WorldWideScience

Sample records for satellite gravity mission

  1. Gravitacijske satelitske misije : Satellite gravity missions

    Directory of Open Access Journals (Sweden)

    Medžida Mulić

    2012-12-01

    Full Text Available Sila teže se smatra osnovnom fizikalnom silom u prirodi. Savremene satelitske misije: CHAMP, GRACE i GOCE omogućile su dobivanje globalnih modela polja sile teže s veoma visokom tačnošću, kao i njegovih prostornih i temporalnih varijacija. U ovom radu istaknuti su ciljevi, karakteristike i rezultati navedenih misija, te iznesena očekivanja u budućnosti, kao i njihov značaj i doprinos za geodetsku praksu kao i istraživanja u oblasti geodezije, geofizike i hidrologije. : Gravity is considered as the basic physical force in the nature. Modern satellite missions: CHAMP, GRACE and GOCE allowed modeling of the global gravity field with very high accuracy, as well as its spatial and temporal variations. This paper describes the main objectives, characteristics, the latest results of these missions, as well as the expectations of the future observations, and their importance and contributions for the surveying and geodetic practice, and scientific achievements as well, in geodesy, geophysics and hydrology.

  2. Global gravity field recovery from the ARISTOTELES satellite mission

    Science.gov (United States)

    Visser, P. N. A. M.; Wakker, K. F.; Ambrosius, B. A. C.

    1994-02-01

    One of the primary objectives of the future ARISTOTELES satellite mission is to map Earth's gravity field with high resolution and accuracy. In order to achieve this objective, the ARISTOTELES satellite will be equipped with a gravity gradiometer and a Global Positioning System (GPS) receiver. Global gravity field error analyses have been performed for several combinations of gradiometer and GPS observations. These analyses indicated that the bandwidth limitation of the gradiometer prevents a stable high-accuracy, high-resolution gravity solution if no additional information is available. However, with the addition of high-accuracy GPS observations, a stable gravity field solution can be obtained. A combination of the measurements acquired by the high-quality GPS receiver and the bandwidth-limited gradiometer on board ARISTOTELES will yield a global gravity field model with a resolution of less than 100 km and with an accuracy of better than 5 mGal for gravity anomalies and 10 cm for geoid undulations.

  3. The German joint research project "concepts for future gravity satellite missions"

    Science.gov (United States)

    Reubelt, Tilo; Sneeuw, Nico; Fichter, Walter; Müller, Jürgen

    2010-05-01

    Within the German joint research project "concepts for future gravity satellite missions", funded by the Geotechnologies programme of the German Federal Ministry of Education and Research, options and concepts for future satellite missions for precise (time-variable) gravity field recovery are investigated. The project team is composed of members from science and industry, bringing together experts in geodesy, satellite systems, metrology, sensor technology and control systems. The majority of team members already contributed to former gravity missions. The composition of the team guarantees that not only geodetic aspects and objectives are investigated, but also technological and financial constraints are considered. Conversely, satellite, sensor and system concepts are developed and improved in a direct exchange with geodetic and scientific claims. The project aims to develop concepts for both near and mid-term future satellite missions, taking into account e.g. advanced satellite formations and constellations, improved orbit design, innovative metrology and sensor systems and advances in satellite systems.

  4. Performance analysis of satellite constellations for the next generation of gravity missions

    Science.gov (United States)

    Raimondo, J.; Flechtner, F.; Löcher, A.; Kusche, J.

    2011-12-01

    The GOCE and GRACE gravity missions have dramatically improved the knowledge of the Earth's static and time-variable gravity field due to their highly precise on-board instrumentation. This resulted in new information about the mass distribution and transport within or around the Earth system to be used in solid Earth geophysics, oceanography and sea level studies, hydrology, ice mass budget investigations and geodesy. GFZ Potsdam and IGG Bonn, with partners from German industry and universities, have conducted several studies in order to develop a concept for a future gravity mission based on low-low satellite-to-satellite tracking, but realized with laser metrology. In our poster we summarize the performance of different mission scenarios through full-scale simulations and their capacity to reach the science objectives.

  5. Cubesat Gravity Field Mission

    Science.gov (United States)

    Burla, Santoshkumar; Mueller, Vitali; Flury, Jakob; Jovanovic, Nemanja

    2016-04-01

    CHAMP, GRACE and GOCE missions have been successful in the field of satellite geodesy (especially to improve Earth's gravity field models) and have established the necessity towards the next generation gravity field missions. Especially, GRACE has shown its capabilities beyond any other gravity field missions. GRACE Follow-On mission is going to continue GRACE's legacy which is almost identical to GRACE mission with addition of laser interferometry. But these missions are not only quite expensive but also takes quite an effort to plan and to execute. Still there are few drawbacks such as under-sampling and incapability of exploring new ideas within a single mission (ex: to perform different orbit configurations with multi satellite mission(s) at different altitudes). The budget is the major limiting factor to build multi satellite mission(s). Here, we offer a solution to overcome these drawbacks using cubesat/ nanosatellite mission. Cubesats are widely used in research because they are cheaper, smaller in size and building them is easy and faster than bigger satellites. Here, we design a 3D model of GRACE like mission with available sensors and explain how the Attitude and Orbit Control System (AOCS) works. The expected accuracies on final results of gravity field are also explained here.

  6. Understanding data noise in gravity field recovery on the basis of inter-satellite ranging measurements acquired by the satellite gravimetry mission GRACE

    NARCIS (Netherlands)

    Ditmar, P.; Teixeira da Encarnacao, J.; Hashemi Farahani, H.

    2012-01-01

    Spectral analysis of data noise is performed in the context of gravity field recovery from inter-satellite ranging measurements acquired by the satellite gravimetry mission GRACE. The motivation of the study is two-fold: (i) to promote a further improvement of GRACE data processing techniques and

  7. Signature of range observable in non-dynamical Chern-Simons modified gravity and the measurements with satellite-satellite tracking missions. Theoretical Studies

    CERN Document Server

    Qiang, Li-E

    2014-01-01

    Having great accuracy in the range and range rate measurements, the operating GRACE mission and the planed GRACE Follow On mission can in principle be employed to place strong constraints on certain relativistic gravity theories. In this paper, we work out in details the range observable in the non-dynamical Chern-Simons modified gravity for these Satellite-Satellite Tracking measurements. We find out that an characteristic time accumulating signal appears in the range observable in the non-dynamical Chern-Simons gravity, which has no analogy found in the standard metric theories of gravity. The magnitude of this Chern-Simons range signal will reach to a few times of $(\\frac{\\dot{\\theta}}{100r})meters$ for each free flight of these SST missions, here $\\dot{\\theta}$ measures the length scale of the theory and $r$ denotes the orbital radius of the SST mission. Therefore, with the 12 years data from the GRACE mission and the proper data analysis methods, one expects that the mass scale of the non-dynamical CS gr...

  8. Science Instrument Support Electronics Systems for the Relativity Mission Satellite, Gravity Probe B

    Science.gov (United States)

    Bencze, W. J.; Brumley, R. W.; Buchman, S.; Clarke, B.; Hipkins, D. N.; Farley, R.; Shestople, P.; Meriwether, D.; Gray, C.

    The Relativity Mission, Gravity Probe B (GP-B), uses four redundant high precision electrostatically suspended mechanical gyroscopes for measuring the relativistic precessions of the frame of reference in a 640 km polar orbit. The two precessions to be measured are predicted in General Relativity are the geodetic effect, 6.6 arcsec/year, and the frame dragging effect, 0.042 arcsec/year. The Science Instrument Support Electronics or Payload Electronics Package enables this measurement to be performed by providing the necessary control and monitoring functions for the Science Instrument Assembly that contains the four gyroscopes and reference star tracking telescope. This paper describes the overall architecture of the Payload Electronics system and the design and operation of its component parts: 1) the SQUID Readout electronics (SRE) for gyroscope orientation measurement, 2) The Gyroscope Suspension System (GSS) for gyroscope electrostatic suspension and spin axis alignment, 3) the Telescope Readout Electronics (TRE) for measurement of the reference star location, 4) the Experiment Control Unit (ECU) for heater, valve, and rotor electrostatic charge control and thermometry, 5) the custom GPS receiver for orbital position determination and time reference generation, and 6) the Gas Management Assembly (GMA) that controls and routes the gaseous helium used for initial gyroscope spin-up. Contingent upon a successful launch of Gravity Probe on April 17 2004, preliminary performance results will be presented along side the predicated performance estimates derived from system analysis and test on the ground prior to launch.

  9. Satellite orbit determination and gravity field recovery from satellite-to-satellite tracking

    Science.gov (United States)

    Wakker, K. F.; Ambrosius, B. A. C.; Leenman, H.

    1989-07-01

    Studies on satellite-to-satellite tracking (SST) with POPSAT (a geodetic satellite concept) and a ERS-class (Earth observation) satellite, a Satellite-to-Satellite Tracking (SST) gravity mission, and precise gravity field determination methods and mission requirements are reported. The first two studies primarily address the application of SST between the high altitude POPSAT and an ERS-class or GRM (Geopotential Research Mission) satellite to the orbit determination of the latter two satellites. Activities focussed on the determination of the tracking coverage of the lower altitude satellite by ground based tracking systems and by POPSAT, orbit determination error analysis and the determination of the surface forces acting on GRM. The third study surveys principles of SST, uncertainties of existing drag models, effects of direct luni-solar attraction and tides on orbit and the gravity gradient observable. Detailed ARISTOTELES (which replaced POPSAT) orbit determination error analyses were performed for various ground based tracking networks.

  10. The Gravity Recovery and Interior Laboratory Mission

    Science.gov (United States)

    Lehman, David H.; Hoffman, Tom L.; Havens, Glen G.

    2013-01-01

    The Gravity Recovery and Interior Laboratory (GRAIL) mission, launched in September 2011, successfully completed its Primary Science Mission in June 2012 and is currently in Extended Mission operations. Competitively selected under a NASA Announcement of Opportunity in December 2007, GRAIL is a Discovery Program mission subject to a mandatory project cost cap. The purpose of the mission is to precisely map the gravitational field of the Moon to reveal its internal structure from crust to core, determine its thermal evolution, and extend this knowledge to other planets. The mission uses twin spacecraft flying in tandem to provide the gravity map. The GRAIL Flight System, consisting of the spacecraft and payload, was developed based on significant heritage from previous missions such an experimental U.S. Air Force satellite, the Mars Reconnaissance Orbiter (MRO) mission, and the Gravity Recovery and Climate Experiment (GRACE) mission. The Mission Operations System (MOS) was based on high-heritage multimission operations developed by NASA's Jet Propulsion Laboratory and Lockheed Martin. Both the Flight System and MOS were adapted to meet the unique challenges posed by the GRAIL mission design. This paper summarizes the implementation challenges and accomplishments of getting GRAIL ready for launch. It also discusses the in-flight challenges and experiences of operating two spacecraft, and mission results.

  11. Shallow-earth rheology from glacial isostasy and satellite gravity: a sensitivity analysis for GOCE

    NARCIS (Netherlands)

    Schotman, H.H.A.

    2008-01-01

    In recent years, satellite gravity missions have been launched that probe the earth's long- to mediumwavelength (1000 - 500 km) gravity field. The upcoming ESA satellite gravity mission GOCE is predicted to measure the gravity field with an accuracy of a few centimeters at spatial scales of 100 km.

  12. Retrieving hydrological signals from current and future gravity field missions

    Science.gov (United States)

    Pail, Roland; Horvath, Alexander

    2017-04-01

    The Global Geodetic Observing System is formed by three pillars: Changes in Earth's shape, gravity field and rotation. Dedicated satellite missions are crucial in the determination and monitoring of the Earth's gravity field. Monitoring the gravity field and studying mass transport phenomena, responsible for the temporal variability of the gravity field, are of high interest. Especially the hydrology is of importance since the mechanisms of water redistribution and unexpected events like floods and droughts can have significant socio-economic impact. The presented study investigates in the possibilities and limits of current space geodetic missions like GRACE to observe such effects. The main target of the study is to determine the potential gain in accuracy as well as spatial and temporal resolution of target signals like hydrological events, whilst operating future mission scenarios. The results from a series of comprehensive simulation runs are presented to demonstrate the benefits to society operating dedicated future space geodetic gravity field missions.

  13. Multi-mission Satellite Management

    Science.gov (United States)

    Jamilkowski, M. L.; Teter, M. A.; Grant, K. D.; Dougherty, B.; Cochran, S.

    2015-12-01

    NOAA's next-generation environmental satellite, the Joint Polar Satellite System (JPSS) replaces the current Polar-orbiting Operational Environmental Satellites (POES). JPSS satellites carry sensors which collect meteorological, oceanographic, climatological, and solar-geophysical observations of the earth, atmosphere, and space. The first JPSS satellite was launched in 2011 and is currently NOAA's primary operational polar satellite. The JPSS ground system is the Common Ground System (CGS), and provides command, control, and communications (C3) and data processing (DP). A multi-mission system, CGS provides combinations of C3/DP for numerous NASA, NOAA, DoD, and international missions. In preparation for the next JPSS satellite, CGS improved its multi-mission capabilities to enhance mission operations for larger constellations of earth observing satellites with the added benefit of streamlining mission operations for other NOAA missions. CGS's multi-mission capabilities allows management all of assets as a single enterprise, more efficiently using ground resources and personnel and consolidating multiple ground systems into one. Sophisticated scheduling algorithms compare mission priorities and constraints across all ground stations, creating an enterprise schedule optimized to mission needs, which CGS executes to acquire the satellite link, uplink commands, downlink and route data to the operations and data processing facilities, and generate the final products for delivery to downstream users. This paper will illustrate the CGS's ability to manage multiple, enterprise-wide polar orbiting missions by demonstrating resource modeling and tasking, production of enterprise contact schedules for NOAA's Fairbanks ground station (using both standing and ad hoc requests), deconflicting resources due to ground outages, and updating resource allocations through dynamic priority definitions.

  14. Gravity Science with The JUICE Mission

    Science.gov (United States)

    Parisi, M.; Finocchiaro, S.; Iess, L.

    2012-04-01

    JUICE (Jupiter Icy Moon Explorer) is a European mission to the Jovian system, proposed in the frame of the ESA Cosmic Vision program. The spacecraft will reach the Jovian system and fly several times by the moons Callisto and Europa before being inserted in a nearly circular, polar orbit around Ganymede. After its arrival in 2030, the mission timeline entails two Europa flybys (2030), twelve Callisto flybys (2031) and the orbital phase at Ganymede (2033) [1]. Gravity measurements will provide crucial information on the interior structure of the three satellites. If the bodies are in hydrostatic equilibrium, the radial density distribution may be constrained from their moment of inertia factor and low-degree gravity field coefficients [2]. Furthermore, the determination of the high-degree harmonics will provide the distribution of gravity anomalies. Evidence for subsurface oceans within Ganymede and Callisto, one of the main scientific goals of the mission, will be obtained by the determination of the tidal Love number k2 as part of a global solution for the static and variable gravity field. Gravity fields and tidal deformations will be determined by means of precise Doppler tracking of the spacecraft in Ka-band (32.5-34 GHz). The Radio Science Instrument (RSI) is enabled by a Ka-band transponder which, complemented by suitable ground instrumentation, will enable a radio link with a very high phase stability. The main observable quantity for gravity field determination is the range rate (to 3 micron/s at 1000 s integration time, two-way). The spacecraft range (accurate to 20 cm, two-way) will be used to improve the ephemerides of the Jupiter system. Gravity science at Ganymede will be carried out during the orbital phase. According to the mission profile (subject to change), the first 102 days will be spent at an altitude of 500 km. The orbit will be lowered to 200 km in the last 32 days of the mission. If the spacecraft will be endowed with a steerable medium gain

  15. SATELLITE GRAVITY SURVEYING TECHNOLOGY AND RESEARCH OF EARTH'S GRAVITY FIELD

    Institute of Scientific and Technical Information of China (English)

    Ning Jinsheng

    2003-01-01

    This is a summarized paper. Two topics are discussed: Firstly, the concept, development and application of four kinds of satellite gravity surveying technology are introduced; Secondly, some problems of theory and method, which must be considered in the study of the Earth's gravity field based on satellite gravity data, are expounded.

  16. Magnetic Satellite Missions and Data

    DEFF Research Database (Denmark)

    Olsen, Nils; Kotsiaros, Stavros

    2011-01-01

    for exploring the Earth’s magnetic field from space. In this chapter we discuss characteristics of satellites measuring the geomagnetic field and report on past, present and upcoming magnetic satellite missions. We conclude with some basics about space magnetic gradiometry as a possible path for future...

  17. Magnetic Satellite Missions and Data

    DEFF Research Database (Denmark)

    Olsen, Nils; Kotsiaros, Stavros

    2011-01-01

    Although the first satellite observations of the Earth’s magnetic field were already taken more than 50 years ago, continuous geomagnetic measurements from space are only available since 1999. The unprecedented time-space coverage of this recent data set opened revolutionary new possibilities...... for exploring the Earth’s magnetic field from space. In this chapter we discuss characteristics of satellites measuring the geomagnetic field and report on past, present and upcoming magnetic satellite missions. We conclude with some basics about space magnetic gradiometry as a possible path for future...... exploration of Earth’s magnetic field with satellites....

  18. Aristoteles - An ESA mission to study the earth's gravity field

    Science.gov (United States)

    Lambeck, K.

    In preparing for its first Solid-Earth Program, ESA has studied a satellite concept for a mission dedicated to the precise determination of the earth's geopotential (gravitational and magnetic) fields. Data from such a mission are expected to make substantial contributions to a number of research and applications fields in solid-earth geophysics, oceanography and global-change monitoring. The impact of a high-resolution gravity-field mission on studies of the various earth-science problems is assessed. The current state of our knowledge in this area is discussed and the ability of low-orbit satellite gradiometry to contribute to their solution is demonstrated.

  19. Chameleon gravity and satellite geodesy

    CERN Document Server

    Morris, J R

    2014-01-01

    We consider the possibility of the detection of a chameleon effect by an earth orbiting satellite such as LAGEOS, and possible constraints that might be placed on chameleon model parameters. Approximate constraints presented here result from using a simple monopole approximation for the gravitational field of the earth, along with results from the Khoury-Weltman chameleon model, solar system constraints obtained from the Cassini mission, and parameter bounds obtained from the LAGEOS satellite. It is furthermore suggested that a comparison of ground-based and space-based multipole moments of the geopotential could reveal a possible chameleon effect.

  20. GRACE Gravity Field Product Description and Mission Profile

    Science.gov (United States)

    Bettadpur, S.; Flechtner, F.; Watkins, M. M.

    2003-12-01

    A time sequence of approximately monthly estimates of the Earth's gravity field, derived from the Gravity Recovery And Climate Mission (GRACE) science data, have been recently made available to the user community. In addition to these monthly estimates, a long-term mean gravity field has also been made available. These gravity field products are generated by the GRACE Science Data System team elements at the UT-CSR, Jet Propulsion Laboratory and at GFZ-Potsdam. In this presentation, we briefly describe the gravity field processing standards and methodology in use at UT-CSR. The traditional linearized least-squares implementation of gravity field determination from GRACE tracking data is reviewed with particular attention the to a-priori gravitational force models in use. The evolution of GRACE mission since its launch in March 2002 is then discussed. The main mission events, and the flight dynamic profile (pointing, inter-satellite separation, ground-track evolution, etc) are presented - with the purpose of aiding the interpretation and assessment of the gravity field product quality. The presentation closes with the description of the likely future evolution of the flight profile.

  1. Main methods of trajectory synthesis for scenarios of space missions with gravity assist maneuvers in the system of Jupiter and with landing on one of its satellites

    Science.gov (United States)

    Golubev, Yu. F.; Tuchin, A. G.; Grushevskii, A. V.; Koryanov, V. V.; Tuchin, D. A.; Morskoy, I. M.; Simonov, A. V.; Dobrovolskii, V. S.

    2016-12-01

    The development of a methodology for designing trajectories of spacecraft intended for the contact and remote studies of Jupiter and its natural satellites is considered. This methodology should take into account a number of specific features. Firstly, in order to maintain the propellant consumption at an acceptable level, the flight profile, ensuring the injection of the spacecraft into orbit around the Jovian moon, should include a large number of gravity assist maneuvers both in the interplanetary phase of the Earth-to-Jupiter flight and during the flight in the system of the giant planet. Secondly, the presence of Jupiter's powerful radiation belts also imposes fairly strict limitations on the trajectory parameters.

  2. Validation of GOCE Satellite Gravity Gradient Observations by Orbital Analysis

    Science.gov (United States)

    Visser, P.

    The upcoming European Space Agency ESA Gravity Field and Steady-State Ocean Circular Explorer GOCE mission foreseen to be launched in 2007 will carry a highly sensitive gradiometer consisting of 3 orthogonal pairs of ultra-sensitive accelerometers A challenging calibration procedure has been developed to calibrate the gradiometer not only before launch by a series of on-ground tests but also after launch by making use of on-board cold-gas thrusters to provoke a long series of gradiometer shaking events which will provide observations for its calibration This calibration can be checked by a combined analysis of GPS Satellite-to-Satellite Tracking SST and Satellite Gravity Gradient SGG observations An assessment has been made of how well SGG calibration parameters can be estimated in a combined orbit and gravity field estimation from these observations

  3. The lunar gravity mission MAGIA: preliminary design and performances

    Science.gov (United States)

    Fermi, Marco; Gregnanin, Marco; Mazzolena, Marco; Chersich, Massimiliano; Reguzzoni, Mirko; Sansò, Fernando

    2011-10-01

    The importance of an accurate model of the Moon gravity field has been assessed for future navigation missions orbiting and/or landing on the Moon, in order to use our natural satellite as an intermediate base for next solar system observations and exploration as well as for lunar resources mapping and exploitation. One of the main scientific goals of MAGIA mission, whose Phase A study has been recently funded by the Italian Space Agency (ASI), is the mapping of lunar gravitational anomalies, and in particular those on the hidden side of the Moon, with an accuracy of 1 mGal RMS at lunar surface in the global solution of the gravitational field up to degree and order 80. MAGIA gravimetric experiment is performed into two phases: the first one, along which the main satellite shall perform remote sensing of the Moon surface, foresees the use of Precise Orbit Determination (POD) data available from ground tracking of the main satellite for the determination of the long wavelength components of gravitational field. Improvement in the accuracy of POD results are expected by the use of ISA, the Italian accelerometer on board the main satellite. Additional gravitational data from recent missions, like Kaguya/Selene, could be used in order to enhance the accuracy of such results. In the second phase the medium/short wavelength components of gravitational field shall be obtained through a low-to-low (GRACE-like) Satellite-to-Satellite Tracking (SST) experiment. POD data shall be acquired during the whole mission duration, while the SST data shall be available after the remote sensing phase, when the sub-satellite shall be released from the main one and both satellites shall be left in a free-fall dynamics in the gravity field of the Moon. SST range-rate data between the two satellites shall be measured through an inter-satellite link with accuracy compliant with current state of art space qualified technology. SST processing and gravitational anomalies retrieval shall

  4. Future missions for observing Earth's changing gravity field: a closed-loop simulation tool

    Science.gov (United States)

    Visser, P. N.

