreover, CASSINI RNA was induced in human ALL cells treated with vincristine. Surprisingly, cassini belongs to the previously reported murine family of γ-satellite/major satellite DNA sequences, which were not known to be present in other species. Our results show that the transcription of at least one member of these sequences is regulated, suggesting that this has a function in normal and transformed immune cells. Expression of these sequences may protect cells when they are exposed to specific stress stimuli.

  5. Estimation and Modeling of Enceladus Plume Density Using Attitude Control Data Collected by the Cassini Spacecraft During Low-Altitude Enceladus Flybys

    Science.gov (United States)

    Wang, Eric K.; Lee, Allan Y.

    2011-01-01

    The Cassini spacecraft was launched on 15 October 1997. After an interplanetary cruise of almost seven years, it arrived at Saturn on June 30, 2004. Major science objectives of the Cassini mission include investigations of the configuration and dynamics of Saturn's magnetosphere, the structure and composition of the rings, the characterization of several of Saturn's icy satellites, and Titan's atmosphere constituent abundance

  6. Cassini RTG Acceptance Test Results and RTG Performance on Galileo and Ulysses

    Science.gov (United States)

    Kelly, C. E.; Klee, P. M.

    1997-06-01

    Flight acceptance testing has been completed for the RTGs to be used on the Cassini spacecraft which is scheduled for an October 6, 1997 launch to Saturn. The acceptance test program includes vibration tests, magnetic field measurements, properties (weight and c.g.) and thermal vacuum test. This paper presents The thermal vacuum test results. Three RTGs are to be used, F 2, F 6, and F 7. F 5 is tile back up RTG, as it was for the Galileo and Ulysses missions launched in 1989 and 1990, respectively. RTG performance measured during the thermal vacuum tests carried out at die Mound Laboratory facility met all specification requirements. Beginning of mission (BOM) and end of mission (EOM) power predictions have been made based on than tests results. BOM power is predicted to be 888 watts compared to the minimum requirement of 826 watts. Degradation models predict the EOM power after 16 years is to be 640 watts compared to a minimum requirement of 596 watts. Results of small scale module tests are also showing. The modules contain couples from the qualification and flight production runs. The tests have exceeded 28,000 hours (3.2 years) and are continuing to provide increased confidence in the predicted long term performance of the Cassini RTGs. All test results indicate that the power requirements of the Cassini spacecraft will be met. BOM and EOM power margins of over five percent are predicted. Power output from telemetry for the two Galileo RTGs are shown from the 1989 launch to the recent Jupiter encounter. Comparisons of predicted, measured and required performance are shown. Telemetry data are also shown for the RTG on the Ulysses spacecraft which completed its planned mission in 1995 and is now in the extended mission.

  7. Abundances of C3Hx Hydrocarbons in Titan's Stratosphere from Cassini CIRS

    Science.gov (United States)

    Nixon, C. A.; Jennings, D. E.; Bezard, B.; Vinatier, S.; Teanby, N. A.; Sung, K.; Ansty, T. M.; Irwin, P. G.; Gorius, N.; Cottini, V.; Coustenis, A.; Flasar, F. M.

    2014-12-01

    During the ten years since entry into Saturn orbit in 2004, the Cassini spacecraft has made more than 100 close flybys of Titan, measuring the properties of the atmosphere by both in situ and remote sensing techniques. Cassini's Composite Infrared Spectrometer (CIRS) senses the infrared spectrum from 7-1000 μm (1400-10 cm-1), a region which exhibits the vibrational emissions of many different molecular species. CIRS has therefore been able to map the spatial distributions and temporal variations of hydrocarbons, nitriles and other gas species in Titan's atmosphere, yielding information about the chemistry and dynamics. Recently, Nixon et al. (2013) made the first detection of a new stratospheric gas species from Cassini using CIRS - the C3H6 molecule (propene). This filled in a long-time missing link in the chemical picture of Titan's lower atmosphere, since the C3H4 (propyne) and C3H8 (propane) molecules had been detected in 1981 by Voyager 1 IRIS. The inferred abundance of C3H6 is less than both C3H8 and C3H4, and this pattern is repeated also in the C2Hx molecules where C2H4 is less abundant than C2H2 and C2H6. Therefore a pattern emerges whereby: alkanes > alkynes > alkenes within the C2Hx and C3Hx chemical families in the lower stratosphere. We comment on how this trend compares to published photochemical model predictions, and also give updates on the search for C3Hx isomers (allene: CH2CCH2, and cyclopropane: c-C3H6) and C4Hx species using CIRS.

  8. Temperature variations in Titan's upper atmosphere: Impact on Cassini/Huygens

    Directory of Open Access Journals (Sweden)

    B. Kazeminejad

    2005-06-01

    Full Text Available Temperature variations of Titan's upper atmosphere due to the plasma interaction of the satellite with Saturn's magnetosphere and Titan's high altitude monomer haze particles can imply an offset of up to ±30K from currently estimated model profiles. We incorporated these temperature uncertainties as an offset into the recently published Vervack et al. (2004 (Icarus, Vol. 170, 91-112 engineering model and derive extreme case (i.e. minimum and maximum profiles temperature, pressure, and density profiles. We simulated the Huygens probe hypersonic entry trajectory and obtain, as expected, deviations of the probe trajectory for the extreme atmosphere models compared to the simulation based on the nominal one. These deviations are very similar to the ones obtained with the standard Yelle et al. (1997 (ESA SP-1177 profiles. We could confirm that the difference in aerodynamic drag is of an order of magnitude that can be measured by the probe science accelerometer. They represent an important means for the reconstruction of Titan's upper atmospheric properties. Furthermore, we simulated a Cassini low Titan flyby trajectory. No major trajectory deviations were found. The atmospheric torques due to aerodynamic drag, however, are twice as high for our high temperature profile as the ones obtained with the Yelle maximum profile and more than 5 times higher than the worst case estimations from the Cassini project. We propose to use the Cassini atmospheric torque measurements during its low flybys to derive the atmospheric drag and to reconstruct Titan's upper atmosphere density, pressure, and temperature. The results could then be compared to the reconstructed profiles obtained from Huygens probe measurements. This would help to validate the probe measurements and decrease the error bars.

  9. Thermal mapping of Saturn's main rings by Cassini CIRS: Temperature variations with changing viewing geometry

    Science.gov (United States)

    Spilker, L.; Altobelli, N.; Pilorz, S.; Leyrat, C.; Ferrari, C.; Edgington, S.; Wallis, B.; Pearl, J.; Flasar, F.

    2007-08-01

    After three years in orbit around Saturn, the Cassini Composite Infrared Spectrometer (CIRS) has acquired an broad set of thermal measurements of Saturn's main rings (A, B, C and Cassini Division) for a number of different viewing geometries, most of which are not available from Earth. These thermal measurements include information on physical temperature as well as filling factor. Thermal mapping of both the lit and unlit faces of the rings is being performed within a multidimensional observation space that includes solar phase angle, spacecraft elevation, solar elevation and local hour angle. The largest temperature variations on the lit face of the rings are driven by variations in phase angle while differences in temperature with changing spacecraft elevation are a secondary effect. Ring temperatures decrease with increasing phase angle suggesting a population of slowly rotating ring particles [1]. The largest ring temperatures are measured at zero degrees phase angle. The lit A and B rings both show temperature decreases with decreasing solar elevation while temperature changes in the C ring and Cassini Division are more muted. Variations in the geometrical filling factor are driven primarily by changes in spacecraft elevation. For the least optically thick region of the C ring, the filling factor variations are almost exclusively driven by spacecraft elevation. Our preliminary evaluation of the data set acquired to date will be presented. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA, and at CEA Saclay supported by the "Programme National de Planetologie". References [1] L. Spilker et al., PSS, 54, 1167 (2006).

  10. Birotor dipole model for Saturn's inner magnetic field from CASSINI RPWS measurements and MAG data

    Science.gov (United States)

    Galopeau, Patrick H. M.

    2016-10-01

    The radio and plasma wave science (RPWS) experiment on board the Cassini spacecraft, orbiting around Saturn since July 2004, revealed the presence of two distinct and variable rotation periods in the Saturnian kilometric radiation (SKR). These two periods were attributed to the northern and southern hemispheres respectively. The existence of a double period makes the study of the planetary magnetic field much more complicated and the building of a field model, based on the direct measurements of the MAG experiment from the magnetometers embarked on board Cassini, turns out to be uncertain. The first reason is the difficulty for defining a longitude system linked to the variable period, because the internal magnetic field measurements from MAG are not continuous. The second reason is the existence itself of two distinct periods which could imply the existence of a double rotation magnetic structure generated by Saturn's dynamo. However, the radio observations from the RPWS experiment allow a continuous and accurate follow-up of the rotation phase of the variable two periods, since the SKR emission is permanently observable and produced very close to the planetary surface. A wavelet transform analysis of the intensity of the SKR signal received at 290 kHz was performed in order to calculate the rotation phase of each Saturnian hemisphere. A dipole model was proposed for Saturn's inner magnetic field: this dipole presents the particularity to rotate around Saturn's axis at two different angular velocities; it is tilted and not centered. Then it is possible to fit the MAG data for each Cassini's revolution around the planet the periapsis of which is less than 5 Saturnian radii. This study suggests that Saturn's inner magnetic field is neither stationary nor fully axisymmetric. Such a result can be used as a boundary condition for modelling and constraining the planetary dynamo.

  11. Cassini RTG acceptance test results and RTG performance on Galileo and Ulysses

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, C.E.; Klee, P.M. [Lockheed Martin Corp., Philadelphia, PA (United States)

    1997-12-31

    Flight acceptance testing has been completed for the RTGs to be used on the Cassini spacecraft which is scheduled for an October 6, 1997 launch to Saturn. The acceptance test program includes vibration tests, magnetic field measurements, mass properties (weight and c.g.) and thermal vacuum test. This paper presents the thermal vacuum test results. Three RTGs are to be used, F-2, F-6, and F-7. F-5 is the backup RTG, as it was for the Galileo and Ulysses missions launched in 1989 and 1990, respectively. RTG performance measured during the thermal vacuum tests carried out at the Mound Laboratory facility met all specification requirements. Beginning of mission (BOM) and end of mission (EOM) power predictions have been made based on these tests results. BOM power is predicted to be 888 watts compared to the minimum requirement of 826 watts. Degradation models predict the EOM power after 16 years is to be 640 watts compared to a minimum requirement of 596 watts. Results of small scale module tests are also shown. The modules contain couples from the qualification and flight production runs. The tests have exceeded 28,000 hours (3.2 years) and are continuing to provide increased confidence in the predicted long term performance of the Cassini RTGs. All test results indicate that the power requirements of the Cassini spacecraft will be met. BOM and EOM power margins of over 5% are predicted. Power output from telemetry for the two Galileo RTGs are shown from the 1989 launch to the recent Jupiter encounter. Comparisons of predicted, measured and required performance are shown. Telemetry data are also shown for the RTG on the Ulysses spacecraft which completed its planned mission in 1995 and is now in the extended mission.

  12. Precision Navigation of Cassini Images Using Rings, Icy Satellites, and Fuzzy Bodies

    Science.gov (United States)

    French, Robert S.; Showalter, Mark R.; Gordon, Mitchell K.

    2016-10-01

    Before images from the Cassini spacecraft can be analyzed, errors in the published pointing information (up to ~110 pixels for the Imaging Science Subsystem Narrow Angle Camera) must be corrected so that the line of sight vector for each pixel is known. This complicated and labor-intensive process involves matching the image contents with known features such as stars, rings, or moons. Metadata, such as lighting geometry or ring radius and longitude, must be computed for each pixel as well. Both steps require mastering the SPICE toolkit, a highly capable piece of software with a steep learning curve. Only after these steps are completed can the actual scientific investigation begin.We have embarked on a three-year project to perform these steps for all 400,000+ Cassini ISS images as well as images taken by the VIMS, UVIS, and CIRS instruments. The result will be a series of SPICE kernels that include accurate pointing information and a series of backplanes that include precomputed metadata for each pixel. All data will be made public through the PDS Ring-Moon Systems Node (http://www.pds-rings.seti.org). We expect this project to dramatically decrease the time required for scientists to analyze Cassini data.In a previous poster (French et al. 2014, DPS #46, 422.01) we discussed our progress navigating images using stars, simple ring models, and well-defined icy bodies. In this poster we will report on our current progress including the use of more sophisticated ring models, navigation of "fuzzy" bodies such as Titan and Saturn, and use of crater matching on high-resolution images of the icy satellites.

  13. Improved orbits of Saturn and Jupiter from the Cassini and Juno missions

    Science.gov (United States)

    Folkner, William M.; Jacobson, Robert Arthur; Jones, Dayton

    2015-08-01

    Since entering orbit about Saturn in 2004, radio tracking data of the Cassini spacecraft has provided accurate measurements of its position leading to marked improvement in the Saturn ephemeris. The Cassini spacecraft orbit period has varied between 14 and 30 days as the orbit was changed to provide views of Saturn’s rings and satellites. This relatively large orbit period has required care to separate the spacecraft orbit relative to Saturn from the orbit of Saturn relative to the Sun. The resulting estimates give a series of range measurements of Saturn relative to Earth with accuracy of ~30 m. In addition to improving the Saturn ephemeris, the range measurements have been used to place stringent upper bounds on possible deviation from General Relativity suggested by the theory of Modified Newtonian Dynamics. The Very Large Baseline Array has been used to observe Cassini and determine the right ascension and declination of Saturn approximately every year since entering orbit. The combination of range and VLBA measurements over more than one-quarter of the Saturn orbit period have resulted in Saturn ephemeris accuracy comparable to that of the inner planets.The Juno spacecraft will enter orbit about Jupiter in July 2016. Juno will be the second spacecraft to orbit Jupiter, but the first to provide a time series of ranging measurements since the Galileo spacecraft high-gain antenna failure prevented range measurements from that mission. Ranging measurements to Juno, combined with VLBA observations, will cover less than one-quarter of an orbit period. But, when combined with the accurate measurements of the Ulysses spacecraft during Jupiter flyby in February 1992, the Jupiter ephemeris accuracy is expected to be close to that of Saturn and the inner planets.

  14. Titan Density Reconstruction Using Radiometric and Cassini Attitude Control Flight Data

    Science.gov (United States)

    Andrade, Luis G., Jr.; Burk, Thomas A.

    2015-01-01

    This paper compares three different methods of Titan atmospheric density reconstruction for the Titan 87 Cassini flyby. T87 was a unique flyby that provided independent Doppler radiometric measurements on the ground throughout the flyby including at Titan closest approach. At the same time, the onboard accelerometer provided an independent estimate of atmospheric drag force and density during the flyby. These results are compared with the normal method of reconstructing atmospheric density using thruster on-time and angular momentum accumulation. Differences between the estimates are analyzed and a possible explanation for the differences is evaluated.

  15. Searching for modifications to the exponential radioactive decay law with the Cassini spacecraft

    CERN Document Server

    Cooper, Peter S

    2008-01-01

    Data from the power output of the radioisotope thermoelectric generators aboard the Cassini spacecraft are used to test the conjecture that small deviations observed in terrestrial measurements of the exponential radioactive decay law are correlated with the Earth-Sun distance. No significant deviations from exponential decay are observed over a range of 0.7 - 1.6 A.U. A 90% Cl upper limit of 0.84 x 10^-4 is set on a term in the decay rate of Pu-238 proportional to 1/R^2 and 0.99 x 10^-4 for a term proportional to 1/R.

  16. The electron and the ion density characteristic near the F ring by Cassini/RPWS/LP

    Science.gov (United States)

    Morooka, Michiko; Wahlund, Jan-Erik; Andrews, David; Ye, Sheng-Yi; Kurth, William

    2017-04-01

    Cassini observations revealed that there are a large amount of nm and μm sized dust grains and their electrical interaction with the surrounding plasma near the moon Enceladus and the E ring. In this region, the small grains are negatively charged by attaching the electrons, resulting the unbalance in the ion and the electron densities (the ion density higher than the electron density). Similar type observations are expected near the faint F and G ring that are composed of small grains. During the grand finale, from December 2016, Cassini has been orbiting Saturn with closest approach just outside the F ring. We will show the electron and ion densities of those orbits obtained by the Langmuir probe onboard Cassini (RPWS/LP). Preliminary results showed: 1) both the electron and the ion density enhancement occurred near the equator (Z = ±0.5RS). 2) The electron densities at the equator are about the order of 1 cm-3 (varies from 2 to 8), while the ion densities are an order of magnitude larger than the electrons up to 300 cm-3. 3) The electron density depletion has been observed centered at the equator around ±0.05 RS in Z. Coincide this region, the LP sweep current noise due to the dust grain's hitting the probe were observed. On the other hand, the peak of the electron density seems to be located slightly northward above the equator at ˜0.05 RS. 4) One of the events showed a local electron density enhancement near the L-shell at L = 3. The obtained characteristics are similar to what have been found in the E ring near the Enceladus orbit. In the E ring, the electron density enhancement region was centered at the equator in Z ±˜0.5RS, the electron bite out occurred at Z = ±0.045RS, and the electron density peaks were somewhat higher in the northern hemisphere. A possible explanation for the location differences in the charged dust density peak and the plasma density peak can be due to that the magnetic equator is located slightly north (+0.04RS) of the equator

  17. Cassini Maneuver Experience for the Fourth Year of the Solstice Mission

    Science.gov (United States)

    Vaquero, Mar; Hahn, Yungsun; Stumpf, Paul; Valerino, Powtawche; Wagner, Sean; Wong, Mau

    2014-01-01

    After sixteen years of successful mission operations and invaluable scientific discoveries, the Cassini orbiter continues to tour Saturn on the most complex gravity-assist trajectory ever flown. To ensure that the end-of-mission target of September 2017 is achieved, propellant preservation is highly prioritized over maneuver cycle minimization. Thus, the maneuver decision process, which includes determining whether a maneuver is performed or canceled, designing a targeting strategy and selecting the engine for execution, is being continuously re-evaluated. This paper summarizes the maneuver experience throughout the fourth year of the Solstice Mission highlighting 27 maneuvers targeted to nine Titan flybys.

  18. Titan Density Reconstruction Using Radiometric and Cassini Attitude Control Flight Data

    Science.gov (United States)

    Andrade, Luis G., Jr.; Burk, Thomas A.

    2015-01-01

    This paper compares three different methods of Titan atmospheric density reconstruction for the Titan 87 Cassini flyby. T87 was a unique flyby that provided independent Doppler radiometric measurements on the ground throughout the flyby including at Titan closest approach. At the same time, the onboard accelerometer provided an independent estimate of atmospheric drag force and density during the flyby. These results are compared with the normal method of reconstructing atmospheric density using thruster on-time and angular momentum accumulation. Differences between the estimates are analyzed and a possible explanation for the differences is evaluated.

  19. Titan's Elusive Lakes? Properties and Context of Dark Spots in Cassini TA Radar Data

    Science.gov (United States)

    Lorenz, R. D.; Elachi, C.; Stiles, B.; West, R.; Janssen, M.; Lopes, R.; Stofan, E.; Paganelli, F.; Wood, C.; Kirk, R.

    2005-01-01

    Titan's atmospheric methane abundance suggests the likelihood of a surface reservoir of methane and a surface sink for its photochemical products, which might also be predominantly liquid. Although large expanses of obvious hydrocarbon seas have not been unambiguously observed, a number of rather radar-dark spots up to approximately 30 km across are observed in the Synthetic Aperture Radar (SAR) data acquired during the Cassini TA encounter on October 26th 2004. Here we review the properties and setting of these dark spots to explore whether these may be hydrocarbon lakes.

  20. The Science from Cassini CIRS, Today and over the Next Three Years

    Science.gov (United States)

    Flasar, F. M.

    2014-12-01

    The longevity of the Cassini Mission has provided an unusual opportunity to study the Saturn system, and we report major results on temperatures, atmospheric composition, and condensates from CIRS thermal-infrared spectra. Titan has a pronounced seasonal cycle, and its winter poles are characterized by strong circumpolar winds enclosing a region of cold stratospheric temperatures, enhanced trace organic gases, and condensates. Cassini arrived in early northern winter and now it is mid-spring. The northern vortex has dissolved gradually, but the buildup of Titan's south polar vortex has been quite rapid, evidenced by the marked increase of trace organic gases and condensates. Saturn has seasonal and more irregular behavior. Like Earth, its stratosphere has an equatorial oscillation, with a descending pattern detected in Cassini's extended tour. The great northern storm that erupted in late 2010 was unexpected, leading to perturbations in tropospheric composition, and stratospheric anticyclones. Although the visible storm died out in a few months, the highly disturbed stratosphere persisted until this year. In the remainder of Cassini's tour, there will also be new observations of the thermally anomalous "Pac-Man" features on Mimas, Tethys, and Dione, which will provide better constraints on their physical surface properties and spatial distribution. Regions of Hyperion, Epimetheus, Janus, Pandora and Atlas will be mapped for the first time or at significantly better spatial-resolution than before. Two close flybys of Enceladus in late 2015 will allow the sampling of the structure of tiger stripe thermal emission on sub-kilometer scales. As the southern winter deepens, its endogenic signature will be less polluted by passive emission, providing the best opportunity to determine its heat flow and constrain its source. The F-ring and Proximal orbits will provide close views to obtain limb sounding of Saturn's equatorial region and map the thermal structure and

  1. Cassini Imaging of Iapetus and Solution of the Albedo Asymmetry Enigma

    Science.gov (United States)

    Denk, Tilmann; Spencer, John

    2014-05-01

    Cassini imaging of Iapetus during one close and several more distant flybys mainly in the first years of the mission revealed an alien and often unique landscape of this third-largest moon in the Saturnian system [1]. The data show numerous impact craters on the bright and dark terrain, equator-facing dark and pole-facing bright crater walls, huge impact basins, rather minor endogenic geologic features, a non-spherical, but ellipsoidal shape, a giant ridge which spans across half of Iapetus' circumference exactly along the equator, a newly detected global 'color dichotomy' presumably formed by dust from retrograde irregular moons, and of course the famous extreme global albedo asymmetry which has been an enigma for more than three centuries. Revealing the cause of this 'albedo dichotomy' enigma of Iapetus, where the trailing side and poles are more than 10x brighter than the leading side, was one of the major tasks for the Cassini mission. It has now been solved successfully. In the mid-1970es, deposition of exogenic dark material on the leading side, originating from outer retrograde moon Phoebe, was proposed as the cause. But this alone could not explain the global shape, sharpness, and complexity of the transition between Iapetus' bright and dark terrain. Mainly with Cassini spectrometer (CIRS) and imaging (ISS) data, all these characteristics and the asymmetry's large amplitude are now plausibly explained by runaway global thermal migration of water ice, triggered by the deposition of dark material on the leading hemisphere. This mechanism is unique to Iapetus among the Saturnian satellites for many reasons. Most important are Iapetus' slow rotation which produces unusually high daytime temperatures and water ice sublimation rates, and the size (gravity) of Iapetus which is small enough for global migration of water ice but large enough that much of the ice is retained on the surface [2]. References: [1] Denk, T., Neukum, G., Roatsch, Th., Porco, C.C., Burns, J

  2. Cassini Plasma Spectrometer Ion Observations Close to Enceladus: E3, E5 and E7

    Science.gov (United States)

    Tokar, R. L.; Johnson, R. E.; Thomsen, M. F.; Wilson, R. J.; Crary, F. J.; Young, D. T.; Goldstein, R.; Reisenfeld, D. B.; Sittler, E. C.; Coates, A. J.; Paty, C. S.; Jia, Y.; Omidi, N.; Russell, C.

    2009-12-01

    The Cassini Plasma Spectrometer (CAPS) detected freshly-produced water-group ions (O+, OH+, H2O+, H3O+) and heavier water dimer ions (HxO2)+ very close to Enceladus where the plasma begins to emerge from the south polar plume (1). The data were obtained during two close (52 and 25 km) flybys of Enceladus in 2008 (E3 and E5) and are consistent with measurements from the Cassini Ion Neutral Mass Spectrometer (INMS). The ions are observed in CAPS detectors looking in the Cassini ram direction close to the ram kinetic energy, indicative of a nearly stagnant plasma flow in the plume. North of Enceladus the plasma slowing commences about 4 to 6 Enceladus radii away, while south of Enceladus signatures of the plasma interaction with the plume are detected 22 Enceladus radii away. Here we review and contrast these observations including the E7 flyby (anticipated Nov. 2, 2009). E7 is planned for a closest approach ~103 km south of Enceladus and CAPS should detect ions at rest with respect to Enceladus and over a broad range of gyrophase angles. Plasma fluid parameters both upstream and downstream of these encounters are extracted from the CAPS data. In addition, we compare the CAPS ion measurements with both fluid and 3D hybrid simulations. The MHD simulations (BATSRUS) are tuned to agree with Cassini Magnetometer (MAG) observations during the encounters then compared with CAPS observations. For example, for the E3 encounter the CAPS/BATSRUS comparison is striking, with features reproduced such as: the overall spatial scale of the interaction, the slowing of the ion flow within the dust plume to less than 5 km/s with respect to Enceladus, the temperature, flow and density signature of the geometric wake, and the flow perturbation along the magnetic field due to wake expansion. For E5, BATSRUS tuned against MAG suggests a 15 km/s bulk plasma flow toward Saturn during the encounter. We search for signatures of this flow in the CAPS ion data. 1.) Tokar,R.L. et al. Geophys. Res

  3. Dynamics of Saturn's great storm of 2010-2011 from Cassini ISS and RPWS

    CERN Document Server

    Sayanagi, Kunio M; Ewald, Shawn P; Fischer, Georg; Ingersoll, Andrew P; Kurth, William S; Muro, Gabriel D; Porco, Carolyn C; West, Robert A

    2016-01-01

    Saturn's quasi-periodic planet-encircling storms are the largest convecting outbursts in the Solar System. The last eruption was in 1990. A new eruption started in December 2010 and presented the first-ever opportunity to observe such episodic storms from a spacecraft in orbit around Saturn. Here, we analyze images acquired with the Cassini Imaging Science Subsystem (ISS), which captured the storm's birth, evolution and demise. In studying the end of the convective activity, we also analyze the Saturn Electrostatic Discharge (SED) signals detected by the Radio and Plasma Wave Science (RPWS) instrument. [...

  4. Scheme of Saturn rings origination and nature of the Cassini's division

    Energy Technology Data Exchange (ETDEWEB)

    Davydov, V.D.

    The united solution of two problems: the problem of Cassini division width and the problem of the former Saturn satellite plunging into the tidal destruction zone is suggested on the base of the analysis of observed properties of the Saturn rings. The scheme of the ring system formation is built up; the concrete characteristics of the former satellite from which this system has been formed are found out. The literature data on the Saturn rings observation from the ''Voyadger-1'', ''Voyadger-2'' space probes are used in the paper.

  5. Cassini radio and plasma wave investigation: Data compression and scientific applications

    Science.gov (United States)

    Woolliscroft, L. J. C.; Farrell, W. M.; Alleyne, H. St. C.; Gurnett, D. A.; Kirchner, D. L.; Kurth, W. S.; Thompson, J. A.

    1993-01-01

    The Radio and Plasma Wave Science (RPWS) experiment being built for the Cassini spacecraft will study a wide range of plasma and radio wave phenomena in the magnetosphere of Saturn and will also make valuable measurements during the cruise phase and at other encounters. A feature of data from wave receivers is the capability of producing vastly more data than the spacecraft telemetry link is capable of transmitting back to the Earth. Thus, techniques of on-board data compression and data reduction are important. The RPWS instrument has one processor dedicated to data compression tasks.

  6. Cassini radio and plasma wave investigation - Data compression and scientific applications

    Science.gov (United States)

    Woolliscroft, L. J. C.; Farrell, W. M.; Alleyne, H. St. C.; Gurnett, D. A.; Kirchner, D. L.; Kurth, W. S.; Thompson, J. A.

    1993-01-01

    The Radio and Plasma Wave Science (RPWS) experiment being built for the Cassini spacecraft will study a wide range of plasma and radio wave phenomena in the magnetosphere of Saturn and will also make valuable measurements during the cruise phase and at other encounters. A feature of data from wave receivers is the capability of producing vastly more data than the spacecraft telemetry link is capable of transmitting back to the Earth. Thus, techniques of on-board data compression and data reduction are important. The RPWS instrument has one processor dedicated to data compression tasks.

  7. Light weight radioisotope heater unit (LWRHU) production for the Cassini mission

    Science.gov (United States)

    Rinehart, Gary H.

    1997-01-01

    The LWRHU is a 238PuO2 fueled heat source designed to provide one thermal watt in each of various locations on a spacecraft. The heat sources are required to maintain the temperature of specific components within normal operating ranges. The heat source consists of a hot-pressed 238PuO2 fuel pellet, a Pt-30Rh vented capsule, a pyrolytic graphite insulator, and a woven graphite aeroshell assembly. Los Alamos National Laboratory has fabricated 180 heat sources, 157 of which will be used on the Cassini mission.

  8. Cassini Growth of Population Between Two Metropolitan Cities——A Case Study of Beijing-Tianjin Region, China

    Institute of Scientific and Technical Information of China (English)

    ZONG Yueguang; YANG Wei; MA Qiang; XUE Song

    2009-01-01

    The existing models of population distribution often focus on the region with a single city or even multiple centers, and lack the detailed explorations of the common and special type of urbanization areas with two centers. Taking Beijing-Tianjin region of China, which is a distinct dual-nuclei metropolitan area in the world, as an example and choosing Landsat-5 TM image in 2005, population, etc. As the data, this paper devotes to comprehending and illus-trating a model of Cassini growth of population between the two metropolitan cities through the research of spatial population distribution pattern, aided with RS and GIS techniques. Main technical processes include Kriging interpola-tion of the population data and character simulation of the Cassini ovals. According to the calculation of a/b, a key characteristic index of Cassini growth model, the spatial structures of population distribution were given. When a/b1,it is a curve with two separated loops with a population density more than 3000 persons/km2. When a/b=1, it is a lem-niscate curve with a population density about 3000 persons/km2. When 1(√2), there is an oval-shaped convex curve with a population density less than 500 persons/km2. The results show that owing to the combined action and influence of the regional dual-nuclei, the population distribution of Beijing-Tianjin region is in accord with Cassini model significantly. There-fore, there is Cassini growth of population between the two metropolitan cities in Beijing-Tianjin region. In addition,the process of Cassini growth has extraordinarily instructive significance for judging the development stages of the dual-nuclei metropolitan areas.

  9. Jupiter’s Phase Variations from Cassini: A Testbed for Future Direct-imaging Missions

    Science.gov (United States)

    Mayorga, L. C.; Jackiewicz, J.; Rages, K.; West, R. A.; Knowles, B.; Lewis, N.; Marley, M. S.

    2016-12-01

    We present empirical phase curves of Jupiter from ∼0° to 140° as measured in multiple optical bandpasses by Cassini/Imaging Science Subsystem (ISS) during the Millennium flyby of Jupiter in late 2000 to early 2001. Phase curves are of interest for studying the energy balance of Jupiter and understanding the scattering behavior of the planet as an exoplanet analog. We find that Jupiter is significantly darker at partial phases than an idealized Lambertian planet by roughly 25% and is not well fit by Jupiter-like exoplanet atmospheric models across all wavelengths. We provide analytic fits to Jupiter’s phase function in several Cassini/ISS imaging filter bandpasses. In addition, these observations show that Jupiter’s color is more variable with phase angle than predicted by models. Therefore, the color of even a near Jupiter-twin planet observed at a partial phase cannot be assumed to be comparable to that of Jupiter at full phase. We discuss how the Wide-Field Infrared Survey Telescope and other future direct-imaging missions can enhance the study of cool giants.

  10. THERMAL AND CHEMICAL STRUCTURE VARIATIONS IN TITAN'S STRATOSPHERE DURING THE CASSINI MISSION

    Energy Technology Data Exchange (ETDEWEB)

    Bampasidis, Georgios; Coustenis, A.; Vinatier, S. [Laboratoire d' Etudes Spatiales et d' Instrumentation en Astrophysique (LESIA), Observatoire de Paris, CNRS, UPMC Univ. Paris 06, Univ. Paris-Diderot, 5, place Jules Janssen, F-92195 Meudon Cedex (France); Achterberg, R. K. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Lavvas, P. [GSMA, Universite Reims Champagne-Ardenne, F-51687 Reims Cedex 2 (France); Nixon, C. A.; Jennings, D. E.; Flasar, F. M.; Carlson, R. C.; Romani, P. N.; Guandique, E. A. [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Teanby, N. A. [School of Earth Sciences, University of Bristol, Bristol BS8 1RJ (United Kingdom); Moussas, X.; Preka-Papadema, P.; Stamogiorgos, S., E-mail: gbabasid@phys.uoa.gr [Faculty of Physics, National and Kapodistrian University of Athens, Panepistimioupolis, GR 15783 Zographos, Athens (Greece)

    2012-12-01

    We have developed a line-by-line Atmospheric Radiative Transfer for Titan code that includes the most recent laboratory spectroscopic data and haze descriptions relative to Titan's stratosphere. We use this code to model Cassini Composite Infrared Spectrometer data taken during the numerous Titan flybys from 2006 to 2012 at surface-intercepting geometry in the 600-1500 cm{sup -1} range for latitudes from 50 Degree-Sign S to 50 Degree-Sign N. We report variations in temperature and chemical composition in the stratosphere during the Cassini mission, before and after the Northern Spring Equinox (NSE). We find indication for a weakening of the temperature gradient with warming of the stratosphere and cooling of the lower mesosphere. In addition, we infer precise concentrations for the trace gases and their main isotopologues and find that the chemical composition in Titan's stratosphere varies significantly with latitude during the 6 years investigated here, with increased mixing ratios toward the northern latitudes. In particular, we monitor and quantify the amplitude of a maximum enhancement of several gases observed at northern latitudes up to 50 Degree-Sign N around mid-2009, at the time of the NSE. We find that this rise is followed by a rapid decrease in chemical inventory in 2010 probably due to a weakening north polar vortex with reduced lateral mixing across the vortex boundary.

  11. Cusp observation at Saturn's high-latitude magnetosphere by the Cassini spacecraft.

    Science.gov (United States)

    Jasinski, J M; Arridge, C S; Lamy, L; Leisner, J S; Thomsen, M F; Mitchell, D G; Coates, A J; Radioti, A; Jones, G H; Roussos, E; Krupp, N; Grodent, D; Dougherty, M K; Waite, J H

    2014-03-16

    We report on the first analysis of magnetospheric cusp observations at Saturn by multiple in situ instruments onboard the Cassini spacecraft. Using this we infer the process of reconnection was occurring at Saturn's magnetopause. This agrees with remote observations that showed the associated auroral signatures of reconnection. Cassini crossed the northern cusp around noon local time along a poleward trajectory. The spacecraft observed ion energy-latitude dispersions-a characteristic signature of the terrestrial cusp. This ion dispersion is "stepped," which shows that the reconnection is pulsed. The ion energy-pitch angle dispersions suggest that the field-aligned distance from the cusp to the reconnection site varies between ∼27 and 51 RS . An intensification of lower frequencies of the Saturn kilometric radiation emissions suggests the prior arrival of a solar wind shock front, compressing the magnetosphere and providing more favorable conditions for magnetopause reconnection. We observe evidence for reconnection in the cusp plasma at SaturnWe present evidence that the reconnection process can be pulsed at SaturnSaturn's cusp shows similar characteristics to the terrestrial cusp.

  12. Surface current balance and thermoelectric whistler wings at airless astrophysical bodies: Cassini at Rhea.

    Science.gov (United States)

    Teolis, B D; Sillanpää, I; Waite, J H; Khurana, K K

    2014-11-01

    Sharp magnetic perturbations found by the Cassini spacecraft at the edge of the Rhea flux tube are consistent with field-aligned flux tube currents. The current system results from the difference of ion and electron gyroradii and the requirement to balance currents on the sharp Rhea surface. Differential-type hybrid codes that solve for ion velocity and magnetic field have an intrinsic difficulty modeling the plasma absorber's sharp surface. We overcome this problem by instead using integral equations to solve for ion and electron currents and obtain agreement with the magnetic perturbations at Rhea's flux tube edge. An analysis of the plasma dispersion relations and Cassini data reveals that field-guided whistler waves initiated by (1) the electron velocity anisotropy in the flux tube and (2) interaction with surface sheath electrostatic waves on topographic scales may facilitate propagation of the current system to large distances from Rhea. Current systems like those at Rhea should occur generally, for plasma absorbers of any size such as spacecraft or planetary bodies, in a wide range of space plasma environments. Motion through the plasma is not essential since the current system is thermodynamic in origin, excited by heat flow into the object. The requirements are a difference of ion and electron gyroradii and a sharp surface, i.e., without a significant thick atmosphere. Surface current balance condition yields a current system at astronomical bodiesCurrent system possible for sharp (airless) objects of any sizeCurrent system is thermoelectric and motion through the plasma nonessential.

  13. Measurements of C02 Distribution in Saturn's Atmosphere by Cassini-Infrared Observations

    Science.gov (United States)

    Abbas, M. M.; LeClair, A.; Woodard, E.; Young, M.; Stanbro, M.; Flasar, M.

    2013-01-01

    The Fourier transform infrared spectrometer aboard the Cassini spacecraft, inserted in Saturn s orbit in July 2004, has been providing high resolution/high sensitivity infrared (IR) spectra of the Saturnian system. The measurements cover the spectral range of 10-1400/cm with variable spectral resolutions of 0.53 to 15/cm, exhibiting spectral features of a series of trace gases including CO2 and H2O. The observed spectra may be analyzed for retrieval of global P/T and gas density profiles of Saturn. The infrared measurements of Saturn by ISO(SWS) have indicated unexpected large abundances of CO2 in Saturn's atmosphere. The rigorous photochemical models of Saturn's atmosphere that have been developed indicate exogenic oxygen influx of icy dust grains that lead to the production of CO2. The distribution of CO2 in Saturn's atmosphere needs to be confirmed, and the nature of exogenic sources remains to be investigated. This paper presents comprehensive measurements of the CO2 distribution in Saturn's atmosphere by Cassini IR observations.

  14. Reducing Pointing Errors During Cassini Reaction Control System Orbit Trim Maneuvers

    Science.gov (United States)

    Rizvi, Farheen

    2013-01-01

    The effect of altering a gain parameter in the Cassini reaction control system (RCS) delta-V controller on the maneuver execution errors during orbit trim maneuvers (OTMs) is explored. Cassini consists of two reaction control thruster branches (A & B) each with eight thrusters. Currently, the B-branch is operational while the A-branch serves as a back-up. The four Z-thrusters control the X and Y-axes, while the four Y-thrusters control the Z-axis. During an OTM, the Z-thrusters fire to maintain the X and Y-axes pointing within an attitude control dead-zone (-10 to 10 milliradians). The errors do not remain at zero due to pointing error sources such as spacecraft center of mass offset from the geometric center of the Z-facing thrusters, and variability in the thruster forces due to the thruster hardware differences. The delta-V reaction control system (RCS) controller ensures that the attitude error remains within this dead-zone. Gain parameters within the RCS delta-V controller affect the maneuver execution errors. Different parameter values are used to explore effect on these errors. It is found that pointing error decreases and magnitude error increases rapidly for gain parameters 10 times greater than the current parameter values used in the flight software.