    2008-12-01

    The GRACE mission has successfully demonstrated the observation from space of the changing Earth's gravity field at length and time scales of typically 1000 km and 10-30 days, respectively. Many scientific communities strongly advertise the need for continuity of observing Earth's gravity field from space. Moreover, a strong interest is being expressed to have gravity missions that allow a more detailed sampling of the Earth's gravity field both in time and in space. Designing a gravity field mission for the future is a complicated process that involves making many trade-offs, such as trade-offs between spatial, temporal resolution and financial budget. Moreover, it involves the optimization of many parameters, such as orbital parameters (height, inclination), distinction between which gravity sources to observe or correct for (for example are gravity changes due to ocean currents a nuisance or a signal to be retrieved?), observation techniques (low-low satellite-to-satellite tracking, satellite gravity gradiometry, accelerometers), and satellite control systems (drag-free?). A comprehensive tool has been developed and implemented that allows the closed-loop simulation of gravity field retrievals for different satellite mission scenarios. This paper provides a description of this tool. Moreover, its capabilities are demonstrated by a few case studies. Acknowledgments. The research that is being done with the closed-loop simulation tool is partially funded by the European Space Agency (ESA). An important component of the tool is the GEODYN software, kindly provided by NASA Goddard Space Flight Center in Greenbelt, Maryland.

  5. GOCE and Future Gravity Missions for Geothermal Energy Exploitation

    Science.gov (United States)

    Pastorutti, Alberto; Braitenberg, Carla; Pivetta, Tommaso; Mariani, Patrizia

    2016-08-01

    Geothermal energy is a valuable renewable energy source the exploitation of which contributes to the worldwide reduction of consumption of fossil fuels oil and gas. The exploitation of geothermal energy is facilitated where the thermal gradient is higher than average leading to increased surface heat flow. Apart from the hydrologic circulation properties which depend on rock fractures and are important due to the heat transportation from the hotter layers to the surface, essential properties that increase the thermal gradient are crustal thinning and radiogenic heat producing rocks. Crustal thickness and rock composition form the link to the exploration with the satellite derived gravity field, because both induce subsurface mass changes that generate observable gravity anomalies. The recognition of gravity as a useful investigation tool for geothermal energy lead to a cooperation with ESA and the International Renewable Energy Agency (IRENA) that included the GOCE derived gravity field in the online geothermal energy investigation tool of the IRENA database. The relation between the gravity field products as the free air gravity anomaly, the Bouguer and isostatic anomalies and the heat flow values is though not straightforward and has not a unique relationship. It is complicated by the fact that it depends on the geodynamical context, on the geologic context and the age of the crustal rocks. Globally the geological context and geodynamical history of an area is known close to everywhere, so that a specific known relationship between gravity and geothermal potential can be applied. In this study we show the results of a systematic analysis of the problem, including some simulations of the key factors. The study relies on the data of GOCE and the resolution and accuracy of this satellite. We also give conclusions on the improved exploration power of a gravity mission with higher spatial resolution and reduced data error, as could be achieved in principle by flying

  6. Ravens satellite mission concept study

    CERN Document Server

    Donovan, Eric F

    2011-01-01

    The concept for Ravens satellite mission was proposed in response to a CSA AO for potential Canadian mission contributions to the International Living With a Star (ILWS) program. Ravens was conceived of to fill an important gap in the ILWS program: global imaging. Ravens will build on the heritage of world-class global imaging carried out in Canada. It would do much more than provide global observations to complete the system level capabilities of ILWS. Ravens would be comprised of two satellites on elliptical polar orbits, relatively phased on those orbits to provide the first-ever continuous (ie., 24 hours per day 7 days per week) global imaging of the northern hemisphere auroral and polar cap regions. This would provide the first-ever unbroken sequences of global images of the auroral response during long duration geomagnetic processes like storms and steady magnetospheric convection events. Ravens could track the spatio-temporal evolution of the global electron and proton auroral distribution, and would o...

  7. Secular Gravity Gradients in Non-Dynamical Chern-Simons Modified Gravity for Satellite Gradiometry Measurements

    CERN Document Server

    Qiang, Li-E

    2016-01-01

    With continuous advances in related technologies, relativistic gravitational experiments with orbiting gradiometers becomes feasible, which could naturally be incorporated into future satellite gravity missions. Tests of Chern-Simons modified gravity are meaningful since such a modification gives us insights into (possible) parity-violations in gravitation. In this work, we derive, at the post-Newtonian level, the new observables of secular gradients from the non-dynamical Chern-Simons modified gravity, which will greatly improve the constraint on the mass scale $M_{CS}$ that may be drawn from satellite gradiometry measurements. For superconducting gradiometers, a strong bound $M_{CS}\\geq 10^{-7}\\ eV$ could in principle be obtained. For future optical gradiometers based on similar technologies from the LISA PathFinder mission, a even stronger bound $M_{CS}\\geq 10^{-5}\\ eV$ might be expected.

  8. High-resolution gravity field modeling using GRAIL mission data

    Science.gov (United States)

    Lemoine, F. G.; Goossens, S. J.; Sabaka, T. J.; Nicholas, J. B.; Mazarico, E.; Rowlands, D. D.; Neumann, G. A.; Loomis, B.; Chinn, D. S.; Smith, D. E.; Zuber, M. T.

    2015-12-01

    The Gravity Recovery and Interior Laboratory (GRAIL) spacecraft were designed to map the structure of the Moon through high-precision global gravity mapping. The mission consisted of two spacecraft with Ka-band inter-satellite tracking complemented by tracking from Earth. The mission had two phases: a primary mapping mission from March 1 until May 29, 2012 at an average altitude of 50 km, and an extended mission from August 30 until December 14, 2012, with an average altitude of 23 km before November 18, and 20 and 11 km after. High-resolution gravity field models using both these data sets have been estimated, with the current resolution being degree and order 1080 in spherical harmonics. Here, we focus on aspects of the analysis of the GRAIL data: we investigate eclipse modeling, the influence of empirical accelerations on the results, and we discuss the inversion of large-scale systems. In addition to global models we also estimated local gravity adjustments in areas of particular interest such as Mare Orientale, the south pole area, and the farside. We investigate the use of Ka-band Range Rate (KBRR) data versus numerical derivatives of KBRR data, and show that the latter have the capability to locally improve correlations with topography.

  9. The use of satellites in gravity field determination and model adjustment

    Science.gov (United States)

    Visser, Petrus Nicolaas Anna Maria

    1992-06-01

    Methods to improve gravity field models of the Earth with available data from satellite observations are proposed and discussed. In principle, all types of satellite observations mentioned give information of the satellite orbit perturbations and in conjunction the Earth's gravity field, because the satellite orbits are affected most by the Earth's gravity field. Therefore, two subjects are addressed: representation forms of the gravity field of the Earth and the theory of satellite orbit perturbations. An analytical orbit perturbation theory is presented and shown to be sufficiently accurate for describing satellite orbit perturbations if certain conditions are fulfilled. Gravity field adjustment experiments using the analytical orbit perturbation theory are discussed using real satellite observations. These observations consisted of Seasat laser range measurements and crossover differences, and of Geosat altimeter measurements and crossover differences. A look into the future, particularly relating to the ARISTOTELES (Applications and Research Involving Space Techniques for the Observation of the Earth's field from Low Earth Orbit Spacecraft) mission, is given.

  10. Solid Earth ARISTOTELES mission data preprocessing simulation of gravity gradiometer

    Science.gov (United States)

    Avanzi, G.; Stolfa, R.; Versini, B.

    Data preprocessing of the ARISTOTELES mission, which measures the Earth gravity gradient in a near polar orbit, was studied. The mission measures the gravity field at sea level through indirect measurements performed on the orbit, so that the evaluation steps consist in processing data from GRADIO accelerometer measurements. Due to the physical phenomena involved in the data collection experiment, it is possible to isolate at an initial stage a preprocessing of the gradiometer data based only on GRADIO measurements and not needing a detailed knowledge of the attitude and attitude rate sensors output. This preprocessing produces intermediate quantities used in future stages of the reduction. Software was designed and run to evaluate for this level of data reduction the achievable accuracy as a function of knowledge on instrument and satellite status parameters. The architecture of this element of preprocessing is described.

  11. Time-variable gravity fields from satellite tracking

    Science.gov (United States)

    Bettadpur, Srinivas; Cheng, Minkang; Ries, John

    2014-05-01

    At the University of Texas Center for Space Research (CSR), we routinely deliver time-series of Earth's gravity field variations, some of it spanning more than two decades. These time-series are derived - in a consistent manner - from satellite laser ranging (SLR) data, from low-Earth orbiters tracked using GPS, and from low-low satellite to satellite tracking data from GRACE. In this paper, we review the information content in the gravity field time-series derived from each of these methods. We provide a comparison of the time-series at the decadal and annual time-scales, and identify the spatial modes of variability that are well or poorly estimated by each of the observing systems. The results have important bearing on the prospects of extending GRACE time-variable gravity time-series in the event of gaps between dedicated gravity missions, and for extending the time-series into the past. Support for this research from joint NASA/DLR GRACE mission, the NASA MEASURs program, and the NASA ROSES/GRACE Science Team is gratefully acknowledged.

  12. Lunar Orbit Stability for Small Satellite Mission Design

    Science.gov (United States)

    Dono, Andres

    2015-01-01

    The irregular nature of the lunar gravity field will severely affect the orbit lifetime and behavior of future lunar small satellite missions. These spacecraft need stable orbits that do not require large deltaV budgets for station-keeping maneuvers. The initial classical elements of any lunar orbit are critical to address its stability and to comply with mission requirements. This publication identifies stable regions according to different initial conditions at the time of lunar orbit insertion (LOI). High fidelity numerical simulations with two different gravity models were performed. We focus in low altitude orbits where the dominant force in orbit propagation is the existence of unevenly distributed lunar mass concentrations. These orbits follow a periodic oscillation in some of the classical elements that is particularly useful for mission design. A set of orbital maintenance strategies for various mission concepts is presented.

  13. Gravity field data products from the ARISTOTELES mission.

    Science.gov (United States)

    Balmino, G.

    1991-12-01

    The ARISTOTELES mission will bring a wealth of homogeneous information about the Earth gravity field enabling new direct and inverse modeling of geophysical structures at various scales, yielding a reference geoid surface of great quality for oceanographic studies, leading to global models of high resolution for versatile applications and in particular precise orbit determination of artificial satellites. The author's purpose is to review the different types of measurements involved in these investigations, the various levels of processing and how they can be phased with the scientific activities, and the expected products. Also, some general schemes are proposed along which the different tasks can be undertaken.

  14. Next Generation Gravity Mission: a Step Forward in the Earth's Gravity Field Determination

    Science.gov (United States)

    Silvestrin, P.; Aguirre, M.; Massotti, L.; Cesare, S.

    2009-04-01

    This paper concerns with the "System Support to Laser Interferometry Tracking Technology Development for Gravity Field Monitoring" study of the European Space Agency, a mission study for monitoring the variations of Earth's gravity field at high resolution (up to harmonic degree 200) over a long time period (>5 years). The mission exploits the use of a heterodyne laser interferometer for the high-resolution measurement of the displacement between two satellites flying at low altitude (around 325 km). More in details, employing a formation of two co-orbiting satellites at 10 km relative distance, a resolution of about 1 nm rms is needed in the inter-satellite distance measurement, and the non gravitational accelerations must be measured with a resolution of about 10-10 m/s2 rms to achieve geoid height variation rate error equal to 0.1 mm/year at degree 200. Starting from the geophysical phenomena to be investigated, a detailed derivation of the mission requirements on the orbit, satellite formation and control, measurement instruments (laser interferometer and accelerometer) was performed using analytical models and numerical simulations, and the satellite GNC (Guidance, Navigation & Control) was approached through different techniques. A possible solution for the optical metrology suitable for the realization of a Next-Generation Gravimetric Mission has been identified, designed, breadboarded and tested to a level of detail sufficient to assess its feasibility. The main elements of this optical metrology are: 1) a Michelson-type heterodyne laser interferometer for measuring the distance variation between the retro-reflectors installed on two satellites. The innovative feature of the interferometer consists in chopping the laser beam with a frequency related to the satellite distance. This enables its proper functioning with a retro-reflector placed at large distances (around 10 km) from the source; 2) an optical device consisting of three small telescopes endowed

  15. Antarctic outlet glacier mass change resolved at basin scale from satellite gravity gradiometry

    NARCIS (Netherlands)

    Bouman, J.; Fuchs, M.; Ivins, E.; Van der Wal, W.; Schrama, E.J.O.; Visser, P.N.A.M.; Horwath, M.

    2014-01-01

    The orbit and instrumental measurement of the Gravity Field and Steady State Ocean Circulation Explorer (GOCE) satellite mission offer the highest ever resolution capabilities for mapping Earth's gravity field from space. However, past analysis predicted that GOCE would not detect changes in ice

  16. Antarctic outlet glacier mass change resolved at basin scale from satellite gravity gradiometry

    NARCIS (Netherlands)

    Bouman, J.; Fuchs, M.; Ivins, E.; Van der Wal, W.; Schrama, E.J.O.; Visser, P.N.A.M.; Horwath, M.

    2014-01-01

    The orbit and instrumental measurement of the Gravity Field and Steady State Ocean Circulation Explorer (GOCE) satellite mission offer the highest ever resolution capabilities for mapping Earth's gravity field from space. However, past analysis predicted that GOCE would not detect changes in ice she

  17. Designing Electrostatic Accelerometers for Next Gravity Missions

    Science.gov (United States)

    Huynh, Phuong-Anh; Foulon, Bernard; Christophe, Bruno; Liorzou, Françoise; Boulanger, Damien; Lebat, Vincent

    2016-04-01

    Square cuboid electrostatic accelerometers sensor core have been used in various combinations in recent and still flying missions (CHAMP, GRACE, GOCE). ONERA is now in the process of delivering such accelerometers for the GRACE Follow-On mission. The goal is to demonstrate the performance benefits of an interferometry laser ranging method for future low-low satellite to satellite missions. The electrostatic accelerometer becoming thus the system main performance limiter, we propose for future missions a new symmetry which will allow for three ultrasensitive axes instead of two. This implies no performance ground testing, as the now cubic proof-mass will be too heavy, but only free fall tests in catapult mode, taking advantage of the additional microgravity testing time offered by the updated ZARM tower. The updated mission will be in better adequacy with the requirements of a next generation of smaller and drag compensated micro-satellites. In addition to the measurement of the surface forces exerted on the spacecraft by the atmospheric drag and by radiation pressures, the accelerometer will become a major part of the attitude and orbit control system by acting as drag free sensor and by accurately measuring the angular accelerations. ONERA also works on a hybridization of the electrostatic accelerometer with an atomic interferometer to take advantage of the absolute nature of the atomic interferometer acceleration measurement and its great accuracy in the [5-100] mHz bandwidth. After a description of the improvement of the GRACE-FO accelerometer with respect to the still in-orbit previous models and a status of its development, the presentation will describe the new cubic configuration and how its operations and performances can be verified in the Bremen drop tower.

  18. Gravity Fields from CHAMP Mission Data

    Science.gov (United States)

    Lemoine, Frank G.; Luthcke, S. B.; Cox, C. M.; Rowlands, D. D.; Thompson, B. F.; Chinn, D. S.; Williams, T. A.; Nerem, R. S.

    2002-01-01

    The CHAMP mission, launched in July 2000, is the first in a series of missions that will revolutionize our ability to model the Earth s geopotential. The CHAMP spacecraft is equipped for precision tracking by the Global Positioning System (GPS) and Satellite Laser Ranging (SLR) along with a precision accelerometer to provide measurements of the surface forces. Preliminary satellite-only geopotential solutions with only 30 days of CHAMP data are, by some criteria, as strong as solutions made from tracking data collected over the previous 30 years of the space age. Compared to EGM96, CHAMP makes notable contributions in regions where the terrestrial data (surface gravimetry and altimetry) were weak, for example in the polar regions, in the Amazon and the Himalayas. The CHAMP data allow us to separate the geoid from the dynamic ocean topography (DOT) up to at least degree 25 rather than just under degree 20 as in EGM96. We report on satellite-only and combination models that incorporate up to 100 days of CHAMP data as well as other satellite data. We report on our updated processing of the CHAMP tracking and accelerometer data and evaluate the performance of the geopotential models using a variety of tests.

  19. Local gravity disturbance estimation from multiple-high-single-low satellite-to-satellite tracking

    Science.gov (United States)

    Jekeli, Christopher

    1989-01-01

    The idea of satellite-to-satellite tracking in the high-low mode has received renewed attention in light of the uncertain future of NASA's proposed low-low mission, Geopotential Research Mission (GRM). The principal disadvantage with a high-low system is the increased time interval required to obtain global coverage since the intersatellite visibility is often obscured by Earth. The U.S. Air Force has begun to investigate high-low satellite-to-satellite tracking between the Global Positioning System (GPS) of satellites (high component) and NASA's Space Transportation System (STS), the shuttle (low component). Because the GPS satellites form, or will form, a constellation enabling continuous three-dimensional tracking of a low-altitude orbiter, there will be no data gaps due to lack of intervisibility. Furthermore, all three components of the gravitation vector are estimable at altitude, a given grid of which gives a stronger estimate of gravity on Earth's surface than a similar grid of line-of-sight gravitation components. The proposed Air Force mission is STAGE (Shuttle-GPS Tracking for Anomalous Gravitation Estimation) and is designed for local gravity field determinations since the shuttle will likely not achieve polar orbits. The motivation for STAGE was the feasibility to obtain reasonable accuracies with absolutely minimal cost. Instead of simulating drag-free orbits, STAGE uses direct measurements of the nongravitational forces obtained by an inertial package onboard the shuttle. The sort of accuracies that would be achievable from STAGE vis-a-vis other satellite tracking missions such as GRM and European Space Agency's POPSAT-GRM are analyzed.

  20. Acceleration Noise Considerations for Drag-free Satellite Geodesy Missions

    Science.gov (United States)

    Hong, S. H.; Conklin, J. W.

    2016-12-01

    The GRACE mission, which launched in 2002, opened a new era of satellite geodesy by providing monthly mass variation solutions with spatial resolution of less than 200 km. GRACE proved the usefulness of a low-low satellite-to-satellite tracking formation. Analysis of the GRACE data showed that the K-Band ranging system, which is used to measure the range between the two satellites, is the limiting factor for the precision of the solution. Consequently, the GRACE-FO mission, schedule for launch in 2017, will continue the work of GRACE, but will also test a new, higher precision laser ranging interferometer compared with the K-Band ranging system. Beyond GRACE-FO, drag-free systems are being considered for satellite geodesy missions. GOCE tested a drag-free attitude control system with a gravity gradiometer and showed improvements in the acceleration noise compensation compared to the electrostatic accelerometers used in GRACE. However, a full drag-free control system with a gravitational reference sensor has not yet been applied to satellite geodesy missions. More recently, this type of drag-free system was used in LISA Pathfinder, launched in 2016, with an acceleration noise performance two orders of magnitude better than that of GOCE. We explore the effects of drag-free performance in satellite geodesy missions similar to GRACE-FO by applying three different residual acceleration noises from actual space missions: GRACE, GOCE and LISA Pathfinder. Our solutions are limited to degree 60 spherical harmonic coefficients with biweekly time resolution. Our analysis shows that a drag-free system with acceleration noise performance comparable to GOCE and LISA-Pathfinder would greatly improve the accuracy of gravity solutions. In addition to these results, we also present the covariance shaping process used in the estimation. In the future, we plan to use actual acceleration noise data measured using the UF torsion pendulum. This apparatus is a ground facility at

  1. Satellite gravity gradient grids for geophysics.

    Science.gov (United States)

    Bouman, Johannes; Ebbing, Jörg; Fuchs, Martin; Sebera, Josef; Lieb, Verena; Szwillus, Wolfgang; Haagmans, Roger; Novak, Pavel

    2016-02-11

    The Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite aimed at determining the Earth's mean gravity field. GOCE delivered gravity gradients containing directional information, which are complicated to use because of their error characteristics and because they are given in a rotating instrument frame indirectly related to the Earth. We compute gravity gradients in grids at 225 km and 255 km altitude above the reference ellipsoid corresponding to the GOCE nominal and lower orbit phases respectively, and find that the grids may contain additional high-frequency content compared with GOCE-based global models. We discuss the gradient sensitivity for crustal depth slices using a 3D lithospheric model of the North-East Atlantic region, which shows that the depth sensitivity differs from gradient to gradient. In addition, the relative signal power for the individual gradient component changes comparing the 225 km and 255 km grids, implying that using all components at different heights reduces parameter uncertainties in geophysical modelling. Furthermore, since gravity gradients contain complementary information to gravity, we foresee the use of the grids in a wide range of applications from lithospheric modelling to studies on dynamic topography, and glacial isostatic adjustment, to bedrock geometry determination under ice sheets.

  2. The Earth's gravity field from satellite geodesy - a 30 year adventure.

    Science.gov (United States)

    Rapp, R. H.

    1991-12-01

    The first information on the Earth's gravitational field from artificial satellite observations was published in 1958. The next years have seen a dramatic improvement in the resolution and accuracy of the series representation of the Earth's gravity field. The improvements have taken place slowly taking advantage of improved measurement accuracy and the increasing number of satellites. The proposed ARISTOTELES mission would provide the opportunity to take a significant leap in improving our knowledge of the Earth's gravity field.

  3. Teamwork Reasoning and Multi-Satellite Missions

    Science.gov (United States)

    Marsella, Stacy C.; Plaunt, Christian (Technical Monitor)

    2002-01-01

    NASA is rapidly moving towards the use of spatially distributed multiple satellites operating in near Earth orbit and Deep Space. Effective operation of such multi-satellite constellations raises many key research issues. In particular, the satellites will be required to cooperate with each other as a team that must achieve common objectives with a high degree of autonomy from ground based operations. The multi-agent research community has made considerable progress in investigating the challenges of realizing such teamwork. In this report, we discuss some of the teamwork issues that will be faced by multi-satellite operations. The basis of the discussion is a particular proposed mission, the Magnetospheric MultiScale mission to explore Earth's magnetosphere. We describe this mission and then consider how multi-agent technologies might be applied in the design and operation of these missions. We consider the potential benefits of these technologies as well as the research challenges that will be raised in applying them to NASA multi-satellite missions. We conclude with some recommendations for future work.

  4. The role of satellite altimetry in gravity field modelling in coastal areas

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Knudsen, Per

    2000-01-01

    During recent years altimetry from the two geodetic missions of GEOSAT and ERS-1 has enabled the derivation of high resolution near global gravity field from altimetry [Andersen and Knudsen, 1995, 1996; Sandwell and Smith, 1997]. Altimetric gravity fields are unique in the sense that they provide...... global uniform gravity information with very high resolution, and these global marine gravity fields are registered on a two by two minute grid corresponding to 4 by 4 kilometres at the equator. In this presentation several coastal complications in deriving the marine gravity field from satellite...... altimetry will be investigated using the KMS98 gravity field. Comparison with other sources of gravity field information like airborne and marine gravity observations will be carried out and two fundamentally different test areas (Azores and Skagerak) will be studied to investigated the different role...

  5. The Gravity Fields of the Saturnian Satellites

    Science.gov (United States)

    Iess, L.

    2011-12-01

    In its tour of the Saturnian system, begun on July 1st, 2004, the Cassini spacecraft had many close flybys of Saturn's main satellites. However, due to impossibility to carry out simultaneously remote sensing observations and microwave tracking from ground, only a small fraction of those flybys could be exploited for gravity measurements. So far, the quadrupole field has been mapped only for Titan, Rhea and Enceladus, while for Hyperion and Iapetus the mass was the only accessible parameter. For Titan and Enceladus, the only satellites targeted more than once for gravity observations, also a rough geoid to degree and order 3 has been determined. Satellite gravity investigations rely upon accurate measurements of the spacecraft range rate, enabled by coherent, two-way radio links at X and Ka band (8.4 and 32.5 GHz). The use of hydrogen masers frequency standards at the ground station and the consid-erable suppression of plasma noise at X and Ka band frequen-cies provide range rate accuracies of 10-30 micron/s at integra-tion times of 60 s. Thanks to the higher frequency of the radio link, these measurement accuracies are in the average a factor of 10 better than those attained by Galileo in its tour of the Jovian system. However, in order to attain a reliable determination of the low degree field, good measurements must be combined with appropriate flyby geometries and adequate sampling, a condition that necessarily requires multiple flybys. We review the main results obtained so far by Cassini for Titan, Rhea and Enceladus, and discuss the methods of analysis used by the Radio Science Team.

  6. SATELLITE GRAVITY SURVEYING TECHNOLOGY AND RESEARCH OF EARTH'S GRAVITY FIELD

    Institute of Scientific and Technical Information of China (English)

    NingJinsheng

    2003-01-01

    This is a summarized paper.Two topics are discussed:Firstly,the comcept,development and application of four kinds of satellite gravity surveying technology are introduced;Secondly,some problems of theory and method,which must be considered in the study lf the Earth's gravity field based on satellite gravity data,are expounded.

  7. First champ mission results for gravity, magnetic and atmospheric studies

    CERN Document Server

    Lühr, Hermann; Schwintzer, Peter

    2003-01-01

    In the summer of 2000 the German geo-research satellite CHAMP was launched into orbit. Its innovative payload arrangement and the low intial orbit allow CHAMP to simultaneously collect and almost continuously analyse precise data relating to gravity and magnetic fields at low altitude. In addition to this CHAMP also measures the neutral atmosphere and ionosphere using GPS techniques. Eighteen months after the launch, CHAMP research groups from all over the world met at the Geo-Forschungs-Zentrum in Potsdam for an initial exchange of experiences and results. The main outcome of this user meeting is summarized in this volume. Apart from technical information about the mission, the book offers a comprehensive insight into the present status of CHAMP data exploitation for Earth system research and practical applications in geodesy, geophysics and meteorology.

  8. The Infrared Astronomical Satellite (IRAS) mission

    Science.gov (United States)

    Neugebauer, G.; Habing, H. J.; Van Duinen, R.; Aumann, H. H.; Beichman, C. A.; Baud, B.; Beintema, D. A.; Boggess, N.; Clegg, P. E.; De Jong, T.

    1984-01-01

    The Infrared Astronomical Satellite (IRAS) consists of a spacecraft and a liquid helium cryostat that contains a cooled IR telescope. The telescope's focal plane assembly is cooled to less than 3 K, and contains 62 IR detectors in the survey array which are arranged so that every source crossing the field of view can be seen by at least two detectors in each of four wavelength bands. The satellite was launched into a 900 km-altitude near-polar orbit, and its cryogenic helium supply was exhausted on November 22, 1983. By mission's end, 72 percent of the sky had been observed with three or more hours-confirming scans, and 95 percent with two or more hours-confirming scans. About 2000 stars detected at 12 and 25 microns early in the mission, and identified in the SAO (1966) catalog, have a positional uncertainty ellipse whose axes are 45 x 9 arcsec for an hours-confirmed source.

  9. The DNSC08GRA global marine gravity field from double retracked satellite altimetry

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Knudsen, Per; Berry, P.A.M.

    2010-01-01

    Satellite radar altimetry has been monitoring the earth's oceans from space for several decades. However, only the GEOSAT and ERS-1 geodetic mission data recorded more than a decade ago provide altimetry with adequate spatial coverage to derive a high-resolution marine gravity field. The original...

  10. Drag-free Small Satellite Platforms for Future Geodesy Missions

    Science.gov (United States)

    Conklin, J. W.; Hong, S.; Nguyen, A.; Serra, P.; Balakrishnan, K.; Buchman, S.; De Bra, D. B.; Hultgren, E.; Zoellner, A.

    2013-12-01

    Continuous satellite geodesy measurements lasting into the foreseeable future are critical for the understanding of our changing planet. It is therefore imperative that we explore ways to reduce costs, while maintaining science return. Small satellite platforms represent a promising path forward if ways can be found to reduce the size, weight, and power of the necessary instrumentation. One key enabling technology is a precision small-scale drag-free system under development at the University of Florida and Stanford University. A drag-free satellite (a) contains and shields a free-floating test mass from all non-gravitational forces, and (b) precisely measures the position of the test mass inside the satellite. A feedback control system commands thrusters to fly the 'tender' spacecraft with respect to the test mass. Thus, both test mass and spacecraft follow a pure geodesic in spacetime. By tracking the relative positions of low Earth orbiting drag-free satellites, using laser interferometry for example, the detailed shape of geodesics, and through analysis, the higher order harmonics of the Earth's geopotential can be determined. Drag-free systems can be orders of magnitude more accurate that accelerometer-based systems because they fundamentally operate at extremely low acceleration levels, and are therefore not limited by dynamic range like accelerometers. Since no test mass suspension force is required, larger gaps between the test mass and satellite are possible, which reduces the level of unwanted disturbing forces produced by the satellite itself. The small satellite platform also enables cost-effective constellations, which can increase the temporal resolution of gravity field maps by more-frequently observing given locations on the Earth. Mixed-orbit constellations can also markedly enhance observational strength, decorrelate gravity coefficient estimates, and help address the fundamental aliasing problem that exists with previous missions. The

  11. Time variable gravity retrieval and treatment of temporal aliasing using optical two-way links between GALILEO and LEO satellites

    Science.gov (United States)

    Hauk, Markus; Pail, Roland; Murböck, Michael; Schlicht, Anja

    2016-04-01

    For the determination of temporal gravity fields satellite missions such as GRACE (Gravity Recovery and Climate Experiment) or CHAMP (Challenging Minisatellite Payload) were used in the last decade. These missions improved the knowledge of atmospheric, oceanic and tidal mass variations. The most limiting factor of temporal gravity retrieval quality is temporal aliasing due to the undersampling of high frequency signals, especially in the atmosphere and oceans. This kind of error causes the typical stripes in spatial representations of global gravity fields such as from GRACE. As part of the GETRIS (Geodesy and Time Reference in Space) mission, that aims to establish a geodetic reference station and precise time- and frequency reference in space by using optical two-way communication links between geostationary (GEO) and low Earth orbiting (LEO) satellites, a possible future gravity field mission can be set up. By expanding the GETRIS space segment to the global satellite navigation systems (GNSS) the optical two-way links also connect the GALILEO satellites among themselves and to LEO satellites. From these links between GALILEO and LEO satellites gravitational information can be extracted. In our simulations inter-satellite links between GALILEO and LEO satellites are used to determine temporal changes in the Earth's gravitational field. One of the main goals of this work is to find a suitable constellation together with the best analysis method to reduce temporal aliasing errors. Concerning non-tidal aliasing, it could be shown that the co-estimation of short-period long-wavelength gravity field signals, the so-called Wiese approach, is a powerful method for aliasing reduction (Wiese et al. 2013). By means of a closed loop mission simulator using inter-satellite observations as acceleration differences along the line-of-sight, different mission scenarios for GALILEO-LEO inter-satellite links and different functional models like the Wiese approach are analysed.

  12. Global and Local Gravity Field Models of the Moon Using GRAIL Primary and Extended Mission Data

    Science.gov (United States)

    Goossens, Sander; Lemoine, Frank G.; Sabaka, Terence J.; Nicholas, Joseph B.; Mazarico, Erwan; Rowlands, David D.; Loomis, Bryant D.; Chinn, Douglas S.; Neumann, Gregory A.; Smith, David E.; Zuber, Maria T.

    2015-01-01

    The Gravity Recovery and Interior Laboratory (GRAIL) mission was designed to map the structure of the lunar interior from crust to core and to advance the understanding of the Moon's thermal evolution by producing a high-quality, high-resolution map of the gravitational field of the Moon. The mission consisted of two spacecraft, which were launched in September 2011 on a Discovery-class NASA mission. Ka-band tracking between the two satellites was the single science instrument, augmented by tracking from Earth using the Deep Space Network (DSN).

  13. The Earth's gravity field from satellite geodesy: A 30 year adventure

    Science.gov (United States)

    Rapp, Richard H.

    1991-12-01

    The history of research in the Earth's gravity field from satellite geodesy is described and limitations of existing geopotential models are indicated. Although current solutions have made outstanding achievements, their limited accuracy restricts their use for some oceanographic applications. An example is discussed where there appears to be an incompatibility of the long wavelength geoid undulation obtained through satellite analysis with independent estimates that have become available. The future Aristoteles mission is seen as providing a significant leap in Earth gravity field knowledge improvement.

  14. Error analysis for satellite gravity field determination based on two-dimensional Fourier methods

    CERN Document Server

    Cai, Lin; Hsu, Houtse; Gao, Fang; Zhu, Zhu; Luo, Jun

    2012-01-01

    The time-wise and space-wise approaches are generally applied to data processing and error analysis for satellite gravimetry missions. But both the approaches, which are based on least-squares collocation, address the whole effect of measurement errors and estimate the resolution of gravity field models mainly from a numerical point of indirect view. Moreover, requirement for higher accuracy and resolution gravity field models could make the computation more difficult, and serious numerical instabilities arise. In order to overcome the problems, this study focuses on constructing a direct relationship between power spectral density of the satellite gravimetry measurements and coefficients of the Earth's gravity potential. Based on two-dimensional Fourier transform, the relationship is analytically concluded. By taking advantage of the analytical expression, it is efficient and distinct for parameter estimation and error analysis of missions. From the relationship and the simulations, it is analytically confir...

  15. Drag-Free Motion Control of Satellite for High-Precision Gravity Field Mapping

    DEFF Research Database (Denmark)

    2002-01-01

    , sensors, actuators and environmental disturbances to the required micro-Newton accuracy. A control system is designed to compensate the non-gravitational disturbances on the satellite in three axes using an H∞-design. Performance is validated against mission requirements. Keywords: Spacecraft Attitude......High precision mapping of the geoid and the Earth's gravity field are of importance to a wide range of ongoing studies in areas like ocean circulation, solid Earth physics and ice sheet dynamics. Using a satellite in orbit around the Earth gives the opportunity to map the Earth's gravity field in 3...... dimensions with much better accuracy and spatial resolution than ever accomplished. To reach the desired quality of measurements, the satellite must fly in a low Earth orbit where disturbances from atmospheric drag and the Earth's magnetic field will perturb the satellite's motion. These effects...

  16. Ice Mass Change in Greenland and Antarctica Between 1993 and 2013 from Satellite Gravity Measurements

    Science.gov (United States)

    Talpe, Matthieu J.; Nerem, R. Steven; Forootan, Ehsan; Schmidt, Michael; Lemoine, Frank G.; Enderlin, Ellyn M.; Landerer, Felix W.

    2017-01-01

    We construct long-term time series of Greenland and Antarctic ice sheet mass change from satellite gravity measurements. A statistical reconstruction approach is developed based on a principal component analysis (PCA) to combine high-resolution spatial modes from the Gravity Recovery and Climate Experiment (GRACE) mission with the gravity information from conventional satellite tracking data. Uncertainties of this reconstruction are rigorously assessed; they include temporal limitations for short GRACE measurements, spatial limitations for the low-resolution conventional tracking data measurements, and limitations of the estimated statistical relationships between low- and high-degree potential coefficients reflected in the PCA modes. Trends of mass variations in Greenland and Antarctica are assessed against a number of previous studies. The resulting time series for Greenland show a higher rate of mass loss than other methods before 2000, while the Antarctic ice sheet appears heavily influenced by interannual variations.

  17. MPI Parallel Algorithm in Satellite Gravity Field Model Inversion on the Basis of Least Square Method

    Directory of Open Access Journals (Sweden)

    ZHOU Hao

    2015-08-01

    Full Text Available In order to solve the intensive computing tasks and high memory demand problem in satellite gravity field model inversion on the basis of huge amounts of satellite gravity observations, the parallel algorithm for high truncated order and degree satellite gravity field model inversion with least square method on the basis of MPI was introduced. After analyzing the time and space complexity of each step in the solving flow, the parallel I/O, block-organized storage and block-organized computation algorithm on the basis of MPI are introduced to design the parallel algorithm for building design matrix, establishing and solving normal equation, and the simulation results indicate that the parallel efficiency of building design matrix, establishing and solving normal equation can reach to 95%, 68%and 63% respectively. In addition, on the basis of GOCE simulated orbits and radial disturbance gravity gradient data(518 400 epochs in total, two earth gravity models truncated to degree and order 120, 240 are inversed, and the relative computation time and memory demand are only about 40 minutes and 7 hours, 290 MB and 1.57 GB respectively. Eventually, a simulation numerical calculation for earth gravity field model inversion with the simulation data, which has the equivalent noise level with GRACE and GOCE mission, is conducted. The accuracy of inversion model has a good consistent with current released model, and the combined mode can complement the spectral information of each individual mission, which indicates that the parallel algorithm in this paper can be applied to inverse the high truncated degree and order earth gravity model efficiently and stably.

  18. Detection of co-seismic earthquake gravity field signals using GRACE-like mission simulations

    Science.gov (United States)

    Sharifi, Mohammad Ali; Shahamat, Abolfazl

    2017-05-01

    After launching the GRACE satellite mission in 2002, the earth's gravity field and its temporal variations are measured with a closer inspection. Although these variations are mainly because of the mass transfer of land water storage, they can also happen due to mass movements related to some natural phenomena including earthquakes, volcanic eruptions, melting of polar ice caps and glacial isostatic adjustment. Therefore this paper shows which parameters of an earthquake are more sensitive to GRACE-Like satellite missions. For this purpose, the parameters of the Maule earthquake that occurred in recent years and Alaska earthquake that occurred in 1964 have been chosen. Then we changed their several parameters to serve our purpose. The GRACE-Like sensitivity is observed by using the simulation of the earthquakes along with gravity changes they caused, as well as using dislocation theory under a half space earth. This observation affects the various faulting parameters which include fault length, width, depth and average slip. These changes were therefore evaluated and the result shows that the GRACE satellite missions tend to be more sensitive to Width among the Length and Width, the other parameter is Dip variations than other parameters. This article can be useful to the upcoming scenario designers and seismologists in their quest to study fault parameters.

  19. Global detailed gravimetric geoid. [based on gravity model derived from satellite tracking and surface gravity data

    Science.gov (United States)

    Vincent, S.; Marsh, J. G.

    1973-01-01

    A global detailed gravimetric geoid has been computed by combining the Goddard Space Flight Center GEM-4 gravity model derived from satellite and surface gravity data and surface 1 deg-by-1 deg mean free air gravity anomaly data. The accuracy of the geoid is + or - 2 meters on continents, 5 to 7 meters in areas where surface gravity data are sparse, and 10 to 15 meters in areas where no surface gravity data are available. Comparisons have been made with the astrogeodetic data provided by Rice (United States), Bomford (Europe), and Mather (Australia). Comparisons have also been carried out with geoid heights derived from satellite solutions for geocentric station coordinates in North America, the Caribbean, Europe, and Australia.

  20. Mission Design of the Dutch-Chinese FAST Micro-Satellite Mission

    NARCIS (Netherlands)

    Maessen, D.C.; Guo, J.; Gill, E.; Laan, E.; Moon, S.; Zheng, G.T.

    2009-01-01

    The paper treats the mission design for the Dutch-Chinese FAST (Formation for Atmospheric Science and Technology demonstration) mission. The space segment of the 2.5 year mission consists out of two formation flying micro-satellites. During the mission, new technologies will be demonstrated and, usi

  1. Mission Design of the Dutch-Chinese FAST Micro-Satellite Mission

    NARCIS (Netherlands)

    Maessen, D.C.; Guo, J.; Gill, E.; Laan, E.; Moon, S.; Zheng, G.T.

    2009-01-01

    The paper treats the mission design for the Dutch-Chinese FAST (Formation for Atmospheric Science and Technology demonstration) mission. The space segment of the 2.5 year mission consists out of two formation flying micro-satellites. During the mission, new technologies will be demonstrated and, usi

  2. Gravity Fields and Interiors of the Saturnian Satellites

    Science.gov (United States)

    Rappaport, N. J.; Armstrong, J. W.; Asmar, Sami W.; Iess, L.; Tortora, P.; Somenzi, L.; Zingoni, F.

    2006-01-01

    This viewgraph presentation reviews the Gravity Science Objectives and accomplishments of the Cassini Radio Science Team: (1) Mass and density of icy satellites (2) Quadrupole field of Titan and Rhea (3) Dynamic Love number of Titan (4) Moment of inertia of Titan (in collaboration with the Radar Team) (5) Gravity field of Saturn. The proposed measurements for the extended tour are: (1) Quadrupole field of Enceladus (2) More accurate measurement of Titan k2 (3) Local gravity/topography correlations for Iapetus (4) Verification/disproof of "Pioneer anomaly".

  3. Earth's gravity field modelling based on satellite accelerations derived from onboard GPS phase measurements

    Science.gov (United States)

    Guo, X.; Ditmar, P.; Zhao, Q.; Klees, R.; Farahani, H. H.

    2017-09-01

    GPS data collected by satellite gravity missions can be used for extracting the long-wavelength part of the Earth's gravity field. We propose a new data processing method which makes use of the `average acceleration' approach to gravity field modelling. In this method, satellite accelerations are directly derived from GPS carrier phase measurements with an epoch-differenced scheme. As a result, no ambiguity solutions are needed and the systematic errors that do not change much from epoch to epoch are largely eliminated. The GPS data collected by the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite mission are used to demonstrate the added value of the proposed method. An analysis of the residual accelerations shows that accelerations derived in this way are more precise, with noise being reduced by about 20 and 5% at the cross-track component and the other two components, respectively, as compared to those based on kinematic orbits. The accelerations obtained in this way allow the recovery of the gravity field to a slightly higher maximum degree compared to the solution based on kinematic orbits. Furthermore, the gravity field solution has an overall better performance. Errors in spherical harmonic coefficients are smaller, especially at low degrees. The cumulative geoid height error is reduced by about 15 and 5% up to degree 50 and 150, respectively. An analysis in the spatial domain shows that large errors along the geomagnetic equator, which are caused by a high electron density coupled with large short-term variations, are substantially reduced. Finally, the new method allows for a better observation of mass transport signals. In particular, sufficiently realistic signatures of regional mass anomalies in North America and south-west Africa are obtained.

  4. Earth's gravity field modelling based on satellite accelerations derived from onboard GPS phase measurements

    Science.gov (United States)

    Guo, X.; Ditmar, P.; Zhao, Q.; Klees, R.; Farahani, H. H.

    2017-02-01

    GPS data collected by satellite gravity missions can be used for extracting the long-wavelength part of the Earth's gravity field. We propose a new data processing method which makes use of the `average acceleration' approach to gravity field modelling. In this method, satellite accelerations are directly derived from GPS carrier phase measurements with an epoch-differenced scheme. As a result, no ambiguity solutions are needed and the systematic errors that do not change much from epoch to epoch are largely eliminated. The GPS data collected by the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite mission are used to demonstrate the added value of the proposed method. An analysis of the residual accelerations shows that accelerations derived in this way are more precise, with noise being reduced by about 20 and 5% at the cross-track component and the other two components, respectively, as compared to those based on kinematic orbits. The accelerations obtained in this way allow the recovery of the gravity field to a slightly higher maximum degree compared to the solution based on kinematic orbits. Furthermore, the gravity field solution has an overall better performance. Errors in spherical harmonic coefficients are smaller, especially at low degrees. The cumulative geoid height error is reduced by about 15 and 5% up to degree 50 and 150, respectively. An analysis in the spatial domain shows that large errors along the geomagnetic equator, which are caused by a high electron density coupled with large short-term variations, are substantially reduced. Finally, the new method allows for a better observation of mass transport signals. In particular, sufficiently realistic signatures of regional mass anomalies in North America and south-west Africa are obtained.

  5. Electrostatic Accelerometer for the Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    Science.gov (United States)

    Perrot, Eddy; Boulanger, Damien; Christophe, Bruno; Foulon, Bernard; Liorzou, Françoise; Lebat, Vincent

    2014-05-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, that will produce an accurate model of the Earth's gravity field variation providing global climatic data during five year at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link, and optionally a laser link, measuring the inter-satellites distance variation. Non-uniformities in the distribution of the Earth's mass cause the distance between the two satellites to vary. This variation is measured to recover gravity, after subtracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing, manufacturing and testing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics - SUM - and the Front-End Electronic Unit - FEEU) and the Interface Control Unit. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained in a center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the measurement output of the accelerometer. The Preliminary Design Review was achieved successfully on November 2013. The FEEU Engineering Model is under test. Preliminary results on electronic unit will be compared with the expected performance. The integration of the SUM Engineering Model and the first ground levitation of the proof-mass will be presented. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with

  6. Sensitivity of gravity gradient sensors for future planetary missions

    Science.gov (United States)

    Sotin, C.; Gratton, R.; Flokstra, J.

    2003-04-01

    Gravity gradient sensors technology may provide important information on the internal structure of planets if they can accommodate the specific requirements for space exploration. The present study investigate the sensitivity required for these devices to answer questions such as the presence of oceans within icy satellites of the outer planets or the depth of mass anomalies on Mars and to characterize Mercury's gravity field. Europa, the second Galilean satellite, may have an ocean in between an outer ice I layer and the silicate core. Life is even envisaged at the interface between the core and the ocean. However, gravity measurements can provide a proof of such an ocean whereas the geological information and geophysical information obtained so far (magnetic field, gravity field) are not conclusive. We show that he sensitivity of the gradiometer must be equal to 100 mEtvos to determine the moment of inertia, 10 mEtvos to determine whether there is an ocean (value of k2), and less than 1 mEtvos if one wants to determine the depth of the ocean. In the case of Mars, the study describes the sensitivity required to determine the compensation depth of relief in agreement with the recent MGS data obtained by Doppler shift measurements. A preliminary study for Mercury shows that gradiometers could be very complementary to the usual radio science measurements in order to determine the depth of the core/mantle boundary and the structure of the lithosphere beneath impact craters.