  15. Photochemical enrichment of deuterium in Titan's atmosphere: new insights from Cassini-Huygens

    CERN Document Server

    Cordier, D; Lunine, I J; Moudens, A; Vuitton, V

    2008-01-01

    Cassini-Huygens data are used to re-examine the potential sources of the D/H enhancement over solar, measured in methane, in Titan's atmosphere. Assuming that the system is closed with respect to carbon, the use of constraints from the Huygens probe for the determination of the current mass of atmospheric methane and the most up-to-date determination of D/H from Cassini/CIRS infrared spectra allow us to show that photochemical enrichment of deuterium is not sufficient to be the sole mechanism yielding the measured D/H value. A possible fractionation between CH3D and CH4 during the escape process may slightly enhance the deuterium enrichment, but is not sufficient to explain the observed D/H value over the range of escape values proposed in the literature. Hence, alternative mechanisms such as a primordial deuterium enrichment must be combined with the photochemical enrichment in Titan's atmosphere in order to explain its current D/H value.

  16. Computer Analysis of Spectrum Anomaly in 32-GHz Traveling-Wave Tube for Cassini Mission

    Science.gov (United States)

    Dayton, James A., Jr.; Wilson, Jeffrey D.; Kory, Carol L.

    1999-01-01

    Computer modeling of the 32-GHz traveling-wave tube (TWT) for the Cassini Mission was conducted to explain the anomaly observed in the spectrum analysis of one of the flight-model tubes. The analysis indicated that the effect, manifested as a weak signal in the neighborhood of 35 GHz, was an intermodulation product of the 32-GHz drive signal with a 66.9-GHz oscillation induced by coupling to the second harmonic'signal. The oscillation occurred only at low- radiofrequency (RF) drive power levels that are not expected during the Cassini Mission. The conclusion was that the anomaly was caused by a generic defect inadvertently incorporated in the geometric design of the slow-wave circuit and that it would not change as the TWT aged. The most probable effect of aging on tube performance would be a reduction in the electron beam current. The computer modeling indicated that although not likely to occur within the mission lifetime, a reduction in beam current would reduce or eliminate the anomaly but would do so at the cost of reduced RF output power.

  17. Jupiter's Phase Variations from Cassini: a testbed for future direct-imaging missions

    CERN Document Server

    Mayorga, L C; Rages, K; West, R A; Knowles, B; Lewis, N; Marley, M S

    2016-01-01

    We present phase curves of Jupiter from 0-140 degrees as measured in multiple optical bandpasses by Cassini/ISS during the Millennium flyby of Jupiter in late 2000 to early 2001. Phase curves are of interest for studying the energy balance of Jupiter and understanding the scattering behavior of Jupiter as an exoplanet analog. We find that Jupiter is significantly darker at partial phases than an idealized Lambertian planet by roughly 25% and is not well fit by Jupiter-like exoplanet atmospheric models across all wavelengths. We provide analytic fits to Jupiter's phase function in several Cassini/ISS imaging filter bandpasses. In addition, these observations show that Jupiter's color is more variable with phase angle than predicted by models. Therefore, the color of even a near Jupiter-twin planet observed at a partial phase cannot be assumed to be comparable to that of Jupiter at full phase. We discuss how WFIRST and other future direct-imaging missions can enhance the study of cool giants.

  18. Titan's Topside Ionospheric Composition: Cassini Plasma Spectrometer Ion Mass Spectrometer Measurements

    Science.gov (United States)

    Sittler, Edward; Hartle, Richard; Ali, Ashraf; Cooper, John; Lipatov, Alexander; Simpson, David; Sarantos, Menelaos; Chornay, Dennis; Smith, Todd

    2017-01-01

    We present ion composition measurements of Titan's topside ionosphere using both T9 and T15 Cassini Plasma Spectrometer (CAPS) Ion Mass Spectrometer (IMS) measurements. The IMS is able to make measurements of Titan's ionosphere due to ionospheric outflows as originally reported for the T9 flyby. This allows one to take advantage of the unique capabilities of the CAPS IMS which measures both the mass-per-charge (M/Q) of the ions and the fragments of the ions produced inside the sensor such as carbon, nitrogen and oxygen fragments. Specific attention will be given to such ions as NH4 +, N +, O +, CH4 +, CxHy +, and HCNH + ions as examples. The CAPS IMS uses a time-of-flight (TOF) technique which accelerates ions up to 14.6 kV, so they can pass through ultra-thin carbon foils. Neutral fragments are used to measure the ion M/Q and positive fragments to measure the atomic components. We preliminarily find, by using IMS measurements of T9 and T15 ionospheric outflows, evidence for methane group ions, nitrogen ions, ammonium ions, water group ions and CnHm + ions with n = 2, 3, and 4 within Titan's topside ionosphere. E.C. Sittler acknowledges support at Goddard Space Flight Center by the CAPS Cassini Project from JPL funds under contract # NAS703001TONMO711123/1405851.

  19. Dynamics Of Saturn'S Mid-scale Storms In The Cassini Era.

    Science.gov (United States)

    Del Rio Gaztelurrutia, Teresa; Hueso, R.; Sánchez-Lavega, A.

    2010-10-01

    Convective storms, similar to those in Earth, but of much larger scale, develop often in Saturn's atmosphere. During the Voyagers’ flybys of Saturn in 1981 mid-scale storms, with an horizontal extension of the order of 1000-3000 km were observed to occur mainly in a narrow tropical-latitude band in the Northern hemisphere at latitudes 38-40 deg North. Contrasting with the Voyagers’ era, since the starting of the Cassini mission in 2004, a similar mid-scale convective activity has concentrated in the so-called "storm alley", a narrow band at a symmetric Southern latitude of 38 deg.. In this work, we characterize this storm activity using available visual information provided by Cassini ISS cameras and the continuous survey from the Earth by the International Outer Planets Watch (IOPW) and its online database PVOL (Hueso et al., Planetary and Space Science, 2010). We study the frequency of appearance of storms with sizes above 2000 km, their characteristic size and life-time, as well as their interaction with surrounding dynamical features. In particular we examine the possibility that storms might provide a mechanism of injection of energy into Saturn's jets, the influence of storms in the generation of atmospheric vortices, and the analogies and differences of Voyagers’ and present day jet structure at the relevant latitudes. Acknowledgments: This work has been funded by the Spanish MICIIN AYA2009-10701 with FEDER support and Grupos Gobierno Vasco IT-464

  20. Cassini CAPS-ELS observations of carbon-based anions and aerosol growth in Titan's ionosphere

    Science.gov (United States)

    Desai, Ravindra; Coates, Andrew; Wellbrock, Anne; Kataria, Dhiren; Jones, Geraint; Lewis, Gethyn; Waite, J.

    2016-06-01

    Cassini observations of Titans ionosphere revealed an atmosphere rich in positively charged ions with masses up to > 350 amu and negatively charged ions and aerosols with mass over charge ratios as high as 13,800 amu/q. The detection of negatively charged molecules by the Cassini CAPS Electron Spectrometer (CAPS-ELS) was particularly surprising and showed how the synthesis of large aerosol-size particles takes place at altitudes much greater than previously thought. Here, we present further analysis into this CAPS-ELS dataset, through an enhanced understanding of the instrument's response function. In previous studies the intrinsic E/E energy resolution of the instrument did not allow specific species to be identified and the detections were classified into broad mass ranges. In this study we use an updated fitting procedure to show how the ELS mass spectrum can be resolved into specific peaks at multiples of carbon-based anions up to > 100 amu/q. The negatively charged ions and aerosols in Titans ionosphere increase in mass with decreasing altitude, the lightest species being observed close to Titan's exobase of ˜1,450km and heaviest species observed at altitudes < 950km. We identify key stages in this apparent growth process and report on key intermediaries which appear to trigger the rapid growth of the larger aerosol-size particles.

  1. Titan Aerosol Analogs from Aromatic Precursors: Comparisons to Cassini CIRS Observations in the Thermal Infrared

    Science.gov (United States)

    Trainer, Melissa G.; Sebree, Joshua A.; Anderson, Carrie M.; Loeffler, Mark J.

    2012-01-01

    Since Cassini's arrival at Titan, ppm levels of benzene (C6H6) as well as large positive ions, which may be polycyclic aromatic hydrocarbons (PAHs). have been detected in the atmosphere. Aromatic molecules. photolytically active in the ultraviolet, may be important in the formation of the organic aerosol comprising the Titan haze layer even when present at low mixing ratios. Yet there have not been laboratory simulations exploring the impact of these molecules as precursors to Titan's organic aerosol. Observations of Titan by the Cassini Composite Infrared Spectrometer (CIRS) in the far-infrared (far-IR) between 560 and 20/cm (approx. 18 to 500 microns) and in the mid-infrared (mid-IR) between 1500 and 600/cm (approx. 7 to 17 microns) have been used to infer the vertical variations of Titan's aerosol from the surface to an altitude of 300 km in the far-IR and between 150 and 350 km in the mid-IR. Titan's aerosol has several observed emission features which cannot be reproduced using currently available optical constants from laboratory-generated Titan aerosol analogs, including a broad far-IR feature centered approximately at 140/cm (71 microns).

  2. The Cassini-Huygens visit to Saturn an historic mission to the ringed planet

    CERN Document Server

    Meltzer, Michael

    2015-01-01

    Cassini-Huygens was the most ambitious and successful space journey ever launched to the outer Solar System. This book examines all aspects of the journey: its conception and planning; the lengthy political processes needed to make it a reality; the engineering and development required to build the spacecraft; its 2.2-billion mile journey from Earth to the Ringed Planet; and the amazing discoveries from the mission. The author traces how the visions of a few brilliant scientists matured, gained popularity, and eventually became a reality. Innovative technical leaps were necessary to assemble such a multifaceted spacecraft and reliably operate it while it orbited a planet so far from our own. The Cassini-Huygens spacecraft design evolved from other deep space efforts, most notably the Galileo mission to Jupiter, enabling the voluminous, paradigm-shifting scientific data collected by the spacecraft.  Some of these discoveries are absolute gems. A small satellite that scientists once thought of as a dead pi...

  3. Energetic Neutral Atom (ENA) Movies and Other Cool Data from Cassini's Magnetosphere Imaging Instrument (MIMI)

    Science.gov (United States)

    Kusterer, M. B.; Mitchell, D. G.; Krimigis, S. M.; Vandegriff, J. D.

    2014-12-01

    Having been at Saturn for over a decade, the MIMI instrument on Cassini has created a rich dataset containing many details about Saturn's magnetosphere. In particular, the images of energetic neutral atoms (ENAs) taken by the Ion and Neutral Camera (INCA) offer a global perspective on Saturn's plasma environment. The MIMI team is now regularly making movies (in MP4 format) consisting of consecutive ENA images. The movies correct for spacecraft attitude changes by projecting the images (whose viewing angles can substantially vary from one image to the next) into a fixed inertial frame that makes it easy to view spatial features evolving in time. These movies are now being delivered to the PDS and are also available at the MIMI team web site. Several other higher order products are now also available, including 20-day energy-time spectrograms for the Charge-Energy-Mass Spectrometer (CHEMS) sensor, and daily energy-time spectrograms for the Low Energy Magnetospheric Measurements system (LEMMS) sensor. All spectrograms are available as plots or digital data in ASCII format. For all MIMI sensors, a Data User Guide is also available. This paper presents details and examples covering the specifics of MIMI higher order data products. URL: http://cassini-mimi.jhuapl.edu/

  4. Could Jean-Dominique Cassini see the famous division in Saturn's rings?

    CERN Document Server

    Lozi, Julien; Semery, Alain; Lhomé, Emilie; Jacquinod, Sophie; Combes, Michel; Bernardi, Pernelle; Andretta, Rémi; Motisi, Maxime; Bobis, Laurence; Kaftan, Emilie

    2013-01-01

    Nowadays, astronomers want to observe gaps in exozodiacal disks to confirm the presence of exoplanets, or even make actual images of these companions. Four hundred and fifty years ago, Jean-Dominique Cassini did a similar study on a closer object: Saturn. After joining the newly created Observatoire de Paris in 1671, he discovered 4 of Saturn's satellites (Iapetus, Rhea, Tethys and Dione), and also the gap in its rings. He made these discoveries observing through the best optics at the time, made in Italy by famous opticians like Giuseppe Campani or Eustachio Divini. But was he really able to observe this black line in Saturn's rings? That is what a team of optical scientists from Observatoire de Paris - LESIA with the help of Onera and Institut d'Optique tried to find out, analyzing the lenses used by Cassini, and still preserved in the collection of the observatory. The main difficulty was that even if the lenses have diameters between 84 and 239 mm, the focal lengths are between 6 and 50 m, more than the f...

  5. Rhea and Dione Exospheric Dynamics and Magnetospheric Current Systems Revealed by Cassini

    Science.gov (United States)

    Teolis, B. D.

    2015-12-01

    Cassini's close Rhea and Dione flybys have provided the most detailed in situ field, plasma, and neutral gas measurements ever acquired at a large icy satellite, and have transformed understanding of the magnetospheric interaction of plasma absorbing bodies. This talk will review four key discoveries resulting from Cassini's observations: (1) Rhea and Dione O2 and CO2 [Teolis et al 2010; Simon et al 2011; Tokar et al 2012] exospheres with drastic seasonal variability [Teolis & Waite, submitted] (2) possible refractory lag material which suppresses surface sputtering two orders of magnitude below expectations from laboratory experiments [Teolis & Waite, submitted], (3) a heretofore unknown thermoelectric type flux tube current system, formed to mantain current balance on Rhea's surface [Teolis et al 2014], and (4) secondary Alfvenic induction currents [Simon et al 2012; Khurana et al 2012] stimulated as the diamagnetic and flux tube currents perturb the ambient plasma flow. The findings will be extrapolated to other possible solar system moon-plasma interaction enviroments including Jupiter's icy satellites.

  6. Impact of aerosols present in Titan's atmosphere on the CASSINI radar experiment

    CERN Document Server

    Rodríguez, S; Dobrijevic, M; Ruffié, G; Coll, P; Bernard, J M; Encrenaz, P; 10.1016/S0019-1035(03)00125-8

    2009-01-01

    Simulations of Titan's atmospheric transmission and surface reflectivity have been developed in order to estimate how Titan's atmosphere and surface properties could affect performances of the Cassini radar experiment. In this paper we present a selection of models for Titan's haze, vertical rain distribution, and surface composition implemented in our simulations. We collected dielectric constant values for the Cassini radar wavelength ($\\sim 2.2$ cm) for materials of interest for Titan: liquid methane, liquid mixture of methane-ethane, water ice and light hydrocarbon ices. Due to the lack of permittivity values for Titan's haze particles in the microwave range, we performed dielectric constant ($\\varepsilon_r$) measurements around 2.2 cm on tholins synthesized in laboratory. We obtained a real part of $\\varepsilon_r$ in the range of 2-2.5 and a loss tangent between $10^{-3}$ and $5.10^{-2}$. By combining aerosol distribution models (with hypothetical condensation at low altitudes) to surface models, we find...

  7. Theory of physical libration of the Moon caused by a liquid core: Cassini's motion

    Science.gov (United States)

    Barkin, Yu. V.

    2016-07-01

    This is the first part of a study to develop a modern theory of physical libration of the Moon caused by a liquid core. We use a special approach to studying Moon's rotation relying on Poincaré's planetary model and special forms of equations of motion in Andoyer and Poincaré variables. We construct expansions of the force function of the problem (the second harmonic of the selenopotential) in Andoyer and Poincaré variables for a high-precision description of disturbed orbital motion of the Moon. We investigate the main regularities in lunar rotational motion taken as a body with a solid nonspherical mantle and an ellipsoidal liquid core. The motion of the ideal liquid of the core is simple according to Poincaré. The Cassini laws can be dinamically interpreted for the motion of a synchronous satellite with a liquid core. The Cassini angle (the inclination of the rotation axis relative to the normal to the ecliptic plane) determined by us is very consistent with its determinations from laser observations.

  8. Framing Space: UK Newspaper Reporting of the Beagle 2 and Cassini-Huygens Space Missions

    Science.gov (United States)

    Jergovic, B.; Miller, S.

    2008-05-01

    Relatively little scholarly work has been done on looking at the portrayal of astronomy and space science in the media. This short article examines the UK press coverage of two space missions: the Beagle 2 mission to Mars and the Cassini-Huygens mission to Saturn and its moon Titan. In both cases, the leading scientists exerted a strong influence on what journalists reported, to the extent that some journalists appeared to be almost "embedded" in the mission. For the most part the coverage is positive in tone and the loss of the Beagle 2 spacecraft does not reflect badly on the (later) Cassini-Huygens coverage. Most journalists only covered the actual mission events and, in the case of Huygens, did not follow up to cover the peer-reviewed scientific articles that appeared later. Off-the-cuff comments made by scientists at the time of the missions were widely reported. There appears to be an appreciation by journalists and (by inference) their readership that this was science in the making, and that allowances should be made if these comments later turned out to be inaccurate.

  9. Isochromate fringes simulation by Cassini-like curves for photoelastic analysis of birefringent crystals

    Energy Technology Data Exchange (ETDEWEB)

    Rinaldi, D. [Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio, Universita Politecnica delle Marche, via Brecce Bianche, 60131 Ancona (Italy); INFN, Section of Perugia (Italy)], E-mail: d.rinaldi@univpm.it; Pietroni, P. [Dipartimento di Meccanica, Universita Politecnica delle Marche, via Brecce Bianche, 60131 Ancona (Italy); Davi, F. [Dipartimento di Architettura, Costruzioni e Strutture, Universita Politecnica delle Marche, via Brecce Bianche, 60131 Ancona (Italy)

    2009-05-21

    In optically birefringent uniaxial and biaxial crystals, analyzed by plane polariscope, isochromate interference fringes can be observed. By means of the classical electromagnetic theory a Cassini-like analytical equation of the isochromate fringes, depending on the refraction indexes, has been obtained. The proposed analytical equation is a useful tool to evaluate the internal stress state, as it is related to the isochromate shapes owing to the induced variation of the refraction indexes. Uniaxial crystals can assume complex biaxial behaviour due to particular stress configurations. PbWO{sub 4} (PWO) uniaxial scintillating crystals have been studied. The Cassini-like curves fit well experimental measurements in the case of uniaxial stress. In this research work, a simple model has been proved in the case of strong isochromate fringes distortion due to a stress gradient induced by the bending load. The model fits well the interference pattern, acquired experimentally. This study can pave the way for the quality control on scintillating crystals, used in the fields of high-energy detectors, security and biomedical applications, with complex internal stress state.

  10. iPhone App for Cassini's Magnetospheric Imaging Instrument (MIMI) Browse Products

    Science.gov (United States)

    Myers, H. Y.; Kusterer, M. B.; Mitchell, D. G.; Steele, R. J.; Vandegriff, J. D.

    2016-12-01

    We have created a mobile app on the iOS platform to view the years of browse plots from data collected by the MIMI instruments on Cassini. The focus of the app is to bring the browsing capabilities of the MIMI database to the touchscreen technologies that exist on mobile devices such as smartphones and tablets. Among the data products within the MIMI suite that are viewable through the app include the Energetic Neutral Atom (ENA) images and movies of Saturn taken with the Ion and Neutral Camera (INCA), and spectrograms and line plots from the LEMMS and CHEMS particle detectors. The release of this app also coincides with access to a number of MIMI data products previously not available to the public. We will unveil the features of the app and provide a working demo. The CassiniMIMI app will be available for free from Apple's iTunes Store. A sneak preview of some selection screens and a representative plot are shown in the separate image file.

  11. Emitted Power of Jupiter Based on Cassini CIRS and VIMS Observations

    Science.gov (United States)

    Li, Liming; Baines, Kevin H.; Smith, Mark A.; West, Robert A.; Perez-Hoyos, Santiago; Trammel, Harold J.; Simon-Miller, Amy A.; Conrath, Barney J.; Gierasch, Peter J.; Orton, Glenn S.; hide

    2012-01-01

    The emitted power of Jupiter and its meridional distribution are determined from observations by the Composite Infrared Spectrometer (CIRS) and Visual and Infrared Spectrometer (VIMS) onboard Cassini during its flyby en route to Saturn in late 2000 and early 2001. Jupiter's global- average emitted power and effective temperature are measured to be 14.10+/-0.03 W/sq m and 125.57+/-0.07 K, respectively. On a global scale, Jupiter's 5-micron thermal emission contributes approx. 0.7+/-0.1 % to the total emitted power at the global scale, but it can reach approx. 1.9+/-0.6% at 15degN. The meridional distribution of emitted power shows a significant asymmetry between the two hemispheres with the emitted power in the northern hemisphere 3.0+/-0.3% larger than that in the southern hemisphere. Such an asymmetry shown in the Cassini epoch (2000-01) is not present during the Voyager epoch (1979). In addition, the global-average emitted power increased approx. 3.8+/-1.0% between the two epochs. The temporal variation of Jupiter's total emitted power is mainly due to the warming of atmospheric layers around the pressure level of 200 mbar. The temporal variation of emitted power was also discovered on Saturn (Li et al., 2010). Therefore, we suggest that the varying emitted power is a common phenomenon on the giant planets.

  12. An atlas of bright star spectra in the near infrared from Cassini-VIMS

    CERN Document Server

    Stewart, Paul N; Nicholson, Philip D; Sloan, G C; Hedman, Matthew M

    2015-01-01

    We present the Cassini Atlas Of Stellar Spectra (CAOSS), comprised of near-infrared low-resolution spectra of bright stars recovered from space-based observations by the Cassini spacecraft. The 65 stellar targets in the atlas are predominately M, K and S giants. However it also contains spectra of other bright nearby stars including carbon stars and main sequence stars from A to F. The spectra presented are free of all spectral contamination caused by the Earth's atmosphere, including the detrimental telluric molecular bands which put parts of the near-infrared spectrum out of reach of terrestrial observations. With a single instrument, a spectro-photometric dataset is recovered that spans the near-infrared from 0.8 to 5.1 microns with spectral resolution ranging from R=53.5 to R=325. Spectra have been calibrated into absolute flux units after careful characterisation of the instrumental spectral efficiency. Spectral energy distributions for most stars match closely with literature values. All final data prod...

  13. AN ATLAS OF BRIGHT STAR SPECTRA IN THE NEAR-INFRARED FROM CASSINI-VIMS

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, Paul N.; Tuthill, Peter G. [Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006 (Australia); Nicholson, Philip D. [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States); Sloan, G. C. [Cornell Center for Astrophyics and Planetary Science, Cornell University, Ithaca, NY 14853 (United States); Hedman, Matthew M., E-mail: p.stewart@physics.usyd.edu.au [Department of Physics, University of Idaho, Moscow, ID 83844 (United States)

    2015-12-15

    We present the Cassini Atlas Of Stellar Spectra (CAOSS), comprised of near-infrared, low-resolution spectra of bright stars recovered from space-based observations by the Cassini spacecraft. The 65 stellar targets in the atlas are predominately M, K, and S giants. However, it also contains spectra of other bright nearby stars including carbon stars and main-sequence stars from A to F. The spectra presented are free of all spectral contamination caused by the Earth's atmosphere, including the detrimental telluric molecular bands which put parts of the near-infrared spectrum out of reach of terrestrial observations. With a single instrument, a spectro-photometric data set is recovered that spans the near-infrared from 0.8 to 5.1 μm with spectral resolution ranging from R = 53.5 to R = 325. Spectra have been calibrated into absolute flux units after careful characterization of the instrumental spectral efficiency. Spectral energy distributions for most stars match closely with literature values. All final data products have been made available online.

  14. Cassini-VIMS observations of particles in Enceladus' plume and the E ring

    Science.gov (United States)

    Hedman, M. M.; Nicholson, P. D.; Showalter, M. R.

    2008-09-01

    One of the most surprising discoveries from the Cassini mission is that Saturn's moon Enceladus vents material from its interior, launching gas and particulate matter high above its surface to supply water molecules to the inner magnetosphere and ice-rich grains to the E ring. While data from various instruments onboard Cassini have already provided important information about such parameters as the heat flux from the surface and the distributions of dust and gas within the plume, there is still considerable debate regarding several aspects of this phenomenon. In particular, there are several different models for how solid material is produced and accelerated within the moon, some involve boiling liquids [1] and others disassociating clathrates [2]. We report here on an investigation of the near infrared spectra of the plume between 0.85 and 5.1microns obtained by the Visual and Infrared Mapping Spectrometer (VIMS) instrument [3]. These data provide information on the velocity distribution of particles launched from the surface, which should constrain possible models for the acceleration of solids within the moon [4]. The relevant plume spectral data were obtained at high phase angles (roughly 160°), where diffraction by small particles is the dominant process responsible for scattering light from the sun into the instrument. In fact, provided the particle size distribution is sufficiently steep and the particles' optical constants do not vary too much with wavelength (which should be true outside of the strong water-ice absorption band at three microns), particles of a given size s will most efficiently scatter light with a wavelength ? proportional to s (the constant of proportionality being determined primarily by the phase angle of the observation). Thus there is a relatively direct mapping between the shape of the spectrum and the shape of the particle size distribution, which allows us to compute approximate model spectra for a fairly comprehensive suite of

  15. Contribution to the study of several chemical hazards in the Centre d'Etudes Nucleaires of Fontenay-aux-Roses; Contribution a l'etude de quelques nuisances chimiques au centre d'etudes nucleaires de Fontenay-aux-Roses

    Energy Technology Data Exchange (ETDEWEB)

    Megemont, C.; Grau, C. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1968-10-01

    From the checking of 2750 index cards of hazards, the study relates the distribution of the chemical hazards in the Centre d'Etudes Nucleaires of Fontenay-aux-Roses. Those concerning the greatest number of agents in the Centre are classified according to the categories corresponding to the different conditions of working. Thus, the most important are put forward. Then, the authors rapidly make a review of hazards which may have some special interest because they appear more specific of the nuclear energy or because they are the most frequently noted on the index cards of hazards. The case of the tributylphosphate is studied more precisely. (authors) [French] A partir de l'examen de 2750 fiches de nuisances, l'etude porte sur la repartition des nuisances chimiques au Centre d'Etudes Nucleaires de Fontenay-aux-Roses. Celles qui concernent le plus grand nombre d'agents du Centre sont classees selon les categories correspondant aux differentes conditions de travail. Les plus importantes d'entre elles sont ainsi mises en evidence. | Les auteurs passent ensuite en revue, rapidement, les nuisances qui peuvent presenter un interet particulier soit parce qu'elles semblent plus specifiques de l'Energie Nucleaire, soit parce qu'on les rencontre le plus frequemment sur les fiches de nuisances. Le cas du tributylphosphate est envisage de facon plus detaillee. (auteurs)

  16. GPHS-RTGs in support of the Cassini Mission. Semi annual technical report, March 31, 1997--September 28, 1997

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-10-20

    This progress report describes work on the Radioisotope Thermoelectric Generators and Ancillary Activities carried out as part of the Cassini project. Seperate sections of the report describe activities carried out in support of different tasks assigned as part of this contract.

  17. ESA and NASA agree new mission scenario for Cassini-Huygens

    Science.gov (United States)

    2001-07-01

    After six months of investigations and analysis by a joint ESA/NASA Huygens Recovery Task Force (HRTF), senior management from the two space agencies and members of the Cassini-Huygens scientific community have endorsed several modifications to the mission. These will ensure a return close to 100% of the Huygens science data, with no impact on the nominal prime Cassini tour after the third Titan encounter. The modifications have been introduced because of a design flaw in the Huygens communication system. This problem meant that the Huygens receiver was unable to compensate for the frequency shift between the signal emitted by the Probe and the one received by the Orbiter, due to the Doppler shift (**). This would have resulted in the loss of most of the unique data returned from the Probe during its descent through Titan’s dense atmosphere. To ensure that as much data as possible is returned from the pioneering Probe, the HRTF proposed a new schedule for Cassini’s first orbits around Saturn. The agreed scenario involves shortening Cassini’s first two orbits around the ringed planet and adding a third which provides the required new geometry for the Huygens mission to Titan. In the new scenario, the arrival at Saturn on 1 July 2004 remains unchanged. However, Cassini’s first flyby of Titan will now occur on 26 October, followed by another on 13 December. The Huygens Probe will be released towards Titan on 25 December, for an entry into the moon’s atmosphere 22 days later, on 14 January 2005, seven weeks later than originally planned. To reduce the Doppler shift in the signal from Huygens, the Cassini Orbiter will fly over Titan’s cloud tops at a much higher altitude than originally planned - 65,000 km instead of 1,200 km. This higher orbit has the added advantage that Cassini will be able to preserve the four-year baseline tour through the Saturn system, by resuming its original orbital plan in mid-February 2005. “In any complex space mission problems

  18. A despeckle filter for the Cassini SAR images of Titan's surface

    Science.gov (United States)

    Bratsolis, Emmanuel; Solomonidou, Anezina; Bampasidis, Georgios; Le Mouelic, Stephane; Sotin, Christophe; Coustenis, Athena; Moussas, Xenophon; Kyriakopoulos, Konstantinos

    2010-05-01

    Cassini carries a multimode Ku-band (13.78 GHz) radar instrument designed to probe the surface of Titan and that of other targets in the Saturn system in four operating modes: imaging, altimetry, scatterometry, and radiometry. The Synthetic Aperture Radar (SAR) mode is used at altitudes under ~4000 km, resulting in spatial resolution ranging from ~350 m to >1 km. Images are acquired either left or right of nadir using 2-7 looks. A swath 120-450 km wide is created from 5 antenna beams. SAR coverage is dependent on spacecraft range and orbital geometry. Radar backscatter variations in SAR images can be interpreted in terms of variations of surface slope, near-surface roughness, or near-surface dielectric properties. The images obtained using SAR revealed that Titan has very complex surface (Elachi et al. 2005). A filtering technique is applied to obtain the restored image. One of the major problems hampering the derivation of meaningful texture information from SAR imagery is the speckle noise. It overlays "real" structures and causes gray value variations even in homogeneous parts of the image. Our method is based on probabilistic methods and regards an image as a random element drawn from a prespecified set of possible images. The TSPR (Total Sum Preserving Regularization) filter used here is based on a membrane model Markov random field approximation with a Gaussian conditional probability density function optimized by a synchronous local iterative method. The final form of despeckling gives a sum-preserving regularization for the pixel values of the image. The TSPR method preserves the mean values of local homogeneous regions and decreases the standard deviation up to six times (Bratsolis and Sigelle, 2003). The despeckle filter can be used as intermediate stage for the extraction of meaningful regions that correspond to structural units in the scene or distinguish objects of interest (Bratsolis, 2009). References E. Bratsolis, and M. Sigelle, "Fast SAR Image

  19. Bathymetry and Composition of Titan's Hydrocarbon Seas from the Cassini RADAR Altimeter

    Science.gov (United States)

    Mastrogiuseppe, Marco; Hayes, Alex; Poggiali, Valerio; Lunine, Jonathan; Seu, Roberto; Hofgartner, Jason; Le Gall, Alice; Lorenz, Ralph

    2016-04-01

    The Cassini RADAR's altimetry mode has been successfully used for probing the depth and composition of Titan's hydrocarbons seas. In May 2013, during the spacecraft's T91 flyby of Titan, the instrument demonstrated its capabilities as a radar sounder, presenting a unique opportunity to constraint the depth and composition of Titan's second largest sea, Ligeia Mare. Later, observations of Kraken Mare and Punga Mare were planned and executed in August 2014 (T104) and January 2015 (T108), respectively. While most of the seafloor was not detected at Kraken, suggesting the sea was either too deep or too absorptive in these areas to observe a return from the seafloor, shallow areas near Moray Sinus did show subsurface reflections. At Punga Mare, a clear detection of the subsurface was observed with a maximum depth of 120 m along the radar altimetry transect. Herein we present a re-analysis of altimetry data acquired over Ligeia Mare and, earlier in the Cassini mission (in December 2008 during T49), over the southern Ontario Lacus. Depths measurements and liquid composition are obtained using a novel technique which makes use of radar simulations and Monte Carlo-based inversions. Simulation is based on a two-layer model, where the surface is represented by a specular reflection and the seafloor is modeled using a facet-based synthetic surface, including thermal noise, speckle effects, analog to digital conversion (ADC), block adaptive quantization (BAQ), and allows for possible receiver saturation. This new analysis provides an update to the Ku-band attenuation (the Cassini RADAR operates at a wavelength of 2 cm) and results in a new estimate for loss tangent and composition. We found a value of specific attenuation of the liquid equal to 0.14±0.02 dB/m and 0.2±0.1 dB/m, which is equivalent to a loss tangent of 4.4±0.9x10^-5 and 7±3x10^-5 for Ligeia Mare and Ontario Lacus, respectively. Assuming that Titan's liquid bodies are composed by a ternary mixture of methane

  20. Cassini SAR, radiometry, scatterometry and altimetry observations of Titan's dune fields

    Science.gov (United States)

    Le, Gall A.; Janssen, M.A.; Wye, L.C.; Hayes, A.G.; Radebaugh, J.; Savage, C.; Zebker, H.; Lorenz, R.D.; Lunine, J.I.; Kirk, R.L.; Lopes, R.M.C.; Wall, S.; Callahan, P.; Stofan, E.R.; Farr, Tom

    2011-01-01

    Large expanses of linear dunes cover Titan's equatorial regions. As the Cassini mission continues, more dune fields are becoming unveiled and examined by the microwave radar in all its modes of operation (SAR, radiometry, scatterometry, altimetry) and with an increasing variety of observational geometries. In this paper, we report on Cassini's radar instrument observations of the dune fields mapped through May 2009 and present our key findings in terms of Titan's geology and climate. We estimate that dune fields cover ???12.5% of Titan's surface, which corresponds to an area of ???10millionkm2, roughly the area of the United States. If dune sand-sized particles are mainly composed of solid organics as suggested by VIMS observations (Cassini Visual and Infrared Mapping Spectrometer) and atmospheric modeling and supported by radiometry data, dune fields are the largest known organic reservoir on Titan. Dune regions are, with the exception of the polar lakes and seas, the least reflective and most emissive features on this moon. Interestingly, we also find a latitudinal dependence in the dune field microwave properties: up to a latitude of ???11??, dune fields tend to become less emissive and brighter as one moves northward. Above ???11?? this trend is reversed. The microwave signatures of the dune regions are thought to be primarily controlled by the interdune proportion (relative to that of the dune), roughness and degree of sand cover. In agreement with radiometry and scatterometry observations, SAR images suggest that the fraction of interdunes increases northward up to a latitude of ???14??. In general, scattering from the subsurface (volume scattering and surface scattering from buried interfaces) makes interdunal regions brighter than the dunes. The observed latitudinal trend may therefore also be partially caused by a gradual thinning of the interdunal sand cover or surrounding sand sheets to the north, thus allowing wave penetration in the underlying

  1. Earth-based and Cassini-spacecraft Observations of Irregular Moons of Jupiter and Saturn

    Science.gov (United States)

    Denk, Tilmann; Mottola, S.; Roatsch, T.; Rosenberg, H.; Neukum, G.

    2010-10-01

    We observed irregular satellites of Jupiter and Saturn with the ISS camera of the Cassini spacecraft [1] and with the 1.23-m telescope of the Calar Alto observatory in Spain [2]. Scientific goals are the determination of rotation periods, rotation-axis orientations, spin directions, size parameters, color properties, phase curves, and searches for binaries. Himalia (J6), the largest of the irregular jovian moons, has been imaged by Cassini on 18 Dec 2000; a body size of 120±5 km x 150±10 km and an albedo of 0.05±0.01 have been measured [3,4]. Earth-based observations revealed that Himalia's rotation period is probably 9.3 h, which is in agreement with the 9.2 to 9.8 h suggested by [5], although periods of 7.8 or 11.7 h cannot be ruled out yet. In the saturnian system, 10 irregular moons were scheduled for Cassini ISS observations over time spans >9 hrs until end-of-August, 2010. Observation distances vary between 5.6 and 22 million km, corresponding to ISS pixel scales of 34 to 130 km. For the objects measured so far, the rotation periods vary significantly. For instance, Siarnaq (S/2000 S3; size 40 km) and Ymir (S/2000 S1; 18 km) exhibit rotation periods of 6.7 h and 7.3 h, respectively, while Kiviuq (S/2000 S5; 16 km) might take about 22 h for one rotation. First results from the observation campaigns will be presented at the meeting. References: [1] Porco, C.C., et al. (2004), Space Sci. Rev. 115, 363; [2] http://www.caha.es/CAHA/Telescopes/1.2m.html; [3] Denk, T. et al. (2001), Conference on Jupiter (Planet, Satellites & Magnetosphere), Boulder, CO, 25-30 June 2001, abstracts book p. 30-31; [4] Porco, C.C., et al. (2003), Science 299, 1541; [5] Degewij, J., et al. (1980), Icarus 44, 520. We gratefully acknowledge funding by the German Space Agency (DLR) Bonn through grant no. 50 OH 0305.

  2. Water vapor on Titan: the stratospheric vertical profile from Cassini/CIRS infrared spectra

    Science.gov (United States)

    Cottini, V.; Jennings, D. E.; Nixon, C. A.; Anderson, C. M.; Gorius, N.; Bjoraker, G. L.; Coustenis, A.; Achterberg, R. K.; Teanby, N. A.; de Kok, R.; Irwin, P. G. J.; Bézard, B.; Lellouch, E.; Flasar, F. M.; Bampasidis, G.

    2012-04-01

    Water vapor in Titan’s middle atmosphere has previously been detected only by disk-average observations from the Infrared Space Observatory (Coustenis et al., 1998). We report here the successful detection of stratospheric water vapor using the Cassini Composite Infrared Spectrometer (CIRS, Flasar et al., 2004) following an earlier null result (de Kok et al., 2007a). CIRS senses water emissions in the far-infrared spectral region near 50 microns, which we have modeled using two independent radiative transfer and inversion codes (NEMESIS, Irwin et al 2008 and ART, Coustenis et al., 2010). From the analysis of nadir spectra we have derived a mixing ratio of (0.14 ± 0.05) ppb at 100 km, corresponding to a column abundance of approximately (3.7 ± 1.3) × 10^14 mol/cm2. Using limb observations, we obtained mixing ratios of (0.13 ± 0.04) ppb at 125 km and (0.45 ± 0.15) ppb at 225 km of altitude, confirming that the water abundance has a positive vertical gradient as predicted by photochemical models. In the latitude range (80˚S - 30˚N) we see no evidence for latitudinal variations in these abundances within the error bars. References: Coustenis, A.; Salama, A.; Lellouch, E.; Encrenaz, Th.; Bjoraker, G. L.; Samuelson, R. E.; de Graauw, Th.; Feuchtgruber, H.; Kessler, M. F., 1998. Evidence for water vapor in Titan's atmosphere from ISO/SWS data. Astronomy and Astrophysics, v.336, p.L85-L89 Coustenis, A.; Jennings, D. E.; Nixon, C. A.; Achterberg, R. K.; Lavvas, P.; Vinatier, S.; Teanby, N. A.; Bjoraker, G. L.; Carlson, R. C.; Piani, L.; Bampasidis, G.; Flasar, F. M.; Romani, P. N., 2010. Titan trace gaseous composition from CIRS at the end of the Cassini-Huygens prime mission. Icarus, Volume 207, Issue 1, p. 461-476. de Kok, R.; Irwin, P. G. J.; Teanby, N. A.; Lellouch, E.; Bézard, B.; Vinatier, S.; Nixon, C. A.; Fletcher, L.; Howett, C.; Calcutt, S. B.; Bowles, N. E.; Flasar, F. M.; Taylor, F. W. , 2007a. Oxygen compounds in Titan's stratosphere as observed by

  3. Cassini Radio Occultation of Saturn's Rings: a Bayesian Approach to Particle Size Distribution Recovery

    Science.gov (United States)

    Wong, K. K.; Marouf, E. A.