  7. Cryofenix Mission- Study of Liquid Hydrogen Under Low Gravity

    Science.gov (United States)

    Leudiere, V.; Bianchi, S.; Lundin, M.; Andersson, G.; Loth, K.

    2015-09-01

    For the first time in Europe a cryogenic sounding rocket experiment was performed, canying liquid hydrogen. For this purpose was the well proven SSC Sounding rocket system MASER selected. The Cryofenix was launched from ESC, Esrange Space Center on February 22, 2015. The main objective for the mission was to study the global behaviour of liquid hydrogen under controlled gravity conditions. The controlled gravity during the mission was created by a cold gas thruster module. The experiment data obtained during the flight in terms of high resolution videos, pressure and temperature data are well in line with the expected results. The experiment data will support future development of liquid propellant management systems for Ariane.

  8. 基于激光干涉星间测距原理的下一代月球卫星重力测量计划需求论证%Demonstration of Requirement for Future Lunar Satellite Gravity Exploration Mission Based on Interferometric Laser Intersatellite Ranging Principle

    Institute of Scientific and Technical Information of China (English)

    郑伟; 许厚泽; 钟敏; 员美娟

    2011-01-01

    development trend and focus of deep space exploration in the 21st century. The accurate measurement of lunar gravitational field is an important part of international lunar exploration mission , which determines the optimum design of lunar probe orbit and the suitable selection of ideal landing point from manned apacecraft in the lunar surface. Firstly, the future twin-satellite program for the Gravity Recovery and Interior Laboratory ( GRAIL) lunar gravitational field exploration is introduced , including general overview , pivotal payloads ,and scientific objectives and research direction. Secondly. the executive suggestions including the feasible demonstration of lunar satellite tracking modes, the optimal selection of key payloads from lunar satellite, the optimized design of lunar satellite orbital parameters, and the previous implementation of simulation research are expatiated. ( 1 ) Because the measurement accuracy of the medium-long-wavelength lunar gravitational field ia high based on the Satellite-to-Satellite High-Low/Low-Low Tracking associated with the Doppler and Very Long Baseline Interferometry mode ( SST-HL/LL-Doppler-VLBI) ,its technical requirement is low , the lunar gravitational field can be quickly , low-costly and high-efficiently determined , the successful experiences of integrated system from the dedicated Earth' s gravity satellite - the Gravity Recovery and Climate Experiment ( GRACE) are used for reference, the requirement to orbital accuracy is low, and the farside signals of lunar gravitational field can be obtained effectively , it is optimal to use the SST-HL/LL-Doppler-VLBI mode in the future first lunar satellite gravitational exploration mission in China. (2) The high-accuracy key paylaads including the interferometric laser ranging system, compensating system of nonconservative force from lunar gravity satellite and Earth ' s Doppler-VLBI system should be developed in advance. (3) The optimal design of orbit altitude (50 ~ 100 km) and

  9. Advancements in satellite gravity gradient data for crustal studies

    NARCIS (Netherlands)

    Ebbing, J.; Bauman, J.; Fuchs, M.; Lieb, V.; Haagmans, R.; Meekes, J.A.C.; Abdul Fattah, R.

    2013-01-01

    In recent years, global gravity models, both based only on satellite data and from combination with terrestrial data, are increasingly available and particularly useful to construct regional models before more local interpretations on the exploration scale are carried out. Often it is challenging to

  10. Advancements in satellite gravity gradient data for crustal studies

    NARCIS (Netherlands)

    Ebbing, J.; Bauman, J.; Fuchs, M.; Lieb, V.; Haagmans, R.; Meekes, J.A.C.; Abdul Fattah, R.

    2013-01-01

    In recent years, global gravity models, both based only on satellite data and from combination with terrestrial data, are increasingly available and particularly useful to construct regional models before more local interpretations on the exploration scale are carried out. Often it is challenging to

  11. Progress on the use of satellite technology for gravity exploration

    Directory of Open Access Journals (Sweden)

    Yanwei Ding

    2015-07-01

    Full Text Available In this paper, the technological progress on Chinese gravity exploration satellites is presented. Novel features such as ultra-stable structure, high accurate thermal control, drag-free and attitude control, micro-thrusters, aerodynamic configuration, the ability to perform micro-vibration analyses, microwave ranging system and mass center trimmer are described.

  12. Monte Carlo Analysis as a Trajectory Design Driver for the Transiting Exoplanet Survey Satellite (TESS) Mission

    Science.gov (United States)

    Nickel, Craig; Parker, Joel; Dichmann, Don; Lebois, Ryan; Lutz, Stephen

    2016-01-01

    The Transiting Exoplanet Survey Satellite (TESS) will be injected into a highly eccentric Earth orbit and fly 3.5 phasing loops followed by a lunar flyby to enter a mission orbit with lunar 2:1 resonance. Through the phasing loops and mission orbit, the trajectory is significantly affected by lunar and solar gravity. We have developed a trajectory design to achieve the mission orbit and meet mission constraints, including eclipse avoidance and a 30-year geostationary orbit avoidance requirement. A parallelized Monte Carlo simulation was performed to validate the trajectory after injecting common perturbations, including launch dispersions, orbit determination errors, and maneuver execution errors. The Monte Carlo analysis helped identify mission risks and is used in the trajectory selection process.

  13. Space and Astrophysical Plasmas : High energy universe – Satellite missions

    Indian Academy of Sciences (India)

    Vinod Krishan

    2000-11-01

    A variety of satellite missions to observe the high energy universe are currently operating and some more with more versatility and capability are on the anvil. In this paper, after giving a brief introduction to the constituents of the high energy universe and the related plasma physical problems, general as well as specific features of the current and future x-ray and gamma-ray satellite missions are described.

  14. Designing Mission Operations for the Gravity Recovery and Interior Laboratory Mission

    Science.gov (United States)

    Havens, Glen G.; Beerer, Joseph G.

    2012-01-01

    NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission, to understand the internal structure and thermal evolution of the Moon, offered unique challenges to mission operations. From launch through end of mission, the twin GRAIL orbiters had to be operated in parallel. The journey to the Moon and into the low science orbit involved numerous maneuvers, planned on tight timelines, to ultimately place the orbiters into the required formation-flying configuration necessary. The baseline GRAIL mission is short, only 9 months in duration, but progressed quickly through seven very unique mission phases. Compressed into this short mission timeline, operations activities and maneuvers for both orbiters had to be planned and coordinated carefully. To prepare for these challenges, development of the GRAIL Mission Operations System began in 2008. Based on high heritage multi-mission operations developed by NASA's Jet Propulsion Laboratory and Lockheed Martin, the GRAIL mission operations system was adapted to meet the unique challenges posed by the GRAIL mission design. This paper describes GRAIL's system engineering development process for defining GRAIL's operations scenarios and generating requirements, tracing the evolution from operations concept through final design, implementation, and validation.

  15. Designing Mission Operations for the Gravity Recovery and Interior Laboratory Mission

    Science.gov (United States)

    Havens, Glen G.; Beerer, Joseph G.

    2012-01-01

    NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission, to understand the internal structure and thermal evolution of the Moon, offered unique challenges to mission operations. From launch through end of mission, the twin GRAIL orbiters had to be operated in parallel. The journey to the Moon and into the low science orbit involved numerous maneuvers, planned on tight timelines, to ultimately place the orbiters into the required formation-flying configuration necessary. The baseline GRAIL mission is short, only 9 months in duration, but progressed quickly through seven very unique mission phases. Compressed into this short mission timeline, operations activities and maneuvers for both orbiters had to be planned and coordinated carefully. To prepare for these challenges, development of the GRAIL Mission Operations System began in 2008. Based on high heritage multi-mission operations developed by NASA's Jet Propulsion Laboratory and Lockheed Martin, the GRAIL mission operations system was adapted to meet the unique challenges posed by the GRAIL mission design. This paper describes GRAIL's system engineering development process for defining GRAIL's operations scenarios and generating requirements, tracing the evolution from operations concept through final design, implementation, and validation.

  16. LARES succesfully launched in orbit: satellite and mission description

    CERN Document Server

    Paolozzi, Antonio

    2013-01-01

    On February 13th 2012, the LARES satellite of the Italian Space Agency (ASI) was launched into orbit with the qualification flight of the new VEGA launcher of the European Space Agency (ESA). The payload was released very accurately in the nominal orbit. The name LARES means LAser RElativity Satellite and summarises the objective of the mission and some characteristics of the satellite. It is, in fact, a mission designed to test Einstein's General Relativity Theory (specifically 'frame dragging' and Lense-Thirring effect). The satellite is passive and covered with optical retroreflectors that send back laser pulses to the emitting ground station. This allows accurate positioning of the satellite, which is important for measuring the very small deviations from Galilei-Newton's laws. In 2008, ASI selected the prime industrial contractor for the LARES system with a heavy involvement of the universities in all phases of the programme, from the design to the construction and testing of the satellite and separation...

  17. Parameter sensitivity in satellite-gravity-constrained geothermal modelling

    Science.gov (United States)

    Pastorutti, Alberto; Braitenberg, Carla

    2017-04-01

    The use of satellite gravity data in thermal structure estimates require identifying the factors that affect the gravity field and are related to the thermal characteristics of the lithosphere. We propose a set of forward-modelled synthetics, investigating the model response in terms of heat flow, temperature, and gravity effect at satellite altitude. The sensitivity analysis concerns the parameters involved, as heat production, thermal conductivity, density and their temperature dependence. We discuss the effect of the horizontal smoothing due to heat conduction, the superposition of the bulk thermal effect of near-surface processes (e.g. advection in ground-water and permeable faults, paleoclimatic effects, blanketing by sediments), and the out-of equilibrium conditions due to tectonic transients. All of them have the potential to distort the gravity-derived estimates.We find that the temperature-conductivity relationship has a small effect with respect to other parameter uncertainties on the modelled temperature depth variation, surface heat flow, thermal lithosphere thickness. We conclude that the global gravity is useful for geothermal studies.

  18. A university-based distributed satellite mission control network for operating professional space missions

    Science.gov (United States)

    Kitts, Christopher; Rasay, Mike

    2016-03-01

    For more than a decade, Santa Clara University's Robotic Systems Laboratory has operated a unique, distributed, internet-based command and control network for providing professional satellite mission control services for a variety of government and industry space missions. The system has been developed and is operated by students who become critical members of the mission teams throughout the development, test, and on-orbit phases of these missions. The mission control system also supports research in satellite control technology and hands-on student aerospace education. This system serves as a benchmark for its comprehensive nature, its student-centric nature, its ability to support NASA and industry space missions, and its longevity in providing a consistent level of professional services. This paper highlights the unique features of this program, reviews the network's design and the supported spacecraft missions, and describes the critical programmatic features of the program that support the control of professional space missions.

  19. Orbit Determination of the SELENE Satellites Using Multi-Satellite Data Types and Evaluation of SELENE Gravity Field Models

    Science.gov (United States)

    Goossens, S.; Matsumoto, K.; Noda, H.; Araki, H.; Rowlands, D. D.; Lemoine, F. G.

    2011-01-01

    The SELENE mission, consisting of three separate satellites that use different terrestrial-based tracking systems, presents a unique opportunity to evaluate the contribution of these tracking systems to orbit determination precision. The tracking data consist of four-way Doppler between the main orbiter and one of the two sub-satellites while the former is over the far side, and of same-beam differential VLBI tracking between the two sub-satellites. Laser altimeter data are also used for orbit determination. The contribution to orbit precision of these different data types is investigated through orbit overlap analysis. It is shown that using four-way and VLBI data improves orbit consistency for all satellites involved by reducing peak values in orbit overlap differences that exist when only standard two-way Doppler and range data are used. Including laser altimeter data improves the orbit precision of the SELENE main satellite further, resulting in very smooth total orbit errors at an average level of 18m. The multi-satellite data have also resulted in improved lunar gravity field models, which are assessed through orbit overlap analysis using Lunar Prospector tracking data. Improvements over a pre-SELENE model are shown to be mostly in the along-track and cross-track directions. Orbit overlap differences are at a level between 13 and 21 m with the SELENE models, depending on whether l-day data overlaps or I-day predictions are used.

  20. U.S. rainfall satellite missions in flux

    Science.gov (United States)

    Zielinski, Sarah

    NASA's Tropical Rainfall Measuring Mission (TRMM) received a reprieve in September when the agency decided to continue the mission until at least fiscal year 2009 and possibly until 2012. Earlier agency plans had called for discontinuing TRMM this year while the satellite still had enough fuel for a controlled re-entry.Despite the TRMM reprieve, however, the U.S. National Oceanic and Atmospheric Administration (NOAA) is already preparing for TRMM's replacement, the Global Precipitation Measurement (GPM) mission.

  1. Tests Results of the Electrostatic Accelerometer Flight Models for Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    Science.gov (United States)

    Perrot, E.; Boulanger, D.; Christophe, B.; Foulon, B.; Lebat, V.; Huynh, P. A.; Liorzou, F.

    2015-12-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, which will produce an accurate model of the Earth's gravity field variation providing global climatic data during five years at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link measuring the inter-satellites distance variation. Earth's mass distribution non-uniformities cause variations of the inter-satellite distance. This variation is measured to recover gravity, after subtracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing, manufacturing and testing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics - SUM - and the Front-End Electronic Unit - FEEU) and the Interface Control Unit - ICU. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained at the center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the output measurement of the accelerometer. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with micro-gravity pendulum bench on ground and with drops in ZARM catapult. The Critical Design Review was achieved successfully on September 2014. The Engineering Model (EM) was integrated and tested successfully, with ground levitation, drops, Electromagnetic Compatibility and thermal vacuum. The integration of the two Flight Models was done on July 2015. The

  2. Status of Electrostatic Accelerometer Development for Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    Science.gov (United States)

    Perrot, Eddy; Boulanger, Damien; Christophe, Bruno; Foulon, Bernard; Liorzou, Françoise; Lebat, Vincent; Huynh, Phuong-Anh

    2015-04-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, which will produce an accurate model of the Earth's gravity field variation providing global climatic data during five years at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link measuring the inter-satellites distance variation. Earth's mass distribution non-uniformities cause variations of the inter-satellite distance. This variation is measured to recover gravity, after subtracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing, manufacturing and testing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics - SUM - and the Front-End Electronic Unit - FEEU) and the Interface Control Unit - ICU. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained at the center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the measurement output of the accelerometer. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with micro-gravity pendulum bench on ground and with drops in ZARM catapult. The Critical Design Review was achieved successfully on September 2014. The Engineering Model (EM) was integrated and tested successfully, with ground levitation, drops, Electromagnetic Compatibility and thermal vacuum. The integration of the first Flight Model has begun on December 2014

  3. Reduction of ocean tide aliasing in the context of a next generation gravity field mission

    Science.gov (United States)

    Hauk, Markus; Daras, Ilias; Pail, Roland

    2017-04-01

    Ocean tide aliasing is currently one of the main limiting factors for temporal gravity field determination and the derivation of mass transport processes in the Earth system. This will be true even more for future gravity field missions with improved measurement technology, which cannot be fully exploited due to this dominant systematic error source. In several previous studies it has been shown that temporal aliasing, related to tidal and non-tidal sources, can be significantly reduced by double-pair formations, e.g., in a so-called Bender configuration, and its effects can be migrated to higher frequencies by an optimum orbit choice, especially the orbit altitude (Murböck et al. 2013). Improved processing strategies and extended parameter models should be able to further reduce the problem. Concerning non-tidal aliasing, it could be shown that the parameterization of short-period long-wavelength gravity field signals, the so-called Wiese approach, is a powerful method for aliasing reduction (Wiese et al. 2013), but it does not really work for the very short-period signals of ocean tides with mainly semi-diurnal and diurnal periods (Daras 2015). In this contribution, several methods dealing with the reduction of ocean tide aliasing are investigated both from a methodological and a numerical point of view. One of the promising strategies is the co-estimation of selected tidal constituents over long time periods, also considering the basic orbit frequencies of the satellites. These improved estimates for ocean tide signals can then be used in a second step as an enhanced de-aliasing product for the computation of short-period temporal gravity fields. From a number of theoretical considerations and numerical case-studies, recommendations for an optimum orbit selection with respect to reduction of ocean tide aliasing shall be derived for two main mission scenarios. The first one is a classical Bender configuration being composed of a (near-) polar and an inclined in

  4. The impact of using jason-1 and cryosat-2 geodetic mission altimetry for gravity field modeling

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Jain, Maulik; Knudsen, Per

    2016-01-01

    operating in a geodetic mission as part its end of life mission. In this presentation, we perform an investigation of the impact of the Cryosat-2 and Jason-1 geodetic missions on high resolution marine gravity field mapping through comparison with recent high quality marine gravity measured by the United...

  5. Probing gravity with the proposed MAGIA and ILN lunar missions.

    Science.gov (United States)

    Garattini, M.; Lops, C.; Dell'Agnello, S.; Boni, A.; Berardi, S.; Cantone, C.; Delle Monache, G. O.; Intaglietta, N.; Maiello, M.; Martini, M.; Patrizi, G.; Porcelli, L.; Tibuzzi, M.; Currie, D. G.; Vittori, R.; Bianco, G.; Murphy, T.; Coradini, A.; Dionisio, C.; March, R.; Bellettini, G.; Tauraso, R.

    MAGIA (Missione Altimetrica Gravimetrica GeochImica Lunare) is a mission approved by the Italian Space Agency (ASI) for Phase A study. Using a single large-diameter laser retroreflector, a large laser retroreflector array and an atomic clock onboard MAGIA, we propose to perform several fundamental physics and absolute positioning metrology experiments: VESPUCCI, an improved test of the gravitational redshift in the Earth-Moon system predicted by General Relativity; MoonLIGHT-P, a precursor test of a second generation Lunar Laser Ranging (LLR) payload for precision gravity Network (ILN). Future ILN geodetic nodes equipped with MoonLIGHT and the Apollo/Lunokhod retroreflectors will become the first realization of the International Moon Reference Frame (IMRF), the lunar analog of the ITRF (International Terrestrial Reference Frame).

  6. LCROSS: A High Return, Small Satellite Mission

    Science.gov (United States)

    Andrews, Daniel R.

    2010-01-01

    Early in 2006, the NASA Exploration Systems Mission Directorate (ESMD) held a competition for NASA Centers to propose innovative ideas for a secondary payload mission to launch with the Lunar Reconnaissance Orbiter (LRO) to the Moon. The successful proposal could cost no more than $80 million dollars (less was preferred), would have to be ready to launch with the LRO in 31 months, could weigh no more than 1000 kg (fuelled), and would be designated a risk-tolerant "Class D" mission. In effect, NASA was offering a fixed-price contract to the winning NASA team to stay within a cost and schedule cap by accepting an unusually elevated risk position. To address this Announcement of Opportunity to develop a cost-and-schedule-capped secondary payload mission to fly with LRO, NASA Ames Research Center (ARC) in Moffett Field, CA, USA embarked on a brainstorming effort termed "Blue Ice" in which a small team was asked to explore a number of mission scenarios that might have a good chance for success and still fit within the stated programmatic constraints. From this work, ARC developed and submitted six of the nineteen mission proposals received by ESMD from throughout the Agency, one of which was LCROSS - a collaborative effort between ARC and its industrial partner, Northrop-Grumman (NG) in Redondo Beach, CA, USA.

  7. High resolution gravity models combining terrestrial and satellite data

    Science.gov (United States)

    Rapp, Richard H.; Pavlis, Nikolaos K.; Wang, Yan M.

    1992-01-01

    Spherical harmonic expansions to degree 360 have been developed that combine satellite potential coefficient information, terrestrial gravity data, satellite altimeter information as a direct tracking data type and topographic information. These models define improved representations of the Earth's gravitational potential beyond that available from just satellite or terrestrial data. The development of the degree 360 models, however, does not imply a uniform accuracy in the determination of the gravity field as numerous geographic areas are devoid of terrestrial data or the resolution of such data is limited to, for example, 100 km. This paper will consider theoretical and numerical questions related to the combination of the various data types. Various models of the combination process are discussed with a discussion of various correction terms for the different models. Various sources of gravity data will be described. The new OSU91 360 model will be discussed with comparisons made to previous 360 models and to other potential coefficient models that are complete to degree 50. Future directions in high degree potential coefficient models will be discussed.

  8. Simulator Technology of the Gravity Probe-B Mission

    Science.gov (United States)

    Hipkins, David; Brumley, Robert; Ohshima, Yoshimi; Holmes, Thomas

    2007-04-01

    The Gravity Probe B mission relied on simulators extensively both in the development and operational phases. They played a critical role in the mission's overall success. The primary simulator was the Integrated Test Facility (ITF) built by Lockheed-Martin. This simulator was assembled to provide spacecraft dynamics simulation as well as flight software validation and verification. There were also subsystem simulators that played equally important roles. The gyroscope suspension system team developed and built a hardware-in-the-loop gyroscope simulator designed to be able to operate over 10 orders of magnitude in force domain. This simulator evolved during on-orbit operations into a state of the art drag-free simulator. Simulated sensors for the SQUID readout system, telescope readout system and even an artificial star to test the performance of the telescope optics were used extensively for qualification tests prior to launch. One of the more important lessons learned is for missions where the spacecraft to payload coupling becomes the greatest challenge, simulators of the future need to be designed with coupled interfaces and these simulators must be employed early in the design and build phase of the mission.

  9. Analysis of the Lunar Gravity Field by Using GL0660B Model and Its Effect on Lunar Satellite Orbit

    Directory of Open Access Journals (Sweden)

    HUANG Kunxue

    2016-07-01

    Full Text Available The lunar gravity field provides a way to research moon's evolution and probes the interior structure of the moon. It is an important factor influencing the lunar satellite precise orbit determination as well. The new lunar gravity model GL0660B from GRAIL mission dramatically improves the gravity spectrum and spectral ranges. Using the model GL0660B, it can be computed that the corresponding degree-wise RMS and correlation of topography, with which the quality of model GL0660B can be analyzed. Then different characters of the lunar gravity field comparing with other lunar gravity fields are analyzed. Besides, gravity anomaly distribution figures at different height of the models are given, and the character and difference of the lunar gravity models at different height are compared. In addition, lunar satellite orbit revolutionary at different height are modeled by GEODYN. The result shows that the trend of lunar satellite eccentricity changes is a complex and long cycle of change trend. It is different affected by the perturbation of the mascons of different height, which causes different changes of apolune, perilune and eccentricity.

  10. Offset of a Drag-Free Sensor from the Center of Gravity of Its Satellite

    Science.gov (United States)

    Starin, Scott R.