    2004-12-01

    The radio occultation technique was first used to study Saturn's rings through their effects on quasi-monochromatic radio signals transmitted from Voyager 1 during its flyby of Saturn in 1980. Almost a quarter of a century later, Cassini is planned to conduct a more extensive set of radio occultation experiments during its tour of the Saturn system. Cassini enjoys the advantage of a wide range of ring viewing geometry as well as the unique new capability of simultaneously transmitting 0.94, 3.6 and 13 cm-wavelength coherent radio signals (Ka-, X-, and S-band, respectively). Observed extinction of the direct signal and time-sequence spectra (spectrogram) of the near-forward scattered signal can be used to infer the size distribution of particles of resolved ring features (among other objectives). The inference requires solving three distinct inversion problems to recover from the measurements: i) the multiply-scattered collective diffraction lobe of a resolved ring feature, ii) the first-order scattering contribution to the collective lobe, and iii) the corresponding particle size distribution. Although various classical regularization techniques may be used for this purpose, a subjective valuation of solution smoothness usually needs to be introduced. We investigate an alternative approach based on Bayesian function learning schemes which provides a rigorous probabilistic framework to address the tradeoff between data fit residuals and prior knowledge about the character of the solution. In contrast with the regularization approach, the Bayesian approach provides estimates of confidence intervals for the most-likely solution achieved, an important advantage. The approach is particularly adaptable to some Cassini occultations of relatively unfavorable alignment between contours of constant Doppler shift in the ring plane and circular boundaries of ring features, as the approach naturally "fuses" time-sequence of spectra each containing contributions from adjacent

  4. The Calm Methane Northern Seas of Titan from Cassini Radio Science Observations

    Science.gov (United States)

    Marouf, Essam A.; French, Richard G.; Wong, Kwok; Anabtawi, Aseel; Schinder, Paul J.; Cassini Radio Science Team

    2016-10-01

    We report on results from 3 bistatic scattering observations of Titan northern seas conducted by the Cassini spacecraft in 2014 ( flybys T101, T102, and T106). The onboard Radio Science instrument transmits 3 sinusoidal signals of 0.94, 3.6, and 13 cm wavelengths. The spacecraft is continuously maneuvered to point in incidence direction so that mirror-like reflections from Titan's surface are observed at the ground stations of the NASA Deep Space Network. The corresponding ground-track in all 3 cases crossed different regions of Kraken Mare, and in the case of T101 also crossed Ligeia Mare. A nearly pure sinusoidal reflected signal was clearly detectable in the observed echoes spectra over surface regions identified in the Cassini RADAR images as potential liquid regions. Weaker quasi-specular echoes were also evident over some intermediate dry land and near sea shores. Cassini transmits right-circularly-polarized (RCP) signals and both the RCP and LCP echo components are observed. Their spectral shape, bandwidth, and total power are the observables used to infer/constrain physical surface properties. Presented results are limited to the 3.6 cm wavelength signal which has the largest SNR. The remarkably preserved sinusoidal echo spectral shape and the little detectable Doppler broadening strongly suggest surface that is smooth on scales large compared to 3.6 cm. If long wavelength gravity waves are present, they must be very subtle. The measured RCP/LCP echo power ratio provides direct measurement of the surface dielectric constant and is diagnostic of the liquid composition. The power ratio measurements eliminate possible significant ethane contribution and strongly imply predominantly liquid methane and nitrogen composition. Carefully calibrated measurements of the absolute echo power and the inferred dielectric constant constrain the presence of any capillary waves of wavelength << 3.6 cm. The latter affect wave coherence across the Fresnel region, reducing the

  5. Ions in the Enceladus plume: Cassini/CAPS ion measurements at high energy resolution

    Science.gov (United States)

    Crary, F.; Coates, A. J.; Hill, T. W.; Jones, G. H.; Tokar, R. L.

    2012-12-01

    During several Cassini encounters with Saturn's satellite, Enceladus, the spacecraft crossed through the plume of water vapor and dust south of the satellite with a spacecraft orientation which allowed the Cassini Plasma Spectrometer (CAPS) to observe ions and nanograin dust particles associated with the plume. During three of these encounters, E7 (November 2, 2009), E17 (March XX, 2012) and E18 (April YY, 2012), the trajectories were very similar and parallel to the equatorial plane (i.e. little north-south velocity, so that the spacecraft moved perpendicular to the rotation axis of Enceladus.) Previous analysis, using data from the CAPS ion mass spectrometer (IMS) and electron spectrometer (ELS), identified cold ions at rest with respect to Enceladus [1], negative water group and water cluster ions [2], and both positively and negatively charged dust particles in the 0.5 to 2 nm (1000 to 20,000 AMU) size range [3,4]. We present observations from the third CAPS sensor, the ion beam spectrometer (IBS). Although this sensor lacks the angular resolution of the other CAPS sensors, it has an energy resolution of 1.4%, roughly an order of magnitude greater than the ELS and IMS sensors. The IBS data allows us to estimate the temperature and flow speed of the low energy ions in the plume, and characterize the structure of the plume ionosphere. We find that the plume is highly structured, down to the 2-s (17 km along track) limit of the instrument's sampling. Distinct regions of cold, dense ions, resembling a collisional ionosphere, are intermixed with a broad background of warmer, non-thermal ions, possibly resulting from charge exchange between magnetospheric ions and plume neutrals. Despite the sensor's lack of intrinsic angular resolution, the ion flux and energy spectra are consistent with a drift velocity away from Saturn and in the direction of the upstream flow. References: [1] Tokar et al., 2009, Cassini detection of Enceladus' cold water-group plume ionosphere

  6. Saturn's Magnetic Field Model: Birotor Dipole From Cassini RPWS and MAG Experiments

    Science.gov (United States)

    Galopeau, P. H. M.

    2016-12-01

    The radio and plasma wave science (RPWS) experiment on board the Cassini spacecraft, orbiting around Saturn since July 2004, revealed the presence of two distinct and variable rotation periods in the Saturnian kilometric radiation (SKR) which were attributed to the northern and southern hemispheres respectively. We believe that the periodic time modulations present in the SKR are mainly due to the rotation of Saturn's inner magnetic field. The existence of a double period implies that the inner field is not only limited to a simple rotation dipole but displays more complex structures having the same time periodicities than the radio emission. In order to build a model of this complex magnetic field, it is absolutely necessary to know the accurate phases of rotation linked with the two periods. The radio observations from the RPWS experiment allow a continuous and accurate follow-up of these rotation phases, since the SKR emission is permanently observable and produced very close to the planetary surface. A wavelet transform analysis of the intensity of the SKR signal received at 290 kHz between July 2004 and June 2012 was performed in order to calculate in the same time the different periodicities and phases. A dipole model was proposed for Saturn's inner magnetic field: this dipole presents the particularity to have North and South poles rotating around Saturn's axis at two different angular velocities; this dipole is tilted and not centered. 57 Cassini's revolutions, the periapsis of which is less than 5 Saturnian radii, have been selected for this study. For each of these chosen orbits, it is possible to fit with high precision the measurements of the MAG data experiment given by the magnetometers embarked on board Cassini. A nonrotating external magnetic field completes the model. This study suggests that Saturn's inner magnetic field is neither stationary nor fully axisymmetric. These results can be used as a boundary condition for modelling and constraining

  7. Magnetic signatures of ion cyclotron waves during Cassini's high-inclination orbits of Saturn

    Science.gov (United States)

    Meeks, Zachary; Simon, Sven

    2017-02-01

    Based on magnetic field data from Cassini's high-inclination orbits of Saturn (radius RS = 60 , 268 km), we analyze the latitudinal distribution of ion cyclotron waves in the giant planet's magnetosphere. Our survey takes into account magnetic field data from all high-inclination orbits between 2004 and 2015. We analyze the dependency of the occurrence rate and amplitude of the ion cyclotron waves on radial distance ρ to Saturn's rotation axis, vertical distance z to Saturn's equatorial plane, and magnetic latitude λ. The occurrence rate of ion cyclotron waves is approximately 100% in Saturn's equatorial plane between the orbits of Enceladus and Dione and decreases to 50% at altitudes of | z | ≈ 0.6RS . Ion cyclotron waves were detected up to | z | = 2.0RS . The occurrence rate displays strong, non-monotonic variations with respect to ρ, z, and λ. The vertical amplitude profile of the waves exhibits an M-like pattern with two distinct peaks near z = ± 0.3RS and the central minimum at z=0. Compared to earlier observations, we find this M-like structure to be inflated in±z direction by a factor of three. The available magnetic field data provides only weak evidence for a local impact of Enceladus and Dione on the ion cyclotron wave field. Using the observed Doppler shift of the ion cyclotron wave frequency during Cassini's high-inclination orbits, we demonstrate the existence of a narrow band of bidirectional wave propagation. This band is centered around Saturn's equatorial plane and possesses a half-width of | z | = 0.15RS , which agrees well with the vertical scale height of Saturn's neutral cloud. To the north of this band, all ion cyclotron waves propagate towards the north (z > 0); and to the south, all waves propagate towards the south (z < 0). In companion with our previous study (Meeks et al., 2016), this survey provides the complete three-dimensional picture of the ion cyclotron wave field between the orbits of Enceladus and Rhea during the Cassini

  8. First Results From the Gas Chromatograph Mass Spectrometer (GCMS) Experiment on the Cassini-Huygens Probe

    Science.gov (United States)

    Niemann, Hasso B.; Demick, J.; Haberman, J.; Harpold, D.; Kasprzak, W.; Raaen, E.; Way, S.; Atreya, S.; Carignan, G.; Bauer, S.

    2005-01-01

    The Huygens Probe of the Cassini Huygens Mission entered the atmosphere of the moon Titan on January 14,2005. The GCMS was part of the instrument complement on the Probe to measure in situ the chemical composition of the atmosphere during the probe descent and to support the Aerosol Collector Pyrolyser (ACP) experiment by serving as detector for the pyrolization products. The GCMS employed a quadrupole mass filter with a secondary electron multiplier detection system and a gas sampling system providing continuous direct atmospheric composition measurements and batch sampling through three gas chromatographic (GC) columns. The mass spectrometer employed five electron impact ion sources with available electron energies of either 70 or 25 eV. Three ion sources served as detectors for the GC columns and two were dedicated to direct atmosphere sampling and ACP gas sampling, respectively. The GCMS gas inlet was heated to prevent condensation, and served to evaporate surface constituents after impact.

  9. Imaging the interaction of the heliosphere with the interstellar medium from Saturn with Cassini.

    Science.gov (United States)

    Krimigis, S M; Mitchell, D G; Roelof, E C; Hsieh, K C; McComas, D J

    2009-11-13

    We report an all-sky image of energetic neutral atoms (ENAs) >6 kilo-electron volts produced by energetic protons occupying the region (heliosheath) between the boundary of the extended solar atmosphere and the local interstellar medium (LISM). The map obtained by the Ion and Neutral Camera (INCA) onboard Cassini reveals a broad belt of energetic protons whose nonthermal pressure is comparable to that of the local interstellar magnetic field. The belt, centered at approximately 260 degrees ecliptic longitude extending from north to south and looping back through approximately 80 degrees, appears to be ordered by the local interstellar magnetic field. The shape revealed by the ENA image does not conform to current models, wherein the heliosphere resembles a cometlike figure aligned in the direction of Sun's travel through the LISM.

  10. Cassini/VIMS observes rough surfaces on Titan's Punga Mare in specular reflection.

    Science.gov (United States)

    Barnes, Jason W; Sotin, Christophe; Soderblom, Jason M; Brown, Robert H; Hayes, Alexander G; Donelan, Mark; Rodriguez, Sebastien; Mouélic, Stéphane Le; Baines, Kevin H; McCord, Thomas B

    Cassini/VIMS high-phase specular observations of Titan's north pole during the T85 flyby show evidence for isolated patches of rough liquid surface within the boundaries of the sea Punga Mare. The roughness shows typical slopes of 6°±1°. These rough areas could be either wet mudflats or a wavy sea. Because of their large areal extent, patchy geographic distribution, and uniform appearance at low phase, we prefer a waves interpretation. Applying theoretical wave calculations based on Titan conditions our slope determination allows us to infer winds of 0.76±0.09 m/s and significant wave heights of [Formula: see text] cm at the time and locations of the observation. If correct, these would represent the first waves seen on Titan's seas, and also the first extraterrestrial sea-surface waves in general.

  11. Improvement of the basis for the solution of the Dirac equation in Cassini coordinates

    Science.gov (United States)

    Hahn, W.; Artemyev, A. N.; Surzhykov, A.

    2017-08-01

    We propose an improvement of the basis for the solution of the stationary two-centre Dirac equation in Cassini coordinates using the finite-basis-set method presented in our earlier article [J. Phys. B 43, 235207 (2010)]. For the calculations in the above article, we constructed the basis for approximating the energy eigenfunctions by using smooth piecewise defined polynomials, called B-splines. In the present article, we report that an analysis of the employed representation of the Dirac matrices shows that the above approximation is not efficient using B-splines only. Therefore, we include basis functions which are defined using functions with step-like behavior instead of B-splines. Thereby, we achieve a significant increase of accuracy of results.

  12. Improvement of the Basis for the Solution of the Dirac Equation in Cassini Coordinates

    CERN Document Server

    Hahn, Walter; Surzhykov, Andrey

    2016-01-01

    We propose an improvement of the basis for the solution of the stationary two-centre Dirac equation in Cassini coordinates using the finite-basis-set method presented in [1]. For the calculations in [1], we constructed the basis for approximating the energy eigenfunctions by using smooth piecewise defined polynomials, called B-splines. In the present article, we report that an analysis of the employed representation of the Dirac matrices shows that the above approximation is not efficient using B-spines only. Therefore, we include basis functions which are defined using functions with step-like behaviour instead of B-splines. Thereby, we achieve a significant increase of accuracy of results as compared to [1].

  13. Iapetus: unique surface properties and a global color dichotomy from Cassini imaging.

    Science.gov (United States)

    Denk, Tilmann; Neukum, Gerhard; Roatsch, Thomas; Porco, Carolyn C; Burns, Joseph A; Galuba, Götz G; Schmedemann, Nico; Helfenstein, Paul; Thomas, Peter C; Wagner, Roland J; West, Robert A

    2010-01-22

    Since 2004, Saturn's moon Iapetus has been observed repeatedly with the Imaging Science Subsystem of the Cassini spacecraft. The images show numerous impact craters down to the resolution limit of approximately 10 meters per pixel. Small, bright craters within the dark hemisphere indicate a dark blanket thickness on the order of meters or less. Dark, equator-facing and bright, poleward-facing crater walls suggest temperature-driven water-ice sublimation as the process responsible for local albedo patterns. Imaging data also reveal a global color dichotomy, wherein both dark and bright materials on the leading side have a substantially redder color than the respective trailing-side materials. This global pattern indicates an exogenic origin for the redder leading-side parts and suggests that the global color dichotomy initiated the thermal formation of the global albedo dichotomy.

  14. Cassini finds molecular hydrogen in the Enceladus plume: Evidence for hydrothermal processes

    Science.gov (United States)

    Waite, J. Hunter; Glein, Christopher R.; Perryman, Rebecca S.; Teolis, Ben D.; Magee, Brian A.; Miller, Greg; Grimes, Jacob; Perry, Mark E.; Miller, Kelly E.; Bouquet, Alexis; Lunine, Jonathan I.; Brockwell, Tim; Bolton, Scott J.

    2017-04-01

    Saturn’s moon Enceladus has an ice-covered ocean; a plume of material erupts from cracks in the ice. The plume contains chemical signatures of water-rock interaction between the ocean and a rocky core. We used the Ion Neutral Mass Spectrometer onboard the Cassini spacecraft to detect molecular hydrogen in the plume. By using the instrument’s open-source mode, background processes of hydrogen production in the instrument were minimized and quantified, enabling the identification of a statistically significant signal of hydrogen native to Enceladus. We find that the most plausible source of this hydrogen is ongoing hydrothermal reactions of rock containing reduced minerals and organic materials. The relatively high hydrogen abundance in the plume signals thermodynamic disequilibrium that favors the formation of methane from CO2 in Enceladus’ ocean.

  15. Tidal Control of Jet Eruptions on Enceladus as Observed by Cassini ISS between 2005 and 2007

    Science.gov (United States)

    Hurford, T. A.; Helfenstein, P.; Spitale, J. N.

    2012-01-01

    Observations of Enceladus have revealed active jets of material erupting from cracks on its south polar surface. It has previously been proposed that diurnal tidal stress, driven by Enceladus' orbital eccentricity, may actively produce surface movement along these cracks daily and thus may regulate when eruptions occur. Our analysis of the stress on jet source regions identified in Cassini ISS images reveals tidal stress as a plausible controlling mechanism of jet activity. However, the evidence available in the published and preliminary observations of jet activity between 2005 and 2007 may not be able to solidify the link between tidal stress and eruptions from fissures. Ongoing, far more comprehensive analyses based on recent, much higher resolution jetting observations have the potential to prove otherwise.

  16. Cassini UVIS observations of Titan ultraviolet airglow intensity dependence with solar zenith angle

    Science.gov (United States)

    Royer, E. M.; Ajello, J. M.; Holsclaw, G. M.; West, R. A.; Esposito, L. W.; Bradley, E. T.

    2017-01-01

    The Cassini Ultraviolet Imaging Spectrometer (UVIS) observed the airglow (dayglow and nightglow) of Titan over a range of solar zenith angles (SZA) from 14 to 150° on five separate observations obtained between 2008 and 2012. The modeling of the solar cycle normalized UVIS observations indicates that a Chapman layer function provides a satisfactory fit to the intensity of the EUV and FUV airglow molecular emissions of the N2 Lyman-Birge-Hopfield band system (LBH a1Πg→X1>∑g+), the Carroll-Yoshino band system (c4'1>∑u+→X1>∑g+), and of several atomic multiplets of nitrogen (NI, II) as a function of SZA. This result shows that the strongest contribution to the Titan dayglow occurs by processes (photoelectrons and photodissociation) involving the solar EUV flux rather than magnetospheric particle precipitation that dominates emission excitation in the nightglow.

  17. Astrometry of Cassini with the VLBA to improve the Saturn ephemeris

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Dayton L.; Folkner, William M.; Jacobson, Robert A.; Jacobs, Christopher S. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Dhawan, Vivek; Romney, Jon [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Fomalont, Ed, E-mail: dayton.jones@jpl.nasa.gov [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States)

    2015-01-01

    Planetary ephemerides have been developed and improved over centuries. They are a fundamental tool for understanding solar system dynamics, and essential for planetary and small body mass determinations, occultation predictions, high-precision tests of general relativity, pulsar timing, and interplanetary spacecraft navigation. This paper presents recent results from a continuing program of high-precision astrometric very long baseline interferometry (VLBI) observations of the Cassini spacecraft orbiting Saturn, using the Very Long Baseline Array (VLBA). We have previously shown that VLBA measurements can be combined with spacecraft orbit determinations from Doppler and range tracking and VLBI links to the inertial extragalactic reference frame to provide the most accurate barycentric positions currently available for Saturn. Here we report an additional five years of VLBA observations along with improved phase reference source positions, resulting in an improvement in residuals with respect to the Jet Propulsion Laboratory's dynamical ephemeris.

  18. Flyby Error Analysis Based on Contour Plots for the Cassini Tour

    Science.gov (United States)

    Stumpf, P. W.; Gist, E. M.; Goodson, T. D.; Hahn, Y.; Wagner, S. V.; Williams, P. N.

    2008-01-01

    The maneuver cancellation analysis consists of cost contour plots employed by the Cassini maneuver team. The plots are two-dimensional linear representations of a larger six-dimensional solution to a multi-maneuver, multi-encounter mission at Saturn. By using contours plotted with the dot product of vectors B and R and the dot product of vectors B and T components, it is possible to view the effects delta V on for various encounter positions in the B-plane. The plot is used in operations to help determine if the Approach Maneuver (ensuing encounter minus three days) and/or the Cleanup Maneuver (ensuing encounter plus three days) can be cancelled and also is a linear check of an integrated solution.

  19. Flux transfer event observation at Saturn's dayside magnetopause by the Cassini spacecraft

    Science.gov (United States)

    Jasinski, Jamie M.; Slavin, James A.; Arridge, Christopher S.; Poh, Gangkai; Jia, Xianzhe; Sergis, Nick; Coates, Andrew J.; Jones, Geraint H.; Waite, J. Hunter

    2016-07-01

    We present the first observation of a flux rope at Saturn's dayside magnetopause. This is an important result because it shows that the Saturnian magnetopause is conducive to multiple X-line reconnection and flux rope generation. Minimum variance analysis shows that the magnetic signature is consistent with a flux rope. The magnetic observations were well fitted to a constant-α force-free flux rope model. The radius and magnetic flux content of the rope are estimated to be 4600-8300 km and 0.2-0.8 MWb, respectively. Cassini also observed five traveling compression regions (remote signatures of flux ropes), in the adjacent magnetosphere. The magnetic flux content is compared to other estimates of flux opening via reconnection at Saturn.

  20. On the nature of MHD and kinetic scale turbulence in the magnetosheath of Saturn: Cassini observations

    Science.gov (United States)

    Hadid, L.; Sahraoui, F.; Kiyani, K. H.; Retino, A.; Modolo, R.; Masters, A.; Dougherty, M.

    2015-10-01

    Low frequency turbulence in Saturn's magnetosheath is investigated using in-situ measurements of the Cassini spacecraft. We focus on the magnetic energy spectra computed in the frequency range # [10-4, 1]Hz. Three main results are reported: 1) The magnetic energy spectra showed a # f-1 scaling at MHD scales followed by an # f-2.6 scaling at the sub-ion scales without forming the so-called inertial range, breaking the universality of the Kolmogorov spectrum in the magnetosheath; 2) The magnetic compressibility and the cross-correlation between the parallel component of the magnetic field and density fluctuations C(#n, #B||) indicate the dominance of the compressible magnetosonic slow modes at MHD scales rather than the Alfvén mode [3] ; 3) Higher order statistics revealed a monofractal (resp. multifractal) behaviour of the turbulent flow behind a quasiperpendicular (resp. quasi-parallel) shock at the subion scales.

  1. Jupiter's Phase Variations from Cassini: a testbed for future direct-imaging missions

    Science.gov (United States)

    Mayorga, Laura; Jackiewicz, Jason; Rages, Kathy; West, Robert; Knowles, Ben; Marley, Mark; Lewis, Nikole

    2016-10-01

    Phase curves are important for our understanding of the energy balance and scattering behavior of an exoplanet's atmosphere. In preparation for future direct-imaging missions of Jupiter-like planets, we present phase curves of Jupiter from 0--150 degrees as measured in multiple optical bandpasses by Cassini/ISS during the Millennium flyby of Jupiter in late 2000 to early 2001. We demonstrate and confirm that Jupiter is not well represented by a Lambertian phase function and that its color is more variable with phase angle than predicted by Jupiter-like models. This indicates that a Jupiter-twin observed near quadrature may not be as straightforward to classify as a Jupiter-like planet.

  2. Cassini/VIMS Observes Rough Surfaces on Titan's Punga Mare in Specular Reflection

    Science.gov (United States)

    Barnes, Jason W.; Sotin, Christophe; Soderblom, Jason M.; Brown, Robert H.; Hayes, Alexander G.; Donelan, Mark; Rodriguez, Sebastien; Le Mouelic, Stephane; Baines, Kevin H.; McCord, Thomas B.

    2014-08-01

    Cassini/VIMS high-phase specular observations of Titan's north pole during the T85 flyby show evidence for isolated patches of rough liquid surface within the boundaries of the sea Punga Mare. The roughness shows typical slopes of 6°±1°. These rough areas could be either wet mudflats or a wavy sea. Because of their large areal extent, patchy geographic distribution, and uniform appearance at low phase, we prefer a waves interpretation. Applying theoretical wave calculations based on Titan conditions our slope determination allows us to infer winds of 0.76±0.09 m/s and significant wave heights of 2+2-1 cm at the time and locations of the observation. If correct, these would represent the first waves seen on Titan's seas, and also the first extraterrestrial sea-surface waves in general.

  3. Strong Temporal Variation Over One Saturnian Year: From Voyager to Cassini

    Science.gov (United States)

    Li, Liming; Achterberg, Richard K.; Conrath, Barney J.; Gierasch, Peter J.; Smith, Mark A.; Simon-Miller, Amy A.; Nixon, Conor A.; Orton, Glenn S.; Flasar, F. Michael; Jiang, Xun; hide

    2013-01-01

    Here we report the combined spacecraft observations of Saturn acquired over one Saturnian year (approximately 29.5 Earth years), from the Voyager encounters (1980-81) to the new Cassini reconnaissance (2009-10). The combined observations reveal a strong temporal increase of tropic temperature (approximately 10 Kelvins) around the tropopause of Saturn (i.e., 50 mbar), which is stronger than the seasonal variability (approximately a few Kelvins). We also provide the first estimate of the zonal winds at 750 mbar, which is close to the zonal winds at 2000 mbar. The quasi-consistency of zonal winds between these two levels provides observational support to a numerical suggestion inferring that the zonal winds at pressures greater than 500 mbar do not vary significantly with depth. Furthermore, the temporal variation of zonal winds decreases its magnitude with depth, implying that the relatively deep zonal winds are stable with time.

  4. Weak Waves and Wakes in Saturn's Rings: Observations by Cassini ISS

    Science.gov (United States)

    Burns, J. A.; Tiscareno, M. S.; Porco, C. C.; Dones, H.; Murray, C. D.; Cassini Imaging

    2004-11-01

    At Saturn Orbit Insertion (SOI), the Cassini Imaging Science Subsystem (ISS) imaged the rings of Saturn with unprecedented resolution and signal/noise. Many features are present with remarkable clarity, including density waves excited by first-order Lindblad resonances with the tiny satellite Atlas, as well as density waves excited by second-order Lindblad resonances with Janus, Prometheus, and Pandora. Additionally, we find much structure due to Pan, the satellite embedded in the Encke Gap. As one moves away from the gap, the Pan disturbances undergo a transition, from features best described as gravitional wakes to features best described as density waves. We will present examples of these phenomena and discuss their implications.

  5. Cryo-Cooled Sapphire Oscillator for the Cassini Ka-Band Experiment

    Science.gov (United States)

    Wang, Rabi T.; Dick, G. John

    1997-01-01

    We present features for an ultra-stable sapphire cryogenic oscillator which has been designed to support the Cassini Ka-band Radio Science experiment. The design of this standard is new in several respects. It is cooled by a commercial cryocooler instead of liquid cryogens to increase operating time, and it uses a technology to adjust the temperature turn-over point to extend the upper operating temperature limit and to enable construction of multiple units with uniform operating characteristics. Objectives are 3 x 10(exp -15) stability for measuring times 1 second less than or equal to (tau) less than or equal to 100 seconds, phase noise of -85 dBc/Hz from offset frequencies of 1 Hz to 1000 Hz at 10 GHz carrier frequency, and a one year continuous operating period.

  6. Design of a Cryocooled Sapphire Oscillator for the Cassini Ka-Band Experiment

    Science.gov (United States)

    Dick, G. J.; Wang, R. T.

    1998-04-01

    We present design aspects of a cryogenic sapphire oscillator that is being developed for ultra-high short-term stability and low phase noise in support of the Cassini Ka-band (32-GHz) radio science experiment. With cooling provided by a commercial cryocooler instead of liquid helium, this standard is designed to operate continuously for periods of a year or more. Performance targets are a stability of 3 x 10^(-15) (1 second ≤ τ ≤ 100 seconds) and a phase noise of -73 dBc/Hz at 1 Hz measured at 34 GHz. Test results are reported for several subsystems, including the cryocooler, vibration isolation system, and ruby compensating element.

  7. Jupiter's Phase Variations from Cassini: a testbed for future direct-imaging missions

    Science.gov (United States)

    Mayorga, Laura; Jackiewicz, Jason; Rages, Kathy; West, Robert A.; Knowles, Ben; Lewis, Nikole K.; Marley, Mark S.

    2017-01-01

    Phase curves are important for our understanding of the energy balance and scattering behavior of an exoplanet's atmosphere. In preparation for future direct-imaging missions of Jupiter-like planets, in particular WFIRST, we present phase curves of Jupiter from 0--150 degrees as measured in multiple optical bandpasses by Cassini/ISS during the Millennium flyby of Jupiter in late 2000 to early 2001. We demonstrate and confirm that Jupiter is not well represented by a Lambertian phase function and that its color is more variable with phase angle than predicted by Jupiter-like models. This indicates that a Jupiter-twin observed near quadrature may not be as straightforward to classify as a Jupiter-like planet and comment on the implications for future missions.

  8. Laser Mode Behavior of the Cassini CIRS Fourier Transform Spectrometer at Saturn

    Science.gov (United States)

    Brasunas, John C.

    2012-01-01

    The CIRS Fourier transform spectrometer aboard the NASA/ESA/ASI Cassini orbiter has been acquiring spectra of the Saturnian system since 2004. The CIRS reference interferometer employs a laser diode to trigger the interferogram sampling. Although the control of laser diode drive current and operating temperature are stringent enough to restrict laser wavelength variation to a small fraction of CIRS finest resolution element, the CIRS instrument does need to be restarted every year or two, at which time it may start in a new laser mode. By monitoring the Mylar absorption features in uncalibrated spectra due to the beam splitter Mylar substrate, it can be shown that these jumps are to adjacent modes and that most of the eight-year operation so far is restricted to three adjacent modes. For a given mode, the wavelength stability appears consistent with the stability of the laser diode drive curren.t and operating temperature.

  9. Cassini finds an oxygen-carbon dioxide atmosphere at Saturn's icy moon Rhea.

    Science.gov (United States)

    Teolis, B D; Jones, G H; Miles, P F; Tokar, R L; Magee, B A; Waite, J H; Roussos, E; Young, D T; Crary, F J; Coates, A J; Johnson, R E; Tseng, W-L; Baragiola, R A

    2010-12-24

    The flyby measurements of the Cassini spacecraft at Saturn's moon Rhea reveal a tenuous oxygen (O(2))-carbon dioxide (CO(2)) atmosphere. The atmosphere appears to be sustained by chemical decomposition of the surface water ice under irradiation from Saturn's magnetospheric plasma. This in situ detection of an oxidizing atmosphere is consistent with remote observations of other icy bodies, such as Jupiter's moons Europa and Ganymede, and suggestive of a reservoir of radiolytic O(2) locked within Rhea's ice. The presence of CO(2) suggests radiolysis reactions between surface oxidants and organics or sputtering and/or outgassing of CO(2) endogenic to Rhea's ice. Observations of outflowing positive and negative ions give evidence for pickup ionization as a major atmospheric loss mechanism.

  10. Cassini in situ observations of long-duration magnetic reconnection in Saturn's magnetotail

    CERN Document Server

    Arridge, Christopher S; Jackman, Caitriona M; Poh, Gang-Kai; Slavin, James A; Thomsen, Michelle F; André, Nicolas; Jia, Xianzhe; Kidder, Ariah; Lamy, Laurent; Radioti, Aikaterina; Reisenfeld, Dan B; Sergis, Nick; Volwerk, Martin; Walsh, Andrew P; Zarka, Philippe; Coates, Andrew J; Dougherty, Michele K

    2015-01-01

    Magnetic reconnection is a fundamental process in solar system and astrophysical plasmas, through which stored magnetic energy associated with current sheets is converted into thermal, kinetic and wave energy. Magnetic reconnection is also thought to be a key process involved in shedding internally produced plasma from the giant magnetospheres at Jupiter and Saturn through topological reconfiguration of the magnetic field. The region where magnetic fields reconnect is known as the diffusion region and in this letter we report on the first encounter of the Cassini spacecraft with a diffusion region in Saturn's magnetotail. The data also show evidence of magnetic reconnection over a period of 19 h revealing that reconnection can, in fact, act for prolonged intervals in a rapidly rotating magnetosphere. We show that reconnection can be a significant pathway for internal plasma loss at Saturn. This counters the view of reconnection as a transient method of internal plasma loss at Saturn. These results, although d...

  11. High Angular Resolution Stellar Imaging with Occultations from the Cassini Spacecraft II: Kronocyclic Tomography

    CERN Document Server

    Stewart, Paul N; Nicholson, Philip D; Hedman, Matthew M; Lloyd, James P

    2015-01-01

    We present an advance in the use of Cassini observations of stellar occultations by the rings of Saturn for stellar studies. Stewart et al. (2013) demonstrated the potential use of such observations for measuring stellar angular diameters. Here, we use these same observations, and tomographic imaging reconstruction techniques, to produce two dimensional images of complex stellar systems. We detail the determination of the basic observational reference frame. A technique for recovering model-independent brightness profiles for data from each occulting edge is discussed, along with the tomographic combination of these profiles to build an image of the source star. Finally we demonstrate the technique with recovered images of the {\\alpha} Centauri binary system and the circumstellar environment of the evolved late-type giant star, Mira.

  12. Possible Niches for Extant Life on Titan in Light of Cassini/Huygens Results

    Science.gov (United States)

    Grinspoon, D. H.; Bullock, M. A.; Spencer, J. R.; Schulze-Makuch, D.

    2005-08-01

    Results from the first year of the Cassini mission show that Titan has an active surface with few impact craters and abundant hints of cryovolcanism, tectonism, aeolian and fluvial activity (Porco et al., 2005; Elachi et al., 2005). Methane clouds and surface characteristics strongly imply the presence of an active global methane cycle analogous to Earth's hydrological cycle. Astrobiological interest in Titan has previously focused on possible prebiological chemical evolution on a moon with a thick nitrogen atmosphere and rich organic chemistry (Raulin and Owen, 2002). Yet the emerging new picture of Titan has raised prospects for the possibility of extant life. Several key requirements for life appear to be present, including liquid reservoirs, organic molecules and ample energy sources. One promising location may be hot springs in contact with hydrocarbon reservoirs. Hydrogenation of photochemically produced acetylene could provide metabolic energy for near-surface organisms and also replenish atmospheric methane (Schulze-Makuch and Grinspoon, 2005). The energy released could be used by organisms to drive endothermic reactions, or go into heating their surroundings, helping to create their own liquid microenvironments. In environments which are energy-rich but liquid-poor, like the near-surface of Titan, natural selection may favor organisms that use their ``waste heat" to melt their own watering holes. Downward transport of high energy photochemical compounds could provide an energy supply for near-surface organisms which could be used, in part, to maintain the liquid environments conducive to life. We will present the results of thermal modeling designed to test the feasibility of biothermal melting on Titan. C. Porco and the Cassini Imaging Team (2005) Nature 434, 159-168; C. Elachi et al, Science, 308, 970-974; F. Raulin and T. Owen (2002) Space Sci. Rev. 104, 377 - 394.; D. Schulze-Makuch and D. H. Grinspoon (2005) Astrobiology, in press.

  13. Saturns Thermal Emission at 2.2-cm Wavelength as Imaged by the Cassini RADAR Radiometer

    Science.gov (United States)

    Janssen, M. A.; Ingersoll, A. P.; Allison, M. D.; Gulkis, S.; Laraia, A. L.; Baines, K. H.; Edgington, S. G.; Anderson, Y. Z.; Kelleher, K.; Oyafuso, F. A.

    2013-01-01

    We present well-calibrated, high-resolution maps of Saturn's thermal emission at 2.2-cm wavelength obtained by the Cassini RADAR radiometer through the Prime and Equinox Cassini missions, a period covering approximately 6 years. The absolute brightness temperature calibration of 2% achieved is more than twice better than for all previous microwave observations reported for Saturn, and the spatial resolution and sensitivity achieved each represent nearly an order of magnitude improvement. The brightness temperature of Saturn in the microwave region depends on the distribution of ammonia, which our radiative transfer modeling shows is the only significant source of absorption in Saturn's atmosphere at 2.2-cm wavelength. At this wavelength the thermal emission comes from just below and within the ammonia cloud-forming region, and yields information about atmospheric circulations and ammonia cloud-forming processes. The maps are presented as residuals compared to a fully saturated model atmosphere in hydrostatic equilibrium. Bright regions in these maps are readily interpreted as due to depletion of ammonia vapor in, and, for very bright regions, below the ammonia saturation region. Features seen include the following: a narrow equatorial band near full saturation surrounded by bands out to about 10deg planetographic latitude that demonstrate highly variable ammonia depletion in longitude; narrow bands of depletion at -35deg latitude; occasional large oval features with depleted ammonia around -45deg latitude; and the 2010-2011 storm, with extensive saturated and depleted areas as it stretched halfway around the planet in the northern hemisphere. Comparison of the maps over time indicates a high degree of stability outside a few latitudes that contain active regions.

  14. Temperature Variations with Changing Solar Elevation in Saturn's Main Rings as Seen by Cassini CIRS

    Science.gov (United States)

    Spilker, Linda J.; Flandes, A.; Altobelli, N.; Leyrat, C.; Pilorz, S.; Ferrari, C.

    2008-09-01

    During four years in orbit around Saturn, the Cassini Composite Infrared Spectrometer (CIRS) has acquired an extensive set of thermal measurements of Saturn's main rings (A, B, C and Cassini Division). Temperatures were retrieved for the lit and unlit rings over a variety of ring geometries that include solar phase angle, spacecraft elevation, solar elevation and local hour angle. To first order, the largest temperature changes on the lit face of the rings are driven by variations in phase angle while differences in temperature with changing spacecraft elevation and local time are a secondary effect. Once phase angle and local time effects are taken into account, decreases in ring temperature with decreasing solar elevation are observed for both the lit and unlit faces of the rings. For the lit rings,decreases of 2- 4 K are observed in the C ring and larger decreases, 7-10 and 10 - 13 K, are observed in the A and B rings respectively. Our thermal data cover a range of solar elevations from -21 to -12 degrees (south side of the rings). We test two simple models to assess how well they fit the observed decreases in temperature. The first model assumes that the particles are so widely spaced that they do not cast shadows on one another while the second model assumes that the particles are so close together they essentially form a slab. The optically thinnest and optically thickest regions of the rings show the best fits to these two end member models. We present a preliminary report on ring temperature variations as a function of solar elevation in Saturn's rings. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2008 California Institute of Technology. Government sponsorship acknowledged.

  15. Water Vapor in Titan’s Stratosphere from Cassini CIRS Far-infrared Spectra

    Science.gov (United States)

    Cottini, Valeria; Nixon, C. A.; Jennings, D. E.; Anderson, C. M.; Gorius, N.; Bjoraker, G. L.; Coustenis, A.; Teanby, N. A.; Achterberg, R. K.; Bézard, B.; de Kok, R.; Lellouch, E.; Irwin, P. G. J.; Flasar, F. M.; Bampasidis, G.

    2012-10-01

    We will report the measurement of water vapor in Titan’s stratosphere (Cottini et al. 2012), using the Cassini Composite Infrared Spectrometer (CIRS, Flasar et al. 2004). CIRS senses water emissions in the far infrared spectral region near 50 microns, which we have modeled using a radiative transfer code (NEMESIS, Irwin et al. 2008). From the analysis of nadir spectra we have derived a mixing ratio of 0.14 ± 0.05 ppb at an altitude of 97 km, which corresponds to an integrated (from 0 to 600 km) surface normalized column abundance of 3.7±1.3 × 1014 molecules/cm2. In the latitude range 80°S to 30°N we see no evidence for latitudinal variations in these abundances within the error bars. Using limb observations, we obtained mixing ratios of 0.13 ± 0.04 ppb at an altitude of 115 km and 0.45 ± 0.15 ppb at an altitude of 230 km, confirming that the water abundance has a positive vertical gradient as predicted by previous photochemical models. We have also fitted our data using scaling factors of 0.1-0.6 to these photochemical model profiles, indicating that the models over-predict the water abundance in Titan’s lower stratosphere. Valeria Cottini is supported by the NASA Postdoctoral Program. References Cottini V. et al., 2012. Detection of water vapor in Titan’s atmosphere from Cassini/CIRS infrared spectra. Icarus, 220, 2, 855-862 Flasar, F.M., and 44 colleagues, 2004. Exploring the Saturn system in the thermal infrared: The Composite Infrared Spectrometer. Space Sci. Rev., 115, 169-297 Irwin, P.G.J., et al., 2008. The NEMESIS planetary atmosphere radiative transfer and retrieval tool. J. Quant. Spectrosc. Radiat. Trans., 109, 1136-1150.

  16. Radiation Transport of Heliospheric Lyman-alpha from Combined Cassini and Voyager Data Sets

    Science.gov (United States)

    Pryor, W.; Gangopadhyay, P.; Sandel, B.; Forrester, T.; Quemerais, E.; Moebius, E.; Esposito, L.; Stewart, I.; McClintock, W.; Jouchoux, A.; hide

    2008-01-01

    Heliospheric neutral hydrogen scatters solar Lyman-alpha radiation from the Sun with '27-day' intensity modulations observed near Earth due to the Sun's rotation combined with Earth's orbital motion. These modulations are increasingly damped in amplitude at larger distances from the Sun due to multiple scattering in the heliosphere, providing a diagnostic of the interplanetary neutral hydrogen density independent of instrument calibration. This paper presents Cassini data from 2003-2004 obtained downwind near Saturn at approximately 10 AU that at times show undamped '27-day' waves in good agreement with the single-scattering models of Pryor et al., 1992. Simultaneous Voyager 1 data from 2003- 2004 obtained upwind at a distance of 88.8-92.6 AU from the Sun show waves damped by a factor of -0.21. The observed degree of damping is interpreted in terms of Monte Carlo multiple-scattering calculations (e.g., Keller et al., 1981) applied to two heliospheric hydrogen two-shock density distributions (discussed in Gangopadhyay et al., 2006) calculated in the frame of the Baranov-Malama model of the solar wind interaction with the two-component (neutral hydrogen and plasma) interstellar wind (Baranov and Malama 1993, Izmodenov et al., 2001, Baranov and Izmodenov, 2006). We conclude that multiple scattering is definitely occurring in the outer heliosphere. Both models compare favorably to the data, using heliospheric neutral H densities at the termination shock of 0.085 cm(exp -3) and 0.095 cm(exp -3). This work generally agrees with earlier discussions of Voyager data in Quemerais et al., 1996 showing the importance of multiple scattering but is based on Voyager data obtained at larger distances from the Sun (with larger damping) simultaneously with Cassini data obtained closer to the Sun.

  17. The bubble-like shape of the heliosphere observed by Voyager and Cassini

    Science.gov (United States)

    Dialynas, K.; Krimigis, S. M.; Mitchell, D. G.; Decker, R. B.; Roelof, E. C.

    2017-04-01

    For more than five decades, the shape and interactions of the heliosphere with the local interstellar medium have been discussed in the context of two competing models, posited in 1961 1 : a magnetosphere-like heliotail and a more symmetric bubble shape. Although past models broadly assumed the magnetosphere-like concept, the accurate heliospheric configuration remained largely undetermined due to lack of measurements. In recent years, however, Voyagers 1 and 2 (V1 and V2) crossed the termination shock — the boundary where the solar wind drops — north and south of the ecliptic plane at 94 au 2,3 and 84 au 4 in 2004 and 2007, respectively, and discovered the reservoir of ions and electrons that constitute the heliosheath, while Cassini remotely imaged the heliosphere 5 for the first time in 2003. Here we report 5.2-55 keV energetic neutral atom (ENA) global images of the heliosphere obtained with the Cassini/Ion and Neutral Camera (INCA). We compare them with 28-53 keV ions measured within the heliosheath by the low-energy charged particle (LECP) experiment onboard V1 and V2 over an 11-year period (2003-2014). We show that the heliosheath ions are the source of ENA. These observations also demonstrate that the heliosphere responds promptly, within ~2-3 years, to outward propagating solar wind changes in both the nose and tail directions. These results, together with the V1 measurement of a ~0.5 nT interstellar magnetic field 6 and the enhanced ratio between particle pressure and magnetic pressure in the heliosheath 7 , strongly suggest a diamagnetic bubble-like heliosphere with few substantial tail-like features. Our results are consistent with recent modelling 8-11 .

  18. The Determination of Titan Gravity Field from Doppler Tracking of the Cassini Spacecraft

    Science.gov (United States)

    Iess, L.; Armstrong, J. W.; Aamar, S. W.; DiBenedetto, M.; Graziani, A.; Mackenzie, R.; Racioppa, P.; Rappaport, N.; Tortora, P.

    2007-01-01

    In its tour of the Saturnian system, the spacecraft Cassini is carrying out measurements of the gravity field of Titan, whose knowledge is crucial for constraining the internal structure of the satellite. In the five flybys devoted to gravity science, the spacecraft is tracked in X (8.4 GHz) and Ka band (32.5 GHz) from the antennas of NASA's Deep Space Network. The use of a dual frequency downlink is used to mitigate the effects of interplanetary plasma, the largest noise source affecting Doppler measurements. Variations in the wet path delay are effectively compensated by means of advanced water vapor radiometers placed close to the ground antennas. The first three flybys occurred on February 27, 2006, December 28, 2006, and June 29, 2007. Two additional flybys are planned in July 2008 and May 2010. This paper presents the estimation of the mass and quadrupole field of Titan from the first two flybys, carried out by the Cassini Radio Science Team using a short arc orbit determination. The data from the two flybys are first independently fit using a dynamical model of the spacecraft and the bodies of the Saturnian system, and then combined in a multi-arc solution. Under the assumption that the higher degree harmonics are negligible, the estimated values of the gravity parameters from the combined, multi-arc solution are GM = 8978.1337 +/- 0.0025 km(exp 3) / s(exp 2), J (sub 2) = (2.7221 +/- 0.0185) 10 (exp -5) and C (sub 22) = (1.1159 +/- 0.0040) 10 (exp -5) The excellent agreement (within 1.7 sigma) of the results from the two flybys further increases the confidence in the solution and provides an a posteriori validation of the dynamical model.

  19. Overview of Cassini radio science at Saturn, Titan, and the icy satellites

    Science.gov (United States)

    Kliore, A. J.; Ambrosini, R.; Armstrong, J. W.; Flasar, F. M.; French, R. G.; Iess, L.; Marouf, E. A..; Nagy, A. F.; Rappaport, N. J.; Tortora, P.; Jpl/Dsn Radio Science Support Team

    The Cassini spacecraft which has been in orbit about Saturn for over two years is the first Radio Science platform to provide three downlink frequencies In addition to the X-band telemetry link 3 56 cm w l two other frequencies S-band 13 04 cm and Ka-band 0 94 cm are available This plus the high SNR 50 dBHz at X-band afforded by the 4 m diameter s c high gain antenna in combination with the excellent low noise receivers of the DSN as well as overall system stabilities of 1 part in 10 13 when referenced to the on-board ultra-stable oscillator USO in one-way operation and 1 part inx 10 15 for a two-way link make Cassini an unprecedented instrument of radio science The orbital tour phase of the mission has the following main radio science objectives a determination of the masses and gravity fields of Saturn s icy satellites Titan and Saturn through two-way tracking during fly-bys To date the masses of Phoebe Iapetus Dione Enceladus Rhea and Titan have been measured and will be reported here b Measurement of the structure and other properties of Saturn s rings through three-band occultation Seven near-diametric occultations at a high ring opening angle have been completed and the results will be presented here c Measurement of the vertical structure of the atmosphere and ionosphere of Saturn The same series of occultations have provided nearly equatorial observations of the atmosphere structure and the ionosphere and the results will be described here d Measurement of the vertical structure of

  20. Dione and Rhea seasonal exospheres revealed by Cassini CAPS and INMS

    Science.gov (United States)

    Teolis, B. D.; Waite, J. H.

    2016-07-01

    A Dione O2 and CO2 exosphere of similar composition and density to Rhea's is confirmed by Cassini spacecraft Ion Neutral Mass Spectrometer (INMS) flyby data. INMS results from three Dione and two Rhea flybys show exospheric spatial and temporal variability indicative of seasonal exospheres, modulated by winter polar gas adsorption and desorption at the equinoxes. Cassini Plasma Spectrometer (CAPS) pickup ion fluxes also show exospheric structure and evolution at Rhea consistent with INMS, after taking into consideration the anticipated charge exchange, electron impact, and photo-ionization rates. Data-model comparisons show the exospheric evolution to be consistent with polar frost diffusion into the surface regolith, which limits surface exposure and loss of the winter frost cap by sputtering. Implied O2 source rates of ∼45(7) × 1021 s-1 at Dione(Rhea) are ∼50(300) times less than expected from known O2 radiolysis yields from ion-irradiated pure water ice measured in the laboratory, ruling out secondary sputtering as a major exospheric contributor, and implying a nanometer scale surface refractory lag layer consisting of concentrated carbonaceous impurities. We estimate ∼30:1(2:1) relative O2:CO2 source rates at Dione(Rhea), consistent with a stoichiometric bulk composition below the lag layer of 0.01(0.13) C atoms per H2O molecule, deriving from endogenic constituents, implanted micrometeoritic organics, and (in particular at Dione) exogenous H2O delivery by E-ring grains. Impact deposition, gardening and vaporization may thereby control the global O2 source rates by fresh H2O ice exposure to surface radiolysis and trapped oxidant ejection.

  1. OPUS: A Comprehensive Search Tool for Remote Sensing Observations of the Outer Planets. Now with Enhanced Geometric Metadata for Cassini and New Horizons Optical Remote Sensing Instruments.

    Science.gov (United States)

    Gordon, M. K.; Showalter, M. R.; Ballard, L.; Tiscareno, M.; French, R. S.; Olson, D.

    2017-06-01

    The PDS RMS Node hosts OPUS - an accurate, comprehensive search tool for spacecraft remote sensing observations. OPUS supports Cassini: CIRS, ISS, UVIS, VIMS; New Horizons: LORRI, MVIC; Galileo SSI; Voyager ISS; and Hubble: ACS, STIS, WFC3, WFPC2.

  2. Ka-band and X-band observations of the solar corona acquired during the Cassini 2001 superior conjunction

    Science.gov (United States)

    Morabito, D. D.

    2002-01-01

    Simultaneous dual-frequency Ka-band (32 GHz) and X-band (8.4 GHz) carrier signal data have been acquired during the superior conjunction of the Cassini spacecraft June 2001, using the NASA Deep Space Network's facilities located in Goldstone, California. The solar elongation angle of the observations varied from -4.1 degrees (-16 solar radii) to -0.6 degrees (-2.3 solar radii). The observed coronal and solar effects on the signals include spectral broadening, amplitude scintillation, phase scintillation, and increased noise. The measurements were generally consistent with existing solar models, except during solar transient events when the signatures of the measurements were observed to increase significantly above the quiet background levels. This is the second solar conjunction of Cassini for which simultaneous X/Ka data were acquired. Both solar conjunctions, conducted in May 2000 and June 2001, occurred near the peak of the current 11 year solar cycle.

  3. Etude de la variation de transmission optique dans l'UltraViolet du quartz "Nippon Silica Glass" après expositions à des rayonnements - Etude du système d'acquisition de données et du système de contrôle de Hautes Tensions appliquées aux chambres à fils du BARREL RICH de DELPHI

    CERN Document Server

    Delorme, Sophie

    1992-01-01

    Etude de la variation de transmission optique dans l'UltraViolet du quartz "Nippon Silica Glass" après expositions à des rayonnements - Etude du système d'acquisition de données et du système de contrôle de Hautes Tensions appliquées aux chambres à fils du BARREL RICH de DELPHI

  4. Etude spectroscopique des noyaux riches en protons dans la region 22 < Z < 28 et T$_(Z)$ < -3/2

    OpenAIRE

    Dossat, Cedric

    2004-01-01

    La region des noyaux riches en protons tels que 22 < Z < 28 et T$_(Z)$ < -3/2 a pu etre etudiee de maniere tres detaillee grace a trois experiences menees au GANIL entre 1999 et 2002 : cette etude porte sur 23 isotopes allant du $^(39)$Ti au $^(53)$Ni. Nous avons mesure pour la premiere fois les durees de vie du $^(43)$V, du $^(51)$Ni et du $^(51)$Co, et considerablement ameliore la precision de celles deja connues. De nouvelles transitions par emission de protons et de rayonnement $\\gamma$ o...

  5. Near-infrared spectra of liquid/solid acetylene under Titan relevant conditions and implications for Cassini/VIMS detections

    Science.gov (United States)

    Singh, S.; Cornet, T.; Chevrier, V. F.; Combe, J.-Ph.; McCord, T. B.; Roe, L. A.; Le Mouélic, S.; Le Menn, E.; Wasiak, F. C.

    2016-05-01

    Acetylene is thought to be abundant on Titan according to most photochemical models. While detected in the atmosphere, its likely presence at the surface still lacks physical evidence. It is thought that solid acetylene could be a major component of Titan's lakes shorelines and dry lakebed, detected as the 5 μm-bright deposits with the Cassini/VIMS instrument. Acetylene could also be present under its liquid form as dissolved solids in Titan's methane-ethane lakes, as emphasized by thermodynamics studies. This paper is devoted to the near-infrared spectroscopy study of acetylene under solid and liquid phases between 1 and 2.2 μm, synthesized in a Titan simulation chamber that is able to reproduce extreme temperature conditions. From experiments, we observed a ∼10% albedo increase between liquid acetylene at 193-188 K and solid acetylene at 93 K. Using the NIR spectroscopy technique we successfully calculated the reflectivity ratio of solid/liquid acetylene as 1.13. The second difference we observed between liquid and solid acetylene is a shift in the major absorption band detected at 1.54 μm, the shift of ∼0.01 μm occurring toward higher wavelength. In order to assess the detectability of acetylene on Titan using the Cassini/VIMS instrument, we adapted our spectra to the VIMS spectral resolution. The spectral band at 1.55 μm and a negative slope at 2.0 μm falls in the Cassini/VIMS atmospheric windows over several VIMS infrared spectels, thus Cassini/VIMS should be able to detect acetylene.

  6. The Gravity Field of Saturn and the Mass of the Saturnian Rings at the end of the Cassini Mission

    Science.gov (United States)

    Jacobson, Robert A.; Brozovic, Marina; Roth, Duane C.

    2016-05-01

    Following its flyby of Titan on 2016 November 29, Cassini will begin a set 20 high inclination orbits, known as the F-ring orbits, that pass over the ring plane and have periapses near the F-ring. The final Titan flyby on 2017 April 22 will redirect the spacecraft into the proximal orbits, a series 22 orbits with periapses between the innermost D-ring and the upper layer of Saturn’s atmosphere. The proximal orbits will be strongly perturbed the gravitational field of Saturn and slightly perturbed by the gravity of rings. The ring gravity will also affect the F-ring orbits. This paper presents the results of an analysis of simulated radiometric data acquired during the final 42 Cassini orbits. We investigate the sensitivity of the data to the ring mass and gravitational harmonics of the planet. We limit the simulated data quantity to the DSN coverage currently being requested by the Cassini Project augumented by several critical passes expected to be obtained from ESA southern hemisphere stations. We assume a data accuracy consistent with projected effects of solar plasma. In the dynamical model of the spacecraft motion we account for non-gravitational accelerations caused by the planned momentum management to be performed with Reaction Wheel Assembly and thrusters, by the Radioisotope Thermo-electric Generator, and by solar radiation pressure. We use a weighted-least squares procedure to obtain estimates of spacecraft’s state, masses of the rings, the gravity harmonics, and the non-gravitational accelerations. We find that the final orbits of the Cassini mission should yield high accuracy estimates of the gravitational harmonics through J12 and statistically meaningful estimates of the A- and B-ring masses.The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Adminstration.

  7. SATURNʼS INNER SATELLITES: ORBITS, MASSES, AND THE CHAOTIC MOTION OF ATLAS FROM NEW CASSINI IMAGING OBSERVATIONS

    OpenAIRE

    Cooper, Nicholas J.; Renner, Stéfan; Murray, Carl D.; Evans, Michael W.

    2015-01-01

    International audience; We present numerically derived orbits and mass estimates for the inner Saturnian satellites, Atlas, Prometheus, Pandora, Janus, and Epimetheus from a fit to 2580 new Cassini Imaging Science Subsystem astrometric observations spanning 2004 February to 2013 August. The observations are provided as machine-readable and Virtual Observatory tables. We estimate GM Atlas = (0.384 ± 0.001) × 10 −3 km 3 s −2 , a value 13% smaller than the previously published estimate but with ...

  8. Titan's cloud seasonal activity from winter to spring with Cassini/VIMS

    Science.gov (United States)

    Rodriguez, S.; Le, Mouelic S.; Rannou, P.; Sotin, Christophe; Brown, R.H.; Barnes, J.W.; Griffith, C.A.; Burgalat, J.; Baines, K.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.

    2011-01-01

    Since Saturn orbital insertion in July 2004, the Cassini orbiter has been observing Titan throughout most of the northern winter season (October 2002-August 2009) and the beginning of spring, allowing a detailed monitoring of Titan's cloud coverage at high spatial resolution with close flybys on a monthly basis. This study reports on the analysis of all the near-infrared images of Titan's clouds acquired by the Visual and Infrared Mapping Spectrometer (VIMS) during 67 targeted flybys of Titan between July 2004 and April 2010.The VIMS observations show numerous sporadic clouds at southern high and mid-latitudes, rare clouds in the equatorial region, and reveal a long-lived cloud cap above the north pole, ubiquitous poleward of 60??N. These observations allow us to follow the evolution of the cloud coverage during almost a 6-year period including the equinox, and greatly help to further constrain global circulation models (GCMs). After 4. years of regular outbursts observed by Cassini between 2004 and 2008, southern polar cloud activity started declining, and completely ceased 1. year before spring equinox. The extensive cloud system over the north pole, stable between 2004 and 2008, progressively fractionated and vanished as Titan entered into northern spring. At southern mid-latitudes, clouds were continuously observed throughout the VIMS observing period, even after equinox, in a latitude band between 30??S and 60??S. During the whole period of observation, only a dozen clouds were observed closer to the equator, though they were slightly more frequent as equinox approached. We also investigated the distribution of clouds with longitude. We found that southern polar clouds, before disappearing in mid-2008, were systematically concentrated in the leading hemisphere of Titan, in particular above and to the east of Ontario Lacus, the largest reservoir of hydrocarbons in the area. Clouds are also non-homogeneously distributed with longitude at southern mid

  9. IMF dependence of Saturn's auroras: modelling study of HST and Cassini data from 12–15 February 2008

    Directory of Open Access Journals (Sweden)

    E. S. Belenkaya

    2010-08-01

    Full Text Available To gain better understanding of auroral processes in Saturn's magnetosphere, we compare ultraviolet (UV auroral images obtained by the Hubble Space Telescope (HST with the position of the open-closed field line boundary in the ionosphere calculated using a magnetic field model that employs Cassini measurements of the interplanetary magnetic field (IMF as input. Following earlier related studies of pre-orbit insertion data from January 2004 when Cassini was located ~ 1300 Saturn radii away from the planet, here we investigate the interval 12–15 February 2008, when UV images of Saturn's southern dayside aurora were obtained by the HST while the Cassini spacecraft measured the IMF in the solar wind just upstream of the dayside bow shock. This configuration thus provides an opportunity, unique to date, to determine the IMF impinging on Saturn's magnetosphere during imaging observations, without the need to take account of extended and uncertain interplanetary propagation delays. The paraboloid model of Saturn's magnetosphere is then employed to calculate the magnetospheric magnetic field structure and ionospheric open-closed field line boundary for averaged IMF vectors that correspond, with appropriate response delays, to four HST images. We show that the IMF-dependent open field region calculated from the model agrees reasonably well with the area lying poleward of the UV emissions, thus supporting the view that the poleward boundary of Saturn's auroral oval in the dayside ionosphere lies adjacent to the open-closed field line boundary.

  10. Cassini RADAR observations of lakes and seas in the Northern Polar region of Titan: Bathymetry and Composition

    Science.gov (United States)

    Mastrogiuseppe, Marco; Hayes, Alex; Poggiali, Valerio; Lunine, Jonathan; Seu, Roberto; Hofgartner, Jason; Le Gall, Alice; Lorenz, Ralph; Mitri, Giuseppe

    2017-04-01

    Recent observations by the Cassini spacecraft has revealed its RADAR to be an invaluable tool for investigating Titan's seas and lakes. The T91 (May 2013) observation of Ligeia Mare, Titan's second largest sea, has demonstrated the capabilities of the RADAR, in its altimeter mode, to measure depth, composition and seafloor topography. The 104 (August 2014) observation provided similar data over the largest sea, Kraken Mare, and the T108 (January 2015) flyby acquired an altimetry pass over Punga Mare. The T49 (December 2007) altimetry pass over Ontario Lacus, the largest southern liquid body, has also been processed to retrieve subsurface echoes. Cassini's final flyby of Titan, T126 (April 2017), is the next and unique opportunity to observe an area in the Northern Polar region of Titan, where several small - medium size (5 - 30 km) lakes are present and have been previously imaged by Cassini. In our presentation, we will report the integrated results of these investigations and discuss them in the overall context of Titan's hydrologic cycle.

  11. GPHS-RTGs in support of the Cassini RTG Program. Final technical report, January 11, 1991--April 30, 1998

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-08-01

    As noted in the historical summary, this program encountered a number of changes in direction, schedule, and scope over the period 11 January 1991 to 31 December 1998. The report provides a comprehensive summary of all the varied aspects of the program over its seven and a quarter years, and highlights those aspects that provide information beneficial to future radioisotope programs. In addition to summarizing the scope of the Cassini GPHS-RTG Program provided as background, the introduction includes a discussion of the scope of the final report and offers reference sources for information on those topics not covered. Much of the design heritage of the GPHS-RTG comes from the Multi-Hundred Watt (MHW) RTGs used on the Lincoln Experimental Satellites (LES) 8/9 and Voyager spacecraft. The design utilized for the Cassini program was developed, in large part, under the GPHS-RTG program which produced the Galileo and Ulysses RTGs. Reports from those programs included detailed documentation of the design, development, and testing of converter components and full converters that were identical to, or similar to, components used in the Cassini program. Where such information is available in previous reports, it is not repeated here.

  12. GPHS RTGs in Support of the Cassini RTG Program. Final Technical Report, January 11, 1991 - April 30, 1998

    Science.gov (United States)

    1998-08-01

    As noted in the historical summary, this program encountered a number of changes in direction, schedule, and scope over the period 11 January 1991 to 31 December 1998. The report provides a comprehensive summary of all the varied aspects of the program over its seven and a quarter years, and highlights those aspects that provide information beneficial to future radioisotope programs. In addition to summarizing the scope of the Cassini GPHS RTG Program provided as background, the introduction includes a discussion of the scope of the final report and offers reference sources for information on those topics not covered. Much of the design heritage of the GPHS RTG comes from the Multi Hundred Watt (MHW) RTGs used on the Lincoln Experimental Satellites (LES) 8/9 and Voyager spacecraft. The design utilized for the Cassini program was developed, in large part, under the GPHS RTG program which produced the Galileo and Ulysses RTGs. Reports from those programs included detailed documentation of the design, development, and testing of converter components and full converters that were identical to, or similar to, components used in the Cassini program.

  13. Preparation and study of dialkyl nitroxide radicals; Preparation et etude de radicaux nitroxydes diacyles

    Energy Technology Data Exchange (ETDEWEB)

    Chenavas, P. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1969-07-01

    These radicals are obtained by oxidation of N-hydroxy-imides with lead tetracetate or p-nitro-perbenzoic acid. These imides are prepared by heating dicarboxylic acids anhydrides with benzyloxy-amine followed by catalytic hydrogenation of N-benzyloxy-imides so obtained. Two series of radicals have mainly been studied, the first concerning five-membered cyclic imides, the second six-membered cyclic imides, these molecules having methyls substituents or no on the carbon ring. N. M. R. spectra of some O-benzyl-imides have been analysed. These different results have made it possible to study the conformation and stereochemistry of these imides. (author) [French] Ces radicaux sont obtenus par oxydation d'imides N-hydroxyles par le tetracetate de plomb ou l'acide p-nitroperbenzoique; ces imides sont prepares par chauffage d'anhydrides de diacides en presence de benzyloxyamine suivie d'une hydrogenation catalytique des N-benzyloxyimides ainsi obtenus. Deux series de radicaux ont principalement ete etudies: la premiere relative a des imides cycliques a cinq chainons, la seconde a des imides cycliques a six chainons, ces molecules ayant des substituants methyles ou non sur la chaine carbonee. Les derives O-benzyles de quelques-uns de ces imides ont ete analyses en R. M. N. Ces differents resultats ont permis une etude de la conformation et de la stereochimie de ces imides. (auteur)

  14. Alecto 2 - interaction studies; Alecto 2 - etudes d'interaction

    Energy Technology Data Exchange (ETDEWEB)

    Brunet, J.P.; Clouet d' Orval, Ch.; Mougniot, J.C.; Penet, F. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-07-01

    Weak interactions were experimentally studies with the tank of the critical assembly Alecto II and one, two or three bottles containing solutions of various concentrations. In particular, was studied the validity of certain classical assumptions, shielding effects, screening and semi-reflexion effects, importance of thermal coupling. The method of the 'k{sub eff}, solid angle' is shown to apply to such a system. The determination by divergence and pulsed neutron technique of the reactivity related to a millimeter of solution level affords the obtention of critical heights in terms of reactivity. (authors) [French] Une etude experimentale d'interactions faibles a ete faite entre la cuve de l'experience critique ALECTO II et une, deux ou trois bouteilles contenant des concentrations variees. On etudie, en particulier, la validite de certaines hypotheses classiques, effets d'ombre, d'ecrans, de semi-reflexion, importance du couplage thermique. On montre d'autre part que la methode du 'K{sub eff}, angle solide' peut s'appliquer a un tel systeme. La determination par divergence et neutrons pulses de la reactivite liee au millimetre de solution permet de traduire les hauteurs critiques obtenues, en terme de reactivite. (auteurs)

  15. 练习曲中的童话画面%The Fairy Tale Pictures in Etudes

    Institute of Scientific and Technical Information of China (English)

    刘铭

    2011-01-01

    The two sets of Etudes-Tableaux op33 and op39 are the most important and most repre- sentative works in Rachmaninoff's piano music as well as a perfect eornbination of art and technique. Selecting the well-known and most representative op39no6 Little Red Riding Hood and the Wolf, this paper analyses the visualization of pictures from the music and its playing techniques, hoping to shed light on its performance and teaching.%音画练习曲op33和op39是拉赫玛尼诺夫钢琴音乐创作中最重要且最具代表性的作品之一.也是艺术性和技术性的完美结合体。选取著名的并最有代表性的op39n06《小红帽与野狼》,从音乐的画面性和演奏的技巧性两方面进行分析,以期在演奏与教学方面得到启发。

  16. Searching for a traveling feature in Saturn's rings in Cassini Imaging Science Subsystem data

    Science.gov (United States)

    Aye, Klaus-Michael; Rehnberg, Morgan; Brown, Zarah; Esposito, Larry W.

    2016-10-01

    Introduction: Using Cassini UVIS occultation data, a traveling wave feature has been identified in the Saturn rings that is most likely caused by the radial positions swap of the moons Janus and Epimetheus [1]. The hypothesis is that non-linear interferences between the linear density waves when being relocated by the moon swap create a solitary wave that is traveling outward through the rings. The observations in [1] further lead to the derivation of values for the radial travel speeds of the identified traveling features, from 39.6 km/yr for the Janus 5:4 resonance up to 45.8 for the Janus 4:3 resonance.Previous confirmations in ISS data: Work in [1] also identified the feature in Cassini Imaging Science Subsystem (ISS) data that was taken around the time of the UVIS occultations where the phenomenon was first discovered, so far one ISS image for each Janus resonances 2:1, 4:3, 5:4, and 6:5.Search guided by predicted locations: Using the observation-fitted radial velocities from [1], we can extrapolate these to identify Saturn radii at which the traveling feature should be found at later times. Using this and new image analysis and plotting tools available in [2], we have identified a potential candidate feature in an ISS image that was taken 2.5 years after the feature causing moon swap in January 2006. We intend to expand our search by identifying candidate ISS data by a meta-database search constraining the radius at future times corresponding to the predicted future locations of the hypothesized solitary wave and present our findings at this conference.References: [1] Rehnberg, M.E., Esposito, L.W., Brown, Z.L., Albers, N., Sremčević, M., Stewart, G.R., 2016. A Traveling Feature in Saturn's Rings. Icarus, accepted in June 2016. [2] K.-Michael Aye. (2016). pyciss: v0.5.0. Zenodo. 10.5281/zenodo.53092

  17. Compositional and spatial variations in Titan dune and interdune regions from Cassini VIMS and RADAR

    Science.gov (United States)

    Bonnefoy, Léa E.; Hayes, Alexander G.; Hayne, Paul O.; Malaska, Michael J.; Le Gall, Alice; Solomonidou, Anezina; Lucas, Antoine

    2016-05-01

    Dunes cover about 15 % of Titan's visible surface, and represent one of the largest reservoirs of hydrocarbon solids on Titan (Rodriguez, S. et al. [2014]. Icarus 230, 168-179; Lopes, R.M.C. et al. [2016]. Icarus 270, 162-182.). Herein, we use data from the Cassini spacecraft to derive constraints on the compositional and regional variability of Titan's dune and interdune regions by combining spectral information from the Visual and Infrared Mapping Spectrometer (VIMS) and spatial information from Synthetic Aperture RADAR (SAR) data. Using the combined datasets, we extract pure infrared spectra of dune and interdune regions by extrapolating linear correlations between VIMS reflectance and dune area fraction calculated in each VIMS footprint from SAR images. We applied the same method using the Cassini RADAR Radiometer dataset to extract the microwave surface emissivity of the dune and interdune regions. Globally the dune spectra show little variation, but we find that the interdune spectra exhibit several different behaviors. Similarly, we extract from passive radiometry a mean dune emissivity of 0.98 ± 0.01, while interdune emissivity varies from 0.86 to 0.98. We find that the interdune regions are often spectrally similar to other Titan terrain units, namely Caladan Planitia, the Adiri Mountains, and Sinlap crater, while the dunes are spectrally distinct from all terrain units. Around Sinlap crater, the interdune regions correspond to the dark blue VIMS unit: the dunes could be forming on top of the ejecta, or the material corresponding to the blue unit could be depositing preferentially in the interdunes areas. There was one region in the Belet sand sea where we were unable to extract the dune and interdune spectra and emissivities in spite of high-quality data, which we interpret to result from a thick sand cover in the interdune regions, implying inactive or saturated dune fields. However, the fact that we were able to extract distinct dune and interdune

  18. Saturn's icy satellites investigated by Cassini-VIMS. II. Results at the end of nominal mission

    Science.gov (United States)

    Filacchione, G.; Capaccioni, F.; Clark, R.N.; Cuzzi, J.N.; Cruikshank, D.P.; Coradini, A.; Cerroni, P.; Nicholson, P.D.; McCord, T.B.; Brown, R.H.; Buratti, B.J.; Tosi, F.; Nelson, R.M.; Jaumann, R.; Stephan, K.

    2010-01-01

    We report the detailed analysis of the spectrophotometric properties of Saturn's icy satellites as derived by full-disk observations obtained by visual and infrared mapping spectrometer (VIMS) experiment aboard Cassini. In this paper, we have extended the coverage until the end of the Cassini's nominal mission (June 1st 2008), while a previous paper (Filacchione, G., and 28 colleagues [2007]. Icarus 186, 259-290, hereby referred to as Paper I) reported the preliminary results of this study. During the four years of nominal mission, VIMS has observed the entire population of Saturn's icy satellites allowing us to make a comparative analysis of the VIS-NIR spectral properties of the major satellites (Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion, Iapetus) and irregular moons (Atlas, Prometheus, Pandora, Janus, Epimetheus, Telesto, Calypso, Phoebe). The results we discuss here are derived from the entire dataset available at June 2008 which consists of 1417 full-disk observations acquired from a variety of distances and inclinations from the equatorial plane, with different phase angles and hemispheric coverage. The most important spectrophotometric indicators (as defined in Paper I: I/F continua at 0.55 ??m, 1.822 ??m and 3.547 ??m, visible spectral slopes, water and carbon dioxide bands depths and positions) are calculated for each observation in order to investigate the disk-integrated composition of the satellites, the distribution of water ice respect to "contaminants" abundances and typical regolith grain properties. These quantities vary from the almost pure water ice surfaces of Enceladus and Calypso to the organic and carbon dioxide rich Hyperion, Iapetus and Phoebe. Janus visible colors are intermediate between these two classes having a slightly positive spectral slope. These results could help to decipher the origins and evolutionary history of the minor moons of the Saturn's system. We introduce a polar representation of the spectrophotometric

  19. A Look Toward the Surface: Radiative Transfer Modelling in Titan's Atmosphere Using Cassini/VIMS data

    Science.gov (United States)

    Cornet, Thomas; Rodriguez, Sebastien; Maltagliati, Luca; Appéré, Thomas; Sotin, Christophe; Le Mouélic, Stéphane; Rannou, Pascal; Solomonidou, Anezina; Hirtzig, Mathieu; Bézard, Bruno; Coustenis, Athena; Brown, Robert H.; Barnes, Jason W.; Baines, Kevin H.; Buratti, Bonnie J.; Clark, Roger N.; Nicholson, Phillip D.

    2017-04-01

    Saturn's moon Titan possesses a thick and opaque atmosphere, strongly absorbing and scattering in the infrared due to the presence of molecular gases (mostly N2 and CH4) and of a thick organic haze. Despite the presence of this atmosphere, the Cassini Visual and Infrared Mapping Spectrometer (VIMS) instrument is able to acquire images of Titan's surface in atmospheric transmission windows centered at 0.93, 1.08, 1.27, 1.59, 2.01, 2.7-2.8 and 5 μm in the infrared [1]. These imaging capabilities already contributed to reveal and investigate the geological diversity of Titan's surface [2,3,4], but the interpretation of the data in terms of surface composition is often limited due to the heavy processing required to disentangle atmospheric to surface contributions. In this context, we are developing an accurate and fast radiative transfer model and inversion scheme for Titan in order to massively invert the Titan VIMS dataset (125 flybys, tens of thousands of data cubes) and compute surface albedo maps to be used for geomorphological and compositional mapping studies using Cassini/VIMS data. The present model operates in plane-parallel approximation using the SHDOMPP solver [5], which mostly constrains our inversions to the equatorial regions of Titan, where the viewing geometry is suitable to the solver. Our inversion strategy in based on the calculation of reference Look-Up Tables (LUTs) [6] with the radiative transfer direct model [6-8], on which we perform a series of interpolations in order to retrieve the exact geometry of the data (incidence, emission and azimuth angles) and the associated haze opacity factor and surface albedo in order to match the input spectra. This methodology of inversion allows us to process VIMS cubes and mosaics of VIMS cubes in a couple of hours only (as compared to several days with classical approaches). We will apply this model to regional VIMS mosaics composed of several flybys, such as the T13-T17 mosaic. [1] Sotin C. et al. (2005

  20. Cassini ISS observation of Saturn's north polar vortex and comparison to the south polar vortex

    Science.gov (United States)

    Sayanagi, Kunio M.; Blalock, John J.; Dyudina, Ulyana A.; Ewald, Shawn P.; Ingersoll, Andrew P.

    2017-03-01

    We present analyses of Saturn's north pole using high-resolution images captured in late 2012 by the Cassini spacecraft's Imaging Science Subsystem (ISS) camera. The images reveal the presence of an intense cyclonic vortex centered at the north pole. In the red and green visible continuum wavelengths, the north polar region exhibits a cyclonically spiraling cloud morphology extending from the pole to 85°N planetocentric latitude, with a 4700 km radius. Images captured in the methane bands, which sense upper tropospheric haze, show an approximately circular hole in the haze extending up to 1.5° latitude away from the pole. The spiraling morphology and the "eye"-like hole at the center are reminiscent of a terrestrial tropical cyclone. In the System III reference frame (rotation period of 10h39m22.4s, Seidelmann et al. 2007; Archinal et al. 2011), the eastward wind speed increases to about 140 m s-1 at 89°N planetocentric latitude. The vorticity is (6.5± 1.5) × 10-4 s-1 at the pole, and decreases to (1.3± 1.2) × 10-4 s-1 at 89°N. In addition, we present an analysis of Saturn's south polar vortex using images captured in January 2007 to compare its cloud morphology to the north pole. The set of images captured in 2007 includes filters that have not been analyzed before. Images captured in the violet filter (400 nm) also reveal a bright polar cloud. The south polar morphology in 2007 was more smooth and lacked the small clouds apparent around the north pole in 2012. Saturn underwent equinox in August 2009. The 2007 observation captured the pre-equinox south pole, and the 2012 observation captured the post-equinox north pole. Thus, the observed differences between the poles are likely due to seasonal effects. If these differences indeed are caused by seasonal effects, continuing observations of the summer north pole by the Cassini mission should show a formation of a polar cloud that appears bright in short-wavelength filters.