    2003-01-01

    The drag-free satellite is one that encloses a proof mass, shielding it from atmospheric drag and solar radiation pressure (SRP). By sensing the location of the proof mass in the body and using thrusters to force the spacecraft to follow the proof mass in a closed-loop fashion, the effects of drag and SRP may be eliminated from the spacecraft orbit. Thus, several benefits may be gained, including improved ephemeris propagation and reduced operational costs. The package including the proof mass and the location sensing equipment may be considered as a single sensor; if generalized, such a sensor could be manufactured and used more easily in satellite designs, similar to how current missions use, for example, rate gyros and magnetometers. The flight heritage of the technology has been such that the proof mass sensor is a primary facet of the mission, allowing it to dominate design considerations. In particular, this paper discusses the effects that may be expected if a generalized drag-free sensor is placed some distance away from the spacecraft center of gravity. The proof mass will follow a given gravitational orbit, and a separation from the spacecraft center of gravity places the spacecraft itself in a different orbit from the proof mass, requiring additional fuel just to maintain function of the drag- free sensor. Conclusions include some guiding principles for determining whether certain mission characteristics may restrict or preclude the use of drag-free sensors for that mission. These principles may be used both by mission planners considering drag-free missions and by hardware designers considering or pursuing the development of such generalized sensors.

  11. Flight results from the gravity-gradient-controlled RAE-1 satellite

    Science.gov (United States)

    Blanchard, D. L.

    1986-01-01

    The in-orbit dynamics of a large, flexible spacecraft has been modeled with a computer simulation, which was used for designing the control system, developing a deployment and gravity-gradient capture procedure, predicting the steady-state behavior, and designing a series of dynamics experiments for the Radio Astronomy Explorer (RAE) satellite. This flexible body dynamics simulator permits three-dimensional, large-angle rotation of the total spacecraft and includes effects of orbit eccentricity, thermal bending, solar pressure, gravitational accelerations, and the damper system. Flight results are consistent with the simulator predictions and are presented for the deployment and capture phases, the steady-state mission, and the dynamics experiments.

  12. The gravity field of the Saturnian satellites Enceladus and Dione

    Science.gov (United States)

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

    2012-12-01

    Enceladus and Dione are the innermost moons of the Saturnian system visited by the spacecraft Cassini for gravity investigations. The small surface gravity (0.11 and 0.23 m/s2 respectively for Enceladus and Dione), the short duration of the gravitational interaction and the small number of available flybys (three for Enceladus and just one for Dione) make the determination of their gravity field particularly challenging. In spite of these limitations, we have measured the low degree gravity field of both satellites with sufficient accuracy to draw preliminary geophysical conclusions. The estimation relied primarily on precise range rate data, whose accuracy reached 10 micron/s at 60 s integration times under favorable conditions. In order to disentangle the effects of the spacecraft orbit, the satellite orbit and the satellite gravity, tracking coverage is required not only across closest approach, but also days before and after the flyby. The dynamical model used for the fits includes all relevant gravitational perturbations and the main non-gravitational accelerations (Cassini RTG's anisotropic thermal emission, solar radiation pressure). In addition to the gravity field coefficients a correction to the orbit of the spacecraft and the satellites was also estimated. The first and so far only Dione's flyby with tracking at closest approach occurred on December 12, 2011, at an altitude of 99 km. (A second gravity flyby is scheduled in 2015.) Although the low solar elongation angle caused a significant increase of the plasma noise in Doppler data, the low spacecraft altitude at closest approach and the otherwise favorable geometry allowed an estimation of the harmonic coefficients J2 and C22 to a relative accuracy below 2%. We have produced, in addition to an unconstrained estimate, a second solution where the quadrupole field is constrained by the requirement of hydrostaticity. Doppler residuals are unbiased and consistent with the expected noise in both cases. When

  13. LCROSS Lunar Impactor - Lessons Learned from a Small Satellite Mission

    Science.gov (United States)

    Andrews, Daniel R.

    2010-01-01

    The Lunar CRater Observation and Sensing Satellite (LCROSS) launched with the Lunar Reconnaissance Orbiter (LRO) on June 18, 2009. While the science function of the LCROSS mission was to determine the presence of water-ice in a permanently-shadowed crater on the moon, the operational purpose was to be a pioneer for future low-cost, risk-tolerant small satellite NASA missions. Recent strategic changes at the Agency level have only furthered the importance of small satellite missions. NASA Ames Research Center and its industry partner, Northrop-Grumman, initiated this spacecraft project two-years after its co-manifest mission had started, with less than one-fifth the budget. With a $79M total cost cap (including operations and reserves) and 31-months until launch, LCROSS needed a game-changing approach to be successful. At the LCROSS Confirmation Review, the ESMD Associate Administrator asked the Project team to keep a close record of lessons learned through the course of the mission and share their findings with the Agency at the end of the mission. This paper summarizes the Project, the mission, its risk position, and some of the more notable lessons learned.

  14. Nano-Satellite Secondary Spacecraft on Deep Space Missions

    Science.gov (United States)

    Klesh, Andrew T.; Castillo-Rogez, Julie C.

    2012-01-01

    NanoSat technology has opened Earth orbit to extremely low-cost science missions through a common interface that provides greater launch accessibility. They have also been used on interplanetary missions, but these missions have used one-off components and architectures so that the return on investment has been limited. A natural question is the role that CubeSat-derived NanoSats could play to increase the science return of deep space missions. We do not consider single instrument nano-satellites as likely to complete entire Discovery-class missions alone,but believe that nano-satellites could augment larger missions to significantly increase science return. The key advantages offered by these mini-spacecrafts over previous planetary probes is the common availability of advanced subsystems that open the door to a large variety of science experiments, including new guidance, navigation and control capabilities. In this paper, multiple NanoSat science applications are investigated, primarily for high risk/high return science areas. We also address the significant challenges and questions that remain as obstacles to the use of nano-satellites in deep space missions. Finally, we provide some thoughts on a development roadmap toward interplanetary usage of NanoSpacecraft.

  15. Gravity field estimation from future space missions - TOPEX/POSEIDON, Gravity Probe B, and ARISTOTELES

    Science.gov (United States)

    Pavlis, Erricos C.

    Accurate knowledge of the gravity field is a firm requirement in any study of Planet Earth. Space techniques have so far demonstrated their superiority in the global mapping of the gravity field based on ground tracking and altimeter data mostly. Numerical and analytical simulation studies of the upcoming geophysically relevant missions that will most likely carry GPS receivers, indicate significant improvements in the accuracy as well as the resolution of the gravity field. TOPEX will improve by some two orders of magnitude the long wavelength part (to degree about 20), while GP-B will contribute in the long as well as medium wavelength part of the spectrum (up to degree about 60). The gradiometer measurements on ARISTOTELES will contribute in the medium and short wavelength regions (from degree 30 up); GPS tracking of the spacecraft though will provide additional information for the long wavelength gravity and will help resolve it to accuracies comparable to those obtained from GP-B. With the mean rms coefficient error per degree kept below 10 exp -10, geophysical signals such as the post-glacial rebound, tidal variations, and secular and periodic variations of the zonal field rise above the noise level and become readily observable processes.

  16. Electrostatic Accelerometer for the Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    Science.gov (United States)

    Lebat, V.; Foulon, B.; Christophe, B.

    2013-12-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, that will produce an accurate model of the Earth's gravity field variation providing global climatic data during five year at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link measuring the inter-satellites distance variation. Non-uniformities in the distribution of the Earth's mass cause the distance between the two satellites to vary. This variation is measured to recover gravity, after subtracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing, manufacturing and testing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics and the Front-End Electronic Unit) and the Interface Control Unit. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained in a center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the measurement output of the accelerometer. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with micro-gravity pendulum bench and with drops in ZARM catapult. Besides, a thermal stability is needed for the accelerometer core and front-end electronics to avoid bias and scale factor variation, and reached by a thermal box designed by Astrium, spacecraft manufacturer. The accelerometers are designed to endure the launch vibrations and the thermal environment at

  17. High-degree Gravity Models from GRAIL Primary Mission Data

    Science.gov (United States)

    Lemoine, Frank G.; Goossens, Sander J.; Sabaka, Terence J.; Nicholas, Joseph B.; Mazarico, Erwan; Rowlands, David D.; Loomis, Bryant D.; Chinn, Douglas S.; Caprette, Douglas S.; Neumann, Gregory A.; Smith, David E.; Zuber, Maria T.

    2013-01-01

    We have analyzed Ka?band range rate (KBRR) and Deep Space Network (DSN) data from the Gravity Recovery and Interior Laboratory (GRAIL) primary mission (1 March to 29 May 2012) to derive gravity models of the Moon to degree 420, 540, and 660 in spherical harmonics. For these models, GRGM420A, GRGM540A, and GRGM660PRIM, a Kaula constraint was applied only beyond degree 330. Variance?component estimation (VCE) was used to adjust the a priori weights and obtain a calibrated error covariance. The global root?mean?square error in the gravity anomalies computed from the error covariance to 320×320 is 0.77 mGal, compared to 29.0 mGal with the pre?GRAIL model derived with the SELENE mission data, SGM150J, only to 140×140. The global correlations with the Lunar Orbiter Laser Altimeter?derived topography are larger than 0.985 between l = 120 and 330. The free?air gravity anomalies, especially over the lunar farside, display a dramatic increase in detail compared to the pre?GRAIL models (SGM150J and LP150Q) and, through degree 320, are free of the orbit?track?related artifacts present in the earlier models. For GRAIL, we obtain an a posteriori fit to the S?band DSN data of 0.13 mm/s. The a posteriori fits to the KBRR data range from 0.08 to 1.5 micrometers/s for GRGM420A and from 0.03 to 0.06 micrometers/s for GRGM660PRIM. Using the GRAIL data, we obtain solutions for the degree 2 Love numbers, k20=0.024615+/-0.0000914, k21=0.023915+/-0.0000132, and k22=0.024852+/-0.0000167, and a preliminary solution for the k30 Love number of k30=0.00734+/-0.0015, where the Love number error sigmas are those obtained with VCE.

  18. Sensor Calibration in Support for NOAA's Satellite Mission

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Sensor calibration, including its definition, purpose, traceability options, methodology, complexity, and importance, is examined in this paper in the context of supporting NOAA's satellite mission. Common understanding of sensor calibration is essential for the effective communication among sensor vendors,calibration scientists, satellite operators, program managers, and remote sensing data users, who must cooperate to ensure that a nation's strategic investment in a sophisticated operational environmental satellite system serves the nation's interest and enhances the human lives around the world. Examples of calibration activities at NOAA/NESDIS/ORA are selected to further illustrate these concepts and to demonstrate the lessons learned from the past experience.

  19. Single pass Doppler positioning for Search and Rescue satellite missions

    Science.gov (United States)

    Schmid, P. E.; Vonbun, F. O.; Lynn, J. J.

    1976-01-01

    This paper describes the implementation of beacon location experiments involving the NASA Nimbus-6 and the Amateur Satellite Corporation (AMSAT) Oscar-6 and Oscar-7 spacecraft. The purpose of these experiments is to demonstrate the feasibility of determining the geographical location of a low power VHF 'distress beacon' via satellite. Doppler data collected during satellite passes is reduced in a mini-computer by means of a simple algorithm resulting in the simultaneous recovery of the unknown receiver coordinates and the unknown Doppler bias frequency. Results indicate point positioning to within a few kilometers - which is within the required accuracies for the positioning of downed aircraft for Search/Rescue missions.

  20. Efficient mission control for the 48-satellite Globalstar Constellation

    Science.gov (United States)

    Smith, Dan

    1994-11-01

    The Globalstar system is being developed by Globalstar, Limited Partnership and will utilize 48 satellites in low earth orbit (See Figure 1) to create a world-wide mobile communications system consistent with Vice President Gore's vision of a Global Information Infrastructure. As a large long term commercial system developed by a newly formed organization, Globalstar provides an excellent opportunity to explore innovative solutions for highly efficient satellite command and control. Design and operational concepts being developed are unencumbered by existing physical and organizational infrastructures. This program really is 'starting with a clean sheet of paper'. Globalstar operations challenges can appear enormous. Clearly, assigning even a single person around the clock to monitor and control each satellite is excessive for Globalstar (it would require a staff of 200] . Even with only a single contact per orbit per satellite, data acquisitions will start or stop every 45 seconds] Although essentially identical, over time the satellites will develop their own 'personalities'and will re quire different data calibrations and levels of support. This paper discusses the Globalstar system and challenges and presents engineering concepts, system design decisions, and operations concepts which address the combined needs and concerns of satellite, ground system, and operations teams. Lessons from past missions have been applied, organizational barriers broken, partnerships formed across the mission segments, and new operations concepts developed for satellite constellation management. Control center requirements were then developed from the operations concepts.

  1. Gravity field models derived from the second degree radial derivatives of the GOCE mission: a case study

    Directory of Open Access Journals (Sweden)

    Alexander N. Marchenko

    2017-01-01

    Full Text Available The GOCE satellite mission is one of the main achievements of the satellite geodesy for the Earth’s gravitational field recovery. Three different approaches have been developed for the estimation of harmonic coefficients from gradiometry data measured on board of GOCE-satellite. In this paper a special version of the space-wise method based on the second method of Neumann for fast determination of the harmonic coefficients Cnm, Snm of the Earth’s gravitational potential is given based on the radial gravity gradients of the EGG_TRF_2 product, except of two polar gaps filled by radial gradients from the EGM2008 gravity model. In the pre-processing stage GOCE-based second degree radial derivatives were averaged to the regular grid through Kalman static filter with additional Gaussean smoothing of residual radial derivatives. All computations are made by iterations. As the first step the determination of the preliminary NULP-01S model up to degree/order 220 derived from the Gaussean grid of the GOCE radial derivatives with respect to the WGS-84 reference field was developed based only one of the radial gradients EGG_TRF_2 in the EFRF-frame. In the second iteration the same algorithm is applied to build the NULP-02S gravity field model up to degree/order 250 using the same Gaussean grid with respect to the NULP-01S reference field. The NULP-02S model was verified by means of applying various approaches for the construction of the gridded gravity anomalies and geoid heights in the Black sea area using processing of datasets from six altimetry satellite missions. Comparison of different models with GNSS-levelling data in the USA area demonstrates the independent verification of achieved accuracy of the constructed NULP-02S Earth’s gravity field model.

  2. Contribution of satellite laser ranging to combined gravity field models

    Science.gov (United States)

    Maier, A.; Krauss, S.; Hausleitner, W.; Baur, O.

    2012-02-01

    In the framework of satellite-only gravity field modeling, satellite laser ranging (SLR) data is typically exploited to recover long-wavelength features. This contribution provides a detailed discussion of the SLR component of GOCO02S, the latest release of combined models within the GOCO series. Over a period of five years (January 2006 to December 2010), observations to LAGEOS-1, LAGEOS-2, Ajisai, Stella, and Starlette were analyzed. We conducted a series of closed-loop simulations and found that estimating monthly sets of spherical harmonic coefficients beyond degree five leads to exceedingly ill-posed normal equation systems. Therefore, we adopted degree five as the spectral resolution for real data analysis. We compared our monthly coefficient estimates of degree two with SLR and Gravity Recovery and Climate Experiment (GRACE) time series provided by the Center for Space Research (CSR) at Austin, Texas. Significant deviations in C20 were noted between SLR and GRACE; the agreement is better for the non-zonal coefficients. Fitting sinusoids together with a linear trend to our C20 time series yielded a rate of (-1.75 ± 0.6) × 10-11/yr; this drift is equivalent to a geoid change from pole to equator of 0.35 ± 0.12 mm/yr or an apparent Greenland mass loss of 178.5 ± 61.2 km3/yr. The mean of all monthly solutions, averaged over the five-year period, served as input for the satellite-only model GOCO02S. The contribution of SLR to the combined gravity field model is highest for C20, and hence is essential for the determination of the Earth's oblateness.

  3. Merging of airborne gravity and gravity derived from satellite altimetry: Test cases along the coast of greenland

    DEFF Research Database (Denmark)

    Olesen, Arne Vestergaard; Andersen, Ole Baltazar; Tscherning, C.C.

    2002-01-01

    for the use of gravity data especially, when computing geoid models in coastal regions. The presence of reliable marine gravity data for independent control offers an opportunity to study procedures for the merging of airborne and satellite data around Greenland. Two different merging techniques, both based...... on collocation, are investigated in this paper. Collocation offers a way of combining the individual airborne gravity observation with either the residual geoid observations derived from satellite altimetry or with gravity derived from these data using the inverse Stokes method implemented by Fast Fourier...

  4. Level-2 product generation for the Swarm satellite constellation mission

    DEFF Research Database (Denmark)

    Olsen, Poul Erik Holmdahl; Tøffner-Clausen, Lars; Olsen, Nils

    In order to take advantage of the unique constellation aspect of ESA's Swarm constellation mission, considerably advanced data analysis tools have been developed. The Swarm ESL/SCARF (Satellite Constellation Application and Research Facility), a consortium of several research institutions, derives...

  5. Level-2 product generation for the Swarm satellite constellation mission

    DEFF Research Database (Denmark)

    Olsen, Poul Erik Holmdahl; Tøffner-Clausen, Lars; Olsen, Nils

    In order to take advantage of the unique constellation aspect of ESA's Swarm constellation mission, considerably advanced data analysis tools have been developed. The Swarm ESL/SCARF (Satellite Constellation Application and Research Facility), a consortium of several research institutions, derives...

  6. Inversion of marine gravity anomalies over southeastern China seas from multi-satellite altimeter vertical deflections

    Science.gov (United States)

    Zhang, Shengjun; Sandwell, David T.; Jin, Taoyong; Li, Dawei

    2017-02-01

    The accuracy and resolution of marine gravity field derived from satellite altimetry mainly depends on the range precision and dense spatial distribution. This paper aims at modeling a regional marine gravity field with improved accuracy and higher resolution (1‧ × 1‧) over Southeastern China Seas using additional data from CryoSat-2 as well as new data from AltiKa. Three approaches are used to enhance the precision level of satellite-derived gravity anomalies. Firstly we evaluate a suite of published retracking algorithms and find the two-step retracker is optimal for open ocean waveforms. Secondly, we evaluate the filtering and resampling procedure used to reduce the full 20 or 40 Hz data to a lower rate having lower noise. We adopt a uniform low-pass filter for all altimeter missions and resample at 5 Hz and then perform a second editing based on sea surface slope estimates from previous models. Thirdly, we selected WHU12 model to update the corrections provided in geophysical data record. We finally calculated the 1‧ × 1‧ marine gravity field model by using EGM2008 model as reference field during the remove/restore procedure. The root mean squares of the discrepancies between the new result and DTU10, DTU13, V23.1, EGM2008 are within the range of 1.8- 3.9 mGal, while the verification with respect to shipboard gravity data shows that the accuracy of the new result reached a comparable level with DTU13 and was slightly superior to V23.1, DTU10 and EGM2008 models. Moreover, the new result has a 2 mGal better accuracy over open seas than coastal areas with shallow water depth.

  7. India's mission to Mars cost less than the movie Gravity: Multidimensional View in Engineering Education

    Science.gov (United States)

    Rani, Meenu; Kumar, Pawan; Vandana, Vandana

    2016-07-01

    Over the years, Mars has been the centre of attraction for science fiction writers, Hollywood movie makers, astrologers, astronomers and the scientific community. For scientists and technologists, Mars continues to be an enigma. This is essentially because even tough humans have dreamt for long about human colonisation of Mars. Indian space programme had a very humble beginning during the early 1960s. India launched its first satellite in 1975 with assistance from the erstwhile USSR. India achieved the status of space-faring nation2 by 1980, and by the end of 2014 has launched around 75 satellites. India has become the first nation to reach Mars on its maiden attempt after its Mars Orbiter Mission completed its 10-month journey and successfully entered the Red Planet's orbit. The Mars Orbiter Mission, a low-cost 74 million project, blasted off from Earth on November 5, 2013, aboard an Indian Polar Satellite Launch Vehicle. At its initial stage, the rocket booster placed the probe into Earth's orbit before the craft fired the engines to break free of Earth's gravity en route to Mars. This is India's first mission into such deep space to search for evidence of life on the Red Planet. But the mission's primary objective is technological-if successful, the country will be joining an elite club of nations: the United States, Russia and Europe. India is becoming known for low-cost innovation in diverse fields such as healthcare and education. The technological capability being demonstrated and the knowledge gained from the operations of the mission will be invaluable in future developments and also in the training of the flight operations and mission control staff. All of this capability can be carried forward to future launches and operations. The sustained presence of methane observed by previous missions suggests that an active production mechanism is at work, most likely tectonic in nature, although there are some suggestions that it may point to a biological origin

  8. A gravity gradient stabilized solar power satellite design

    Science.gov (United States)

    Bowden, M. L.

    1981-01-01

    The concept of a solar power satellite (SPS) is reviewed, and a design proposed for such a satellite taking advantage of solar radiation pressure and gravity gradient forces to eliminate much of the structure from the baseline configuration. The SPS design consists of a solar cell array lying in the orbital plane and a free floating mirror above to reflect sunlight down onto it. The structural modes of the solar cell array are analyzed and found to be well within control limitations. Preliminary calculations concerning the free floating mirror and its position-keeping propellant requirements are also performed. A numerical example is presented, which shows that, even in terms of mass only, this configuration is a competitive design when compared to the conventional Department of Energy reference design. Other advantages, such as easier assembly in orbit, lower position-keeping propellant requirements, possibilities for decreasing necessary solar cell area, and longer solar cell life, may make this design superior.

  9. Mapping the mass distribution of Earth's mantle using satellite-derived gravity gradients

    Science.gov (United States)

    Panet, Isabelle; Pajot-Métivier, Gwendoline; Greff-Lefftz, Marianne; Métivier, Laurent; Diament, Michel; Mandea, Mioara

    2014-02-01

    The dynamics of Earth's mantle are not well known. Deciphering mantle flow patterns requires an understanding of the global distribution of mantle density. Seismic tomography has been used to derive mantle density distributions, but converting seismic velocities into densities is not straightforward. Here we show that data from the GOCE (Gravity field and steady-state Ocean Circulation Explorer) mission can be used to probe our planet's deep mass structure. We construct global anomaly maps of the Earth's gravitational gradients at satellite altitude and use a sensitivity analysis to show that these gravitational gradients image the geometry of mantle mass down to mid-mantle depths. Our maps highlight north-south-elongated gravity gradient anomalies over Asia and America that follow a belt of ancient subduction boundaries, as well as gravity gradient anomalies over the central Pacific Ocean and south of Africa that coincide with the locations of deep mantle plumes. We interpret these anomalies as sinking tectonic plates and convective instabilities between 1,000 and 2,500km depth, consistent with seismic tomography results. Along the former Tethyan Margin, our data also identify an east-west-oriented mass anomaly likely in the upper mantle. We suggest that by combining gravity gradients with seismic and geodynamic data, an integrated dynamic model for Earth can be achieved.