  1. Seasonal variations in Titan's stratosphere observed with Cassini/CIRS after the northern spring equinox

    Science.gov (United States)

    Vinatier, Sandrine; Bézard, Bruno; Teanby, Nicholas A.; Lebonnois, Sebastien; Achterberg, Richard; Gorius, Nicolas; Mamoutkine, Andrei; Flasar, F. Michael; CIRS Team

    2016-10-01

    Since 2004, Cassini has made more than 119 Titan flybys, observing its atmosphere with instruments including the Cassini Composite InfraRed Spectrometer (CIRS). We know from CIRS observations that the global dynamics drastically changed after the northern spring equinox that occurred in August 2009 ([1], [2], [3], [4]). The pole-to-pole middle atmosphere dynamics (above 100 km) experienced a global reversal in less than 2 years after the equinox [4], while the northern hemisphere was entering spring. This new pattern, with downwelling at the south pole, resulted in an enrichment of almost all molecules inside the southern polar vortex since 2011.We will present an analysis of CIRS limb observations up to 2016. We will show that many species (C2H2, HCN, HC3N, C6H6, C4H2, CH3CCH, C2H4) experienced their highest enrichments near the south pole near 500 km in March 2015, with abundances similar to in situ results from INMS at 1000 km [5], suggesting that the air inside the confined polar vortex (observed at latitudes higher than 80°S) was very efficiently transported downward from very high altitudes. In September 2015, an extension of the polar vortex towards lower latitudes (~65°S) was observed, while the molecular abundances decreased by a factor of 10 at 500 km. In the same region, unexpectedly cold stratospheric temperatures were observed below 300 km from May 2013 to the end of 2015, allowing us to detect for the first time the C6H6 ice signature at 680 cm-1. Simultaneously, after the disruption of the north polar vortex after the equinox, the enriched air that was previously confined at very high latitude gradually expended towards mid latitudes at altitudes higher than 300 km. At the beginning of 2016, a zone depleted in molecular gas and aerosol is observed in the entire northern hemisphere between 400 and 500 km, suggesting some complex unknown dynamical effect.References:[1] Teanby, N. et al., 2012, Nature, 491, pp. 733-735.[2] Achterberg et al., DPS 46

  2. Design, Analysis, and Spacecraft Integration of RTGs for CRAF and Cassini Missions

    Energy Technology Data Exchange (ETDEWEB)

    Schock, Alfred; Or, Chuen T; Noravian, Heros

    1991-04-02

    This report consists of two parts. Part 1 describes the development of novel analytical methods needed to predict the BOM performance and the subsequent performance degradation of the mutually obstructed RTGs for the CRAF and Cassini missions. Part II applies those methods to the two missions, presents the resultant predictions, and discusses their programmatic implications.; The results indicate that JPL's original power demand goals could have been met with two standard GPHS RTGs for each mission. However, JPL subsequently raised both the power demand profile and the duration for both missions, to the point where two standard RTGs could no longer provide the desired power margin. Each mission can be satisfied by adding a third RTG, and in the case of the Cassini mission the use of three RTGs appears to be unavoidable. In the case of the CRAF mission, there appears to be a possibility that modest modifications of the RTGs' design and/or operating scheme and meet the missions' power demand without the addition of a third RTG. The potential saving in cost and schedule pressure prompted Fairchild to undertake a study of various obvious and not-so-obvious stratagems, either singly or in combination, to determine whether they would make it possible to meet the specified power demand with two RTSs.; The various stratagems investigated by Fairchild and their effect on performance are presented. The analytical results indicate that a combination of relatively modest RTG modifications could come very close to meeting the JPL-specified CRAF power demand goals. However, since even with the modifications the two RTGs did not provide sufficient margin for possible further growth in power demand, the JPL project team ultimately decided to use three RTGs for the CRAF mission also. This had the decisive advantage of eliminating the need for load switching to reduce the power demand peaks. The report documents the various power enhancement schemes and their computed

  3. Design, Analysis, and Spacecraft Integration of RTGs for CRAF and Cassini Missions

    Energy Technology Data Exchange (ETDEWEB)

    Schock, Alfred; Or, Chuen T; Noravian, Heros

    1991-07-10

    This report consists of two parts. Part 1 describes the development of novel analytical methods needed to predict the BOM performance and the subsequent performance degradation of the mutually obstructed RTGs for the CRAF and Cassini missions. Part II applies those methods to the two missions, presents the resultant predictions, and discusses their programmatic implications.; The results indicate that JPL's original power demand goals could have been met with two standard GPHS RTGs for each mission. However, JPL subsequently raised both the power demand profile and the duration for both missions, to the point where two standard RTGs could no longer provide the desired power margin. Each mission can be satisfied by adding a third RTG, and in the case of the Cassini mission the use of three RTGs appears to be unavoidable. In the case of the CRAF mission, there appears to be a possibility that modest modifications of the RTGs' design and/or operating scheme and meet the missions' power demand without the addition of a third RTG. The potential saving in cost and schedule pressure prompted Fairchild to undertake a study of various obvious and not-so-obvious stratagems, either singly or in combination, to determine whether they would make it possible to meet the specified power demand with two RTGs.; The various stratagems investigated by Fairchild and their effect on performance are presented. The analytical results indicate that a combination of relatively modest RTG modifications could come very close to meeting the JPL-specified CRAF power demand goals. However, since even with the modifications the two RTGs did not provide sufficient margin for possible further growth in power demand, the JPL project team ultimately decided to use three RTGs for the CRAF mission also. This had the decisive advantage of eliminating the need for load switching to reduce the power demand peaks. The report documents the various power enhancement schemes and their computed

  4. Design, Analysis, and Spacecraft Integration of RTGs for CRAF and Cassini Missions

    Energy Technology Data Exchange (ETDEWEB)

    Schock, Alfred; Or, Chuen T; Noravian, Heros

    1991-04-02

    This report consists of two parts. Part 1 describes the development of novel analytical methods needed to predict the BOM performance and the subsequent performance degradation of the mutually obstructed RTGs for the CRAF and Cassini missions. Part II applies those methods to the two missions, presents the resultant predictions, and discusses their programmatic implications. The results indicate that JPL's original power demand goals could have been met with two standard GPHS RTGs for each mission. However, JPL subsequently raised both the power demand profile and the duration for both missions, to the point where two standard RTGs could no longer provide the desired power margin. Each mission can be satisfied by adding a third RTG, and in the case of the Cassini mission the use of three RTGs appears to be unavoidable. In the case of the CRAF mission, there appears to be a possibility that modest modifications of the RTGs' design and/or operating scheme and meet the missions' power demand without the addition of a third RTG. The potential saving in cost and schedule pressure prompted Fairchild to undertake a study of various obvious and not-so-obvious stratagems, either singly or in combination, to determine whether they would make it possible to meet the specified power demand with two RTSs. The various stratagems investigated by Fairchild and their effect on performance are presented. The analytical results indicate that a combination of relatively modest RTG modifications could come very close to meeting the JPL-specified CRAF power demand goals. However, since even with the modifications the two RTGs did not provide sufficient margin for possible further growth in power demand, the JPL project team ultimately decided to use three RTGs for the CRAF mission also. This had the decisive advantage of eliminating the need for load switching to reduce the power demand peaks. The report documents the various power enhancement schemes and their computed

  5. The Sleepy Anticyclonic Eye of the Great Storm on Saturn as seen by Cassini/VIMS

    Science.gov (United States)

    Momary, Thomas W.; Baines, Kevin; Badman, Sarah; Brown, Robert H.; Buratti, Bonnie J.; Clark, Roger Nelson; Nicholson, Philip D.; Sotin, Christophe

    2016-10-01

    The Great Storm that erupted at 34o N on Saturn in late 2010 obliterated the String of Pearls feature in that region and left a lasting remnant - a clear 5-μm bright zone around the entire globe inhabited by a lone anticyclone that persists to the present time. We have observed this enduring oval with Cassini/VIMS since 2011 and note that it exhibits a somewhat latitudinally oscillatory nature as it bobs in Saturn's zonal currents. Centered at 35.9o planetocentric latitude in May 2011, it drifted northward to 37.8o in 2012, floated near 37o through 2013, settled as far south as ~36.5o in 2014, bobbed northward to ~37o in 2015, and now appears to reside at about ~36.3o in early 2016. It has also periodically bumped up against the dark band above it, spinning off material in 2013 and 2015. We measured a prograde zonal drift speed of ~22 m/s in 2012, increasing as much as 60% through 2013, then relaxing back to a more moderate ~15 m/s in 2014 and 2015. Early indications are that it has slowed considerably in 2016 to about ~4.7 m/s, which would be the slowest drift rate we've yet measured for it, but still consistent with the Voyager Wind Profile for this region. The feature has varied in size over time as it spins, spanning 4.9o x 3.2o in 2011, elongating to 7.3o x 2.9o by 2013, contracting to 5.5o x 2.9o in 2014, enlarging again to ~9o x ~4o in 2015, and currently averaging ~6.6o x ~3.5o in 2016. It currently is symmetrically oval in shape. It has varied in terms of cloudiness, being ~ 90% 5-μm dark (obscured) in 2011, whereas by 2013 it was mostly bright (clear) with a thin dark edge, returning to ~90% dark in 2015, and currently about 98% obscured. We have used night observations to isolate thermal flux, and found that the mean 5-μm flux coming from the anticyclone has diminished steadily by about 50% since 2013. We are monitoring this trend. The entire storm latitude of ~34o N itself has remained persistently 5-μm bright since 2011, but is slowly dimming as it

  6. First Cassini Radio Science Bistatic Scattering Observation of Titan's Northern Seas

    Science.gov (United States)

    Marouf, E. A.; Kliore, A. J.; Rappaport, N. J.; French, R. G.; Schinder, P. J.; Anabtawi, A.; Wong, K. K.; Armstrong, J. W.; Asmar, S. W.; Flasar, F. M.; Iess, L.; McGhee-French, C.; Nagy, A. F.; Tortora, P.; Barbinis, E.; Buccino, D.; Kahan, D. S.

    2014-12-01

    On May 17, 2014, the Cassini spacecraft completed its 101 flyby of Saturn's satellite Titan. Mirror-like (quasi-specular) reflections of radio signals transmitted by Cassini were observed on the Earth (bistatic scattering geometry). Three right circularly polarized (RCP) sinusoidal signals were transmitted (wavelength = 0.94, 3.6, and 13 cm). Both the RCP and LCP surface reflections were observed at the Canberra, Australia, complex of the NASA Deep Space Network. The signals probed the region extending from about (lat, long) = (79°N, 315°W) to about (74°N, 232°W). For the first time, two major Titan northern seas, the Ligeia Mare and the Kraken Mare, were probed. Clearly detectable RCP and LCP echo components were observed over both seas at all 3 wavelengths. The echoes were intermittent over the region in between the two seas. The echoes from the seas have narrowband spectra well modeled as pure sinusoids, suggesting very smooth surfaces over > ~1 cm scales. Over shorelines and river like channels the measured spectra reveal a second distinct broadband component, likely reflection from a rough bottom solid interface. Modeling the narrowband echo components as sinusoids, we estimate the RCP and LCP echo power profiles over the observation period. High resolution power profiles (several seconds time average; 0.2 to 2 km along the ground track) reveal remarkable structural detail. The statistical measurement uncertainty improves significantly when the resolution is degraded to about 1 m time average (3 to 30 km). Comparison of the 1 m power profiles with theoretical predictions computed assuming absent surface waves (negligible roughness) reveals excellent agreement with reflections from liquid hydrocarbons. The small statistical uncertainty promises to strongly constrain the liquid composition (ethane vs methane dominance). In principle, the measured RCP/LCP power ratio removes dependence on roughness and enables determination of the dielectric constant

  7. Cassini VIMS and RADAR investigation of Titan's equatorial regions: a case for changes in surface properties

    Science.gov (United States)

    Solomonidou, Anezina; Coustenis, Athena; Lopes, Rosaly M. C.; Rodriguez, Sebastien; Hirtzig, Mathieu; Malaska, Michael; Stephan, Katrin; Sotin, Christophe; Drossart, Pierre; Jaumann, Ralf; Bratsolis, Emmanuel; Le Mouélic, Stephane; Brown, Robert H.

    2015-04-01

    The Cassini-Huygens instruments revealed that Titan, Saturn's largest moon, has - in many aspects - a complex, dynamic and Earth-like surface [1;2;3]. Understanding the distribution and interplay of geologic processes on Titan is important for constraining models of its interior, surface-atmosphere interactions, and climate evolution. Data from the remote sensing instruments have shown the presence of diverse terrains, suggesting exogenic and endogenic processes, whose composition remains largely unknown. Interpreting surface features further requires precise knowledge of the contribution by the dense intervening atmosphere, especially the troposphere, which can be recovered from near-IR data such as those collected by Cassini's Visual and Infrared Mapping Spectrometer (VIMS) collects in the so-called "methane windows". In order to simulate the atmospheric contribution and extract surface information, a statistical tool (PCA) and a radiative transfer code are applied on certain regions of interest (i.e. possibly geologically varying and suggested in some cases to be cryovolcanic and/or evaporitic in origin) [4;5;7]. We also analyze RADAR despeckled SAR images in terms of morphology [6]. For comparison, we also look at undifferentiated plains and dune fields regions that are not expected to change with time. We find that Tui Regio and Sotra Patera change with time becoming darker and brighter respectively in terms of surface albedo while the plains and the suggested evaporitic areas in the equatorial regions do not present any significant change [5]. The surface brightening of Sotra supports a possible internal rather than exogenic origin. The unchanged surface behavior of the plains supports a sedimentary origin rather than cryovolcanic. Preliminary results on the chemical composition of the changed regions with time are also presented. We therefore suggest that temporal variations of surface albedo (in chemical composition and/or morphology) exist for some areas

  8. Nature of the MHD and kinetic scale turbulence in the magnetosheath of Saturn: Cassini observations

    CERN Document Server

    Hadid, L Z; Kiyani, K H; Retinò, A; Modolo, R; Canu, P; Masters, A; Dougherty, M K

    2016-01-01

    Low frequency turbulence in Saturn's magnetosheath is investigated using in-situ measurements of the Cassini spacecraft. Focus is put on the magnetic energy spectra computed in the frequency range $\\sim[10^{-4}, 1]$Hz. A set of 42 time intervals in the magnetosheath were analyzed and three main results that contrast with known features of solar wind turbulence are reported: 1) The magnetic energy spectra showed a $\\sim f^{-1}$ scaling at MHD scales followed by an $\\sim f^{-2.6}$ scaling at the sub-ion scales without forming the so-called inertial range; 2) The magnetic compressibility and the cross-correlation between the parallel component of the magnetic field and density fluctuations $ C(\\delta n,\\delta B_{||}) $ indicates the dominance of the compressible magnetosonic slow-like modes at MHD scales rather than the Alfv\\'en mode; 3) Higher order statistics revealed a monofractal (resp. multifractal) behaviour of the turbulent flow downstream of a quasi-perpendicular (resp. quasi-parallel) shock at the sub-i...

  9. An Analysis of Cassini Observations Regarding the Structure of Jupiter's Equatorial Atmosphere

    Science.gov (United States)

    Choi, David S.; Simon-Miller, Amy A.

    2012-01-01

    A variety of intriguing atmospheric phenomena reside on both sides of Jupiter's equator. 5-micron bright hot spots and opaque plumes prominently exhibit dynamic behavior to the north, whereas compact, dark chevron-shaped features and isolated anticyclonic disturbances periodically occupy the southern equatorial latitudes. All of these phenomena are associated with the vertical and meridional perturbations of Rossby waves disturbing the mean atmospheric state. As previous observational analysis and numerical simulations have investigated the dynamics of the region, an examination of the atmosphere's vertical structure though radiative transfer analysis is necessary for improved understanding of this unique environment. Here we present preliminary analysis of a multispectral Cassini imaging data set acquired during the spacecraft's flyby of Jupiter in 2000. We evaluated multiple methane and continuum spectral channels at available viewing angles to improve constraints on the vertical structure of the haze and cloud layers comprising these interesting features. Our preliminary results indicate distinct differences in the structure for both hemispheres. Upper troposphere hazes and cloud layers are prevalent in the northern equatorial latitudes, but are not present in corresponding southern latitudes. Continued analysis will further constrain the precise structure present in these phenomena and the differences between them.

  10. Cassini in situ observations of long-duration magnetic reconnection in Saturn’s magnetotail

    Science.gov (United States)

    Arridge, C. S.; Eastwood, J. P.; Jackman, C. M.; Poh, G.-K.; Slavin, J. A.; Thomsen, M. F.; André, N.; Jia, X.; Kidder, A.; Lamy, L.; Radioti, A.; Reisenfeld, D. B.; Sergis, N.; Volwerk, M.; Walsh, A. P.; Zarka, P.; Coates, A. J.; Dougherty, M. K.

    2016-03-01

    Magnetic reconnection is a fundamental process in solar system and astrophysical plasmas, through which stored magnetic energy associated with current sheets is converted into thermal, kinetic and wave energy. Magnetic reconnection is also thought to be a key process involved in shedding internally produced plasma from the giant magnetospheres at Jupiter and Saturn through topological reconfiguration of the magnetic field. The region where magnetic fields reconnect is known as the diffusion region and in this letter we report on the first encounter of the Cassini spacecraft with a diffusion region in Saturn’s magnetotail. The data also show evidence of magnetic reconnection over a period of 19 h revealing that reconnection can, in fact, act for prolonged intervals in a rapidly rotating magnetosphere. We show that reconnection can be a significant pathway for internal plasma loss at Saturn. This counters the view of reconnection as a transient method of internal plasma loss at Saturn. These results, although directly relating to the magnetosphere of Saturn, have applications in the understanding of other rapidly rotating magnetospheres, including that of Jupiter and other astrophysical bodies.

  11. An Overview of the Bathymetry and Composition of Titan's Hydrocarbon Seas from the Cassini RADAR Altimeter

    Science.gov (United States)

    Mastrogiuseppe, M.; Hayes, A.; Lunine, J. I.; Poggiali, V.; Seu, R.; Hofgartner, J. D.; Lorenz, R. D.; Le Gall, A. A.

    2015-12-01

    The Cassini RADAR's altimetry mode has been successfully used for probing the depth and composition of Titan's hydrocarbons seas. In May 2013, during the spacecraft's 91stflyby of Titan (T91), the instrument demonstrates its capabilities as a radar sounder, presenting a unique opportunity to constrain direct measurements of the depth and composition of Titan's second largest sea, Ligeia Mare. Later, observations of Kraken Mare and Punga Mare were planned and executed in August 2014 (T104) and January 2015 (T108), respectively. While most of the seafloor was not detected at Kraken, suggesting the sea was either too deep or too absorptive in these areas to observe a return from the seafloor, shallow areas near Moray Sinus did return subsurface detections. At Punga Mare, a clear detection of the subsurface was observed with a maximum depth of 120 m along the interrogated track of the sea. We will present an analysis of all three altimetric observations of Titan's mare, as well a re-analysis of altimetry data acquired over southern Ontario Lacus. Depths measurements and liquid composition are obtained using a novel technique which makes use of radar simulations and Monte Carlo based inversions. Finally, we will show that the estimates obtained from the direct measurements described above can be used along with the RADAR's active (i.e. Synthetic Aperture Radar) and passive (Radiometry) modes to generate bathymetry maps of areas not observed by altimetry.

  12. Cassini UVIS observations of the Io plasma torus. II. Radial variations

    CERN Document Server

    Steffl, Andrew J; Stewart, A Ian F; 10.1016/j.icarus.2004.04.016

    2013-01-01

    On January 14, 2001, shortly after the Cassini spacecraft's closest approach to Jupiter, the Ultraviolet Imaging Spectrometer (UVIS) made a radial scan through the midnight sector of Io plasma torus. The Io torus has not been previously observed at this local time. The UVIS data consist of 2-D spectrally dispersed images of the Io plasma torus in the wavelength range of 561{\\AA}-1912{\\AA}. We developed a spectral emissions model that incorporates the latest atomic physics data contained in the CHIANTI database in order to derive the composition of the torus plasma as a function of radial distance. Electron temperatures derived from the UVIS torus spectra are generally less than those observed during the Voyager era. We find the torus ion composition derived from the UVIS spectra to be significantly different from the composition during the Voyager era. Notably, the torus contains substantially less oxygen, with a total oxygen-to-sulfur ion ratio of 0.9. The average ion charge state has increased to 1.7. We de...

  13. Titan's diverse landscapes as evidenced by Cassini RADAR's third and fourth looks at Titan

    Science.gov (United States)

    Lunine, J.I.; Elachi, C.; Wall, S.D.; Janssen, M.A.; Allison, M.D.; Anderson, Y.; Boehmer, R.; Callahan, P.; Encrenaz, P.; Flamini, E.; Franceschetti, G.; Gim, Y.; Hamilton, G.; Hensley, S.; Johnson, W.T.K.; Kelleher, K.; Kirk, R.L.; Lopes, R.M.; Lorenz, R.; Muhleman, D.O.; Orosei, R.; Ostro, S.J.; Paganelli, F.; Paillou, P.; Picardi, G.; Posa, F.; Radebaugh, J.; Roth, L.E.; Seu, R.; Shaffer, S.; Soderblom, L.A.; Stiles, B.; Stofan, E.R.; Vetrella, S.; West, R.; Wood, C.A.; Wye, L.; Zebker, H.; Alberti, G.; Karkoschka, E.; Rizk, B.; McFarlane, E.; See, C.; Kazeminejad, B.

    2008-01-01

    Cassini's third and fourth radar flybys, T7 and T8, covered diverse terrains in the high southern and equatorial latitudes, respectively. The T7 synthetic aperture radar (SAR) swath is somewhat more straightforward to understand in terms of a progressive poleward descent from a high, dissected, and partly hilly terrain down to a low flat plain with embayments and deposits suggestive of the past or even current presence of hydrocarbon liquids. The T8 swath is dominated by dunes likely made of organic solids, but also contain somewhat enigmatic, probably tectonic, features that may be partly buried or degraded by erosion or relaxation in a thin crust. The dark areas in T7 show no dune morphology, unlike the dark areas in T8, but are radiometrically warm like the dunes. The Huygens landing site lies on the edge of the T8 swath; correlation of the radar and Huygens DISR images allows accurate determination of its coordinates, and indicates that to the north of the landing site sit two large longitudinal dunes. Indeed, had the Huygens probe trajectory been just 10 km north of where it actually was, images of large sand dunes would have been returned in place of the fluvially dissected terrain actually seen-illustrating the strong diversity of Titan's landscapes even at local scales. ?? 2008 Elsevier Inc. All rights reserved.

  14. Mapping and interpretation of Sinlap crater on Titan using Cassini VIMS and RADAR data

    Science.gov (United States)

    Le, Mouelic S.; Paillou, P.; Janssen, M.A.; Barnes, J.W.; Rodriguez, S.; Sotin, Christophe; Brown, R.H.; Baines, K.H.; Buratti, B.J.; Clark, R.N.; Crapeau, M.; Encrenaz, P.J.; Jaumann, R.; Geudtner, D.; Paganelli, F.; Soderblom, L.; Tobie, G.; Wall, S.

    2008-01-01

    Only a few impact craters have been unambiguously detected on Titan by the Cassini-Huygens mission. Among these, Sinlap is the only one that has been observed both by the RADAR and VIMS instruments. This paper describes observations at centimeter and infrared wavelengths which provide complementary information about the composition, topography, and surface roughness. Several units appear in VIMS false color composites of band ratios in the Sinlap area, suggesting compositional heterogeneities. A bright pixel possibly related to a central peak does not show significant spectral variations, indicating either that the impact site was vertically homogeneous, or that this area has been recovered by homogeneous deposits. Both VIMS ratio images and dielectric constant measurements suggest the presence of an area enriched in water ice around the main ejecta blanket. Since the Ku-band SAR may see subsurface structures at the meter scale, the difference between infrared and SAR observations can be explained by the presence of a thin layer transparent to the radar. An analogy with terrestrial craters in Libya supports this interpretation. Finally, a tentative model describes the geological history of this area prior, during, and after the impact. It involves mainly the creation of ballistic ejecta and an expanding plume of vapor triggered by the impact, followed by the redeposition of icy spherules recondensed from this vapor plume blown downwind. Subsequent evolution is then driven by erosional processes and aeolian deposition. Copyright 2008 by the American Geophysical Union.

  15. Distribution of icy particles across Enceladus' surface as derived from Cassini-VIMS measurements

    Science.gov (United States)

    Jaumann, R.; Stephan, K.; Hansen, G.B.; Clark, R.N.; Buratti, B.J.; Brown, R.H.; Baines, K.H.; Newman, S.F.; Bellucci, G.; Filacchione, G.; Coradini, A.; Cruikshank, D.P.; Griffith, C.A.; Hibbitts, C.A.; McCord, T.B.; Nelson, R.M.; Nicholson, P.D.; Sotin, Christophe; Wagner, R.

    2008-01-01

    The surface of Enceladus consists almost completely of water ice. As the band depths of water ice absorptions are sensitive to the size of particles, absorptions can be used to map variations of icy particles across the surface. The Visual and Infrared Mapping Spectrometer (VIMS) observed Enceladus with a high spatial resolution during three Cassini flybys in 2005 (orbits EN 003, EN 004 and EN 011). Based on these data we measured the band depths of water ice absorptions at 1.04, 1.25, 1.5, and 2 ??m. These band depths were compared to water ice models that represent theoretically calculated reflectance spectra for a range of particle diameters between 2 ??m and 1 mm. The agreement between the experimental (VIMS) and model values supports the assumption that pure water ice characterizes the surface of Enceladus and therefore that variations in band depth correspond to variations in water ice particle diameters. Our measurements show that the particle diameter of water ice increases toward younger tectonically altered surface units with the largest particles exposed in relatively "fresh" surface material. The smallest particles were generally found in old densely cratered terrains. The largest particles (???0.2 mm) are concentrated in the so called "tiger stripes" at the south pole. In general, the particle diameters are strongly correlated with geologic features and surface ages, indicating a stratigraphic evolution of the surface that is caused by cryovolcanic resurfacing and impact gardening. ?? 2007 Elsevier Inc. All rights reserved.

  16. Titan's surface from the Cassini RADAR radiometry data during SAR mode

    Science.gov (United States)

    Paganelli, F.; Janssen, M.A.; Lopes, R.M.; Stofan, E.; Wall, S.D.; Lorenz, R.D.; Lunine, J.I.; Kirk, R.L.; Roth, L.; Elachi, C.

    2008-01-01

    We present initial results on the calibration and interpretation of the high-resolution radiometry data acquired during the Synthetic Aperture Radar (SAR) mode (SAR-radiometry) of the Cassini Radar Mapper during its first five flybys of Saturn's moon Titan. We construct maps of the brightness temperature at the 2-cm wavelength coincident with SAR swath imaging. A preliminary radiometry calibration shows that brightness temperature in these maps varies from 64 to 89 K. Surface features and physical properties derived from the SAR-radiometry maps and SAR imaging are strongly correlated; in general, we find that surface features with high radar reflectivity are associated with radiometrically cold regions, while surface features with low radar reflectivity correlate with radiometrically warm regions. We examined scatterplots of the normalized radar cross-section ??0 versus brightness temperature, outlining signatures that characterize various terrains and surface features. The results indicate that volume scattering is important in many areas of Titan's surface, particularly Xanadu, while other areas exhibit complex brightness temperature variations consistent with variable slopes or surface material and compositional properties. ?? 2007.

  17. Cassini Ring Plane Crossings: Hypervelocity Impact Risks to Sun Sensor Assemblies

    Science.gov (United States)

    Lee, Allan Y.

    2016-01-01

    For both F/G and D-ring crossings: Probability of a penetration damage of the SSH (Sun Sensor Head) window glass is very low; Optical attenuation due to craters on the surface of the window glass caused by direct HVI (Hyper-Velocity Impact) by dust particle is estimated to be less than 1 percent; Optical attenuation due to secondary debris cloud generated by the disintegrated ring dust particles is estimated to be less than 1 percent. To better manage the Sun sensor damage risk during selected proximal orbit crossings, it is highly desirable to follow the contingency procedures mentioned in Section VII of the paper: Details of this contingency procedure are given in the paper entitled "Cassini Operational Sun Sensor Risk Management During Proximal Orbit Saturn Ring Plane Crossings" authored by David M. Bates. Based on results of risk analyses documented in this work and contingency planning work described in the paper mentioned above, we judge that the proximal orbit campaign will be safe from the viewpoint of dust HVI hazard.

  18. The relation between the geophysical activity of the Saturnian satellites and the Cassini Division

    Science.gov (United States)

    Noyelles, Benoit; Baillie, Kevin; Charnoz, Sebastien; Lainey, Valery; Tobie, Gabriel

    2017-06-01

    The Cassini Division is a 4,500 km wide gap in the rings of Saturn, which inner edge is at the exact 2:1 Inner Lindblad Resonance with Mimas. We here present our latest results regarding the formation and the stability of the Division, in combining N-body simulations of the main satellites of Saturn with hydrodynamical simulations of the rings, with the 1-D code Hydrorings (Charnoz et al. 2011). We show that an inward migration of Mimas over 8,000 to 9,000 km would create the Division in less than 10 Myr, and we get a final mass distribution in the rings that would look like the density distribution derived from optical depth observations assuming a uniform mass extinction coefficient for the ring particles. We also investigated two sources of inward migration of Mimas, i.e. an intense dissipation of Mimas, and an intense dissipation in Enceladus which would have been locked in a mean-motion resonance with Mimas, provoking the inward migration of the two satellites. The scenario involving a past intense dissipation in Mimas keeps the system of Saturn stable, but is inconsistent with the observed age of the surface of Mimas. However, a past intense dissipation in Enceladus is acceptable from a geophysical point of view owing to its present activity, but would have required an eccentricity so high that the system of Saturn would have been destabilized.

  19. Shoreline features of Titan's Ontario Lacus from Cassini/VIMS observations

    Science.gov (United States)

    Barnes, J.W.; Brown, R.H.; Soderblom, J.M.; Soderblom, L.A.; Jaumann, R.; Jackson, B.; Le, Mouelic S.; Sotin, Christophe; Buratti, B.J.; Pitman, K.M.; Baines, K.H.; Clark, R.N.; Nicholson, P.D.; Turtle, E.P.; Perry, J.

    2009-01-01

    We analyze observations of Titan's south polar lake Ontario Lacus obtained by Cassini's Visual and Infrared Mapping Spectrometer during the 38th flyby of Titan (T38; 2007 December 5). These near-closest-approach observations have the highest signal-to-noise, the finest spatial resolution, and the least atmospheric influence of any near-infrared lake observation to date. We use the large, spatially flat, and low-albedo interior of Ontario Lacus as a calibration target allowing us to derive an analytical atmospheric correction for emission angle. The dark lake interior is surrounded by two separate annuli that follow the lake interior's contours. The inner annulus is uniformly dark, but not so much as the interior lake, and is generally 5-10 kilometers wide at the lake's southeastern margin. We propose that it represents wet lakebed sediments exposed by either tidal sloshing of the lake or seasonal methane loss leading to lower lake-volume. The exterior annulus is bright and shows a spectrum consistent with a relatively low water-ice content relative to the rest of Titan. It may represent fine-grained condensate deposits from a past era of higher lake level. Together, the annuli seem to indicate that the lake level for Ontario Lacus has changed over time. This hypothesis can be tested with observations scheduled for future Titan flybys. ?? 2008 Elsevier Inc.

  20. Spatially resolved near infrared observations of Enceladus' tiger stripe eruptions from Cassini VIMS

    Science.gov (United States)

    Dhingra, Deepak; Hedman, Matthew M.; Clark, Roger N.; Nicholson, Philip D.

    2017-08-01

    Particle properties of individual fissure eruptions within Enceladus' plume have been analyzed using high spatial resolution Visible and Infrared Mapping Spectrometer (VIMS) observations from the Cassini mission. To first order, the spectra of the materials emerging from Cairo, Baghdad and Damascus sulci are very similar, with a strong absorption band around 3 μm due to water-ice. The band minimum position indicates that the ice grains emerging from all the fissures are predominantly crystalline, which implies that the water-ice particles' formation temperatures are likely above 130 K. However, there is also evidence for subtle variations in the material emerging from the different source fissures. Variations in the spectral slope between 1-2.5 μm are observed and probably reflect differences in the size distributions of particles between 0.5 and 5 μm in radius. We also note variations in the shape of the 3 μm water-ice absorption band, which are consistent with differences in the relative abundance of > 5 μm particles. These differences in the particle size distribution likely reflect variations in the particle formation conditions and/or their transport within the fissures. These observations therefore provide strong motivation for detailed modeling to help place important constraints on the diversity of the sub-surface environmental conditions at the geologically active south-pole of Enceladus.

  1. Water Vapor in Titan's Stratosphere from Cassini CIRS Far-Infrared Spectra

    Science.gov (United States)

    Cottini, V.; Nixon, C. A.; Jennings, D. E.; Anderson, C. M.; Gorius, N.; Bjoraker, G. L.; Coustenis, A.; Teanby, N. A.; Achterberg, R. K.; Bezard, B.; deKok, R,; Lellouch, E.; Irwin, P. G. J.; Flasar, F. M.; Bampasidis, G.

    2012-01-01

    Here we report the measurement of water vapor in Titan's stratosphere using the Cassini Composite Infrared Spectrometer (CIRS). CIRS senses water emissions in the far infrared spectral region near 50 micron, which we have modeled using two independent radiative transfer codes. From the analysis of nadir spectra we have derived a mixing ratio of 0.14 +/- 0.05 ppb at an altitude of 97 km, which corresponds to an integrated (from 0 to 600 km) surface normalized column abundance of 3.7 +/- 1.3 1014 molecules/cm2. In the latitude range 80S to 30N we see no evidence for latitudinal variations in these abundances within the error bars. Using limb observations, we obtained mixing ratios of 0.13 +/- 0.04 ppb at an altitude of 115 km and 0.45 +/- 0.15 ppb at an altitude of 230 km, confirming that the water abundance has a positive vertical gradient as predicted by photochemical models. We have also fitted our data using scaling factors of 0.1-0.6 to these photochemical model profiles, indicating that the models over-predict the water abundance in Titan's lower stratosphere.

  2. An Analysis of Cassini Observations Regarding the Structure of Jupiter's Equatorial Atmosphere

    Science.gov (United States)

    Choi, David S.; Simon-Miller, Amy A.

    2012-01-01

    A variety of intriguing atmospheric phenomena reside on both sides of Jupiter's equator. 5-micron bright hot spots and opaque plumes prominently exhibit dynamic behavior to the north, whereas compact, dark chevron-shaped features and isolated anticyclonic disturbances periodically occupy the southern equatorial latitudes. All of these phenomena are associated with the vertical and meridional perturbations of Rossby waves disturbing the mean atmospheric state. As previous observational analysis and numerical simulations have investigated the dynamics of the region, an examination of the atmosphere's vertical structure though radiative transfer analysis is necessary for improved understanding of this unique environment. Here we present preliminary analysis of a multispectral Cassini imaging data set acquired during the spacecraft's flyby of Jupiter in 2000. We evaluated multiple methane and continuum spectral channels at available viewing angles to improve constraints on the vertical structure of the haze and cloud layers comprising these interesting features. Our preliminary results indicate distinct differences in the structure for both hemispheres. Upper troposphere hazes and cloud layers are prevalent in the northern equatorial latitudes, but are not present in corresponding southern latitudes. Continued analysis will further constrain the precise structure present in these phenomena and the differences between them.

  3. A New Look at Titan's Zonal Winds from Cassini Radio Occultations

    Science.gov (United States)

    Flasar, F. M.; Schinder, P. J.

    2012-01-01

    We use the existing thirteen Cassini radio'occultation soundings to construct a meridional cross section of geopotential height vs. pressure and latitude. The assumption of balanced flow permits the construction of a similar cross section of zonal winds, from near the surface to the 0.1'mbar level. In the lower troposphere, the winds are approx.10 m/s, except within 20deg of the equator, where they are much smaller. The winds increase higher up in the troposphere to nearly 40 m/s in the tropopause region, but then decay rapidly in the lower stratosphere to near'zero values at 20 mbar (approx.80 km), reminiscent of the Huygens Doppler Wind Experiment result. This null zone extends over most latitudes, except for limited bands at mid'latitudes. Higher up in the stratosphere, the winds become larger. They are highest in the northern (winter) hemisphere. We compare the occultation results with the DWE and CIRS retrievals and discuss the similarities and differences among the data sets.

  4. Cassini ENA Observations of an Asymmetric Europa Torus and Implications for JUICE

    Science.gov (United States)

    Brandt, Pontus; Westlake, Joseph H.; Smith, Howard T.; mauk, Barry; Mitchell, Don

    2016-10-01

    From about December 2000 to January 2001 the Ion Neutral Camera (INCA) on board the Cassini spacecraft imaged Jupiter in Energetic Neutral Atoms (ENA) that are created when singly charged ions charge exchange with neutral gas atoms or molecules. The INCA observations were obtained from a distance of about 137-250 Jovian planetary radii (RJ) over an energy range from about 10 to 300 keV. Here, we present an analysis of the ENA images implying an asymmetric Europa neutral gas torus with indications of magnetospheric dynamics. The analysis uses images with a minimum integration time and background. A forward model using a parametric energetic ion model and a neutral gas model simulates ENA images through the instrument response function of INCA in order to determine the spatial distribution of the neutral gas. Implications for the ENA observations from the ESA JUICE Mission obtained by the Jovian Energetic Neutrals and Ions (JENI) Camera on the Particle Environment Package (PEP) suite will be discussed.

  5. TITAN’S UPPER ATMOSPHERE FROM CASSINI/UVIS SOLAR OCCULTATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Capalbo, Fernando J.; Bénilan, Yves [Laboratoire Inter-Universitaire des Systèmes Atmosphériques (LISA), UMR 7583 du CNRS, Universités Paris Est Créteil (UPEC) and Paris Diderot - UPD, 61 avenue du Général de Gaulle, F-94010, Créteil Cédex (France); Yelle, Roger V.; Koskinen, Tommi T., E-mail: fernando.capalbo@lisa.u-pec.fr [Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721 (United States)

    2015-12-01

    Titan’s atmosphere is composed mainly of molecular nitrogen, methane being the principal trace gas. From the analysis of 8 solar occultations measured by the Extreme Ultraviolet channel of the Ultraviolet Imaging Spectrograph (UVIS) on board Cassini, we derived vertical profiles of N{sub 2} in the range 1100–1600 km and vertical profiles of CH{sub 4} in the range 850–1300 km. The correction of instrument effects and observational effects applied to the data are described. We present CH{sub 4} mole fractions, and average temperatures for the upper atmosphere obtained from the N{sub 2} profiles. The occultations correspond to different times and locations, and an analysis of variability of density and temperature is presented. The temperatures were analyzed as a function of geographical and temporal variables, without finding a clear correlation with any of them, although a trend of decreasing temperature toward the north pole was observed. The globally averaged temperature obtained is (150 ± 1) K. We compared our results from solar occultations with those derived from other UVIS observations, as well as studies performed with other instruments. The observational data we present confirm the atmospheric variability previously observed, add new information to the global picture of Titan’s upper atmosphere composition, variability, and dynamics, and provide new constraints to photochemical models.