  10. On the spectral combination of satellite gravity model, terrestrial and airborne gravity data for local gravimetric geoid computation

    Science.gov (United States)

    Jiang, Tao; Wang, Yan Ming

    2016-12-01

    One of the challenges for geoid determination is the combination of heterogeneous gravity data. Because of the distinctive spectral content of different data sets, spectral combination is a suitable candidate for its solution. The key to have a successful combination is to determine the proper spectral weights, or the error degree variances of each data set. In this paper, the error degree variances of terrestrial and airborne gravity data at low degrees are estimated by the aid of a satellite gravity model using harmonic analysis. For higher degrees, the error covariances are estimated from local gravity data first, and then used to compute the error degree variances. The white and colored noise models are also used to estimate the error degree variances of local gravity data for comparisons. Based on the error degree variances, the spectral weights of satellite gravity models, terrestrial and airborne gravity data are determined and applied for geoid computation in Texas area. The computed gravimetric geoid models are tested against an independent, highly accurate geoid profile of the Geoid Slope Validation Survey 2011 (GSVS11). The geoid computed by combining satellite gravity model GOCO03S and terrestrial (land and DTU13 altimetric) gravity data agrees with GSVS11 to ±1.1 cm in terms of standard deviation along a line of 325 km. After incorporating the airborne gravity data collected at 11 km altitude, the standard deviation is reduced to ±0.8 cm. Numerical tests demonstrate the feasibility of spectral combination in geoid computation and the contribution of airborne gravity in an area of high quality terrestrial gravity data. Using the GSVS11 data and the spectral combination, the degree of correctness of the error spectra and the quality of satellite gravity models can also be revealed.

  11. GRACE Mission Design: Impact of Uncertainties in Disturbance Environment and Satellite Force Models

    Science.gov (United States)

    Mazanek, Daniel D.; Kumar, Renjith R.; Seywald, Hans; Qu, Min

    2000-01-01

    The Gravity Recovery and Climate Experiment (GRACE) primary mission will be performed by making measurements of the inter-satellite range change between two co-planar, low altitude, near-polar orbiting satellites. Understanding the uncertainties in the disturbance environment, particularly the aerodynamic drag and torques, is critical in several mission areas. These include an accurate estimate of the spacecraft orbital lifetime, evaluation of spacecraft attitude control requirements, and estimation of the orbital maintenance maneuver frequency necessitated by differences in the drag forces acting on both satellites. The FREEMOL simulation software has been developed and utilized to analyze and suggest design modifications to the GRACE spacecraft. Aerodynamic accommodation bounding analyses were performed and worst-case envelopes were obtained for the aerodynamic torques and the differential ballistic coefficients between the leading and trailing GRACE spacecraft. These analyses demonstrate how spacecraft aerodynamic design and analysis can benefit from a better understanding of spacecraft surface accommodation properties, and the implications for mission design constraints such as formation spacing control.

  12. Merging of airborne gravity and gravity derived from satellite altimetry: Test cases along the coast of greenland

    DEFF Research Database (Denmark)

    Olesen, Arne Vestergaard; Andersen, Ole Baltazar; Tscherning, C.C.

    2002-01-01

    The National Survey and Cadastre - Denmark (KMS) has for several years produced gravity anomaly maps over the oceans derived from satellite altimetry. During the last four years, KMS has also conducted airborne gravity surveys along the coast of Greenland dedicated to complement the existing onsh...

  13. Mission design for the infrared astronomical satellite /IRAS/

    Science.gov (United States)

    Lundy, S. A.; Mclaughlin, W. I.; Pouw, A.

    1979-01-01

    IRAS, a joint United States, Netherlands, United Kingdom astronomical satellite, is scheduled to be launched early in 1981 with the purpose of completing an all-sky survey in the infrared wavelengths from 8 to 120 microns and to observe objects of special interest. The mission design is driven by thermal constraints primarily determined by the Sun and Earth; the orbit and survey strategy must be chosen so as to satisfy the mission requirements before the cryogenic system is depleted of its liquid helium. Computer graphics help the designer choose valid survey strategies and evaluate resulting sky coverage.

  14. The Next Landsat Satellite: The Landsat Data Continuity Mission

    Science.gov (United States)

    Rons, James R.; Dwyer, John L.; Barsi, Julia A.

    2012-01-01

    The Landsat program is one of the longest running satellite programs for Earth observations from space. The program was initiated by the launch of Landsat 1 in 1972. Since then a series of six more Landsat satellites were launched and at least one of those satellites has been in operations at all times to continuously collect images of the global land surface. The Department of Interior (DOI) U.S. Geological Survey (USGS) preserves data collected by all of the Landsat satellites at their Earth Resources Observation and Science (EROS) Center in Sioux Falls, South Dakota. This 40-year data archive provides an unmatched record of the Earth's land surface that has undergone dramatic changes in recent decades due to the increasing pressure of a growing population and advancing technologies. EROS provides the ability for anyone to search the archive and order digital Landsat images over the internet for free. The Landsat data are a public resource for observing, characterizing, monitoring, trending, and predicting land use change over time providing an invaluable tool for those addressing the profound consequences of those changes to society. The most recent launch of a Landsat satellite occurred in 1999 when Landsat 7 was placed in orbit. While Landsat 7 remains in operation, the National Aeronautics and Space Administration (NASA) and the DOI/ USGS are building its successor satellite system currently called the Landsat Data Continuity Mission (LDCM). NASA has the lead for building and launching the satellite that will carry two Earth-viewing instruments, the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS). The OLI will take images that measure the amount of sunlight reflected by the land surface at nine wavelengths of light with three of those wavelengths beyond the range of human vision. T1RS will collect coincident images that measure light emitted by the land surface as a function of surface temperature at two longer wavelengths well beyond the

  15. A Battery Certification Testbed for Small Satellite Missions

    Science.gov (United States)

    Cameron, Zachary; Kulkarni, Chetan S.; Luna, Ali Guarneros; Goebel, Kai; Poll, Scott

    2015-01-01

    A battery pack consisting of standard cylindrical 18650 lithium-ion cells has been chosen for small satellite missions based on previous flight heritage and compliance with NASA battery safety requirements. However, for batteries that transit through the International Space Station (ISS), additional certification tests are required for individual cells as well as the battery packs. In this manuscript, we discuss the development of generalized testbeds for testing and certifying different types of batteries critical to small satellite missions. Test procedures developed and executed for this certification effort include: a detailed physical inspection before and after experiments; electrical cycling characterization at the cell and pack levels; battery-pack overcharge, over-discharge, external short testing; battery-pack vacuum leak and vibration testing. The overall goals of these certification procedures are to conform to requirements set forth by the agency and identify unique safety hazards. The testbeds, procedures, and experimental results are discussed for batteries chosen for small satellite missions to be launched from the ISS.

  16. The next Landsat satellite; the Landsat Data Continuity Mission

    Science.gov (United States)

    Irons, James R.; Dwyer, John L.; Barsi, Julia A.

    2012-01-01

    The National Aeronautics and Space Administration (NASA) and the Department of Interior United States Geological Survey (USGS) are developing the successor mission to Landsat 7 that is currently known as the Landsat Data Continuity Mission (LDCM). NASA is responsible for building and launching the LDCM satellite observatory. USGS is building the ground system and will assume responsibility for satellite operations and for collecting, archiving, and distributing data following launch. The observatory will consist of a spacecraft in low-Earth orbit with a two-sensor payload. One sensor, the Operational Land Imager (OLI), will collect image data for nine shortwave spectral bands over a 185 km swath with a 30 m spatial resolution for all bands except a 15 m panchromatic band. The other instrument, the Thermal Infrared Sensor (TIRS), will collect image data for two thermal bands with a 100 m resolution over a 185 km swath. Both sensors offer technical advancements over earlier Landsat instruments. OLI and TIRS will coincidently collect data and the observatory will transmit the data to the ground system where it will be archived, processed to Level 1 data products containing well calibrated and co-registered OLI and TIRS data, and made available for free distribution to the general public. The LDCM development is on schedule for a December 2012 launch. The USGS intends to rename the satellite "Landsat 8" following launch. By either name a successful mission will fulfill a mandate for Landsat data continuity. The mission will extend the almost 40-year Landsat data archive with images sufficiently consistent with data from the earlier missions to allow long-term studies of regional and global land cover change.

  17. Gravity Recovery and Interior Laboratory (GRAIL): Extended Mission and End-Game Status

    Science.gov (United States)

    Zuber, Maria T.; Smith, David E.; Wieczorek, Mark A.; Williams, James G.; Andrews-Hanna, Jeffrey C.; Head, James W.; Kiefer, Walter S.; Matsuyama, Isamu; McGovern, Patrick J.; Nimmo, Francis; Stubbs, Christopher; Weber, Renee; Asmar, Sami W.; Goossens, Sander J.; Kruizinga, Gerhard; Mazarico, Erwan; Park, Ryan S.; Yuan, Dah-Ning; Konopliv, Alexander S.; Lemoine, Frank G.; Melosh, H. Jay; Neumann, Gregory A.; Phillips, Roger J.; Solomon, Sean C.; Watkins, Michael M.

    2013-01-01

    The Gravity Recovery and Interior Laboratory (GRAIL) [1], NASA s eleventh Discovery mission, successfully executed its Primary Mission (PM) in lunar orbit between March 1, 2012 and May 29, 2012. GRAIL s Extended Mission (XM) initiated on August 30, 2012 and was successfully completed on December 14, 2012. The XM provided an additional three months of gravity mapping at half the altitude (23 km) of the PM (55 km), and is providing higherresolution gravity models that are being used to map the upper crust of the Moon in unprecedented detail.

  18. Geodynamics implication of GPS and satellite altimeter and gravity observations to the Eastern Mediterranean

    Directory of Open Access Journals (Sweden)

    Khaled H. Zahran

    2012-06-01

    Results show important zones of mass discontinuity in this region correlated with the seismological activities and temporal gravity variations agree with the crustal deformation obtained from GPS observations. The current study indicates that satellite gravity data is a valuable source of data in understanding the geodynamical behavior of the studied region and that satellite gravity data is an important contemporary source of data in the geodynamical studies.

  19. Mission concepts and operations for asteroid mitigation involving multiple gravity tractors

    Science.gov (United States)

    Foster, Cyrus; Bellerose, Julie; Mauro, David; Jaroux, Belgacem

    2013-09-01

    The gravity tractor concept is a proposed method to deflect an imminent asteroid impact through gravitational tugging over a time scale of years. In this study, we present mission scenarios and operational considerations for asteroid mitigation efforts involving multiple gravity tractors. We quantify the deflection performance improvement provided by a multiple gravity tractor campaign and assess its sensitivity to staggered launches. We next explore several proximity operation strategies to accommodate multiple gravity tractors at a single asteroid including formation-flying and mechanically-docked configurations. Finally, we utilize 99942 Apophis as an illustrative example to assess the performance of a multiple gravity tractor campaign.

  20. Observing coseismic gravity change from the Japan Tohoku-Oki 2011 earthquake with GOCE gravity gradiometry

    NARCIS (Netherlands)

    Fuchs, M.J.; Bouman, J.; Broerse, D.B.T.; Visser, P.N.A.M.; Vermeersen, L.L.A.

    2013-01-01

    The Japan Tohoku-Oki earthquake (9.0 Mw) of 11 March 2011 has left signatures in the Earth's gravity field that are detectable by data of the Gravity field Recovery and Climate Experiment (GRACE) mission. Because the European Space Agency's (ESA) satellite gravity mission Gravity field and

  1. Observing coseismic gravity change from the Japan Tohoku-Oki 2011 earthquake with GOCE gravity gradiometry

    NARCIS (Netherlands)

    Fuchs, M.J.; Bouman, J.; Broerse, T.; Visser, P.; Vermeersen, B.

    2013-01-01

    The Japan Tohoku-Oki earthquake (9.0 Mw) of 11 March 2011 has left signatures in the Earth's gravity field that are detectable by data of the Gravity field Recovery and Climate Experiment (GRACE) mission. Because the European Space Agency's (ESA) satellite gravity mission Gravity field and steady-st

  2. Observing coseismic gravity change from the Japan Tohoku-Oki 2011 earthquake with GOCE gravity gradiometry

    NARCIS (Netherlands)

    Fuchs, M.J.; Bouman, J.; Broerse, D.B.T.; Visser, P.N.A.M.; Vermeersen, L.L.A.

    2013-01-01

    The Japan Tohoku-Oki earthquake (9.0 Mw) of 11 March 2011 has left signatures in the Earth's gravity field that are detectable by data of the Gravity field Recovery and Climate Experiment (GRACE) mission. Because the European Space Agency's (ESA) satellite gravity mission Gravity field and steady-st

  3. Satellites Seek Gravity Signals for Remote Sensing the Seismotectonic Stresses in Earth

    Science.gov (United States)

    Liu, H.; Chen, J.; Li, J.

    2003-12-01

    The ability of the mantle to withstand stress-difference due to superimposed loads would appear to argue against flow in the Earth's mantle, but the ironic fact is that the satellite determined gravity variations are the evidence of density differences associated with mantle flow. The type of flow which is most likely to be involved concerns convection currents. For the past 4 decades, models of mantle convection have made remarkable advancements. Although a large body of evidence regarding the seafloor depth, heat flow, lithospheric strength and forces of slab-pull and swell-push has been obtained, the global seismotectonic stresses in the Earth are yet to be determined. The problem is that no one has been able to come up with a satisfactory scenario that must characterize the stresses in the Earth which cause earthquakes and create tectonic features. The stress generated by mantle convection under the crust are inferable from high degree (n>=13) spherical harmonics of the geopotential. Therefore, satellite gravity missions may be able to seek the Earth's gravity signals for investigating the seismotectonic effect of these subcrustal stresses. It is well known that subcrustal stress patterns for (137.0 from 1976 to 2000 is also given for reference. The intense seismicity in the subcrustal stress concentration belt (the ring of fire around the Pacific) is expected. A broad band of seismicity extends from southern Europe to southeast Europe to southeast Asia; this is associated with the subcrustal stress concentration belts in Europe, Africa, Arabian, and Asia. These results seem to provide significant insights into the origin of the earthquakes and formation of the world.

  4. PoPSat: The Polar Precipitation Satellite Mission

    Science.gov (United States)

    Binder, Matthias J.; Agten, Dries; Arago-Higueras, Nadia; Borderies, Mary; Diaz-Schümmer, Carlos; Jamali, Maryam; Jimenez-Lluva, David; Kiefer, Joshua; Larsson, Anna; Lopez-Gilabert, Lola; Mione, Michele; Mould, Toby JD; Pavesi, Sara; Roth, Georg; Tomicic, Maja

    2017-04-01

    The terrestrial water cycle is one of many unique regulatory systems on planet Earth. It is directly responsible for sustaining biological life on land and human populations by ensuring sustained crop yields. However, this delicate balanced system continues to be influenced significantly by a changing climate, which has had drastic impacts particularly on the polar regions. Precipitation is a key process in the weather and climate system, due to its storage, transport and release of latent heat in the atmosphere. It has been extensively investigated in low latitudes, in which detailed models have been established for weather prediction. However, a gap has been left in higher latitudes above 65°, which show the strongest response to climate changes and where increasing precipitations have been foreseen in the future. In order to establish a global perspective of atmospheric processes, space observation of high-latitude areas is crucial to produce globally consistent data. The increasing demand for those data has driven a critical need to devise a mission which fills the gaps in current climate models. The authors propose the Polar Precipitation Satellite (PoPSat), an innovative satellite mission to provide enhanced observation of light and medium precipitation, focusing on snowfall and light rain in high latitudes. PoPSat is the first mission aimed to provide high resolution 3D structural information about snow and light precipitation systems and cloud structure in the covered areas. The satellite is equipped with a dual band (Ka and W band) phased-array radar. These antennas provide a horizontal resolution of 2 km and 4 km respectively which will exceed all other observations made to date at high-latitudes, while providing the additional capability to monitor snowfall. The data gathered will be compatible and complementary with measurements made during previous missions. PoPSat has been designed to fly on a sun-synchronous, dawn-dusk orbit at 460 km. This orbit

  5. ARISTOTELES: A European approach for an Earth gravity field recovery mission

    Science.gov (United States)

    Benz, R.; Faulks, H.; Langemann, M.

    1989-06-01

    Under contract of the European Space Agency a system study for a spaceborne gravity field recovery mission was performed, covering as a secondary mission objective geodetic point positioning in the cm range as well. It was demonstrated that under the given programmatic constraints including dual launch and a very tight development schedule, a six months gravity field mission in a 200 km near polar, dawn-dusk orbit is adequate to determine gravity anomalies to better than 5 mgal with a spatial resolution of 100 x 100 km half wavelength. This will enable scientists to determine improved spherical harmonic coefficients of the Earth gravity field equation to the order and degree of 180 or better.

  6. Analysis and testing of gyroscope performance for the Gravity Probe B relativity mission

    Science.gov (United States)

    Ohshima, Yoshimi

    2000-11-01

    This dissertation describes the analysis and experimental testing of the performance of electrostatically suspended vacuum gyroscopes (ESVG) designed for the Gravity Probe B Relativity Experiment (GP-B). The GP-B mission is a satellite-based gyroscope experiment currently under joint development by NASA and Stanford University. It is designed to test two predictions of Einstein's General Theory of Relativity: the geodetic effect and the frame-dragging effect. They are predicted to be 6.6 and 0.042 arc-sec/year, respectively, for a planned circular polar orbit. The primary goal of the GP-B mission is to measure the geodetic effect to better than 0.01%, and the frame-dragging effect to better than 1%. In order to achieve this goal, the non-relativistic drift rate of the gyroscope must be less than 0.3 milli-arc-sec/year. Presented is the analysis of the part of the Newtonian torque on the gyroscope rotor that is due to the electrostatic support, estimation of the science-mission drift rate, and experimental validation of the theoretical torque modeling. The analysis of the electrostatic torque indicates that the torque depends on both the close-to-perfect rotor shape with very minor manufacturing asphericity, and the voltage applied to the electrodes. To estimate the science-mission drift rate, we used the measured asphericity of an existing rotor that was below flight quality. Throughout the analysis, the estimated drift rate of the gyroscope induced by the non-relativistic effect was less than the maximum allowed drift rate of 0.3 milli-arc-sec/year for this effect. This result is gratifying because the actual flight rotors will exhibit a much lower non-relativistic drift rate. In the laboratory, parameters that characterize the electrostatic torque were measured by changing the voltages applied to the electrodes and the position of the gyroscope rotor in its housing cavity. The results match well with the theoretical expectations, confirming the validity of the

  7. Demonstration on the indexes design of gravity satellite orbit parameters in the low-low satellite-to-satellite tracking mode

    Directory of Open Access Journals (Sweden)

    Liu Xiaogang

    2013-02-01

    Full Text Available Combining with the exigent demand of the development of satellite gravimetry system in China, aiming at the determination of technical indexes of gravity satellite orbit parameters, on the basis of the numerical experiments and results analysis, the design indexes of gravity satellite orbit height, inter-satellite range and the orbit inclination are analyzed and calculated, and the issues towards twin gravity satellites such as coherence requirement of the orbit semi-major axes, control requirement of the pitch angle and time interval requirement to keep twin satellites formation in mobility are discussed. Results show that the satellite orbit height is 400 km to 500 km, the inter-satellite range is about 220 km, the satellite orbit inclination is between polar orbit and sun-synchronous orbit, the semi-major axes difference of twin satellites orbit is within ±70. 146 m, the pitch angle of twin satellites is about 0.9 degree, and the time interval to keep twin satellites formation in mobility is 7 days to 15 days.

  8. Antarctic marine gravity field from high-density satellite altimetry

    Science.gov (United States)

    Sandwell, David T.

    1992-01-01

    High-density (about 2-km profile spacing) Geosat/GM altimetry profiles were obtained for Antarctic waters (6-deg S to 72 deg S) and converted to vertical gravity gradient, using Laplace's equation to directly calculate gravity gradient from vertical deflection grids and Fourier analysis to construct gravity anomalies from two vertical deflection grids. The resultant gravity grids have resolution and accuracy comparable to shipboard gravity profiles. The obtained gravity maps display many interesting and previously uncharted features, such as a propagating rift wake and a large 'leaky transform' along the Pacific-Antarctic Rise.

  9. Spectral assessment of isostatic gravity models against CHAMP, GRACE, GOCE satellite-only and combined gravity models

    Science.gov (United States)

    Tsoulis, Dimitrios; Patlakis, Konstantinos

    2014-08-01

    The availability of digital elevation databases representing the topographic and bathymetric relief with global homogeneous coverage and increasing resolution permits the computation of crust-related Earth gravity models, the so-called topographic/isostatic Earth gravity models (henceforth T/I models). Although expressing the spherical harmonic content of the topographic masses, the interpretation purpose of T/I models has not been given the attention it deserves, apart from the fact that they express some degree of compensation to the observed spectrum of the topographic heights, depending on the kind of the applied compensation mechanism. The present contribution attempts to improve the interpretation aspects of T/I Earth gravity models. To this end, a rigorous spectral assessment is performed to a standard Airy/Heiskanen T/I model against different CHAllenging Minisatellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), Gravity field and steadystate Ocean Circulation Explorer (GOCE) satellite-only, and combined gravity models. Different correlation bandwidths emerge for these four groups of satellite-based gravity models. The band-limited forward computation of the models using these bandwidths reproduces nicely the main features of the applied T/I model.

  10. Changing inclination of earth satellites using the gravity of the moon

    OpenAIRE

    Karla de Souza Torres; Prado, A. F. B. A.

    2006-01-01

    We analyze the problem of the orbital control of an Earth's satellite using the gravity of the Moon. The main objective is to study a technique to decrease the fuel consumption of a plane change maneuver to be performed in a satellite that is in orbit around the Earth. The main idea of this approach is to send the satellite to the Moon using a single-impulsive maneuver, use the gravity field of the Moon to make the desired plane change of the trajectory, and then return the satellite to its n...

  11. Dynamical effects of General Relativity on the satellite-to-satellite range and range-rate in the GRACE mission

    CERN Document Server

    Iorio, Lorenzo

    2010-01-01

    We numerically investigate the impact of the General Theory of Relativity (GTR) on the satellite-to-satellite range \\rho and range-rate \\dot\\rho of the twin GRACE A/B spacecrafts through their dynamical equations of motion. The present-day accuracies in measuring such observables are \\sigma_\\rho <= 1-10 micron, \\sigma_\\dot\\rho <= 1 micron s^-1. Studies for a follow-on of such a mission points toward a range-rate accuracy of the order of \\sigma_\\dot\\rho = 1 nm s^-1 or better. We also compute the dynamical range and range-rate perturbations caused by the first six zonal harmonic coefficients J_L, L=2,3,4,5,6,7$ of the classical multipolar expansion of the terrestrial gravitational potential in order to evaluate their aliasing impact on the relativistic effects. Conversely, we also quantitatively assessed the possible a-priori \\virg{imprinting} of GTR itself, not solved-for in all the GRACE-based Earth's gravity models produced so far, on the estimated values of the low degree zonals of the geopotential. T...