  6. Titan's ionosphere in the magnetosheath: Cassini RPWS results during the T32 flyby

    Directory of Open Access Journals (Sweden)

    P. Garnier

    2009-11-01

    Full Text Available The Cassini mission has provided much information about the Titan environment, with numerous low altitude encounters with the moon being always inside the magnetosphere. The only encounter taking place outside the magnetopause, in the magnetosheath, occurred the 13 June 2007 (T32 flyby. This paper is dedicated to the analysis of the Radio and Plasma Wave investigation data during this specific encounter, in particular with the Langmuir probe, providing a detailed picture of the cold plasma environment and of Titan's ionosphere with these unique plasma conditions. The various pressure terms were also calculated during the flyby. The comparison with the T30 flyby, whose geometry was very similar to the T32 encounter but where Titan was immersed in the kronian magnetosphere, reveals that the evolution of the incident plasma has a significant influence on the structure of the ionosphere, with in particular a change of the exo-ionospheric shape. The electrical conductivities are given along the trajectory of the spacecraft and the discovery of a polar plasma cavity is reported.

  7. Cloud structure and composition of Jupiter's troposphere from 5-{\\mu}m Cassini VIMS spectroscopy

    CERN Document Server

    Giles, Rohini S; Irwin, Patrick G J

    2015-01-01

    Jupiter's tropospheric composition and cloud structure are studied using Cassini VIMS 4.5-5.1 {\\mu}m thermal emission spectra from the 2000-2001 flyby. We make use of both nadir and limb darkening observations on the planet's nightside, and compare these with dayside observations. Although there is significant spatial variability in the 5-{\\mu}m brightness temperatures, the shape of the spectra remain very similar across the planet, suggesting the presence of a spectrally-flat, spatially inhomogeneous cloud deck. We find that a simple cloud model consisting of a single, compact cloud is able to reproduce both nightside and dayside spectra, subject to the following constraints: (i) the cloud base is located at pressures of 1.2 bar or lower; (ii) the cloud particles are highly scattering; (iii) the cloud is sufficiently spectrally flat. Using this cloud model, we search for global variability in the cloud opacity and the phosphine deep volume mixing ratio. We find that the vast majority of the 5-{\\mu}m inhomoge...

  8. Equatorial distributions of energetic ion moments in Saturn's magnetosphere using Cassini/MIMI measurements

    Science.gov (United States)

    Dialynas, K.; Roussos, E.; Regoli, L.; Paranicas, C.; Krimigis, S. M.; Kane, M.; Mitchell, D. G.; Hamilton, D. C.

    2016-12-01

    We use kappa distribution fits to combined Charge Energy Mass Spectrometer (CHEMS, 3 to 236 keV/e), Low Energy Magnetosphere Measurements System (LEMMS, 0.024 INCA, 5.2 to >220 keV for H+) proton and singly ionized energetic ion spectra to calculate the >20 keV energetic ion moments inside Saturn's magnetosphere. Using a realistic magnetic field model (Khurana et al. 2007) and data from the entire Cassini mission to date (2004-2016), we map the ion measurements to the equatorial plane and via the modeled kappa distribution spectra we produce the equatorial distributions of all ion integral moments, focusing on partial density, integral intensity, partial pressure, integral energy intensity; as well as the characteristic energy (EC=IE/In), Temperature and κ-index of these ions as a function of Local Time (00:00 to 24:00 hrs) and L-Shell (5-20). A modified version of the semi-empirical Roelof and Skinner [2000] model is then utilized to retrieve the equatorial H+ and O+ pressure, density and temperature in Saturn's magnetosphere in both local time and L-shell. We find that a) although the H+ and O+ partial pressures and densities are nearly comparable, the >20 keV protons have higher number and energy intensities at all radial distances (L>5) and local times; b) the 12

  9. Saturn's icy satellites investigated by Cassini - VIMS. IV. Daytime temperature maps

    CERN Document Server

    Filacchione, Gianrico; Capaccioni, Fabrizio; Clark, Roger N; Cruikshank, Dale P; Ciarniello, Mauro; Cerroni, Priscilla; Bellucci, Giancarlo; Brown, Robert H; Buratti, Bonnie J; Nicholson, Phillip D; Jaumann, Ralf; McCord, Thomas B; Sotin, Christophe; Stephan, Katrin; Ore, Cristina M Dalle

    2016-01-01

    The spectral position of the 3.6 micron continuum peak measured on Cassini-VIMS I/F spectra is used as a marker to infer the temperature of the regolith particles covering the surfaces of Saturn's icy satellites. This feature is characterizing the crystalline water ice spectrum which is the dominant compositional endmember of the satellites' surfaces. Laboratory measurements indicate that the position of the 3.6 micron peak of pure water ice is temperature-dependent, shifting towards shorter wavelengths when the sample is cooled, from about 3.65 micron at T=123 K to about 3.55 micron at T=88 K. A similar method was already applied to VIMS Saturn's rings mosaics to retrieve ring particles temperature (Filacchione et al., 2014). We report here about the daytime temperature variations observed on the icy satellites as derived from three different VIMS observation types. Temperature maps are built by mining the complete VIMS dataset collected in years 2004-2009 (pre-equinox) and in 2009-2012 (post equinox) by sel...

  10. Regolith grain sizes of Saturn's rings inferred from Cassini-CIRS far-infrared spectra

    CERN Document Server

    Morishima, Ryuji; Spilker, Linda

    2012-01-01

    We analyze far-infrared (10-650 cm$^{-1}$) emissivity spectra of Saturn's main rings obtained by the Cassini Composite Infrared Spectrometer (CIRS). In modeling of the spectra, the single scattering albedos of regolith grains are calculated using the Mie theory, diffraction is removed with the delta-Eddington approximation, and the hemispherical emissivities of macroscopic free-floating ring particles are calculated using the Hapke's isotropic scattering model. Only pure crystalline water ice is considered and the size distribution of regolith grains is estimated. We find that good fits are obtained if the size distribution is broad ranging from 1 $\\mu$m to 1-10 cm with a power law index of $ \\sim 3$. This means that the largest regolith grains are comparable to the smallest free-floating particles in size and that the power law indices for both free-floating particles and regolith grains are similar to each other. The apparent relative abundance of small grains increases with decreasing solar phase angle (or...

  11. Analysis of the inadvertent reentry of the Cassini Spacecraft{close_quote}s Radioisotope Thermoelectric Generators

    Energy Technology Data Exchange (ETDEWEB)

    Tobery, E.W. [Lockheed Martin Astronautics, King of Prussia, Pennsylvania 19406 (United States); Bhutta, B.A. [AeroTechnologies, Inc, Yorktown, Virginia 23692 (United States)] [Analysis of the inadvertent reentry of the Cassini Spacecrafts Radioisotope Thermoelectric Generators

    1999-01-01

    A rigorous multi-discipline approach has been developed to compute the aero/thermal/structural response of the Cassini Spacecraft{close_quote}s G{underscore}eneral P{underscore}urpose H{underscore}eat S{underscore}ource (GPHS) modules in the unlikely event of accidental reentry of the spacecraft during its Earth gravity-assist maneuver. A new r{underscore}eacting, a{underscore}blating, c{underscore}hemical e{underscore}quilibrium/nonequilibrium with r{underscore}adiation (RACER) full Navier-Stokes code is applied, along with an in-depth, transient-heating code, a nonlinear structural analysis code, and a six-degree-of-freedom flight-dynamics code. Attention is focused on the GPHS modules that would breakaway from the R{underscore}adioisotope T{underscore}hermoelectric G{underscore}enerators (RTGs) at high altitude. In addition, detailed analyses are performed to determine the survival/failure of the Graphite Impact Shells that would be released if the GPHS fails. The reentry velocity of the GPHS module (20 km/sec) is higher than any previously analyzed Earth reentry trajectory. {copyright} {ital 1999 American Institute of Physics.}

  12. Nanodust detection between 1 and 5 AU by using Cassini wave measurements

    CERN Document Server

    Schippers, P; Lecacheux, A; Belheouane, S; Moncuquet, M; Kurth, W S; Mann, I; Mitchell, D G; André, N

    2015-01-01

    The solar system contains solids of all sizes, ranging from km-size bodies to nano-sized particles. Nanograins have been detected in situ in the Earth's atmosphere, near cometary and giant planet environments, and more recently in the solar wind at 1 AU. These latter nano grains are thought to be formed in the inner solar system dust cloud, mainly through collisional break-up of larger grains and are then picked-up and accelerated by the magnetized solar wind because of their large charge-to-mass ratio. In the present paper, we analyze the low frequency bursty noise identified in the Cassini radio and plasma wave data during the spacecraft cruise phase inside Jupiter's orbit. The magnitude, spectral shape and waveform of this broadband noise is consistent with the signature of nano particles impinging at nearby the solar wind speed on the spacecraft surface. Nanoparticles were observed whenever the radio instrument was turned on and able to detect them, at different heliocentric distances between Earth and Ju...

  13. Nature of the MHD and Kinetic Scale Turbulence in the Magnetosheath of Saturn: Cassini Observations

    Science.gov (United States)

    Hadid, L. Z.; Sahraoui, F.; Kiyani, K. H.; Retinò, A.; Modolo, R.; Canu, P.; Masters, A.; Dougherty, M. K.

    2015-11-01

    Low-frequency turbulence in Saturn’s magnetosheath is investigated using in situ measurements of the Cassini spacecraft. Focus is put on the magnetic energy spectra computed in the frequency range of ˜[10-4, 1]Hz. A set of 42 time intervals in the magnetosheath were analyzed, and three main results that contrast with known features of solar wind turbulence are reported. (1) The magnetic energy spectra showed a ˜f-1 scaling at MHD scales followed by an ˜ {f}-2.6 scaling at sub-ion scales without forming the so-called inertial range. (2) The magnetic compressibility and the cross-correlation between the parallel component of the magnetic field and density fluctuations C(δ n,δ {B}| | ) indicate the dominance of the compressible magnetosonic slow-like modes at MHD scales rather than the Alfvén mode. (3) Higher-order statistics revealed a monofractal (multifractal) behavior of the turbulent flow downstream of a quasi-perpendicular (quasi-parallel) shock at sub-ion scales. Implications of these results on theoretical modeling of space plasma turbulence are discussed.

  14. OBSERVED CHANNELS IN SATURN'S F RING BY THE CASSINI SPACECRAFT AND THEIR RELATIONSHIP TO PROMETHEUS

    Directory of Open Access Journals (Sweden)

    C. E. Chávez

    2008-01-01

    Full Text Available Los anillos planetarios delgados se cree que son estabilizados por peque as lunas a las cuales se les llaman pastoras que orbitan dentro o cerca de los anillos y ayudan a estabilizarlos por sus in uencias gravitacionales. El anillo F de Saturno (el cual se encuentra justo afuera del sistema principal de anillos tiene como pastoras a dos lunas. Prometeo (cuyo di metro mide 100 km orbita justamente dentro del anillo F, mientras que Pandora (de 85 km en d metro se mueve alrededor de Saturno en una rbita justo fuera del anillo F. Las im genes de la regi n alrededor del anillo de F captadas por la Sonda espacial Cassini y sus c maras ISS (Subsistema de Imagen Cient ca han revelado una estructura que no ha sido observada en ning n otro anillo planetario. Se han descubierto estructuras peri dicas que recuerdan canales azimutales (\\canales" de profundidad ptica baja y \\chorros". Nosotros reportamos estas estructuras previamente en Murray et al. (2005. Aqu usamos rbitas recientemente publicadas; la rbita de Prometeo fue tomada de Spitale et al. (2006, la rbita del centro del anillo F de Bosh et al. (2002. Las dimensiones y la masa de Prometeo fueron tomadas de Porco et al. (2006. Nosotros hemos hecho una comparaci n directa de los resultados num ericos previos reportados por Murray et al. (2005 y nuestro modelo num rico para la misma con guraci n, y hemos encontrado una excelente concordancia entre ellos.

  15. Saturn's inner satellites : orbits, masses and the chaotic motion of Atlas from new Cassini imaging observations

    CERN Document Server

    Cooper, N J; Murray, C D; Evans, M W

    2014-01-01

    We present numerically-derived orbits and mass estimates for the inner Saturnian satellites, Atlas, Prometheus, Pandora, Janus and Epimetheus from a fit to 2580 new Cassini ISS astrometric observations spanning February 2004 to August 2013. The observations are provided in a supplementary table. We estimate GM_ Atlas=0.384+/-0.001 x 10^(-3)km^3s^(-2), a value 13% smaller than the previously published estimate but with an order of magnitude reduction in the uncertainty. We also find GM_ Prometheus=10.677+/-0.006x10(-3)km^3s^(-2), GM_Pandora=9.133+/-0.009x10^(-3)km^3s^(-2), GM_Janus=126.51+/-0.03x10^(-3)km^3s^(-2) and GM_Epimetheus=35.110+/-0.009x10^(-3)km^3s^(-2), consistent with previously published values, but also with significant reductions in uncertainties. We show that Atlas is currently librating in both the 54:53 co-rotation-eccentricity resonance (CER) and the 54:53 inner Lindblad (ILR) resonance with Prometheus, making it the latest example of a coupled CER-ILR system, in common with the Saturnian sa...

  16. The Juno and Cassini gravity measurements: probing the interior dynamics of Jupiter and Saturn

    Science.gov (United States)

    Kaspi, Y.; Galanti, E.; Hubbard, W. B.; Davighi, J. E.

    2015-10-01

    During 2016-2017 both the Juno and Cassini spacecraft will enter into close-by polar orbits of Jupiter and Saturn, respectively. Using Doppler tracking from Earth these flybys will allow high precision gravity measurements of these planets [1]. These will include high order gravity harmonics (at least up to J10), and the yet to be measured odd gravity spectrum. As the dynamics of deep flows relate to perturbations in the density of the planets, this data can be used to probe for the first time the atmospheric and interior flows on these planets [4, 5, 8]. Particularly, this may allow addressing one of the longest-standing questions in planetary atmospheric dynamics regarding the depth of the observed strong east-west jets-streams on Jupiter and Saturn. In this talk we review different approaches to analyze the gravity measurements, discuss the proposed models relating the gravity fields to the dynamics, and the implications of the results for understanding the mechanisms governing the interiors and atmospheres of Jupiter and Saturn.

  17. A Principal Component Analysis of global images of Jupiter obtained by Cassini ISS

    Science.gov (United States)

    Ordóñez Etxeberria, I.; Hueso, R.; Sánchez-Lavega, A.

    2014-04-01

    The Cassini spacecraft flybied Jupiter in December 2000. The Imaging Science Subsystem (ISS) cameras acquired a large number of images at different spatial resolution in several filters sensitive to different altitudes and to cloud color. We have used these images to build high-resolution multi-wavelength nearly full maps of the planet in cylindrical and polar projections. The images have been analyzed by means of a principal component analysis technique (PCA) which looks for spatial covariances in different filtered images and proposes a new set of images (Principal Components, PC) which contains most of the spatial variability. The goal of this research is triple since we: 1) explore correlations between the ammonia cloud layer observed in most filters and the upper hazes observed in methane band images and UV, 2) we explore the spatial distribution of chromophores similarly to previous studies using HST images [1, 2]; 3) we look for image combinations that could be useful for cloud features sharpening. Furthermore, we study a global characterization of reletive altimetry of clouds and hazes from synthetic indexes between images with different contributions from the methane absorption bands (CB1, CB2, CB3, MT1, MT2, MT3).

  18. A despeckle filter for the Cassini synthetic aperture radar images of Titan's surface

    Science.gov (United States)

    Bratsolis, Emmanuel; Bampasidis, Georgios; Solomonidou, Anezina; Coustenis, Athena

    2012-02-01

    Cassini synthetic aperture radar (SAR) images of Titan, the largest satellite of Saturn, reveal surface features with shapes ranging from quasi-circular to more complex ones, interpreted as liquid hydrocarbon deposits assembled in the form of lakes or seas. One of the major problems hampering the derivation of meaningful texture information from SAR imagery is the speckle noise. It overlays real structures and causes gray value variations even in homogeneous parts of the image. We propose a filtering technique which can be applied to obtain restored SAR images. Our technique is based on probabilistic methods and regards an image as a random element drawn from a prespecified set of possible images. The despeckle filter can be used as an intermediate step for the extraction of regions of interest, corresponding to structured units in a given area or distinct objects of interest, such as lake-like features on Titan. This tool can therefore be used, among other, to study seasonal surficial changes of Titan's polar regions. In this study we also present a segmentation technique that allows us to separate the lakes from the local background.

  19. Automatic Preocessing of Impact Ionization Mass Spectra Obtained by Cassini CDA

    Science.gov (United States)

    Villeneuve, M.

    2015-12-01

    Since Cassini's arrival at Saturn in 2004, the Comic Dust Analyzer (CDA) has recorded nearly 200,000 mass spectra of dust particles. A majority of this data has been collected in Saturn's diffuse E ring where sodium salts embedded in water ice particles indicate that many particles are in fact frozen droplets from Enceladus' subsurface ocean that have been expelled from cracks in the icy crust. So far only a small fraction of the obtained spectra have been processed because the steps in processing the spectra require human manipulation. We developed an automatic processing pipeline for CDA mass spectra which will consistently analyze this data. The preprocessing steps are to de-noise the spectra, determine and remove the baseline, calculate the correct stretch parameter, and finally to identify elements and compounds in the spectra. With the E ring constantly evolving due to embedded active moons, this data will provide valuable information about the source of the E ring, the subsurface of Saturn's ice moon Enceladus, as well as about the dynamics of the ring itself.

  20. Vortices in Saturn's Northern Hemisphere (2008-2015) observed by Cassini ISS

    Science.gov (United States)

    Trammell, Harold Justin; Li, Liming; Jiang, Xun; Pan, Yefeng; Smith, Mark A.; Bering, Edgar A.; Hörst, Sarah M.; Vasavada, Ashwin R.; Ingersoll, Andrew P.; Janssen, Michael A.; West, Robert A.; Porco, Carolyn C.; Li, Cheng; Simon, Amy A.; Baines, Kevin H.

    2016-09-01

    We use observations from the Imaging Science Subsystem on Cassini to create maps of Saturn's Northern Hemisphere (NH) from 2008 to 2015, a time period including a seasonal transition (i.e., spring equinox in 2009) and the 2010 giant storm. The processed maps are used to investigate vortices in the NH during the period of 2008-2015. All recorded vortices have diameters (east-west) smaller than 6000 km except for the largest vortex that developed from the 2010 giant storm. The largest vortex decreased its diameter from ~11,000 km in 2011 to ~5000 km in 2015, and its average diameter is ~6500 km during the period of 2011-2015. The largest vortex lasts at least 4 years, which is much longer than the lifetimes of most vortices (less than 1 year). The largest vortex drifts to north, which can be explained by the beta drift effect. The number of vortices displays varying behaviors in the meridional direction, in which the 2010 giant storm significantly affects the generation and development of vortices in the middle latitudes (25-45°N). In the higher latitudes (45-90°N), the number of vortices also displays strong temporal variations. The solar flux and the internal heat do not directly contribute to the vortex activities, leaving the temporal variations of vortices in the higher latitudes (45-90°N) unexplained.

  1. VIS-NIR Spectrophotometric Study of the Saturnian icy Satellites by Cassini-VIMS

    Science.gov (United States)

    Filacchione, G.; Capaccioni, F.; Tosi, F.; Coradini, A.; Cerroni, P.; Adriani, A.; McCord, T. B.; Baines, K. H.; Bellucci, G.; Brown, R. H.; Bibring, J.; Buratti, B. J.; Clark, R. N.; Combes, M.; Cruikshank, D. P.; Formisano, V.; Jaumann, R.; Langevin, Y. G.; Matson, D. L.; Mennella, V.; Nelson, R. M.; Nicholson, P. D.; Sicardy, B.; Sotin, C.

    2007-12-01

    After the first three years of the nominal mission aboard the Cassini probe the VIMS (Visual and Infrared Mapping Spectrometer) experiment has collected more than one thousand useful full-disk observations of both regular (Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion, Iapetus, Phoebe) and minor (Atlas, Prometheus, Pandora, Janus, Epimetheus, Telesto, Calypso) icy moons of Saturn. These data, acquired from a variety of distances and inclinations from the equatorial plane, with different phase angles and hemispheric coverage, are analyzed by using several spectroscopic indicators (I/F continuum level, slopes, bands strengths) in order to identify analogies and differences in the compositional units of satellites and derive the phase curves at different longitudes; many observations acquired close to zero phase angle allow us to measure the opposition surge effect on several satellites. Concerning the composition we have derived the distribution of the water ice abundance and grain size from the almost pure icy surfaces of Enceladus and Calypso to the organic rich Hyperion, Iapetus and Phoebe. We report about the differences observed in the CO2 band position which is shifted at shorter wavelengths on Hyperion respect to Phoebe and Iapetus; this effect is probably related to a different distribution of clathrates on these icy surfaces. This research was completed thanks to the support of the Italian Space Agency (ASI).

  2. Radial Variations in Particle Clumping in Perturbed Regions of Saturn's Rings from Cassini UVIS Stellar Occultations

    Science.gov (United States)

    Colwell, Joshua E.; Esposito, Larry W.; Cooney, James

    2016-10-01

    Showalter and Nicholson (1990, Icarus 87, 285-306) showed that the variance in the Voyager 2 stellar occultation by Saturn's rings could be analyzed to extract information on the sizes of particles in the rings, or, more precisely, on the autocorrelation length, R, of the distribution of ring particles. We have previously reported on applying this principle to the many stellar occultations observed by Cassini's Ultraviolet Imaging Spectrograph (UVIS). Here we present results of the variance at 2 km radial resolution, fine enough to examine changes in the autocorrelation length within the broad troughs of the strongest density waves. We find dips in R in the first several wavelengths of the Janus 2:1 density wave in the inner B ring. In addition, we find a decrease in R in the Mimas 5:3 bending wave. Strong Janus density waves in the A ring show an increase in R in the peaks of the density waves, but no dip below the background level in the troughs. We also see a decrease in R in the broad "halo" regions of the A ring around the strongest resonances, implying less-well-organized self-gravity wakes in those regions and/or smaller or more abundant particles in the gaps between the wakes. We will present our results from multiple occultations and their implications for the collisional environment in strongly perturbed regions in the rings.

  3. Etude des etats electroniques en champ magnetique dans le niveau de Landau N=0 de la tricouche ABC de graphene

    Science.gov (United States)

    Rondeau, Maxime

    Dans cet ouvrage nous etudions les phases du gaz d'electrons bidimensionnel dans la tricouche de graphene en empilement ABC. En partant du modele des liaisons fortes et en faisant l'approximation du continuum autour des vallees K +, K-, nous obtenons un modele effectif a deux bandes qui permet de decrire la physique de basse energie des electrons en champ magnetique dans cette structure. Ce modele contient trois orbitales degenerees dans le niveau de Landau N = O. Ce dernier est donc 12N φ, fois degeneres en incluant les degres de liberte de spin et de vallee. En ajoutant l'interaction de Coulomb au systeme et en considerant seulement les remplissages v = -5, -4, -4, 5 afin d'avoir un systeme a trois niveaux, nous etudions le diagramme de phase du gaz d'electrons en fonction d'un biais electrique entre les couches externes. Nous trouvons une phase d'onde de densite de charge bidimensionnelle (ODC2D) comme etat fondamental du systeme. Cette ODC2D se nomme cristal dans ce memoire et nous derivons ses proprietes de transports et ses modes collectifs. Nous discutons egalement du caractere topologique de ce cristal. Notre etude englobe aussi les phases liquides avec ou sans coherence orbitale. Nous concluons notre memoire par l'etude de quelques signatures experimentales des phases du gaz d'electrons dans la tricouche.

  4. Contribution to the study of french pitchblendes; Contribution a l'etude des pechblendes francaises

    Energy Technology Data Exchange (ETDEWEB)

    Geffroy, J. [Commissariat a l' Energie Atomique, Lab. de Mineralogie, Centre de Chatillon (France). Centre d' Etudes Nucleaires; Sarcia, J.A. [Commissariat a l' Energie Atomique, Div. de la Crouzille, Haute Vienne (France). Centre d' Etudes Nucleaires

    1955-07-01

    The authors first review the characteristics of uraninite-pitchblende, as deduced of present literature. They set apart from typical pitchblende a black oxide aspect, which probably corresponds to neo-formations, and a 'para-pitchblende' aspect, which they relate to deep sur-oxidation of normal pitchblende. They insist on the easy replacement of pitchblende by silica. and give indications as to changes in vein stones (fluorite, quartz, etc...). A detailed study of paragenesis and successions in french uranium districts follows (including discussion of uranium of uranium-bearing coals). The authors attempt to classify french pitchblende veins. They are chiefly epithermal and poor in satellite ores. Three types of deposits are identified: massive - pitchblende type, silica type, fluorite type. These deposits, as those of Portugal, are included in granite, Central-European peri-batholitic types where uranium associates which Ni, Co, Bi and Ag, are in France both rare and poor. Finally, the authors attempt to bring out in the european Hercynian area a particular distribution of paragenetic types. (authors) [French] Les auteurs recapitulent d'abord les caracteres et les occurences de l'uraninite - pechblende, tels qu'ils peuvent etre degages de l'actuelle bibliographie. Ils exposent ensuite les faits qui du point de vue mineralogique seulement ressortent de l'etude mineralogique et chalcographique des pechblendes francaises et de leurs satellites. Ils distinguent de la pechblende-type un facies oxyde noir; correspondant probablement a une neoformation, et un facies parapechblende, qui est rapporte a une sur oxydation hypogene de la pechblende proprement dite. Ils insistent sur le facile remaniement de la pechblende par la slice; et donnent quelques precisions sur les modifications des gangues (fluorine, quartz, etc...). Suit l'etude detaillee des parageneses et des successions dans les districts uraniferes francais: Divisions du

  5. Etude de la dynamique des porteurs dans des nanofils de silicium par spectroscopie terahertz

    Science.gov (United States)

    Beaudoin, Alexandre

    Ce memoire presente une etude des proprietes de conduction electrique et de la dynamique temporelle des porteurs de charges dans des nanofils de silicium sondes par rayonnement terahertz. Les cas de nanofils de silicium non intentionnellement dopes et dopes type n sont compares pour differentes configurations du montage experimental. Les mesures de spectroscopie terahertz en transmission montre qu'il est possible de detecter la presence de dopants dans les nanofils via leur absorption du rayonnement terahertz (˜ 1--12 meV). Les difficultes de modelisation de la transmission d'une impulsion electromagnetique dans un systeme de nanofils sont egalement discutees. La detection differentielle, une modification au systeme de spectroscopie terahertz, est testee et ses performances sont comparees au montage de caracterisation standard. Les instructions et des recommendations pour la mise en place de ce type de mesure sont incluses. Les resultats d'une experience de pompe optique-sonde terahertz sont egalement presentes. Dans cette experience, les porteurs de charge temporairement crees suite a l'absorption de la pompe optique (lambda ˜ 800 nm) dans les nanofils (les photoporteurs) s'ajoutent aux porteurs initialement presents et augmentent done l'absorption du rayonnement terahertz. Premierement, l'anisotropie de l'absorption terahertz et de la pompe optique par les nanofils est demontree. Deuxiemement, le temps de recombinaison des photoporteurs est etudie en fonction du nombre de photoporteurs injectes. Une hypothese expliquant les comportements observes pour les nanofils non-dopes et dopes-n est presentee. Troisiemement, la photoconductivite est extraite pour les nanofils non-dopes et dopes-n sur une plage de 0.5 a 2 THz. Un lissage sur la photoconductivite permet d'estimer le nombre de dopants dans les nanofils dopes-n. Mots-cles: nanofil, silicium, terahertz, conductivite, spectroscopie, photoconductivite.

  6. Etude theorique et experimentale des evaporateurs de dioxyde de carbone operant dans des conditions de givrage

    Science.gov (United States)

    Bendaoud, Adlane Larbi

    Les evaporateurs de refrigeration sont surtout du type tube a ailettes, appeles serpentins, et fonctionnent dans l'une des conditions suivantes: seche, humide ou avec formation de givre. Il a ete demontre que la formation du givre sur la paroi exterieure de l'echangeur engendre une surconsommation energetique a cause des operations de degivrage puisque 15 a 20% seulement de la chaleur produite sert au degivrage tandis que le reste est dissipee dans l'environnement [1]. Avec l'avenement des nouveaux refrigerants, moins nocifs envers l'environnement, l'industrie du froid se trouve penalisee du fait que peu ou pas de composantes mecaniques (compresseur, pompe, echangeur...etc.) adaptees sont disponibles [3]. Il s'agit pour la communaute des frigoristes de combler ce retard technologique en redeveloppant ces composantes mecaniques afin qu'elles soient adaptees aux nouveaux refrigerants. Dans cette optique, et afin de mieux comprendre le comportement thermique des evaporateurs au CO2 fonctionnant dans des conditions seches, qu'un groupe de chercheurs du CanmetENERGIE avaient lance, en 2000, un programme de R & D. Dans le cadre de programme un outil de simulation des evaporateurs au CO2 a ete developpe et un banc d'essai contenant une boucle secondaire de refrigeration utilisant le CO2 comme refrigerant a ete construit. Comme continuite de ce travail de recherche, en 2006 ce meme groupe de recherche a lance un nouveau projet qui consiste a faire une etude theorique et experimentale des evaporateurs au CO2 operants dans des conditions de givrage. Et, c'est exactement dans le cadre de ce projet que se positionne ce travail de these. Ce travail de recherche a ete entrepris pour mieux comprendre le comportement thermique et hydrodynamique des serpentins fonctionnant dans des conditions de givrage, l'effet des circuits de refrigerant ainsi que celui des parametres geometriques et d'operation. Pour cela, un travail theorique supporte par une etude experimentale a ete effectue

  7. Inferring an analytical model from Cassini-CIRS data to predict Saturn's Rings temperature

    Science.gov (United States)

    Altobelli, N.; Lopez Paz, D.; Spilker, L. J.; Pilorz, S.; Edgington, S. G.; Brooks, S. M.

    2012-12-01

    Since Saturn Orbit Insertion (SOI), the Composite Infrared Spectrometer (CIRS) on-board the Cassini Spacecraft has been performing a thermal mapping of Saturn's main rings, by measuring the thermal radiance in the far-infrared (10 to 600 cm-1 ) for different viewing geometries. So far, over 2.5 millions individual spectra have been recorded. Previous analysis have shown that Saturn's Rings measured temperatures are a function of observational geometrical parameters, characterizing the thermal response of Saturn Rings to time dependent illumination conditions. There is no doubt that the complex behavior of the ring temperature in the observational geometrical space contains mixed information on Rings' large scale properties (thermal behavior resulting from an ensemble of particles like mutual shadowing) as well as meso- to micro- scopic scale properties (individual particles properties and surface regolith on particles surface). Recent models have focused mainly at inferring individual particle properties (albedo, thermal inertia and spin rate) by reproducing subsets of temperature measurements. These models assume that the Rings are made of a collection of spinning spherical particles. However, stellar and radio occultations of the Rings have revealed that the particles tend to 'clump' and form larger structures, short-lived or persistent, such that the view of the Rings as a collection of spinning spheres appears somewhat questionable for thermal modeling. We propose in this work a new approach by considering the Rings as a 'planetary' surface, instead of a collection of individual spinning spheres as in previous models. Our goal is to model analytically the thermal response of this Ring-surface to illumination using all data obtained so far. As a preparatory work to our modeling attempt, we address first the question to know wether the temperature measurements taken since 2004 cover sufficiently well the observational phase space to fully characterize the ring

  8. Cassini INMS Observations of Ions and Neutrals in Saturn's Inner Magnetosphere

    Science.gov (United States)

    Perry, M. E.; Cravens, T. E.; Mandt, K.; Teolis, B. D.; Tokar, R. L.; Smith, H. T.; McNutt, R. L.; Waite, J. H.

    2012-12-01

    The Cassini Ion Neutral Mass Spectrometer (INMS) has measured the low-density particles in Saturn's inner magnetosphere (IM). Planning and implementing INMS observations of neutral molecules and water-group ions near the equatorial plane have steadily improved such that INMS now provides measurements that complement other observations of these low-energy ions and neutrals the IM, providing unambiguous resolution of the water-group ions and in situ, three-dimensional spatial dependence of the neutral densities. INMS measurements of neutrals are viable only in the densest regions, inside of 7 Saturn radii (RS) and within 20,000 km of the equatorial plane. Due to a variable background, the INMS detection limit for neutral water is near 103 molecules/cm3, which is the approximate density near 7 RS. High-energy radiation interferes with neutral observations inside of 3.5 RS. The tendency of H2O molecules to adhere to the walls of the INMS inlet aperture requires long integration times to determine the total volume of H2O molecules. Concurrent INMS measurements of associated volatile molecules such as CO2 determine spatial dependence of the neutral density. In the densest part of the neutral cloud that is outside of the Enceladus plumes and north of Enceladus, INMS measures 105 molecules/cm3. Near the equatorial plane, INMS data show that neutral water density drops a factor of ten from 4.2 RS, just outside the orbit of Enceladus, to 7 RS. This decline, caused by photo-ionization, disassociation by ion impact, and distribution by neutral-neutral collisions, is within the range of results derived from remote observations. INMS observations of azimuthal densities, which are not available from remote observations that average multiple observations, show the expected decline for neutrals that near the orbit of Enceladus but separated azimuthally. INMS can measure only one velocity at a time, restricting INMS measurements to only a small area of velocity phase space at a time

  9. Statistical study of Saturn's auroral electron properties with Cassini/UVIS FUV spectral images

    Science.gov (United States)

    Gustin, J.; Grodent, D.; Radioti, A.; Pryor, W.; Lamy, L.; Ajello, J.

    2017-03-01

    About 2000 FUV spectra of different regions of Saturn's aurora, obtained with Cassini/UVIS from December 2007 to October 2014 have been examined. Two methods have been employed to determine the mean energy of the precipitating electrons. The first is based on the absorption of the auroral emission by hydrocarbons and the second uses the ratio between the brightness of the Lyman-α line and the H2 total UV emission (Lyα/H2), which is directly related to via a radiative transfer formalism. In addition, two atmospheric models obtained recently from UVIS polar occultations have been employed for the first time. It is found that the atmospheric model related to North observations near 70° latitude provides the results most consistent with constraints previously published. On a global point of view, the two methods provide comparable results, with mostly in the 7-17 keV range with the hydrocarbon method and in the 1-11 keV range with the Lyα/H2 method. Since hydrocarbons have been detected on ∼20% of the auroral spectra, the Lyα/H2 technique is more effective to describe the primary auroral electrons, as it is applicable to all spectra and allows an access to the lowest range of energies (≤5 keV), unreachable by the hydrocarbon method. The distribution of is found fully compatible with independent HST/ACS constraints (emission peak in the 840-1450 km range) and FUSE findings (emission peaking at pressure level ≤0.2 μbar). In addition, exhibits enhancements in the 3 LT-10 LT sector, consistent with SKR intensity measurements. An energy flux-electron energy diagram built from all the data points strongly suggests that acceleration by field-aligned potentials as described by Knight's theory is a main mechanism responsible for electron precipitation creating the aurora. Assuming a fixed electron temperature of 0.1 keV, a best-fit equatorial electron source population density of 3 × 103 m-3 is derived, which matches very well to the plasma properties observed with

  10. The composition of Titan's stratosphere from Cassini/CIRS mid-infrared spectra

    Science.gov (United States)

    Coustenis, Athena; Achterberg, Richard K.; Conrath, Barney J.; Jennings, Donald E.; Marten, André; Gautier, Daniel; Nixon, Conor A.; Flasar, F. Michael; Teanby, Nick A.; Bézard, Bruno; Samuelson, Robert E.; Carlson, Ronald C.; Lellouch, Emmanuel; Bjoraker, Gordon L.; Romani, Paul N.; Taylor, Fred W.; Irwin, Patrick G. J.; Fouchet, Thierry; Hubert, Augustin; Orton, Glenn S.; Kunde, Virgil G.; Vinatier, Sandrine; Mondellini, Jacqueline; Abbas, Mian M.; Courtin, Regis

    2007-07-01

    We have analyzed data recorded by the Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft during the Titan flybys T0-T10 (July 2004-January 2006). The spectra characterize various regions on Titan from 70° S to 70° N with a variety of emission angles. We study the molecular signatures observed in the mid-infrared CIRS detector arrays (FP3 and FP4, covering roughly the 600-1500 cm -1 spectral range with apodized resolutions of 2.54 or 0.53 cm -1). The composite spectrum shows several molecular signatures: hydrocarbons, nitriles and CO 2. A firm detection of benzene (C 6H 6) is provided by CIRS at levels of about 3.5×10 around 70° N. We have used temperature profiles retrieved from the inversion of the emission observed in the methane ν band at 1304 cm -1 and a line-by-line radiative transfer code to infer the abundances of the trace constituents and some of their isotopes in Titan's stratosphere. No longitudinal variations were found for these gases. Little or no change is observed generally in their abundances from the south to the equator. On the other hand, meridional variations retrieved for these trace constituents from the equator to the North ranged from almost zero (no or very little meridional variations) for C 2H 2, C 2H 6, C 3H 8, C 2H 4 and CO 2 to a significant enhancement at high northern (early winter) latitudes for HCN, HC 3N, C 4H 2, C 3H 4 and C 6H 6. For the more important increases in the northern latitudes, the transition occurs roughly between 30 and 50 degrees north latitude, depending on the molecule. Note however that the very high-northern latitude results from tours TB-T10 bear large uncertainties due to few available data and problems with latitude smearing effects. The observed variations are consistent with some, but not all, of the predictions from dynamical-photochemical models. Constraints are set on the vertical distribution of C 2H 2, found to be compatible with 2-D equatorial predictions by global circulation

  11. Saturn's system ices: a comparative spectral study by Cassini-VIMS

    Science.gov (United States)

    Filacchione, Gianrico; Capaccioni, Fabrizio; Clark, Roger N.; Cuzzi, Jeff N.; Cruikshank, Dale P.; Coradini, Angioletta; Cerroni, Priscilla; Tosi, Federico; Ciarniello, Mauro; Nicholson, Phil D.; McCord, Thomas B.; Brown, Robert H.; Buratti, Bonnie J.; Jaumann, Ralf; Stephan, Katrin

    2010-05-01

    The Visual and Infrared Mapping Spectrometer (VIMS) has observed the entire population of Saturnian icy objects, allowing a comparative analysis of the VIS-NIR spectral properties of the regular satellites (Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion, Iapetus, Phoebe), minor moons (Atlas, Prometheus, Pandora, Janus, Epimetheus, Telesto, Calypso) and main rings (A, B, C and Cassini division). The results we present are derived from the entire dataset available after about 5 years of the Cassini mission, which consists of more than 2000 full-disk observations of the moons as well as several radial mosaics of the ring system. The spectra of Saturn's satellites are characterized by a step red slope in the 0.35-0.55 µm range, which is highly diagnostic of the presence of organic contaminants and darkening agents on icy surfaces; in the 0.55-0.95 µm range the spectra become more flat and featureless. In the IR range the water ice bands at 1.5-2.0-3.0 µm bands are evident everywhere, while the CO2 ice band at 4.26 µm is seen only on the three external satellites Hyperion, Iapetus and Phoebe. Some specific spectrophotometric indicators are chosen to retrieve the macroscopic properties of the ices: I/F continuum levels, 0.35-0.55 and 0.55-0.95 µm spectral slopes, H2O-CO2 ice band depths and band positions. By using these indicators the Saturn's satellites are grouped in distinct classes, noticeably between the almost pure water ice and blue surfaces of Enceladus and Calypso to the organic- and carbon dioxide-rich Hyperion, Iapetus and Phoebe. Hyperion and the leading hemisphere of Iapetus have the reddest VIS slopes of the group. Janus' visible colors are intermediate between these two classes having a slightly positive VIS spectral slope, while Epimetheus is more neutral and similar to Iapetus' bright terrains (trailing hemisphere), Mimas and Tethys. The two F ring's shepherd moons, Prometheus and Pandora, have similarities with Atlas, while Calypso and Telesto

  12. Cost Comparison in 2015 Dollars for Radioisotope Power Systems -- Cassini and Mars Science Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Werner, James Elmer [Idaho National Lab. (INL), Idaho Falls, ID (United States); Johnson, Stephen Guy [Idaho National Lab. (INL), Idaho Falls, ID (United States); Dwight, Carla Chelan [Idaho National Lab. (INL), Idaho Falls, ID (United States); Lively, Kelly Lynn [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-07-01

    Radioisotope power systems (RPSs) have enabled missions requiring reliable, long-lasting power in remote, harsh environments such as space since the early 1960s. Costs for RPSs are high, but are often misrepresented due to the complexity of space missions and inconsistent charging practices among the many and changing participant organizations over the years. This paper examines historical documentation associated with two past successful flight missions, each with a different RPS design, to provide a realistic cost basis for RPS production and deployment. The missions and their respective RPSs are Cassini, launched in 1997, that uses the general purpose heat source (GPHS) radioisotope thermoelectric generator (RTG), and Mars Science Laboratory (MSL), launched in 2011, that uses the multi-mission RTG (MMRTG). Actual costs in their respective years are discussed for each of the two RTG designs and the missions they enabled, and then present day values to 2015 are computed to compare the costs. Costs for this analysis were categorized into two areas: development of the specific RTG technology, and production and deployment of an RTG. This latter category includes material costs for the flight components (including Pu-238 and fine weave pierced fabric (FWPF)); manufacturing of flight components; assembly, testing, and transport of the flight RTG(s); ground operations involving the RTG(s) through launch; nuclear safety analyses for the launch and for the facilities housing the RTG(s) during all phases of ground operations; DOE’s support for NEPA analyses; and radiological contingency planning. This analysis results in a fairly similar 2015 normalized cost for the production and deployment of an RTG—approximately $118M for the GPHS-RTG and $109M for the MMRTG. In addition to these two successful flight missions, the costs for development of the MMRTG are included to serve as a future reference. Note that development costs included herein for the MMRTG do not include

  13. Saturn's tropospheric particles phase function and spatial distribution from Cassini ISS 2010-11 observations

    Science.gov (United States)

    Pérez-Hoyos, Santiago; Sanz-Requena, José Francisco; Sánchez-Lavega, Agustín; Irwin, Patrick G. J.; Smith, Andrew

    2016-10-01

    The phase function describes the way particles scatter the incoming radiation. This is a fundamental piece of knowledge in order to understand how a planetary atmosphere scatters sunlight and so it has a profound influence in the retrieved atmospheric properties such as cloud height, particle density distribution and radiative forcing by aerosols. In this work we analyze data from the Imaging Science Subsystem (ISS) instrument onboard Cassini spacecraft to determine the particle phase function at blue (451 nm) and near infrared wavelengths (727-890 nm) of particles in the upper troposphere, where most of the incoming visible sunlight is scattered. In order to do so, we use observations taken in later 2010 and 2011 covering a broad range of phase angles from ∼10° to ∼160° in the blue (BL1) and near infrared filters associated with intermediate and deep methane absorption bands (MT2, CB2, MT3). Particles at all latitudes are found to be strongly forward scattering. The equatorial particles are in good agreement with laboratory measurements of 10 μm ammonia ice crystals, while mid- and sub-polar latitude particles may be similar to the equatorial particles, but they may also be consistent with 1 μm ellipsoids with moderate aspect ratios. Uncertainties due to limited phase coverage and parameter degeneracy prevent strong constraints of the particle shapes and sizes at these locations. Results for the particle phase function are also used to describe the spatial distribution of tropospheric particles both vertically and latitudinally in the Northern hemisphere.

  14. Investigation of Jupiter's Equatorial Hotspots and Plumes Using Cassini ISS Observations

    Science.gov (United States)

    Choi, David S.; Showman, A. P.; Vasavada, A. R.; Simon-Miller, A. A.

    2012-01-01

    We present updated analysis of Jupiter's equatorial meteorology from Cassini observations. For two months preceding the spacecraft's closest approach, the ISS onboard regularly imaged the atmosphere. We created time-lapse movies from this period in order to analyze the dynamics of equatorial 5-micron hot spots and their interactions with adjacent latitudes. Hot spots are quasi-stable, rectangular dark areas on visible-wavelength images, with defined eastern edges that sharply contrast with surrounding clouds, but a diffuse western edge serving as a nebulous boundary with adjacent equatorial plumes. Hot spots exhibit significant variations in size and shape over timescales of days and weeks. Some of these changes correspond with passing vortex systems from adjacent latitudes interacting with hot spots. Strong anticyclonic gyres present to the south and southeast of the dark areas appear to circulate into hot spots. Impressive, bright white plumes occupy spaces in between hot spots. Compact cirrus-iike 'scooter' clouds flow rapidly through the plumes before disappearing within the dark areas. This raises the possibility that the plumes and fast-moving clouds are at higher altitudes, because their speed does not match previously published zonal wind profiles. Most profiles represent the drift speed of the hot spots at their latitude from pattern matching of the entire longitudinal image strip. If a downward branch of an equatorially-trapped Rossby waves controls the overall appearance of hot spots, however, the westward phase velocity of the wave leads to underestimates of the true jet stream speed. Instead, our expanded data set demonstrating the rapid flow of these scooter clouds may be more illustrative of the actual jet stream speed at these latitudes. This research was supported by a NASA JDAP grant and the NASA Postdoctoral Program.

  15. Structure of self-gravity wakes in Saturn's A ring as measured by Cassini CIRS

    Science.gov (United States)

    Ferrari, C.; Brooks, S.; Edgington, S.; Leyrat, C.; Pilorz, S.; Spilker, L.

    2009-01-01

    The CIRS infrared spectrometer onboard the Cassini spacecraft has scanned Saturn's A ring azimuthally from several viewing angles since its orbit insertion in 2004. A quadrupolar asymmetry has been detected in this ring at spacecraft elevations ranging between 16° to 37°. Its fractional amplitude decreases from 22% to 8% from 20° to 37° elevations. The patterns observed in two almost complete azimuthal scans at elevations 20° and 36° strongly favor the self-gravity wakes as the origin of the asymmetry. The elliptical, infinite cylinder model of Hedman et al. [Hedman, M.M., Nicholson, P.D., Salo, H., Wallis, B.D., Buratti, B.J., Baines, K.H., Brown, R.H., Clark, R.N., 2007. Astron. J. 133, 2624-2629] can reproduce the CIRS observations well. Such wakes are found to have an average height-to-spacing ratio H/λ=0.1607±0.0002, a width-over-spacing W/λ=0.3833±0.0008. Gaps between wakes, which are filled with particles, have an optical depth τ=0.1231±0.0005. The wakes mean pitch angle Φ is 70.70°±0.07°, relative to the radial direction. The comparison of ground-based visible data with CIRS observations constrains the A ring to be a monolayer. For a surface mass density of 40 g cm -2 [Tiscarino, M.S., Burns, J.A., Nicholson, P.D., Hedman, M.M., Porco, C.C., 2007. Icarus 189, 14-34], the expected spacing of wakes is λ≈60 m. Their height and width would then be H≈10 m and W≈24 m, values that match the maximum size of particles in this ring as determined from ground-based stellar occultations [French, R.G., Nicholson, P.D., 2000. Icarus 145, 502-523].

  16. An objective classification of Saturn cloud features from Cassini ISS images

    Science.gov (United States)

    Del Genio, Anthony D.; Barbara, John M.

    2016-06-01

    A k-means clustering algorithm is applied to Cassini Imaging Science Subsystem continuum and methane band images of Saturn's northern hemisphere to objectively classify regional albedo features and aid in their dynamical interpretation. The procedure is based on a technique applied previously to visible-infrared images of Earth. It provides a new perspective on giant planet cloud morphology and its relationship to the dynamics and a meteorological context for the analysis of other types of simultaneous Saturn observations. The method identifies 6 clusters that exhibit distinct morphology, vertical structure, and preferred latitudes of occurrence. These correspond to areas dominated by deep convective cells; low contrast areas, some including thinner and thicker clouds possibly associated with baroclinic instability; regions with possible isolated thin cirrus clouds; darker areas due to thinner low level clouds or clearer skies due to downwelling, or due to absorbing particles; and fields of relatively shallow cumulus clouds. The spatial associations among these cloud types suggest that dynamically, there are three distinct types of latitude bands on Saturn: deep convectively disturbed latitudes in cyclonic shear regions poleward of the eastward jets; convectively suppressed regions near and surrounding the westward jets; and baroclinically unstable latitudes near eastward jet cores and in the anti-cyclonic regions equatorward of them. These are roughly analogous to some of the features of Earth's tropics, subtropics, and midlatitudes, respectively. This classification may be more useful for dynamics purposes than the traditional belt-zone partitioning. Temporal variations of feature contrast and cluster occurrence suggest that the upper tropospheric haze in the northern hemisphere may have thickened by 2014. The results suggest that routine use of clustering may be a worthwhile complement to many different types of planetary atmospheric data analysis.

  17. Disribution and interplay of geologic processes on Titan from Cassini radar data

    Science.gov (United States)

    Lopes, R.M.C.; Stofan, E.R.; Peckyno, R.; Radebaugh, J.; Mitchell, K.L.; Mitri, G.; Wood, C.A.; Kirk, R.L.; Wall, S.D.; Lunine, J.I.; Hayes, A.; Lorenz, R.; Farr, Tom; Wye, L.; Craig, J.; Ollerenshaw, R.J.; Janssen, M.; LeGall, A.; Paganelli, F.; West, R.; Stiles, B.; Callahan, P.; Anderson, Y.; Valora, P.; Soderblom, L.

    2010-01-01

    The Cassini Titan Radar Mapper is providing an unprecedented view of Titan's surface geology. Here we use Synthetic Aperture Radar (SAR) image swaths (Ta-T30) obtained from October 2004 to December 2007 to infer the geologic processes that have shaped Titan's surface. These SAR swaths cover about 20% of the surface, at a spatial resolution ranging from ~350 m to ~2 km. The SAR data are distributed over a wide latitudinal and longitudinal range, enabling some conclusions to be drawn about the global distribution of processes. They reveal a geologically complex surface that has been modified by all the major geologic processes seen on Earth - volcanism, tectonism, impact cratering, and erosion and deposition by fluvial and aeolian activity. In this paper, we map geomorphological units from SAR data and analyze their areal distribution and relative ages of modification in order to infer the geologic evolution of Titan's surface. We find that dunes and hummocky and mountainous terrains are more widespread than lakes, putative cryovolcanic features, mottled plains, and craters and crateriform structures that may be due to impact. Undifferentiated plains are the largest areal unit; their origin is uncertain. In terms of latitudinal distribution, dunes and hummocky and mountainous terrains are located mostly at low latitudes (less than 30 degrees), with no dunes being present above 60 degrees. Channels formed by fluvial activity are present at all latitudes, but lakes are at high latitudes only. Crateriform structures that may have been formed by impact appear to be uniformly distributed with latitude, but the well-preserved impact craters are all located at low latitudes, possibly indicating that more resurfacing has occurred at higher latitudes. Cryovolcanic features are not ubiquitous, and are mostly located between 30 degrees and 60 degrees north. We examine temporal relationships between units wherever possible, and conclude that aeolian and fluvial

  18. Distribution and interplay of geologic processes on Titan from Cassini radar data

    Science.gov (United States)

    Lopes, R.M.C.; Stofan, E.R.; Peckyno, R.; Radebaugh, J.; Mitchell, K.L.; Mitri, G.; Wood, C.A.; Kirk, R.L.; Wall, S.D.; Lunine, J.I.; Hayes, A.; Lorenz, R.; Farr, Tom; Wye, L.; Craig, J.; Ollerenshaw, R.J.; Janssen, M.; LeGall, A.; Paganelli, F.; West, R.; Stiles, B.; Callahan, P.; Anderson, Y.; Valora, P.; Soderblom, L.

    2010-01-01

    The Cassini Titan Radar Mapper is providing an unprecedented view of Titan's surface geology. Here we use Synthetic Aperture Radar (SAR) image swaths (Ta-T30) obtained from October 2004 to December 2007 to infer the geologic processes that have shaped Titan's surface. These SAR swaths cover about 20% of the surface, at a spatial resolution ranging from ???350 m to ???2 km. The SAR data are distributed over a wide latitudinal and longitudinal range, enabling some conclusions to be drawn about the global distribution of processes. They reveal a geologically complex surface that has been modified by all the major geologic processes seen on Earth - volcanism, tectonism, impact cratering, and erosion and deposition by fluvial and aeolian activity. In this paper, we map geomorphological units from SAR data and analyze their areal distribution and relative ages of modification in order to infer the geologic evolution of Titan's surface. We find that dunes and hummocky and mountainous terrains are more widespread than lakes, putative cryovolcanic features, mottled plains, and craters and crateriform structures that may be due to impact. Undifferentiated plains are the largest areal unit; their origin is uncertain. In terms of latitudinal distribution, dunes and hummocky and mountainous terrains are located mostly at low latitudes (less than 30??), with no dunes being present above 60??. Channels formed by fluvial activity are present at all latitudes, but lakes are at high latitudes only. Crateriform structures that may have been formed by impact appear to be uniformly distributed with latitude, but the well-preserved impact craters are all located at low latitudes, possibly indicating that more resurfacing has occurred at higher latitudes. Cryovolcanic features are not ubiquitous, and are mostly located between 30?? and 60?? north. We examine temporal relationships between units wherever possible, and conclude that aeolian and fluvial/pluvial/lacustrine processes are the

  19. Spectroscopy, morphometry, and photoclinometry of Titan's dunefields from Cassini/VIMS

    Science.gov (United States)

    Barnes, J.W.; Brown, R.H.; Soderblom, L.; Sotin, Christophe; Le, Mouelic S.; Rodriguez, S.; Jaumann, R.; Beyer, R.A.; Buratti, B.J.; Pitman, K.; Baines, K.H.; Clark, R.; Nicholson, P.

    2008-01-01

    Fine-resolution (500 m/pixel) Cassini Visual and Infrared Mapping Spectrometer (VIMS) T20 observations of Titan resolve that moon's sand dunes. The spectral variability in some dune regions shows that there are sand-free interdune areas, wherein VIMS spectra reveal the exposed dune substrate. The interdunes from T20 are, variously, materials that correspond to the equatorial bright, 5-??m-bright, and dark blue spectral units. Our observations show that an enigmatic "dark red" spectral unit seen in T5 in fact represents a macroscopic mixture with 5-??m-bright material and dunes as its spectral endmembers. Looking more broadly, similar mixtures of varying amounts of dune and interdune units of varying composition can explain the spectral and albedo variability within the dark brown dune global spectral unit that is associated with dunes. The presence of interdunes indicates that Titan's dunefields are both mature and recently active. The spectrum of the dune endmember reveals the sand to be composed of less water ice than the rest of Titan; various organics are consistent with the dunes' measured reflectivity. We measure a mean dune spacing of 2.1 km, and find that the dunes are oriented on the average in an east-west direction, but angling up to 10?? from parallel to the equator in specific cases. Where no interdunes are present, we determine the height of one set of dunes photoclinometrically to be between 30 and 70 m. These results pave the way for future exploration and interpretation of Titan's sand dunes. ?? 2007 Elsevier Inc. All rights reserved.

  20. Investigating Titan's Atmospheric Chemistry at Low Temperature in Support of the NASA Cassini Mission

    Science.gov (United States)

    Sciamma-O'Brien, Ella; Salama, Farid

    2013-01-01

    Titan's atmosphere, composed mainly of N2 and CH4, is the siege of a complex chemistry induced by solar UV radiation and electron bombardment from Saturn's magnetosphere. This organic chemistry occurs at temperatures lower than 200 K and leads to the production of heavy molecules and subsequently solid aerosols that form the orange haze surrounding Titan. The Titan Haze Simulation (THS) experiment has been developed on the COSMIC simulation chamber at NASA Ames in order to study the different steps of Titan's atmospheric chemistry at low temperature and to provide laboratory data in support for Cassini data analysis. The chemistry is simulated by plasma in the stream of a supersonic expansion. With this unique design, the gas mixture is adiabatically cooled to Titan-like temperature (approx. 150 K) before inducing the chemistry by plasma discharge. Different gas mixtures containing N2, CH4, and the first products of the N2,-CH4 chemistry (C2H2, C2H4, C6H6...) but also heavier molecules such as PAHs or nitrogen containing PAHs can be injected. Both the gas phase and solid phase products resulting from the plasma-induced chemistry can be monitored and analyzed. Here we present the results of recent gas phase and solid phase studies that highlight the chemical growth evolution when injecting heavier hydrocarbon trace elements in the initial N2-CH4 mixture. Due to the short residence time of the gas in the plasma discharge, only the first steps of the chemistry have time to occur in a N2-CH4 discharge. However by adding acetylene and benzene to the initial N2-CH4 mixture, we can study the intermediate steps of Titan's atmospheric chemistry as well as specific chemical pathways. These results show the uniqueness of the THS experiment to help understand the first and intermediate steps of Titan fs atmospheric chemistry as well as specific chemical pathways leading to Titan fs haze formation.

  1. An Objective Classification of Saturn Cloud Features from Cassini ISS Images

    Science.gov (United States)

    Del Genio, Anthony D.; Barbara, John M.

    2016-01-01

    A k -means clustering algorithm is applied to Cassini Imaging Science Subsystem continuum and methane band images of Saturn's northern hemisphere to objectively classify regional albedo features and aid in their dynamical interpretation. The procedure is based on a technique applied previously to visible- infrared images of Earth. It provides a new perspective on giant planet cloud morphology and its relationship to the dynamics and a meteorological context for the analysis of other types of simultaneous Saturn observations. The method identifies 6 clusters that exhibit distinct morphology, vertical structure, and preferred latitudes of occurrence. These correspond to areas dominated by deep convective cells; low contrast areas, some including thinner and thicker clouds possibly associated with baroclinic instability; regions with possible isolated thin cirrus clouds; darker areas due to thinner low level clouds or clearer skies due to downwelling, or due to absorbing particles; and fields of relatively shallow cumulus clouds. The spatial associations among these cloud types suggest that dynamically, there are three distinct types of latitude bands on Saturn: deep convectively disturbed latitudes in cyclonic shear regions poleward of the eastward jets; convectively suppressed regions near and surrounding the westward jets; and baro-clinically unstable latitudes near eastward jet cores and in the anti-cyclonic regions equatorward of them. These are roughly analogous to some of the features of Earth's tropics, subtropics, and midlatitudes, respectively. This classification may be more useful for dynamics purposes than the traditional belt-zone partitioning. Temporal variations of feature contrast and cluster occurrence suggest that the upper tropospheric haze in the northern hemisphere may have thickened by 2014. The results suggest that routine use of clustering may be a worthwhile complement to many different types of planetary atmospheric data analysis.

  2. Spatial and Temporal Variations in Titan's Surface Temperatures from Cassini CIRS Observations

    Science.gov (United States)

    Cottini, V.; Nixon, C. A.; Jennings, D. E.; deKok, R.; Teanby, N. A.; Irwin, P. G. J.; Flasar, F. M.

    2012-01-01

    We report a wide-ranging study of Titan's surface temperatures by analysis of the Moon's outgoing radiance through a spectral window in the thermal infrared at 19 mm (530/cm) characterized by lower atmospheric opacity. We begin by modeling Cassini Composite Infrared Spectrometer (CIRS) far infrared spectra collected in the period 2004-2010, using a radiative transfer forward model combined with a non-linear optimal estimation inversion method. At low-latitudes, we agree with the HASI near-surface temperature of about 94 K at 101S (Fulchignoni et al., 2005). We find a systematic decrease from the equator toward the poles, hemispherically asymmetric, of approx. 1 K at 60 deg. south and approx. 3 K at 60 deg. north, in general agreement with a previous analysis of CIRS data and with Voyager results from the previous northern winter. Subdividing the available database, corresponding to about one Titan season, into 3 consecutive periods, small seasonal changes of up to 2 K at 60 deg N became noticeable in the results. In addition, clear evidence of diurnal variations of the surface temperatures near the equator are observed for the first time: we find a trend of slowly increasing temperature from the morning to the early afternoon and a faster decrease during the night. The diurnal change is approx. 1.5 K, in agreement with model predictions for a surface with a thermal inertia between 300 and 600 J/ sq. m s (exp -1/2) / K. These results provide important constraints on coupled surface-atmosphere models of Titan's meteorology and atmospheric dynamic.

  3. Dynamics of Saturn’s 2010 Great White Spot from high-resolution Cassini ISS observations

    Science.gov (United States)

    Hueso, Ricardo; Sánchez-Lavega, A.; del Río-Gaztelurrutia, T.

    2012-10-01

    On December 5th 2010 a storm erupted in Saturn’s North Temperate latitudes which were experiencing early spring season. The storm quickly developed to a planet-wide disturbance of the Great White Spot type. The ISS instrument onboard Cassini acquired its first images of the storm on 23th December 2010 and performed repeated observations with a variety of spatial resolutions over the nearly 10 months period the storm continued active. Here we present an analysis of two of the image sequences with better spatial resolution of the mature storm when it was fully developed and very active. We used an image correlation algorithm to measure the cloud motions obtained from images separated 20 minutes and obtained 16,000 wind tracers in a domain of 60 degrees longitude per 20 degrees in latitude. Intense zonal and meridional motions accompanied the storm and reached values of 120 m/s in particular regions of the active storm. The storm released a chain of anticyclonic and cyclonic vortices at planetocentric latitudes of 36° and 32° respectively. The short time difference between the images results in estimated wind uncertainties of 15 m/s that did not allow to perform a complete analysis of the turbulence and kinetic spectrum of the motions. We identify locations of the updrafts and link those with the morphology in different observing filters. The global behaviour of the storm was examined in images separated by 10 hours confirming the intensity of the winds and the global behaviour of the vortices. Acknowledgments: This work was supported by the Spanish MICIIN project AYA2009-10701 with FEDER funds, by Grupos Gobierno Vasco IT-464-07 and by Universidad País Vasco UPV/EHU through program UFI11/55.

  4. A Strong High Altitude Narrow Jet At Saturn'S Equator From Cassini/ISS Images

    Science.gov (United States)

    Garcia-Melendo, Enrique; Sánchez-Lavega, A.; Legarreta, J.; Pérez-Hoyos, S.; Hueso, R.

    2010-10-01

    The intense equatorial eastward jets observed at cloud level in Jupiter and Saturn, represent a major challenge for geophysical fluid dynamics. Saturn's equatorial jet is of particular interest in view of its three dimensional structure, suspected large temporal variability, and related stratospheric semiannual oscillation. Here we report the discovery at the upper cloud level of an extremely narrow and strong jet centered in the middle of the broad equatorial jet. Previously published works on Saturn's equatorial winds at cloud level provided only a partial coverage. Automatic correlation of brightness scans and manually tracked cloud features, retrieved from images obtained by the Cassini Imaging Science Subsystem (ISS), show that the jet reaches 430 ms-1 with a peak speed difference of 180 ms-1 relative to nearby latitudes at 60 mbar and 390 ms-1 at depths > 500 mbar. Images were obtained in two filters: MT3, centred at the 889nm strong methane absorption band, and CB3 centred at the near infrared 939nm continuum, which are sensitive to different altitude levels at the upper clouds and hazes. Contrarily to what is observed in other latitudes, its velocity increases with altitude. Our findings helps to extend the view we have of the equatorial stratospheric dynamics of fast rotating planets beyond the best known terrestrial environment, and extract more general consequences of the interaction between waves and mean flow. It remains to be known if this equatorial jet structure, now determined in detail in three dimensions, is permanent or variable with the seasonal solar insolation cycle, including the variable shadow cast by the rings. EGM, ASL, JL, SPH, and RH have been funded by the Spanish MICIIN AYA2009-10701 with FEDER support and ASL, JL, SPH, and RH by Grupos Gobierno Vasco IT-464-07

  5. Global mapping of the surface of Titan through the haze with VIMS onboard Cassini

    Science.gov (United States)

    Le Mouélic, Stéphane; Cornet, Thomas; Rodriguez, Sébastien; Sotin, Christophe; Barnes, Jason W.; Brown, Robert H.; Lasue, Jérémie; Baines, K. H.; Buratti, Bonnie; Clark, Roger Nelson; Nicholson, Philip D.

    2016-10-01

    The Visual and Infrared Mapping Spectrometer (VIMS) onboard Cassini observes the surface of Titan through the atmosphere in seven narrow spectral windows in the infrared at 0.93, 1.08, 1.27, 1.59, 2.01, 2.68-2.78, and 4.9-5.1 microns. We have produced a global hyperspectral mosaic at 32 pixels per degrees of the complete VIMS data set of Titan between T0 (July 2004) and T120 (June 2016) flybys. We merged all the data cubes sorted by increasing spatial resolution, with the high resolution images on top of the mosaic and the low resolution images used as background. One of the main challenge in producing global spectral composition maps is to remove the seams between individual frames taken throughout the entire mission. These seams are mainly due to the widely varying viewing angles between data acquired during the different Titan flybys. These angles induce significant surface photometric effects and a strongly varying atmospheric (absorption and scattering) contribution, the scattering of the atmosphere being all the more present than the wavelength is short. We have implemented a series of empirical corrections to homogenize the maps, by correcting at first order for photometric and atmospheric scattering effects. Recently, the VIMS' IR wavelength calibration has been observed to be drifting from a total of a few nm toward longer wavelengths, the drift being almost continuously present over the course of the mission. Whereas minor at first order, this drift has implications on the homogeneity of the maps when trying to fit images taken at the beginning of the mission with images taken near the end, in particular when using channels in the narrowest atmospheric spectral windows. A correction scheme has been implemented to account for this subtle effect.

  6. Characterizing Observed Limit Cycles in the Cassini Main Engine Guidance Control System

    Science.gov (United States)

    Rizvi, Farheen; Weitl, Raquel M.

    2011-01-01

    The Cassini spacecraft dynamics-related telemetry during long Main Engine (ME) burns has indicated the presence of stable limit cycles between 0.03-0.04 Hz frequencies. These stable limit cycles cause the spacecraft to possess non-zero oscillating rates for extended periods of time. This indicates that the linear ME guidance control system does not model the complete dynamics of the spacecraft. In this study, we propose that the observed limit cycles in the spacecraft dynamics telemetry appear from a stable interaction between the unmodeled nonlinear elements in the ME guidance control system. Many nonlinearities in the control system emerge from translating the linear engine gimbal actuator (EGA) motion into a spacecraft rotation. One such nonlinearity comes from the gear backlash in the EGA system, which is the focus of this paper. The limit cycle characteristics and behavior can be predicted by modeling this gear backlash nonlinear element via a describing function and studying the interaction of this describing function with the overall dynamics of the spacecraft. The linear ME guidance controller and gear backlash nonlinearity are modeled analytically. The frequency, magnitude, and nature of the limit cycle are obtained from the frequency response of the ME guidance controller and nonlinear element. In addition, the ME guidance controller along with the nonlinearity is simulated. The simulation response contains a limit cycle with similar characterstics as predicted analytically: 0.03-0.04 Hz frequency and stable, sustained oscillations. The analytical and simulated limit cycle responses are compared to the flight telemetry for long burns such as the Saturn Orbit Insertion and Main Engine Orbit Trim Maneuvers. The analytical and simulated limit cycle characteristics compare well with the actual observed limit cycles in the flight telemetry. Both have frequencies between 0.03-0.04 Hz and stable oscillations. This work shows that the stable limit cycles occur

  7. What does Cassini ENA observations tell us about gas around Europa?

    Science.gov (United States)

    Brandt, Pontus; Mauk, Barry; Westlake, Joseph; Smith, Todd; Mitchell, Donald

    2015-04-01

    From about December 2000 to January 2001 the Ion and Neutral Camera (INCA) imaged Jupiter in Energetic Neutral Atoms (ENA) from a distance of about 137-250 Jovian planetary radii (RJ) over an energy range from about 10 to 300 keV. A forward model is employed to derive column densities and assumes a neutral gas-plasma model and an energetic ion distribution based on Galileo in-situ measurements. We demonstrate that Jupiter observations by INCA are consistent with a column density peaking around Europa's orbit in the range from 2x1012 cm-2 to 7x1012 cm-2, assuming H2, and are consistent with the upper limits reported from the Cassini/UVIS observations. Most of the INCA observations are consistent with a roughly azimuthally symmetric gas distribution, but some appear consistent with an asymmetric gas distribution centred on Europa, which would directly imply that Europa is the source of the gas. Although our neutral gas model assumes a Europa source, we explore other explanations of the INCA observations including: (1) ENAs are produced by charge exchange between energetic ions and neutral hydrogen originating from charge-exchanged protons in the Io plasma torus. However, estimated densities by Cheng (1986) are about one order of magnitude too low to explain the INCA observations; (2) ENAs are produced by charge exchange between energetic ions and plasma ions such as O+ and S+ originating from Io. However, that would require O+ plasma densities higher than expected to compensate for the low charge-exchange cross section between protons and O+; (3) We re-examine the INCA Point-Spread Function (PSF) to determine if the ENA emissions in the vicinity of Europa's orbit could be explained by internal scattering of ENAs originating from Jupiter's high-latitude upper atmosphere. However, the PSF was well constrained by using Jupiter from distances where it could be considered a point source.

  8. An Overview of Saturn Narrowband Radio Emissions Observed by Cassini RPWS

    Science.gov (United States)

    Ye, S.-Y.; Fischer, G.; Menietti, J. D.; Wang, Z.; Gurnett, D. A.; Kurth, W. S.

    Saturn narrowband (NB) radio emissions are detected between 3 and 70 kHz, with occurrence probability and wave intensity peaking around 5 kHz and 20 kHz. The emissions usually occur periodically for several days after intensification of Saturn kilometric radiation (SKR). Originally detected by the Voyagers, the extended duration of the Cassini mission and the improved capabilities of the Radio and Plasma Wave Science (RPWS) instrument have significantly advanced our knowledge about them. For example, RPWS measurements of the magnetic component have validated the electromagnetic nature of Saturn NB emissions. Evidences show that the 20 kHz NB emissions are generated by mode conversion of electrostatic upper hybrid waves on the boundary of the plasma torus, whereas direction-finding results point to a source in the auroral zone for the 5 kHz component. Similar to SKR, the 5 kHz NB emissions have a clock-like modulation and display two distinct modulation periods identical to the northern and southern hemisphere periods of SKR. Polarization measurements confirm that most NB emissions are propagating in the L-O mode, with the exception of second harmonic NB emissions. At high latitudes closer to the planet, RPWS detected right hand polarized Z-mode NB emissions below the local electron cyclotron frequency (f_ce), which are believed to be the source of the L-O mode NB emissions detected above the local f_ce. Although the energy source for the generation of the Z-mode waves is still unclear, linear growth rate calculations indicate that the observed plasma distributions are unstable to the growth of electrostatic cyclotron harmonic emission. Alternatively, electromagnetic Z-mode might be directly generated by the cyclotron maser instability. The source Z-mode waves, upon reflection, propagate to the opposite hemisphere before escaping through mode conversion, which could explain the fact that both rotational modulation periods of NB emissions are observable in each

  9. An Overview of Observations by the Cassini Radio and Plasma Wave Investigation at Earth

    Science.gov (United States)

    Kurth, W. S.; Hospodarsky, G. B.; Gurnett, D. A.; Kaiser, M. L.; Wahlund, J.-E.; Roux, A.; Canu, P.; Zarka, P.; Tokarev, Y.

    2001-01-01

    On August 18, 1999, the Cassini spacecraft flew by Earth at an altitude of 1186 km on its way to Saturn. Although the flyby was performed exclusively to provide the spacecraft with sufficient velocity to get to Saturn, the radio and plasma wave science (RPWS) instrument, along with several others, was operated to gain valuable calibration data and to validate the operation of a number of capabilities. In addition, an opportunity to study the terrestrial radio and plasma wave environment with a highly capable instrument on a swift fly-through of the magnetosphere was afforded by the encounter. This paper provides an overview of the RPWS observations, at Earth, including the identification of a number of magnetospheric plasma wave modes, an accurate measurement of the plasma density over a significant portion of the trajectory using the natural wave spectrum in addition to a relaxation sounder and Langmuir probe, the detection of natural and human-produced radio emissions, and the validation of the capability to measure the wave normal angle and Poynting flux of whistler-mode chorus emissions. The results include the observation of a double-banded structure at closest' approach including a band of Cerenkov emission bounded by electron plasma and upper hybrid frequencies and an electron cyclotron harmonic band just above the second harmonic of the electron cyclotron frequency. In the near-Earth plasma sheet, evidence for electron phase space holes is observed, similar to those first reported by Geotail in the magnetotail. The wave normal analysis confirms the Polar result that chorus is generated very close to the magnetic equator and propagates to higher latitudes. The integrated power flux of auroral kilometric radiation is also used to identify a series of substorms observed during the outbound passage through the magnetotail.

  10. Morphology of Enceladus's craters by photometric studies with ISS/Cassini

    Science.gov (United States)

    Degiorgio, K.; Rodriguez, S.; Ferrari, C. C.; Brahic, A.

    2010-12-01

    The study of crater morphology (depth to diameter ratio) can bring valuable information on the structural properties of the surface and sub-surface of the impacted body. We report here on the analysis of images of the cratered terrains of the Saturn’s moon Enceladus recorded between 2005 and 2008 by the ISS instrument onboard the Cassini spacecraft. We used a 3D morphological model (Buratti and Veverka, 1985) coupled with a regolith scattering model (Hapke, 1993, 2001) in order to analyze the photometric behavior of a sample of a set of 50 Enceladus’ craters. This method enables us to verify the general photometric properties of Enceladus’ regolith (single scattering albedo and asymmetry factor in very good agreement with previous studies - e.g. Verbiscer and Veverka, 1994) and derive for the first time robust estimations of the craters’ depth. As previously done for other bodies (Schenk, 1989), we used this new information to plot the depth/diameter ratio as a function of the diameter for all the craters of our sample. Such a diagram allows to determine the presence of a transition diameter, which usually defines the transition between two regimes of crater formation (simple to complex craters) and is diagnostic of the structural properties of the crust. The value of the transition diameter for Enceladus is found close to the one of Mimas but slightly differs from the empirical general law derived by Schenk (1989) (inversely proportional to surface gravity), being globally lower than for other icy bodies. We will discuss the possible implications of such a low value on the Enceladus’s geological history and crust properties.

  11. Implications for Titan's potentially active regions: A study on Cassini/VIMS data.

    Science.gov (United States)

    Solomonidou, Anezina; Coustenis, Athena; Rodriguez, Sebastien; Bratsolis, Emmanuel; Le Mouelic, Stephane; Sotin, Christophe; Bampasidis, Georgios; Kyriakopoulos, Konstantinos; Moussas, Xenophon

    Continuing investigations of Titan's surface have shown that this Earth-like Saturnian satellite presents an extremely complex geology [1, 2, 3]. The Cassini Mission Visual and Infrared Mapping Spectrometer (VIMS) acquires data operating as a multi-spectral camera that allow for a complete analysis of the composition, geology and morphology of Titan's surface [4]. Two of the most geologically interesting areas on Titan are Xanadu's Tui Regio (20S, 130W) and Hotei Regio (26S, 78W) as they present higher 5m reflectivities than the surrounding areas [5] and have been interpreted as cryovolcanic in origin [6]. We present our study on both possibly active regions with the aim to identify the composition as well as the alterations of the components that compose the possible calderas and lava flows [7], by using radiative transfer modeling [8] and a classical staitistical method, the Principal Component Analysis [9]. [1] Jaumann, R. et al., (2009) Springer Netherlands pp. 75-140. [2] Nelson, R. M. et al., (2009) Icarus 199, 429-441. [3] Solomonidou, A. et al., (2009) European Planetary Science Congress Vol. 4, EPSC2009-710. [4] Jaumann, R. et al., (2006) Planet Space Science 54:1146-1155. [5] Barnes, J. W. et al., (2006) Geophysical Research Letters Vol. 33, L16204. [6] Lopes, R. M. C. et al., (2010) Icarus Vol. 205 pp:540-558. [7] Sotin, C. (2005) Nature, Vol 435. [8] Rodriguez, S. et al., (2009) Workshop on Hyperspectral Image and Signal Processing: Evolution on Remore Sensing pp. 1-4. [9] Bellucci, G. et al., (2004) Advances in Space Research 34 pp. 1640-1646.

  12. Constrains on the nature of Titan's surface from Cassini/VIMS and RADAR

    Science.gov (United States)

    Solomonidou, Anezina; Coustenis, Athena; Lopes, Rosaly; Rodriguez, Sebastien; Drossart, Pierre; Schmitt, Bernard; Philippe, Sylvain; Malaska, Michael; Janssen, Michael; Maltagliati, Luca; Lawrence, Kenneth; Jaumann, Ralf; Sohl, Frank; Stephan, Katrin; Brown, Robert; Bratsolis, Emannuel; Matsoukas, Christos

    2016-04-01

    Cassini remote-sensing instruments for more than 10 years now and in situ by the Huygens instruments back in 2005. For the surface, the presence of diverse terrains in terms of morphology and composition suggest both exogenic and endogenic processes to be at play. In this study, we investigate the surface and atmospheric contributions from the Visual and Infrared Mapping Spectrometer (VIMS) spectro-imaging data by use of a radiative transfer code in the near-IR range and the RADAR/SAR data for the distinction of geomorphological units. We focus here on those units identified in Lopes et al. (2010, 2015) [1; 2] and Malaska et al. (2015) [3]: mountains, plains, labyrinths, dune fields, and the areas previously suggested to have experienced change such as the possible cryovolcanic and evaporite features (Barnes et al. 2013; Solomonidou et al. 2014; 2015) [4; 5; 6]. With the use of a recently updated radiative transfer code, we evaluate the atmospheric contribution and extract the pure surface albedo information for each region of interest. The extracted albedo shapes and values are then tested against spectra of constituents that are considered to be the best Titan candidate materials, including a very recent library of Titan ice spectra [7]. We find that many of the units show compositional variations while units of significant geomorphological differences seem to consist of very similar materials, which help us provide implications on their endogenic or exogenic origin. Preliminary results on the chemical composition of the regions that have shown temporal changes are also presented. References: [1] Lopes, R.M.C., et al.: Icarus, 205, 540-558, 2010; [2] Lopes, R.M.C., et al.: Icarus, in press; [3] Malaska, M., et al. : Icarus, submitted; [4] Barnes, J., et al.: Planetary Science, 2:1, 2013; [5] Solomonidou, A., et al.: JGR, 119, 1729-1747, 2014; [6] Solomonidou, A., et al.: Icarus, in press; [7] Schmitt, B., et al.: GhoSST datacase (ghosst.osug.fr).