  12. Explaining the thick crust in Paraná basin, Brazil, with satellite GOCE gravity observations

    Science.gov (United States)

    Mariani, Patrizia; Braitenberg, Carla; Ussami, Naomi

    2013-08-01

    Seismologic observations in the last decades have shown that the crustal thickness in Paraná basin locally is over 40 km thick, which is a greater value than expected by the simple isostatic model considering the topographic load. The goal of this work is to explain this apparent discrepancy by modeling the internal crustal density anomalies through the gravity field. We use the latest Earth Gravity Model derived from the observations of the GOCE satellite mission, to retrieve the gravity anomaly and correct it for topographic effects, thus obtaining the Bouguer field. We then model the gravity effect of known stratigraphic units and of the seismological crustal thickness. The large Paraná basin comprises over 3500 m of Paleozoic sedimentary sequence with density between 2400 and 2600 kg/m3. During the Early Cretaceous the same basin was affected by a large amount of igneous activity with a volume of over 0.1 Mkm3. The flood basalt volcanism is known as the Serra Geral Formation, and has a maximum thickness of 1500 m. The stratigraphic units of the basin are topped by post-volcanic deposits of the Bauru Group, of about 300 m thickness, located in the northern part of the basin. The density and thickness of the sedimentary sequence are constrained by sonic logs of drill-holes and exploration seismic. We use the crustal thickness estimated from the newest seismological results for South America to calculate its gravity effect. Further we model the isostatic crustal thickness variation, allowing the comparison between a seismological Moho, an isostatic Moho, and a gravity-based Moho. We find that there is a clear positive Bouguer residual anomaly located in the northern and southern part of the Paraná basin, indicating the presence of a hidden mass, not considered up to now. We propose a model that explains this mass as magmatic rock, probably gabbro in lower crust, with density contrast of 200 kg/m3 and thickness of more than 10 km, thus demonstrating that the

  13. Observatory crustal magnetic biases during CHAMP satellite mission

    Science.gov (United States)

    Verbanac, G.; Mandea, M.; Bandić, M.; Subašić, S.

    2015-01-01

    Taking advantage of nine years of CHAMP satellite mission (June 2000-August 2009), we investigate the temporal evolution of the observatory monthly crustal magnetic biases. To determine biases we compute X (northward), Y (eastward) and Z (vertically downward) monthly means from 42 observatory one-minute or hourly values, and compare them to synthetic monthly means obtained from a GRIMM3 core field model (V. Lesur, personal communication, 2014). Both short period variations and long term trends in the monthly bias time series are analyzed. A comparison with biases based on MAGSAT and Ørsted satellite data, related to the 1979.92 and 1992.92 epochs is performed. Generally, the larger biases averaged over nine years and the larger differences between biases based on different models are found in Z component. This can be the signature of the induced magnetic fields. Although annual trends in most bias series are observed, no clear evidence that the constant crustal field changed significantly over the studied period is found. Time series of monthly biases exhibit distinct oscillatory pattern in the whole time span, which we assign to the external field contributions. The amplitudes of these variations are linked with the phase of the solar cycle, being significantly larger in the period 2000-2005 than in the period 2006-2009. Clear semi-annual variations are evident in all components, with extremes in spring and fall months of each year. Common external field pattern is found for European monthly biases. A dependence of the bias monthly variations on geomagnetic latitudes is not found for the non-European observatories. The results from this study represent a base to further exploit the observatory and repeat stations magnetic biases together with the data from the new satellite mission SWARM.

  14. Tether de-orbiting of satellites at end of mission

    Science.gov (United States)

    Sanmartin, Juan R.; Sánchez-Torres, Antonio

    2012-07-01

    The accumulation of space debris around the Earth has become critical for Space security. The BETs project, financed by the European Commission through its FP7-Space program, is focusing on preventing generation of new debris by de-orbiting satellites at end of mission. The de-orbiting system considered, involving an electrodynamic bare tape-tether, uses no propellant and no power supply, while generating power for on-board use during de-orbiting. As an example, preliminary results are here presented on a specific orbit/satellite case: 1300 km altitude and 65 degrees inclination, and 500 kg mass. Design tether dimensions are 8 km length, 1.5 cm width, and 0.05 mm thickness; subsystem masses are limited to twice tether mass. Simple calculations, using orbit-averaging, solar mid-cycle phase, and ionospheric and geomagnetic field models, yield 2.6 months time for de-orbiting down to 200 km, with a probability of about 1 percent of debris cutting the tape. References: Sanmartin, J.R., Lorenzini, E.C., and Martinez-Sanchez, M., Electrodynamic Tether Applications and Constraints, J. Space. Rockets 47, 442-456, 2010. Sanmartin, J.R. et al., A universal system to de-orbit satellites at end of life, Journal of Space Technology and Science, to appear.

  15. Multi-agent robotic systems and applications for satellite missions

    Science.gov (United States)

    Nunes, Miguel A.

    A revolution in the space sector is happening. It is expected that in the next decade there will be more satellites launched than in the previous sixty years of space exploration. Major challenges are associated with this growth of space assets such as the autonomy and management of large groups of satellites, in particular with small satellites. There are two main objectives for this work. First, a flexible and distributed software architecture is presented to expand the possibilities of spacecraft autonomy and in particular autonomous motion in attitude and position. The approach taken is based on the concept of distributed software agents, also referred to as multi-agent robotic system. Agents are defined as software programs that are social, reactive and proactive to autonomously maximize the chances of achieving the set goals. Part of the work is to demonstrate that a multi-agent robotic system is a feasible approach for different problems of autonomy such as satellite attitude determination and control and autonomous rendezvous and docking. The second main objective is to develop a method to optimize multi-satellite configurations in space, also known as satellite constellations. This automated method generates new optimal mega-constellations designs for Earth observations and fast revisit times on large ground areas. The optimal satellite constellation can be used by researchers as the baseline for new missions. The first contribution of this work is the development of a new multi-agent robotic system for distributing the attitude determination and control subsystem for HiakaSat. The multi-agent robotic system is implemented and tested on the satellite hardware-in-the-loop testbed that simulates a representative space environment. The results show that the newly proposed system for this particular case achieves an equivalent control performance when compared to the monolithic implementation. In terms on computational efficiency it is found that the multi

  16. Mission Status for the Transiting Exoplanet Survey Satellite (TESS)

    Science.gov (United States)

    Ricker, George R.; TESS Science Team

    2017-01-01

    The Transiting Exoplanet Survey Satellite (TESS) will discover thousands of exoplanets in orbit around the brightest stars in the sky. TESS will monitor ~ 200,000 pre-selected bright stars in the solar neighborhood for temporary drops in brightness caused by planetary transits. This first-ever spaceborne all-sky transit survey will identify planets ranging from Earth-sized to gas giants, around a wide range of stellar types and orbital distances.TESS stars will typically be 30 — 100 times brighter than those surveyed by the Kepler satellite; thus, TESS planets will be far easier to characterize with follow-up observations. For the first time it will be possible to study the masses, sizes, densities, orbits, and atmospheres of a large cohort of small planets, including a sample of rocky worlds in the habitable zones of their host stars.An additional data product from the TESS mission will be full frame images (FFI) with a cadence of 30 minutes. These FFI will provide precise photometric information for every object within the 2300 square degree instantaneous field of view of the TESS cameras. In total, more than 30 million stars and galaxies brighter than magnitude I=16 will be precisely photometered during the two-year prime mission. In principle, the lunar-resonant TESS orbit could provide opportunities for an extended mission lasting more than a decade.The baselined long duration survey by TESS of regions surrounding the North and South Ecliptic Poles will provide prime exoplanet targets for characterization with the James Webb Space Telescope (JWST), as well as other large ground-based and space-based telescopes of the future.TESS will issue data releases every 4 months, inviting immediate community-wide efforts to study the new planets, as well as commensal survey candidates from the FFI. A NASA Guest Investigator program is planned for TESS. The TESS legacy will be a catalog of the nearest and brightest main-sequence stars hosting transiting exoplanets

  17. Efficient GOCE satellite gravity field recovery based on least-squares using QR decomposition

    NARCIS (Netherlands)

    Baur, O.; Austen, G.; Kusche, J.

    2007-01-01

    We develop and apply an efficient strategy for Earth gravity field recovery from satellite gravity gradiometry data. Our approach is based upon the Paige-Saunders iterative least-squares method using QR decomposition (LSQR). We modify the original algorithm for space-geodetic applications: firstly,

  18. Quasi-Stationary SST Estimation in the Eastern Mediterranean Sea Using Marine Gravity, GOCE/GRACE Gravity Information and Recent Altimetry Missions Through the Multiple Input/Multiple Output System Theory

    Science.gov (United States)

    Andritsanos, Vassilios D.; Tziavos, Ilias N.

    2016-08-01

    The Multiple Input / Multiple Output System (MIMOS) Theory is used in the spectral combination of marine and satellite data for Quasi-stationary Sea Surface Topography (QSST) estimation. 15 years (2000 - 2015) of altimetric data from ERS2, GEOSAT FOLLOW-ON, ENVISAT and SARAL / Altika satellites are optimally combined with in situ marine gravity observations. The repeated character of the altimetric missions provides more than one sample of Sea Surface Height (SSH) data sets, and the approximation of the input signal and output error power spectral densities is feasible using this successive information. The assimilation of low frequency global gravity information from GOCE/GRACE satellites is considered in data reductions. The geodynamically active area of the Eastern Mediterranean Sea is chosen as test area and the evolution of yearly SST is presented.

  19. High-accuracy, high-resolution gravity profiles from 2 years of the Geosat Exact Repeat Mission

    Science.gov (United States)

    Sandwell, David T.; Mcadoo, David C.

    1990-01-01

    Satellite altimeter data from the first 44 repeat cycles (2 years) of the Geosat Exact Repeat Mission (EWRM) were averaged to improve accuracy, resolution and coverage of the marine gravity field. Individual 17-day repeat cycles were first edited and differentiated, resulting in the along-track vertical deflection (i.e., gravity disturbance). To increase the signal-to-noise ratio, 44 of these cycles were then averaged to form a single highly accurate vertical deflection profile. The largest contribution to the vertical deflection error is short-wavelength altimeter noise and longer-wavelength oceanographic variability; the combined noise level is typically 6 microrad. Both types of noise are reduced by averaging many repeat cycles. Over most ocean areas the uncertainty of the average profile is less than 1 microrad which corresponds to 1 mgal of along-track gravity disturbance. However, in areas of seasonal ice coverage, its uncertainty can exceed 5 microrad. To assess the resolution of individual and average Geosat gravity profiles, the cross-spectral analysis technique was applied to repeat profiles. Individual Geosat repeat cycles are coherent (greater than 0.5) for wavelengths greater than about 30 km and become increasingly incoherent at shorter wavelengths.

  20. A Class for Teachers Featuring a NASA Satellite Mission

    Science.gov (United States)

    Battle, R.; Hawkins, I.

    1996-05-01

    As part of the NASA IDEA (Initiative to Develop Education through Astronomy) program, the UC Berkeley Center for EUV Astrophysics (CEA) received a grant to develop a self-contained teacher professional development class featuring NASA's Extreme Ultraviolet Explorer (EUVE) satellite mission. This class was offered in collaboration with the Physics/Astronomy Department and the Education Department of San Francisco State University during 1994, and in collaboration with the UCB Graduate School of Education in 1995 as an extension course. The class served as the foundation for the Science Education Program at CEA, providing valuable lessons and experience through a full year of intense collaboration with 50 teachers from the diverse school districts of the San Francisco Bay Area teaching in the 3rd--12th grade range. The underlying theme of the class focused on how scientists carry out research using a NASA satellite mission. Emphasis was given to problem-solving techniques, with specific examples taken from the pre- and post-launch stages of the EUVE mission. The two, semester-long classes were hosted by the CEA, so the teachers spent an average of 4 hours/week during 17 weeks immersed in astrophysics, collaborating with astronomers, and working with colleagues from the Lawrence Hall of Science and the Graduate School of Education. The teachers were taught the computer skills and space astrophysics concepts needed to perform hands-on analysis and interpretation of the EUVE satellite data and the optical identification program. As a final project, groups of teachers developed lesson plans based on NASA and other resources that they posted on the World Wide Web using html. This project's model treats teachers as professionals, and allows them to collaborate with scientists and to hone their curriculum development skills, an important aspect of their professional growth. We will summarize class highlights and showcase teacher-developed lesson plans. A detailed evaluation

  1. 3-Axis magnetic control: flight results of the TANGO satellite in the PRISMA mission

    Science.gov (United States)

    Chasset, C.; Noteborn, R.; Bodin, P.; Larsson, R.; Jakobsson, B.

    2013-09-01

    PRISMA implements guidance, navigation and control strategies for advanced formation flying and rendezvous experiments. The project is funded by the Swedish National Space Board and run by OHB-Sweden in close cooperation with DLR, CNES and the Danish Technical University. The PRISMA test bed consists of a fully manoeuvrable MANGO satellite as well as a 3-axis controlled TANGO satellite without any Δ V capability. PRISMA was launched on the 15th of June 2010 on board DNEPR. The TANGO spacecraft is the reference satellite for the experiments performed by MANGO, either with a "cooperative" or "non-cooperative" behaviour. Small, light and low-cost were the keywords for the TANGO design. The attitude determination is based on Sun sensors and magnetometers, and the active attitude control uses magnetic torque rods only. In order to perform the attitude manoeuvres required to fulfil the mission objectives, using any additional gravity gradient boom to passively stabilize the spacecraft was not allowed. After a two-month commissioning phase, TANGO separated from MANGO on the 11th of August 2010. All operational modes have been successfully tested, and the pointing performance in flight is in accordance with expectations. The robust Sun Acquisition mode reduced the initial tip-off rate and placed TANGO into a safe attitude in TANGO points its GPS antenna towards zenith with sufficient accuracy to track as many GPS satellites as MANGO. At the same time, it points its solar panel towards the Sun, and all payload equipments can be switched on without any restriction. This paper gives an overview of the TANGO Attitude Control System design. It then presents the flight results in the different operating modes. Finally, it highlights the key elements at the origin of the successful 3-axis magnetic control strategy on the TANGO satellite.

  2. Can the Gravity Recovery and Climate Experiment (GRACE) mission detect hydrological droughts?

    Science.gov (United States)

    Agustin Brena Naranjo, Jose; Pedrozo Acuña, Adrian

    2016-04-01

    Detecting and characterizing hydrological droughts at the global scale is a difficult task as several thousands of mid-to-large catchments remain ungauged or have limited discharge records. In water-limited regions, research on hydrological drought is even more complex because of the dominant streamflow perennial regime that characterizes small order watersheds. Over the last decade, the emergence of global remote sensing products has remarkably improved the capability to observe different climate and land surface processes that affect catchment discharge. Among several observational satellites that provide continuous data on terrestrial hydrology, the Gravity Recovery and Climate Experiment (GRACE) is perhaps the only tool able to retrieve information about large-scale water storage variations across the world's terrestrial surface. This work tests the hypothesis that water storage deficits derived from GRACE are inextricably linked to below-than-average baseflow values extracted from streamflow records. This study case analyzed several regions in Mexico and USA with different hydro-climate regimes. Drought conditions using total water storage variations and observed streamflow records from 2003 until 2013 were computed and compared. Results indicate that although the GRACE mission is moderately/highly correlated to streamflow and baseflow time series, discrepancies in the magnitude of hydrological deficit exist and can be attributed to active versus passive catchment storage issues. Finally, the suitability of creating an improved product to monitor hydrological drought by merging in situ with remote sensed information will be discussed.

  3. A climatology of gravity wave parameters based on satellite limb soundings

    Science.gov (United States)

    Ern, Manfred; Trinh, Quang Thai; Preusse, Peter; Riese, Martin

    2017-04-01

    Gravity waves are one of the main drivers of atmospheric dynamics. The resolution of most global circulation models (GCMs) and chemistry climate models (CCMs), however, is too coarse to properly resolve the small scales of gravity waves. Horizontal scales of gravity waves are in the range of tens to a few thousand kilometers. Gravity wave source processes involve even smaller scales. Therefore GCMs/CCMs usually parametrize the effect of gravity waves on the global circulation. These parametrizations are very simplified, and comparisons with global observations of gravity waves are needed for an improvement of parametrizations and an alleviation of model biases. In our study, we present a global data set of gravity wave distributions observed in the stratosphere and the mesosphere by the infrared limb sounding satellite instruments High Resolution Dynamics Limb Sounder (HIRDLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). We provide various gravity wave parameters (for example, gravity variances, potential energies and absolute momentum fluxes). This comprehensive climatological data set can serve for comparison with other instruments (ground based, airborne, or other satellite instruments), as well as for comparison with gravity wave distributions, both resolved and parametrized, in GCMs and CCMs. The purpose of providing various different parameters is to make our data set useful for a large number of potential users and to overcome limitations of other observation techniques, or of models, that may be able to provide only one of those parameters. We present a climatology of typical average global distributions and of zonal averages, as well as their natural range of variations. In addition, we discuss seasonal variations of the global distribution of gravity waves, as well as limitations of our method of deriving gravity wave parameters from satellite data.

  4. A Test of General Relativity Using the LARES and LAGEOS Satellites and a GRACE Earth's Gravity Model

    CERN Document Server

    Ciufolini, Ignazio; Pavlis, Erricos C; Koenig, Rolf; Ries, John; Gurzadyan, Vahe; Matzner, Richard; Penrose, Roger; Sindoni, Giampiero; Paris, Claudio; Khachatryan, Harutyun; Mirzoyan, Sergey

    2016-01-01

    We present a test of General Relativity, the measurement of the Earth's dragging of inertial frames. Our result is obtained using about 3.5 years of laser-ranged observations of the LARES, LAGEOS and LAGEOS 2 laser-ranged satellites together with the Earth's gravity field model GGM05S produced by the space geodesy mission GRACE. We measure $\\mu = (0.994 \\pm 0.002) \\pm 0.05$, where $\\mu$ is the Earth's dragging of inertial frames normalized to its General Relativity value, 0.002 is the 1-sigma formal error and 0.05 is the estimated systematic error mainly due to the uncertainties in the Earth's gravity model GGM05S. Our result is in agreement with the prediction of General Relativity.

  5. The infrared astronomical satellite AKARI: overview, highlights of the mission

    Science.gov (United States)

    Murakami, Hiroshi; Matsuhara, Hideo

    2008-07-01

    The AKARI, Japanese infrared astronomical satellite, is a 68.5 cm cooled telescope with two focal-plane instruments providing continuous sky scan at six wavelength bands in mid- and far-infrared. The instruments also have capabilities of imaging and spectroscopy in the wavelength range 2-180 μm in the pointing observations occasionally inserted into the continuous survey. AKARI was launched on 21st Feb. 2006, and has performed the all-sky survey as well as 5380 pointing observations until the liquid helium exhaustion on 26th Aug. 2007. The all sky survey covers more than 90 percent of the entire sky with higher spatial resolutions and sensitivities than the IRAS. First version of the infrared source catalogue will be released in 2009. Here we report the overview of the mission, highlights on the scientific results as well as the performance of the focal-plane instruments. We also present the observation plan with the near infrared camera during the post-helium mission phase started in June 2008.

  6. Geostationary Operational Environmental Satellite (GOES)-8 mission flight experience

    Science.gov (United States)

    Noonan, C. H.; McIntosh, R. J.; Rowe, J. N.; Defazio, R. L.; Galal, K. F.

    1995-05-01

    The Geostationary Operational Environmental Satellite (GOES)-8 spacecraft was launched on April 13, 1994, at 06:04:02 coordinated universal time (UTC), with separation from the Atlas-Centaur launch vehicle occurring at 06:33:05 UTC. The launch was followed by a series of complex, intense operations to maneuver the spacecraft into its geosynchronous mission orbit. The Flight Dynamics Facility (FDF) of the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) was responsible for GOES-8 attitude, orbit maneuver, orbit determination, and station acquisition support during the ascent phase. This paper summarizes the efforts of the FDF support teams and highlights some of the unique challenges the launch team faced during critical GOES-8 mission support. FDF operations experience discussed includes: (1) The abort of apogee maneuver firing-1 (AMF-1), cancellation of AMF-3, and the subsequent replans of the maneuver profile; (2) The unexpectedly large temperature dependence of the digital integrating rate assembly (DIRA) and its effect on GOES-8 attitude targeting in support of perigee raising maneuvers; (3) The significant effect of attitude control thrusting on GOES-8 orbit determination solutions; (4) Adjustment of the trim tab to minimize torque due to solar radiation pressure; and (5) Postlaunch analysis performed to estimate the GOES-8 separation attitude. The paper also discusses some key FDF GOES-8 lessons learned to be considered for the GOES-J launch which is currently scheduled for May 19, 1995.

  7. The study of gravity gradient effect on attitude of low earth orbit satellite

    Science.gov (United States)

    Hamzah, Nor Hazadura; Yaacob, Sazali; Muthusamy, Hariharan; Hamzah, Norhizam; Ghazali, Najah

    2013-04-01

    Simulations and mathematical models are increasingly used to assist the process of decision making in engineering design. The objective of this paper is to simulate the linear attitude dynamics of small satellites under gravity gradient torque which is inherent in low earth orbit. The equations were first derived in their nonlinear form, and then manipulated and simulated in their linear form. Simulation results demonstrate the importance of choosing the appropriate values of satellite's moment of inertia in designing phase of a satellite.

  8. Formation flying within a constellation of nano-satellites the QB50 mission

    NARCIS (Netherlands)

    Gill, E.K.A.; Sundaramoorthy, P.; Bouwmeester, J.; Zandbergen, B.; Reinhard, R.

    2010-01-01

    QB50 is a mission establishing an international network of 50 nano-satellites for multi-point, in-situ measurements in the lower thermosphere and re-entry research. As part of the QB50 mission, the Delft University of Technology intends to contribute two nano-satellites both being equipped with a hi

  9. Improvement of global and regional mean sea level derived from satellite altimetry multi missions

    Science.gov (United States)

    Ablain, M.; Faugere, Y.; Larnicol, G.; Picot, N.; Cazenave, A.; Benveniste, J.