  13. NANODUST DETECTION BETWEEN 1 AND 5 AU USING CASSINI WAVE MEASUREMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Schippers, P.; Vernet, N. Meyer-; Lecacheux, A.; Belheouane, S.; Moncuquet, M. [LESIA—CNRS—Observatoire de Paris, 5 place Jules Janssen, F-92195 Meudon (France); Kurth, W. S. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA (United States); Mann, I. [EISCAT Scientific Association, Kiruna, Sweden and Department of Physics Umeå University (Sweden); Mitchell, D. G. [Applied Physics Laboratory, John Hopkins University, Laurel, MD (United States); André, N. [IRAP, 9 Avenue du Colonel Roche, F-31028 Toulouse (France)

    2015-06-10

    The solar system contains solids of all sizes, ranging from kilometer-sized bodies to nano-sized particles. Nanograins have been detected in situ in the Earth's atmosphere, near cometary and giant planet environments, and more recently in the solar wind at 1 AU. The latter nanograins are thought to be formed in the inner solar system dust cloud, mainly through the collisional break-up of larger grains, and are then picked up and accelerated by the magnetized solar wind because of their large charge-to-mass ratio. In the present paper, we analyze the low frequency bursty noise identified in the Cassini radio and plasma wave data during the spacecraft cruise phase inside Jupiter's orbit. The magnitude, spectral shape, and waveform of this broadband noise are consistent with the signatures of the nano particles that traveled at solar wind speed and impinged on the spacecraft surface. Nanoparticles were observed whenever the radio instrument was turned on and able to detect them at different heliocentric distances between Earth and Jupiter, suggesting their ubiquitous presence in the heliosphere. We analyzed the radial dependence of the nanodust flux with heliospheric distance and found that it is consistent with the dynamics of nanodust originating from the inner heliosphere and picked up by the solar wind. The contribution of the nanodust produced in the asteroid belt appears to be negligible compared to the trapping region in the inner heliosphere. In contrast, further out, nanodust is mainly produced by the volcanism of active moons such as Io and Enceladus.

  14. Towards an Understanding of Thermal Throughput across Saturn's Rings with Cassini CIRS

    Science.gov (United States)

    Brooks, S. M.; Spilker, L. J.

    2015-12-01

    One of the more striking aspects of Saturn's main ring system is its aspect ratio. It spans over 270,000 km from ansa to ansa, yet its thickness normal to the ring plane is less than a million times its breadth. Hence, studies of the rings' structure focus mostly on radial and azimuthal features. But in the thermal infrared the vertical thickness of the main rings is clearly manifest in the measured temperature differences between that face of the rings exposed to direct solar illumination (the lit face) and the opposite (unlit) face derived from observations with Cassini's Composite Infrared Spectrometer (CIRS). Ferrari et al. (2013) and Pilorz et al. (2015) have recently published insightful and thorough analyses of the thermal throughput across the optically thick B ring. The ultimate goal of this work is to understand these lit/unlit temperature differentials and their variation with radius and optical depth across the entire ring system. As previous work has shown (Spilker et al., 2006), the thermal flux from Saturn's rings observed by CIRS is a function of observing geometry. To control for these variations, we designed paired observations of the lit and unlit rings where observing variables such as the emission, phase and local hour angles were kept as similar as possible to facilitate direct comparison between the lit and unlit observations. Constraining the amount of thermal energy exchange between the lit and unlit sides of the rings will allow us to learn about the main rings' structure and dynamics in this third dimension. This presentation is a progress report on our analysis of such observations and our plans for future work. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2015 California Institute of Technology. Government sponsorship acknowledged.

  15. The Evolution and Fate of Saturn's Stratospheric Vortex: Infrared Spectroscopy from Cassini

    Science.gov (United States)

    Fletcher, Leigh N.; Hesman, B. E.; Arhterberg, R. K.; Bjoraker, G.; Irwin, P. G. J.; Hurley, J.; Sinclair, J.; Gorius, N.; Orton, G. S.; Read, P. L.; Simon-Miller, A. A.; Flasar, F. M.

    2012-01-01

    The planet-encircling springtime storm in Saturn's troposphere (December 2010-July 2011) produced dramatic perturbations to stratospheric temperatures, winds and composition at mbar pressures that persisted long after the tropospheric disturbance had abated. Observations from the Cassini Composite Infrared Spectrometer (CIRS), supported by ground-based imaging from the VISIR instrument on the Very Large Telescope,is used to track the evolution of a large, hot stratospheric anticyclone between January 2011 and the present day. The evolutionary sequence can be divided into three phases: (I) the formation and intensification of two distinct warm airmasses near 0.5 mbar between 25 and 35N (one residing directly above the convective storm head) between January-April 2011, moving westward with different zonal velocities; (II) the merging of the warm airmasses to form the large single 'stratospheric beacon' near 40N between April and June 2011, dissociated from the storm head and at a higher pressure (2 mbar) than the original beacons; and (III) the mature phase characterized by slow cooling and longitudinal shrinkage of the anticyclone since July 2011, moving west with a near-constant velocity of 2.70+/-0.04 deg/day (-24.5+/-0.4 m/s at 40N). Peak temperatures of 220 K at 2 mbar were measured on May 5th 2011 immediately after the merger, some 80 K warmer than the quiescent surroundings. Thermal winds hear calculations in August 2011 suggest clockwise peripheral velocities of 200400 mls at 2 mbar, defining a peripheral collar with a width of 65 degrees longitude (50,000 km in diameter) and 25 degrees latitude. Stratospheric acetylene (C2H2) was uniformly enhanced by a factor of three within the vortex, whereas ethane (C2H6) remained unaffected. We will discuss the thermal and chemical characteristics of Saturn's beacon in its mature phase, and implications for stratospheric vortices on other giant planets.

  16. Cassini results on Titan's atmospheric and surface properties changes since the northern equinox

    Science.gov (United States)

    Coustenis, Athena; Drossart, Pierre; Flasar, F. Michael; Achterberg, Richard K.; Rodriguez, Sebastien; Nixon, Conor; Bampasidis, Georgios; Solomonidou, Anezina; Jennings, Donald; Lavvas, Panayiotis

    2016-07-01

    Since 2010, we observe the set in and enhancement at Titan's south pole of several trace species, such as HC3N and C6H6, observed only at high northern latitudes before equinox. We will present an analysis of spectra acquired by Cassini/CIRS at high resolution from 2012 in nadir mode. We investigated here several latitudes of 70°S to 70°N since 2010 (after the Southern Autumnal Equinox) until end of 2014 [1]. For some of the most abundant and longest-lived hydrocarbons (C2H2, C2H6 and C3H8) and CO2, the evolution in the past 4 years at a given latitude is not very significant within error bars especially until mid-2013 [1]. In more recent dates, these molecules show a dramatic trend for increase in the south. The 70°S and 50°S or mid-latitudes show different behavior demonstrating that they are subject to different dynamical processes in and out of the polar vortex region. For most species, we find higher abundances at 50°N compared to 50°S, with the exception of C3H8, CO2, C6H6 and HC3N, which arrive at similar mixing ratios after mid-2013 [1]. While the 70°N data show generally no change with a trend rather to a small decrease for most species within 2014, the 70°S results indicate a strong enhancement in trace stratospheric gases after 2012. In particular, HC3N, HCN and C6H6 have increased by 3 orders of magnitude over the past 3-4 years while other molecules, including C2H4, C3H4 and C4H2, have increased less sharply (by 1-2 orders of magnitude). This is a strong indication of the rapid and sudden buildup of the gaseous inventory in the southern stratosphere during 2013-2014, as expected as the pole moves deeper into winter shadow. Subsidence gases that accumulate in the absence of ultraviolet sunlight, evidently increased quickly since 2012 and some of them may be responsible also for the reported haze decrease in the north and its appearance in the south at the same time [2]. Clearly Titan is a dynamic system with indications of short and long

  17. Search for and limits on plume activity on Mimas, Tethys, and Dione with the Cassini Visual Infrared Mapping Spectrometer (VIMS)

    Science.gov (United States)

    Buratti, B.J.; Faulk, S.P.; Mosher, J.; Baines, K.H.; Brown, R.H.; Clark, R.N.; Nicholson, P.D.

    2011-01-01

    Cassini Visual Infrared Mapping Spectrometer (VIMS) observations of Mimas, Tethys, and Dione obtained during the nominal and extended missions at large solar phase angles were analyzed to search for plume activity. No forward scattered peaks in the solar phase curves of these satellites were detected. The upper limit on water vapor production for Mimas and Tethys is one order of magnitude less than the production for Enceladus. For Dione, the upper limit is two orders of magnitude less, suggesting this world is as inert as Rhea (Pitman, K.M., Buratti, B.J., Mosher, J.A., Bauer, J.M., Momary, T., Brown, R.H., Nicholson, P.D., Hedman, M.M. [2008]. Astrophys. J. Lett. 680, L65-L68). Although the plumes are best seen at ???2.0. ??m, Imaging Science Subsystem (ISS) Narrow Angle Camera images obtained at the same time as the VIMS data were also inspected for these features. None of the Cassini ISS images shows evidence for plumes. The absence of evidence for any Enceladus-like plumes on the medium-sized saturnian satellites cannot absolutely rule out current geologic activity. The activity may below our threshold of detection, or it may be occurring but not captured on the handful of observations at large solar phase angles obtained for each moon. Many VIMS and ISS images of Enceladus at large solar phase angles, for example, do not contain plumes, as the active "tiger stripes" in the south pole region are pointed away from the spacecraft at these times. The 7-year Cassini Solstice Mission is scheduled to gather additional measurements at large solar phase angles that are capable of revealing activity on the saturnian moons. ?? 2011 Elsevier Inc.

  18. Mapping the Methane and Aerosol Distributions within Titan's Troposphere: Complementing The Cassini/VIMS T90 Flyby of Titan

    Science.gov (United States)

    Young, Eliot

    2012-10-01

    Titan's atmosphere is mainly nitrogen gas with several trace constituents, including methane at the few percent level. The presence of methane has been a puzzle for decades, since the CH4 in Titan's atmosphere is expected to be destroyed by UV photolysis in ten million years or so. The source of Titan's atmospheric methane continues to be a major question. We propose a set of three STIS image cubes with the G750M grating at 0.62, 0.72 and 0.89 |*|m methane bands. These bands probe altitudes from the surface to 70 km; unlike CH4 bands at 1.6 or 2.3 |*|m, these cubes will provide a 3-D picture of Titan's troposphere {below 40 km}. The Cassini/VIMS visible channel has not been useful for this purpose for two reasons: its spectral resolution {about R=100} is coarse and its inconsistent background subtraction scheme that can lead to "stripes." HST/STIS resolves Titan's 1" disk into over 80 spatially resolved spectra, each with a spectral resolution greater than R=5000. STIS is a unique tool for mapping the 3-D distributions of CH4 and aerosols in Titan's troposphere.We request observations within a day of the Cassini flyby of Titan on April 5, 2013 around 21:40 UT in order to combine Cassini/VIMS and STIS mage cubes. Together, the visible {STIS} and IR {VIMS} image cubes will probe altitudes from the surface to the stratosphere {several hundred km}. The proposed STIS image cubes will provide the best tropospheric map of CH4 to date, relevant to surface/atmospheric coupling of CH4, latitudinal inhomogeneity of CH4 or aerosols, or the presence of condensates at low altitudes.

  19. Mapping the Atmospheric and Surface Properties of Titan by the Massive Inversion of Cassini/VIMS Spectra

    Science.gov (United States)

    Maltagliati, Luca; Rodriguez, Sébastien; Appéré, Thomas; Vincendon, Mathieu; Douté, Sylvain; LeMouelic, Stéphane; Rannou, Pascal; Sotin, Christophe; Barnes, Jason W.; Coustenis, Athena; Brown, Robert H.

    2014-11-01

    Since the beginning of the Cassini mission, the imaging spectrometer VIMS has acquired ~40000 hyperspectral images of Titan containing several millions of spectra. Such a huge amount of data cannot be analyzed with a radiative transfer solver like SHDOM because of computational limits. Nevertheless, such a solver is the most suited tool to extract simultaneous information of the atmosphere and the surface of Titan from VIMS datacubes. We have developed a method of analyzing VIMS data that consents to use the power of a RT model without the inconvenience of long computational times, by the creation of look-up tables for different values of the RT model's parameters (geometry of the observation, surface albedo, aerosols opacity). We employ up-to-date information on gaseous spectral coefficients, aerosols’ optical properties and Titan’s climatology. These look-up tables, appropriately interpolated, are then used to minimize the observations and create simultaneous maps of aerosols opacity and of surface albedo (at the wavelengths of Titan’s spectral windows). This method lowers the computational time by a factor of several thousands and thus, for the first time, a truly massive treatment of VIMS data. In this paper we present the results of our method applied to the area of the Huygens landing site and their comparison with the results of other Cassini instruments. We also show the retrieved maps of a region observed multiple times at different Cassini flybys with different observational conditions, as the T13/T17 mosaic of the Atzlan area. The perspectives for atmospheric and surface seasonal monitoring are highlighted.

  20. Simultaneous Mapping of Titan's Atmospheric and Surface Properties Through the Massive Inversion of Cassini/VIMS Data

    Science.gov (United States)

    Rodriguez, S.; Maltagliati, L.; Appéré, T.; Vincendon, M.; Douté, S.; Le Mouelic, S.; Rannou, P.; Sotin, C.; Barnes, J. W.; Coustenis, A.; Brown, R. H.

    2014-12-01

    A radiative transfer solver (i.e. SHDOM) is the most powerful tool to extract simultaneous information of the atmosphere and the surface of Titan from the hyperspectral data of the VIMS imaging spectrometer onboard Cassini. However, the sheer amount of data (~40000 VIMS cubes containing several millions of spectra since the beginning of the mission) makes this approach too demanding in computational time. In our analysis we use a radiative transfer model to create look-up tables for different values of the model's parameters (geometry of the observation, surface albedo, aerosols opacity). We employ up-to-date information on gaseous spectral coefficients, aerosols' optical properties and Titan's climatology. These look-up tables, appropriately interpolated, are then used to minimize the observations and create simultaneous maps of surface albedo at the wavelengths of Titan's spectral windows and of aerosols opacity. This approach allows the gain of a factor of several thousands in computational time and thus, for the first time, a truly massive treatment of VIMS data. This capacity of processing full mapping quickly will consent to monitor closely the global and local seasonal evolution of the atmosphere and the surface. We will present the results of our method applied to some cases of interest. We will analyze several hyperspectral images of the Huygens landing site and show the comparison of our results with observations of other Cassini instruments. We will also investigate regions that have been observed multiple times at different Cassini flybys with different observational conditions, as the T13/T17 mosaic of the Atzlan area. The perspectives for atmospheric and surface seasonal monitoring will be highlighted.

  1. Full-disk observations of the saturnian moons in the VIS-NIR spectral range by Cassini- VIMS

    Science.gov (United States)

    Filacchione, G.; Capaccioni, F.; Coradini, A.; Cerroni, P.; Tosi, F.; Adriani, A.; McCord, T. B.; Baines, K. H.; Bellucci, G.; Brown, R. H.; Bibring, J.; Buratti, B. J.; Clark, R. N.; Combes, M.; Cruikshank, D. P.; Drossart, P.; Formisano, V.; Jaumann, R.; Langevin, Y.; Matson, D. L.; Mennella, V.; Robert, N. M.; Nicholson, P. D.; Sicardy, B.; Sotin, C.; Moriconi, M.

    2006-12-01

    During the first two years of the Cassini's nominal mission, VIMS (Visual and Infrared Mapping Spectrometer) has explored the whole system of Saturnian icy satellites. Here we report a comparative analysis of more than 600 full-disk observations obtained from July 2004 to nowadays for 15 regular and minor satellites: Atlas, Prometheus, Pandora, Janus, Epimetheus, Mimas, Enceladus, Tethys, Telesto, Calypso, Dione, Rhea, Hyperion, Iapetus and Phoebe. These observations, done from the equatorial plane, are particularly suitable to highlight the spectral differences between the leading and trailing sides of the regular satellites as function of the illumination angle (Filacchione et al., 2006a, 2006b); a byproduct of this activity is the measurement of the phase curves. The combined use of several VIS and IR spectral quantities (e.g. spectral slopes, water ice bands strengths, continuum levels, etc.) allows to find correlations between classes of satellites orbiting at different distances from Saturn: in this way it is possible to discriminate the almost pure ice surfaces of Enceladus and Calypso from the organic rich Hyperion, Iapetus and Phoebe (Tosi et al., 2006). This research was completed thanks to the support of the Italian Space Agency (ASI), Grant ASI/Cassini I/031/05/0. Filacchione et al., 2006a. Saturn's icy satellites investigated by Cassini-VIMS. I. Full-disk properties: 350-5100 nm reflectance spectra and phase curves, Icarus, in press. Filacchione et al., 2006b. VIS-NIR Spectral Properties of Saturn's Minor Icy Moons. 37th LPSC, abstract no.1271 Tosi et al., 2006. Iapetus, Phoebe and Hyperion: Are They Related? 37th LPSC, abstract no.1582

  2. On magnetospheric electron impact ionisation and dynamics in Titan's ram-side and polar ionosphere – a Cassini case study

    Directory of Open Access Journals (Sweden)

    G. R. Lewis

    2007-11-01

    Full Text Available We present data from the sixth Cassini flyby of Titan (T5, showing that the magnetosphere of Saturn strongly interacts with the moon's ionosphere and exo-ionosphere. A simple electron ionisation model provides a reasonable agreement with the altitude structure of the ionosphere. Furthermore, we suggest that the dense and cold exo-ionosphere (from the exobase at 1430 km and outward to several Titan radii from the surface can be explained by magnetospheric forcing and other transport processes whereas exospheric ionisation by impacting low energy electrons seems to play a minor role.

  3. Auroral current systems in Saturn's magnetosphere: comparison of theoretical models with Cassini and HST observations

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    2008-09-01

    Full Text Available The first simultaneous observations of fields and plasmas in Saturn's high-latitude magnetosphere and UV images of the conjugate auroral oval were obtained by the Cassini spacecraft and the Hubble Space Telescope (HST in January 2007. These data have shown that the southern auroral oval near noon maps to the dayside cusp boundary between open and closed field lines, associated with a major layer of upward-directed field-aligned current (Bunce et al., 2008. The results thus support earlier theoretical discussion and quantitative modelling of magnetosphere-ionosphere coupling at Saturn (Cowley et al., 2004, that suggests the oval is produced by electron acceleration in the field-aligned current layer required by rotational flow shear between strongly sub-corotating flow on open field lines and near-corotating flow on closed field lines. Here we quantitatively compare these modelling results (the "CBO" model with the Cassini-HST data set. The comparison shows good qualitative agreement between model and data, the principal difference being that the model currents are too small by factors of about five, as determined from the magnetic perturbations observed by Cassini. This is suggested to be principally indicative of a more highly conducting summer southern ionosphere than was assumed in the CBO model. A revised model is therefore proposed in which the height-integrated ionospheric Pedersen conductivity is increased by a factor of four from 1 to 4 mho, together with more minor adjustments to the co-latitude of the boundary, the flow shear across it, the width of the current layer, and the properties of the source electrons. It is shown that the revised model agrees well with the combined Cassini-HST data, requiring downward acceleration of outer magnetosphere electrons through a ~10 kV potential in the current layer at the open-closed field line boundary to produce an auroral oval of ~1° width with UV emission intensities of a few tens of kR.

  4. Feasibility Study of Two Candidate Reaction Wheel/thruster Hybrid Control Architecture Designs for the Cassini Spacecraft

    Science.gov (United States)

    Macala, Glenn A.; Lee, Allan Y.; Wang, Eric K.

    2012-01-01

    As the first spacecraft to achieve orbit at Saturn in 2004, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended mission through 2017. Cassini carries a set of three "fixed" reaction wheels and a backup reaction wheel (reaction wheel #4) is mounted on top of an articulable platform. If necessary, this platform could be articulated to orient the backup reaction wheel with the degraded wheel. The reaction wheels are used primarily for attitude control when precise and stable pointing of a science instrument such as the narrow angle camera is required. In 2001-02, reaction wheel #3 exhibited signs of bearing cage instability. As a result, reaction wheel #4 was articulated to align with reaction wheel #3. Beginning in July 2003, Cassini was controlled using wheel #1, #2, and #4. From their first use in the spring of 2000 until today, reaction wheels #1 and #2 have accumulated more than3.5 billions revolutions each. As such, in spite of very carefully management of the wheel spin rates by the mission operation team, there are some observed increases in the drag torque of the wheels' bearings. Hence, the mission operations team must prepare for the contingency scenario in which the reaction wheel #1 (in addition to wheel #3) had degraded. In this hypothetical fault scenario, the two remaining reaction wheels (#2 and #4) will not be able to provide precise and stable three-axis control of the spacecraft. In this study, we evaluate the feasibility of controlling Cassini using the two remaining reaction wheels and four thrusters to meet the science pointing requirements for two key science operational modes: the Optical Remote Sensing and Downlink, Fields, Particles, & Waves operation modes. The performance (e.g., pointing control error, pointing stability, hydrazine consumption rate, etc.) of the hybrid controllers in both operations scenarios will be compared with those achieved

  5. An Efficient Method to Design Premature End-of-Life Trajectories: A Hypothetical Alternate Fate for Cassini

    Science.gov (United States)

    Vaquero, Mar; Senent, Juan

    2015-01-01

    What would happen if, hypothetically, the highly successful Cassini mission were to end prematurely due to lack of propellant or sudden subsystem failure? A solid plan to quickly produce a solution for any given scenario, regardless of where the spacecraft is along its reference path, must be in place to safely dispose of the spacecraft and meet all planetary protection requirements. As a contingency plan for this hypothetical situation, a method to design viable high-fidelity terminating trajectories based on a hybrid approach that exploits two-body and three-body flyby transfers combined with a numerical optimization scheme is detailed in this paper.

  6. Built But Not Used, Needed But Not Built: Ground System Guidance Based On Cassini-Huygens Experience

    Science.gov (United States)

    Larsen, Barbara S.

    2006-01-01

    These reflections share insight gleaned from Cassini-Huygens experience in supporting uplink operations tasks with software. Of particular interest are developed applications that were not widely adopted and tasks for which the appropriate application was not planned. After several years of operations, tasks are better understood providing a clearer picture of the mapping of requirements to applications. The impact on system design of the changing user profile due to distributed operations and greater participation of scientists in operations is also explored. Suggestions are made for improving the architecture, requirements, and design of future systems for uplink operations.

  7. Overview of the Cassini in-situ magnetosphere measurements and solar wind modelling during the 2013 Saturn Aurora Campaign

    Science.gov (United States)

    Bunce, E. J.; Badman, S. V.; Cowley, S. W. H.; Jinks, S. L.; Provan, G.; Burton, M.; Crary, F. J.; Dougherty, M. K.; Kurth, W. S.; Luhmann, J.; Mitchell, D. G.; Zheng, Y.

    2013-09-01

    The Saturn Aurora Campaign 2013 is a coordinated effort to provide a clearer understanding of Saturn's auroral emissions at multiple wavelengths in the upper atmosphere, and their associated magnetospheric signatures and dynamics. In addition, modelling and Earth-based observations of the solar wind conditions throughout the campaign provide an important insight to the way in which Saturn's magnetosphere responds to the changing conditions in interplanetary space. Structures such as Corotating Interaction Regions (CIRs) are thought to play a significant role in the modulation of Saturn's auroral emissions via abrupt changes in the dynamic pressure associated with forward shocks at the start of the CIR compression regions. Recent observations from the Cassini spacecraft at Saturn have also taught us that the "magnetosphere oscillations" observed in magnetic field perturbations in the northern and southern hemispheres, which are associated with the SKR modulations in each hemisphere, significantly affect the magnetosphere and auroral emissions. During April and May 2013 a combination of the Hubble Space Telescope (HST) ultraviolet (UV) instrument the Advanced Camera for Surveys (ACS), and ground-based infrared (IR) telescopes observed the northern hemisphere auroras, whilst the Cassini spacecraft's remote sensing instruments (the Ultraviolet Imaging Spectrograph-UVIS, the Visual and Infrared Mapping Spectrometer-VIMS, and the Imaging Science SubSystem-ISS) made simultaneous (or near-simultaneous) observations of the UV, IR and visible auroras respectively, in one or other hemisphere. At the same time, the "in situ" instruments on board Cassini measured the magnetic field, plasma populations, and radio plasma wave emissions in Saturn's magnetosphere. Here we present an overview of the in situ magnetosphere measurements during the campaign, along with an overview of the predicted solar wind conditions upstream of Saturn from modeling work. We will discuss the evidence

  8. Counter Data of the Cosmic Dust Analyzer aboard the Cassini spacecraft and possible "dust clouds" at Saturn

    OpenAIRE

    Khalisi, Emil; Srama, Ralf; Grün, Eberhard

    2014-01-01

    We present the impact rates of dust particles recorded by the Cosmic Dust Analyzer (CDA) aboard the Cassini spacecraft. The "dust counters" evaluate the quality of an impact and give rise to the apparent density of dust particles in space. The raw data is pre-selected and refined to a new structure that serves to a better investigation of densities, flows, and properties of interplanetary dust grains. Our data is corrected for the dead time of the instrument and corresponds to an assumed Kepl...

  9. Feasibility Study of Two Candidate Reaction Wheel/thruster Hybrid Control Architecture Designs for the Cassini Spacecraft

    Science.gov (United States)

    Macala, Glenn A.; Lee, Allan Y.; Wang, Eric K.

    2012-01-01

    As the first spacecraft to achieve orbit at Saturn in 2004, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended mission through 2017. Cassini carries a set of three "fixed" reaction wheels and a backup reaction wheel (reaction wheel #4) is mounted on top of an articulable platform. If necessary, this platform could be articulated to orient the backup reaction wheel with the degraded wheel. The reaction wheels are used primarily for attitude control when precise and stable pointing of a science instrument such as the narrow angle camera is required. In 2001-02, reaction wheel #3 exhibited signs of bearing cage instability. As a result, reaction wheel #4 was articulated to align with reaction wheel #3. Beginning in July 2003, Cassini was controlled using wheel #1, #2, and #4. From their first use in the spring of 2000 until today, reaction wheels #1 and #2 have accumulated more than3.5 billions revolutions each. As such, in spite of very carefully management of the wheel spin rates by the mission operation team, there are some observed increases in the drag torque of the wheels' bearings. Hence, the mission operations team must prepare for the contingency scenario in which the reaction wheel #1 (in addition to wheel #3) had degraded. In this hypothetical fault scenario, the two remaining reaction wheels (#2 and #4) will not be able to provide precise and stable three-axis control of the spacecraft. In this study, we evaluate the feasibility of controlling Cassini using the two remaining reaction wheels and four thrusters to meet the science pointing requirements for two key science operational modes: the Optical Remote Sensing and Downlink, Fields, Particles, & Waves operation modes. The performance (e.g., pointing control error, pointing stability, hydrazine consumption rate, etc.) of the hybrid controllers in both operations scenarios will be compared with those achieved

  10. GPHS-RTGs in support of the Cassini Mission. Semi annual technical progress report, 1 April 1996--29 September 1996

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-10-20

    This technical progress report discusses work on the Radioisotope Generators and Ancillary Activities for the Cassini spacecraft. The Cassini spacecraft is expected to launch in October 1997, and will explore Saturn and its moons. This progress report discusses issues in: spacecraft integration and liason, engineering support, safety, qualified unicouple fabrication, ETG fabrication and testing, ground support equipment, RTG shipping and launch support, designs, reviews and mission application. Safety analysis of the RTGs during reentry and launch accidents are covered. This report covers the period of April 1 to September 29, 1996.

  11. A study of the aptitude of soils under natural conditions to retain radiostrontium; Etude de la vocation des sols en place a la retention du radiostrontium

    Energy Technology Data Exchange (ETDEWEB)

    Bovard, P.; Grauby, A. [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1960-07-01

    Independently of the theoretical study of the propagation of radioactivity in the soil as a result of submersions or of radioactive rain, the authors have studied directly and practically how this radioactivity can vary in the actual soil. To this end a simple, rapid method has been perfected; it makes it possible to maintain for each soil sample the natural parameters (structure, humidity, etc.) without introducing boundary effects. In the laboratory, after charging the soil samples, part of the study of the propagation of radioactivity is done by autoradiography; finally, as a practical application, the study of an atomic site illustrates the methods described. (author) [French] Independamment de l'etude theorique de la propagation de la radioactivite dans le sol a la suite de submersions ou de pluies radioactives, les auteurs ont etudie directement et pratiquement comment pourrait evoluer cette radioactivite dans les sols en place. Pour cela, une methode simple et rapide a ete mise au point; elle permet de conserver pour chaque echantillon de sol, les parametres naturels (structure, humidite, etc...), sans introduire d'effets de paroi. En laboratoire, apres mise en charge des massifs preleves, une partie de l'etude de la propagation des radioelements est realisee par autoradiographie; enfin, une application pratique, l'etude d'un site atomique, illustre l'expose. (auteur)

  12. The development of a very high stability electrostatic generator (1962); Etude et realisation d'un generateur electrostatique a tres haute stabilite (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Jonckheere, R.E.L. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1962-07-01

    This thesis deals with the study of an electrostatic high voltage generator having a voltage stability of the order of 10{sup -6} per minute. This equipment should be very useful in electron microscopy. The electrostatic generator is studied as a control system element: transfer function, parasitic signals and noise are determined and a mathematical model is proposed. A theoretical study of the open loop transfer function, stability, transient response, voltage stabilization of five different control systems shows which one should be able to fulfill the requirements There follows a detailed study of drift, a description of the actual system and performance data. (author) [French] Cette etude concerne un generateur electrostatique capable de fournir une tres haute tension continue dont la stabilite relative est de l'ordre de 10{sup -6} pendant une minute. Une telle performance rend cet appareillage tres utile en microscopie electronique. La generatrice electrostatique est etudiee en tant qu'element d'un systeme asservi: on determine successivement la fonction de transfert, les perturbations, le bruit de fond et le modele mathematique. L'etude de cinq differents circuits de regulation en ce qui concerne leur fonction de transfert, stabilite, reponse en regime transitoire, attenuation des perturbations, permettra de choisir le systeme qui semble le mieux repondre aux exigences. Viennent ensuite une etude detaillee de la derive, la description de la realisation pratique et les resultats de mesure. (auteur)

  13. Inferring the depth of the atmospheric circulation on Jupiter and Saturn through the gravity measurements by Juno and Cassini

    Science.gov (United States)

    Kaspi, Y.; Galanti, E.

    2014-04-01

    In approximately two years the Juno and Cassini spacecraft will both perform close flybys of Jupiter and Saturn respectively, obtaining for the first time a high precision gravity spectrum for these planets. We discuss how this data can be used to estimate the depth of the observed jet streams on these planets. This can be done in several ways: 1. measurements of the high order even harmonics which beyond J10 are dominated by the dynamics; 2. measurements of odd gravity harmonics which have no contribution from a static planet, and therefore are a pure signature of dynamics; 3. upper limits on the depth can be obtained by comparing low order even harmonics from dynamical models to the difference between the measured low order even harmonics and the largest possible values of a static planet; 4. direct latitudinally varying measurements of the gravity field exerted on the spacecraft. We discuss how these methods may be applied and show that given the expected sensitivities of Juno and Cassini the odd harmonics J3 and J5 will have the best sensitivity to deep dynamics, allowing detection of winds reaching only ~ 100 km deep, if those exist on Jupiter and Saturn (Kaspi, 2013). For this analysis we use a hierarchy of dynamical models ranging from deep compressible GCMs to simplified thermal wind models in order to relate the three-dimensional flow to perturbations of the density field, and therefore to the gravity field.

  14. Possible Niches For Extant Life On Titan In Light Of The First Six Years Of Cassini/Huygens Results

    Science.gov (United States)

    Grinspoon, David H.; Schulze-Makuch, D.

    2010-10-01

    At the 2005 DPS meeting we presented an assessment of the possibility of extant life on Titan after the first year of the Cassini mission at Saturn. We suggested then that hydrogenation of photochemically produced acetylene could provide metabolic energy for near-surface organisms and also replenish atmospheric methane (Schulze-Makuch and Grinspoon, 2005). In this talk we will offer a brief reassessment of the possibility of extant life in light of five more years of the Cassini/Huygens results, including the recent reports suggesting a lack of acetylene on the surface (Clark et al., 2010) and a possible sink of H2 at the surface (Strobel, 2010). Both results are consistent with earlier predictions for the existence of an acetylene-powered biosphere on Titan (Schulze-Makuch and Grinspoon, 2005; McKay and Smith, 2005), but can potentially be explained by more prosaic phenomena. D. Schulze-Makuch and D. H. Grinspoon(2005), Biologically Enhanced Energy and Carbon Cycling on Titan? Astrobiology 5, 560-567; Clarke, R.N. et al. (2020), Detection and Mapping of Hydrocarbon Deposits on Titan, JGR-Planets; Strobel, D.F(2010) Molecular hydrogen in Titan's atmosphere: Implications of the measured tropospheric and thermospheric mole fractions. Icarus; McKay, C.P., Smith, H.D.( 2005) Possibilities for methanogenic life in liquid methane on the surface of Titan. Icarus 178, 274-276.

  15. Hypervelocity impact effect of molecules from Enceladus' plume and Titan's upper atmosphere on NASA's Cassini spectrometer from reactive dynamics simulation.

    Science.gov (United States)

    Jaramillo-Botero, Andres; An, Qi; Cheng, Mu-Jeng; Goddard, William A; Beegle, Luther W; Hodyss, Robert

    2012-11-21

    The NASA/ESA Cassini probe of Saturn analyzed the molecular composition of plumes emanating from one of its moons, Enceladus, and the upper atmosphere of another, Titan. However, interpretation of this data is complicated by the hypervelocity (HV) flybys of up to ~18 km/sec that cause substantial molecular fragmentation. To interpret this data we use quantum mechanical based reactive force fields to simulate the HV impact of various molecular species and ice clathrates on oxidized titanium surfaces mimicking those in Cassini's neutral and ion mass spectrometer (INMS). The predicted velocity dependent fragmentation patterns and composition mixing ratios agree with INMS data providing the means for identifying the molecules in the plume. We used our simulations to predict the surface damage from the HV impacts on the INMS interior walls, which we suggest acts as a titanium sublimation pump that could alter the instrument's readings. These results show how the theory can identify chemical events from hypervelocity impacts in space plumes and atmospheres, providing in turn clues to the internal structure of the corresponding sources (e.g., Enceladus). This may be valuable in steering modifications in future missions.

  16. Storm clouds on Saturn: Lightning-induced chemistry and associated materials consistent with Cassini/VIMS spectra

    Science.gov (United States)

    Baines, K.H.; Delitsky, M.L.; Momary, T.W.; Brown, R.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.

    2009-01-01

    Thunderstorm activity on Saturn is associated with optically detectable clouds that are atypically dark throughout the near-infrared. As observed by Cassini/VIMS, these clouds are ~20% less reflective than typical neighboring clouds throughout the spectral range from 0.8 ??m to at least 4.1 ??m. We propose that active thunderstorms originating in the 10-20 bar water-condensation region vertically transport dark materials at depth to the ~1 bar level where they can be observed. These materials in part may be produced by chemical processes associated with lightning, likely within the water clouds near the ~10 bar freezing level of water, as detected by the electrostatic discharge of lightning flashes observed by Cassini/RPWS (e.g., Fischer et al. 2008, Space Sci. Rev., 137, 271-285). We review lightning-induced pyrolytic chemistry involving a variety of Saturnian constituents, including hydrogen, methane, ammonia, hydrogen sulfide, phosphine, and water. We find that the lack of absorption in the 1-2 ??m spectral region by lightning-generated sulfuric and phosphorous condensates renders these constituents as minor players in determining the color of the dark storm clouds. Relatively small particulates of elemental carbon, formed by lightning-induced dissociation of methane and subsequently upwelled from depth - perhaps embedded within and on the surface of spectrally bright condensates such as ammonium hydrosulfide or ammonia - may be a dominant optical material within the dark thunderstorm-related clouds of Saturn. ?? 2009 Elsevier Ltd. All rights reserved.

  17. High resolution Cassini observations of Saturn’s A ring in the vicinity of object “Peggy”

    Science.gov (United States)

    Murray, Carl; Cooper, Nicholas; Renner, Stéfan; Santos Araújo, Nilton Carlos; Noyelles, Benoit; Tiscareno, Matthew S.

    2017-06-01

    Cassini images of the edge of Saturn’s A ring strongly suggest the presence of an embedded object (nicknamed “Peggy”) producing localised, time-varying structure due to its gravitational perturbation of nearby ring material. “Peggy”’s gravitational signature has been tracked since its discovery in 2013 and, although the deduced semi-major axis has varied between 136766 km and 136775 km, the value has always been within 10 km of the edge location as determined by El Moutamid et al. (2016). In early 2016 a second object was detected, trailing “Peggy” at a larger semi-major axis, with both objects having been tracked since then. Here we discuss the current state of our understanding of this unusual object and its orbital evolution, making use of the most recent, high resolution observations obtained both before and during the ring-grazing and grand finale orbits of the Cassini spacecraft. These images will then be compared with numerical simulations of the effect of an embedded satellite on adjacent, orbiting particles with the goal of obtaining the mass and dimensions of the object.

  18. Observations in the Saturn system during approach and orbital insertion, with Cassini's visual and infrared mapping spectrometer (VIMS)

    Science.gov (United States)

    Brown, R.H.; Baines, K.H.; Bellucci, G.; Buratti, B.J.; Capaccioni, F.; Cerroni, P.; Clark, R.N.; Coradini, A.; Cruikshank, D.P.; Drossart, P.; Formisano, V.; Jaumann, R.; Langevin, Y.; Matson, D.L.; McCord, T.B.; Mennella, V.; Nelson, R.M.; Nicholson, P.D.; Sicardy, B.; Sotin, C.; Baugh, N.; Griffith, C.A.; Hansen, G.B.; Hibbitts, C.A.; Momary, T.W.; Showalter, M.R.

    2006-01-01

    The Visual and Infrared Mapping Spectrometer observed Phoebe, Iapetus, Titan and Saturn's rings during Cassini's approach and orbital insertion. Phoebe's surface contains water ice, CO2, and ferrous iron. lapetus contains CO2 and organic materials. Titan's atmosphere shows methane fluorescence, and night-side atmospheric emission that may be CO2 and CH3D. As determined from cloud motions, the winds at altitude 25-30 km in the south polar region of Titan appear to be moving in a prograde direction at velocity ???1 m s-1. Circular albedo features on Titan's surface, seen at 2.02 ??m, may be palimpsests remaining from the rheological adjustment of ancient impact craters. As such, their long-term persistence is of special interest in view of the expected precipitation of liquids and s