    2012-04-01

    With the satellite altimetry missions, the global mean sea level (GMSL) has been calculated on a continual basis since January 1993. 'Verification' phases, during which the satellites follow each other in close succession (Topex/Poseidon--Jason-1, then Jason-1--Jason-2), help to link up these different missions by precisely determining any bias between them. Envisat, ERS-1 and ERS-2 are also used, after being adjusted on these reference missions, in order to compute Mean Sea Level at high latitudes (higher than 66°N and S), and also to improve spatial resolution by combining all these missions together. The global mean sea level (MSL) deduced from TOPEX/Poseidon, Jason-1 and Jason-2 provide a global rate of 3.2 mm from 1993 to 2010 applying the post glacial rebound (MSL aviso website http://www.jason.oceanobs.com/msl). Besides, the regional sea level trends bring out an inhomogeneous repartition of the ocean elevation with local MSL slopes ranging from + 8 mm/yr to - 8 mm/year. A study published in 2009 [Ablain et al., 2009] has shown that the global MSL trend unceratainty was estimated at +/-0.6 mm/year with a confidence interval of 90%. The main sources of errors at global and regional scales are due to the orbit calculation and the wet troposphere correction. But others sea-level components have also a significant impact on the long-term stability of MSL as for instance the stability of instrumental parameters and the atmospheric corrections. Thanks to recent studies performed in the frame of the SALP project (supported by CNES) and Sea-level Climate Change Initiative project (supported by ESA), strong improvements have been provided for the estimation of the global and regional MSL trends. In this paper, we propose to describe them; they concern the orbit calculation thanks to new gravity fields, the atmospheric corrections thanks to ERA-interim reanalyses, the wet troposphere corrections thanks to the stability improvement, and also empirical corrections

  10. Estimating water storage changes and sink terms in Volta Basin from satellite missions

    Directory of Open Access Journals (Sweden)

    Vagner G. FERREIRA

    2014-01-01

    Full Text Available The insufficiency of distributed in situ hydrological measurements is a major challenge for hydrological studies in many regions of the world. Satellite missions such as the Gravity Recovery and Climate Experiment (GRACE and the Tropical Rainfall Measurement Mission (TRMM can be used to improve our understanding of water resources beyond surface water in poorly gauged basins. In this study we combined GRACE and TRMM to investigate monthly estimates of evaporation plus runoff (sink terms using the water balance equation for the period from January 2005 to December 2010 within the Volta Basin. These estimates have been validated by comparison with time series of sink terms (evaporation plus surface and subsurface runoff from the Global Land Data Assimilation System (GLDAS. The results, for the period under consideration, show strong agreement between both time series, with a root mean square error (RMSE of 20.2 mm/month (0.67 mm/d and a correlation coefficient of 0.85. This illustrates the ability of GRACE to predict hydrological quantities, e.g. evaporation, in the Volta Basin. The water storage change data from GRACE and precipitation data from TRMM all show qualitative agreement, with evidence of basin saturation at approximately 73 mm in the equivalent water column at the annual and semi-annual time scales.

  11. View of a pallet configured to support 51-A satellite-retrieval mission

    Science.gov (United States)

    1984-01-01

    A high angle view of a Spacelab type pallet configured to support NASA's 51-A satellite-retrieval mission. At left are two capture devices called 'stingers' used to enter the communications satellites at the nozzle of the spent engine. Center are circular areas for clamping down and securing the satellites for the remainder of the trip.

  12. The Gravity and Extreme Magnetism Small Expolorer Mission

    Science.gov (United States)

    Kallman, Timothy R.; Swank, J.; Jahoda, K.; GEMS Team

    2011-01-01

    Polarization is an inherently geometric quantity and provides information on source geometry inaccessible via spectroscopy or timing. To date, there have been reliable detections of X-ray polarization from only one object outside the solar system (the Crab nebula). Recent development of photoelectric polarimetry makes it possible to perform sensitive X-ray polarimetry with a modest mission. GEMS was recently selected by NASA to be the 13th Small Explorer mission with launch planned for 2014. GEMS will be 100× more sensitive than any previously flown X-ray polarimeter and should provide useful polarization measurements for dozens of sources, to lower than predicted levels. GEMS will lead to new insights into the nature of accreting black holes, highly magnetized neutron stars, and supernova remnants.

  13. Einstein Gravity Explorer–a medium-class fundamental physics mission

    NARCIS (Netherlands)

    Schiller, S.; Tino, G.M.; Gill, E.; et al.

    2008-01-01

    The Einstein Gravity Explorer mission (EGE) is devoted to a precise measurement of the properties of space-time using atomic clocks. It tests one of the most fundamental predictions of Einstein’s Theory of General Relativity, the gravitational redshift, and thereby searches for hints of quantum effe

  14. Einstein Gravity Explorer–a medium-class fundamental physics mission

    NARCIS (Netherlands)

    Schiller, S.; Tino, G.M.; Gill, E.; et al.

    2008-01-01

    The Einstein Gravity Explorer mission (EGE) is devoted to a precise measurement of the properties of space-time using atomic clocks. It tests one of the most fundamental predictions of Einstein’s Theory of General Relativity, the gravitational redshift, and thereby searches for hints of quantum

  15. The zero gravity curve and surface and radii for geostationary and geosynchronous satellite orbits

    Directory of Open Access Journals (Sweden)

    Sjöberg L.E.

    2017-02-01

    Full Text Available A geosynchronous satellite orbits the Earth along a constant longitude. A special case is the geostationary satellite that is located at a constant position above the equator. The ideal position of a geostationary satellite is at the level of zero gravity, i.e. at the geocentric radius where the gravitational force of the Earth equals the centrifugal force. These forces must be compensated for several perturbing forces, in particular for the lunisolar tides. Considering that the gravity field of the Earth varies not only radially but also laterally, this study focuses on the variations of zero gravity not only on the equator (for geostationary satellites but also for various latitudes. It is found that the radius of a geostationary satellite deviates from its mean value of 42164.2 km only within ±2 m, mainly due to the spherical harmonic coefficient J22, which is related with the equatorial flattening of the Earth. Away from the equator the zero gravity surface deviates from the ideal radius of a geosynchronous satellite, and more so for higher latitudes. While the radius of the former surface increases towards infinity towards the poles, the latter decreases about 520 m from the equator to the pole. Tidal effects vary these radii within ±2.3 km.

  16. Initial Satellite Formation Flight Results from the Magnetospheric Multiscale Mission

    Science.gov (United States)

    Williams, Trevor; Ottenstein, Neil; Palmer, Eric; Farahmand, Mitra

    2016-01-01

    This paper will describe the results that have been obtained to date concerning MMS formation flying. The MMS spacecraft spin at a rate of 3.1 RPM, with spin axis roughly aligned with Ecliptic North. Several booms are used to deploy instruments: two 5 m magnetometer booms in the spin plane, two rigid booms of length 12.5 m along the positive and negative spin axes, and four flexible wire booms of length 60 m in the spin plane. Minimizing flexible motion of the wire booms requires that reorientation of the spacecraft spin axis be kept to a minimum: this is limited to attitude maneuvers to counteract the effects of gravity-gradient and apparent solar motion. Orbital maneuvers must therefore be carried out in essentially the nominal science attitude. These burns make use of a set of monopropellant hydrazine thrusters: two (of thrust 4.5 N) along the spin axis in each direction, and eight (of thrust 18 N) in the spin plane; the latter are pulsed at the spin rate to produce a net delta-v. An on-board accelerometer-based controller is used to accurately generate a commanded delta-v. Navigation makes use of a weak-signal GPS-based system: this allows signals to be received even when MMS is flying above the GPS orbits, producing a highly accurate determination of the four MMS orbits. This data is downlinked to the MMS Mission Operations Center (MOC) and used by the MOC Flight Dynamics Operations Area (FDOA) for maneuver design. These commands are then uplinked to the spacecraft and executed autonomously using the controller, with the ground monitoring the burns in real time.

  17. A mission-oriented orbit design method of remote sensing satellite for region monitoring mission based on evolutionary algorithm

    Science.gov (United States)

    Shen, Xin; Zhang, Jing; Yao, Huang

    2015-12-01

    Remote sensing satellites play an increasingly prominent role in environmental monitoring and disaster rescue. Taking advantage of almost the same sunshine condition to same place and global coverage, most of these satellites are operated on the sun-synchronous orbit. However, it brings some problems inevitably, the most significant one is that the temporal resolution of sun-synchronous orbit satellite can't satisfy the demand of specific region monitoring mission. To overcome the disadvantages, two methods are exploited: the first one is to build satellite constellation which contains multiple sunsynchronous satellites, just like the CHARTER mechanism has done; the second is to design non-predetermined orbit based on the concrete mission demand. An effective method for remote sensing satellite orbit design based on multiobjective evolution algorithm is presented in this paper. Orbit design problem is converted into a multi-objective optimization problem, and a fast and elitist multi-objective genetic algorithm is utilized to solve this problem. Firstly, the demand of the mission is transformed into multiple objective functions, and the six orbit elements of the satellite are taken as genes in design space, then a simulate evolution process is performed. An optimal resolution can be obtained after specified generation via evolution operation (selection, crossover, and mutation). To examine validity of the proposed method, a case study is introduced: Orbit design of an optical satellite for regional disaster monitoring, the mission demand include both minimizing the average revisit time internal of two objectives. The simulation result shows that the solution for this mission obtained by our method meet the demand the users' demand. We can draw a conclusion that the method presented in this paper is efficient for remote sensing orbit design.

  18. A GOCE only gravity model GOSG01S and the validation of GOCE related satellite gravity models

    Directory of Open Access Journals (Sweden)

    Xinyu Xu

    2017-07-01

    Full Text Available We compile the GOCE-only satellite model GOSG01S complete to spherical harmonic degree of 220 using Satellite Gravity Gradiometry (SGG data and the Satellite-to-Satellite Tracking (SST observations along the GOCE orbit based on applying a least-squares analysis. The diagonal components (Vxx, Vyy, Vzz of the gravitational gradient tensor are used to form the system of observation equations with the band-pass ARMA filter. The point-wise acceleration observations (ax, ay, az along the orbit are used to form the system of observation equations up to the maximum spherical harmonic degree/order 130. The analysis of spectral accuracy characteristics of the newly derived gravitational model GOSG01S and the existing models GOTIM04S, GODIR04S, GOSPW04S and JYY_GOCE02S based on their comparison with the ultra-high degree model EIGEN-6C2 reveals a significant consistency at the spectral window approximately between 80 and 190 due to the same period SGG data used to compile these models. The GOCE related satellite gravity models GOSG01S, GOTIM05S, GODIR05S, GOTIM04S, GODIR04S, GOSPW04S, JYY_GOCE02S, EIGEN-6C2 and EGM2008 are also validated by using GPS-leveling data in China and USA. According to the truncation at degree 200, the statistic results show that all GGMs have very similar differences at GPS-leveling points in USA, and all GOCE related gravity models have better performance than EGM2008 in China. This suggests that all these models provide much more information on the gravity field than EGM2008 in areas with low terrestrial gravity coverage. And STDs of height anomaly differences in China for the selected truncation degrees show that GOCE has improved the accuracy of the global models beyond degree 90 and the accuracies of the models improve from 24 cm to 16 cm. STDs of geoid height differences in USA show that GOSG01S model has best consistency comparing with GPS-leveling data for the frequency band of the degree between 20 and 160.

  19. Gravity Anomalies and Estimated Topography Derived from Satellite Altimetry

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — In many areas of the global ocean, the depth of the seafloor is not well known because survey lines by ships are hundreds of kilometers apart. Satellites carrying...

  20. Near Earth Asteroid redirect missions based on gravity assist maneuver

    Science.gov (United States)

    Ledkov, Anton; Shustov, Boris M.; Eismont, Natan; Boyarsky, Michael; Nazirov, Ravil; Fedyaev, Konstantin

    During last years several events attracted world community attention to the hazards of hitting the Earth by sky objects. One of these objects is Apophis asteroid what was expected with nonzero probability to hit the Earth in 2036. Luckily after more precise measurements this event is considered as practically improbable. But the other object has really reached the Earth, entered the atmosphere in the Chelyabinsk area and caused vast damages. After this the hazardous near Earth objects problem received practical confirmation of the necessity to find the methods of its resolution. The methods to prevent collision of the dangerous sky object with the Earth proposed up to now look not practical enough if one mentions such as gravitational tractor or changing the reflectivity of the asteroid surface. Even the method supposing the targeting of the spacecraft to the hazardous object in order to deflect it from initial trajectory by impact does not work because its low mass as compared with the mass of asteroid to be deflected. For example the mass of the Apophis is estimated to be about 40 million tons but the spacecraft which can be launched to intercept the asteroid using contemporary launchers has the mass not more than 5 tons. So the question arises where to find the heavier projectile which is possible to direct to the dangerous object? The answer proposed in our paper is very simple: to search it among small near Earth asteroids. As small ones we suppose those which have the cross section size not more than 12-15 meters and mass not exceeding 1500 -1700 tons. According to contemporary estimates the number of such asteroids is not less than 100000. The other question is how to redirect such asteroid to the dangerous one. In the paper the possibilities are studied to use for that purpose gravity assist maneuvers near Earth. It is shown that even among asteroids included in contemporary catalogue there are the ones which could be directed to the trajectory of the

  1. Satellite Gravity Transforms Unmask Tectonic Pattern of Arabian-African Region

    Science.gov (United States)

    Eppelbaum, Lev; Katz, Youri

    2017-04-01

    Satellite derived geophysical gravity data are the modern powerful tool of regional tectono-geophysical examination of the Earth's crust and upper mantle. It is well known that regional long-term seismological prognosis, strategy of searching economic deposits and many other important geological-geophysical problems are based mainly on constructions derived from the combined tectono-geophysical zonation. Some authors' experience of the tectono-geophysical zonation in the Eastern Mediterranean (both sea and land) with satellite derived gravity field (Eppelbaum and Katz, 2015a, 2015b) indicates a high effectiveness of the data employment for delineation of different tectono-structural units. Therefore, on the basis of the previous successive application, satellite derived gravity field analysis was applied for a giant (covering > 10 mln. km2) and complex Arabian-African region (including Zagros Mts.). The gravity field retracked from the Geosat and ERS-1 altimetry (e.g., Sandwell and Smith, 2009) was processed by the use of different mathematical apparatus employment enabling to underline these or those tectonic (geodynamic) features of the region under study. The main goals of present investigation are following: (1) employment of a new powerful regional geophysical tool - satellite derived gravity data and its transforms for unmasking some buried tectonic and geodynamic peculiarities of the study area, (2) finding definite relationships between the novel tectonic map and the gravity field transformations, (3) development of a novel tectonic map of this area (on the basis of careful examination of and generalization of available geological and geophysical (mostly satellite gravity) data). The compiled gravity map (for the map compiling more than 4 mln. observations were utilized) with the main tectonic features shows the intricate gravity pattern of the investigated area. An initial analysis of the gravity field behavior enabled to separate two main types of

  2. Detailed gravity anomalies from GEOS-3 satellite altimetry data

    Science.gov (United States)

    Gopalapillai, G. S.; Mourad, A. G.

    1978-01-01

    A technique for deriving mean gravity anomalies from dense altimetry data was developed. A combination of both deterministic and statistical techniques was used. The basic mathematical model was based on the Stokes' equation which describes the analytical relationship between mean gravity anomalies and geoid undulations at a point; this undulation is a linear function of the altimetry data at that point. The overdetermined problem resulting from the excessive altimetry data available was solved using Least-Squares principles. These principles enable the simultaneous estimation of the associated standard deviations reflecting the internal consistency based on the accuracy estimates provided for the altimetry data as well as for the terrestrial anomaly data. Several test computations were made of the anomalies and their accuracy estimates using GOES-3 data.

  3. Energy integral method for gravity field determination from satellite orbit coordinates

    NARCIS (Netherlands)

    Visser, P.N.A.M.; Sneeuw, N.; Gerlach, C.

    2003-01-01

    A fast iterative method for gravity field determination from low Earth satellite orbit coordinates has been developed and implemented successfully. The method is based on energy conservation and avoids problems related to orbit dynamics and initial state. In addition, the particular geometry of a re

  4. Satellite Elevation Magnetic and Gravity Models of Major South American Plate Tectonic Features

    Science.gov (United States)

    Vonfrese, R. R. B.; Hinze, W. J.; Braile, L. W.; Lidiak, E. G.; Keller, G. R. (Principal Investigator); Longacre, M. B.

    1984-01-01

    Some MAGSAT scalar and vector magnetic anomaly data together with regional gravity anomaly data are being used to investigate the regional tectonic features of the South American Plate. An initial step in this analysis is three dimensional modeling of magnetic and gravity anomalies of major structures such as the Andean subduction zone and the Amazon River Aulacogen at satellite elevations over an appropriate range of physical properties using Gaus-Legendre quadrature integration method. In addition, one degree average free-air gravity anomalies of South America and adjacent marine areas are projected to satellite elevations assuming a spherical Earth and available MAGSAT data are processed to obtain compatible data sets for correlation. Correlation of these data sets is enhanced by reduction of the MAGSAT data to radial polarization because of the profound effect of the variation of the magnetic inclination over South America.

  5. Satellite Elevation Magnetic and Gravity Models of Major South American Plate Tectonic Features

    Science.gov (United States)

    Vonfrese, R. R. B.; Hinze, W. J.; Braile, L. W.; Lidiak, E. G.; Keller, G. R. (Principal Investigator); Longacre, M. B.

    1984-01-01

    Some MAGSAT scalar and vector magnetic anomaly data together with regional gravity anomaly data are being used to investigate the regional tectonic features of the South American Plate. An initial step in this analysis is three dimensional modeling of magnetic and gravity anomalies of major structures such as the Andean subduction zone and the Amazon River Aulacogen at satellite elevations over an appropriate range of physical properties using Gaus-Legendre quadrature integration method. In addition, one degree average free-air gravity anomalies of South America and adjacent marine areas are projected to satellite elevations assuming a spherical Earth and available MAGSAT data are processed to obtain compatible data sets for correlation. Correlation of these data sets is enhanced by reduction of the MAGSAT data to radial polarization because of the profound effect of the variation of the magnetic inclination over South America.

  6. Swarm satellite mission scheduling & planning using Hybrid Dynamic Mutation Genetic Algorithm

    Science.gov (United States)

    Zheng, Zixuan; Guo, Jian; Gill, Eberhard

    2017-08-01

    Space missions have traditionally been controlled by operators from a mission control center. Given the increasing number of satellites for some space missions, generating a command list for multiple satellites can be time-consuming and inefficient. Developing multi-satellite, onboard mission scheduling & planning techniques is, therefore, a key research field for future space mission operations. In this paper, an improved Genetic Algorithm (GA) using a new mutation strategy is proposed as a mission scheduling algorithm. This new mutation strategy, called Hybrid Dynamic Mutation (HDM), combines the advantages of both dynamic mutation strategy and adaptive mutation strategy, overcoming weaknesses such as early convergence and long computing time, which helps standard GA to be more efficient and accurate in dealing with complex missions. HDM-GA shows excellent performance in solving both unconstrained and constrained test functions. The experiments of using HDM-GA to simulate a multi-satellite, mission scheduling problem demonstrates that both the computation time and success rate mission requirements can be met. The results of a comparative test between HDM-GA and three other mutation strategies also show that HDM has outstanding performance in terms of speed and reliability.

  7. Capturing the fingerprint of Etna volcano activity in gravity and satellite radar data.

    Science.gov (United States)

    Del Negro, Ciro; Currenti, Gilda; Solaro, Giuseppe; Greco, Filippo; Pepe, Antonio; Napoli, Rosalba; Pepe, Susi; Casu, Francesco; Sansosti, Eugenio

    2013-10-30

    Long-term and high temporal resolution gravity and deformation data move us toward a better understanding of the behavior of Mt Etna during the June 1995 - December 2011 period in which the volcano exhibited magma charging phases, flank eruptions and summit crater activity. Monthly repeated gravity measurements were coupled with deformation time series using the Differential Synthetic Aperture Radar Interferometry (DInSAR) technique on two sequences of interferograms from ERS/ENVISAT and COSMO-SkyMed satellites. Combining spatiotemporal gravity and DInSAR observations provides the signature of three underlying processes at Etna: (i) magma accumulation in intermediate storage zones, (ii) magmatic intrusions at shallow depth in the South Rift area, and (iii) the seaward sliding of the volcano's eastern flank. Here we demonstrate the strength of the complementary gravity and DInSAR analysis in discerning among different processes and, thus, in detecting deep magma uprising in months to years before the onset of a new Etna eruption.

  8. A geopotential model from satellite tracking, altimeter, and surface gravity data: GEM-T3

    Science.gov (United States)

    Lerch, F. J.; Nerem, R. S.; Putney, B. H.; Felsentreger, T. L.; Sanchez, B. V.; Marshall, J. A.; Klosko, S. M.; Patel, G. B.; Williamson, R. G.; Chinn, D. S.

    1994-01-01

    An improved model of Earth's gravitational field, Goddard Earth Model T-3 (GEM-T3), has been developed from a combination of satellite tracking, satellite altimeter, and surface gravimetric data. GEM-T3 provides a significant improvement in the modeling of the gravity field at half wavelengths of 400 km and longer. This model, complete to degree and order 50, yields more accurate satellite orbits and an improved geoid representation than previous Goddard Earth Models. GEM-T3 uses altimeter data from GEOS 3 (1975-1976), Seasat (1978) and Geosat (1986-1987). Tracking information used in the solution includes more than 1300 arcs of data encompassing 31 different satellites. The recovery of the long-wavelength components of the solution relies mostly on highly precise satellite laser ranging (SLR) data, but also includes Tracking Network (TRANET) Doppler, optical, and satellite-to-satellite tracking acquired between the ATS 6 and GEOS 3 satellites. The main advances over GEM-T2 (beyond the inclusion of altimeter and surface gravity information which is essential for the resolution of the shorter wavelength geoid) are some improved tracking data analysis approaches and additional SLR data. Although the use of altimeter data has greatly enhanced the modeling of the ocean geoid between 65 deg N and 60 deg S latitudes in GEM-T3, the lack of accurate detailed surface gravimetry leaves poor geoid resolution over many continental regions of great tectonic interest (e.g., Himalayas, Andes). Estimates of polar motion, tracking station coordinates, and long-wavelength ocean tidal terms were also made (accounting for 6330 parameters). GEM-T3 has undergone error calibration using a technique based on subset solutions to produce reliable error estimates. The calibration is based on the condition that the expected mean square deviation of a subset gravity solution from the full set values is predicted by the solutions' error covariances. Data weights are iteratively adjusted until

  9. Changing inclination of earth satellites using the gravity of the moon

    Directory of Open Access Journals (Sweden)

    Karla de Souza Torres

    2006-01-01

    Full Text Available We analyze the problem of the orbital control of an Earth's satellite using the gravity of the Moon. The main objective is to study a technique to decrease the fuel consumption of a plane change maneuver to be performed in a satellite that is in orbit around the Earth. The main idea of this approach is to send the satellite to the Moon using a single-impulsive maneuver, use the gravity field of the Moon to make the desired plane change of the trajectory, and then return the satellite to its nominal semimajor axis and eccentricity using a bi-impulsive Hohmann-type maneuver. The satellite is assumed to start in a Keplerian orbit in the plane of the lunar orbit around the Earth and the goal is to put it in a similar orbit that differs from the initial orbit only by the inclination. A description of the close-approach maneuver is made in the three-dimensional space. Analytical equations based on the patched conics approach are used to calculate the variation in velocity, angular momentum, energy, and inclination of the satellite. Then, several simulations are made to evaluate the savings involved. The time required by those transfers is also calculated and shown.

  10. Mission-constrained design drivers and technical solutions for the MAGIA satellite

    Science.gov (United States)

    Perrotta, Giorgio; Stipa, M.; Silvi, D.; Coltellacci, S.; Curti, G.; Colonna, G.; Formica, T.; Casali, V.; Fossati, T.; Di Matteo, F.; Zelli, M.; Rinaldi, M.; Ansalone, L.; di Salvo, A.

    2011-10-01

    The Mission MAGIA (Missione Altimetrica Geofisica GeochImica lunAre) was proposed in the framework of the "Bando per Piccole Missioni" of ASI (Italian Space Agency) in 2007. The mission was selected for a phase A study by ASI on February 7th 2008. The tight budget allocation, combined with quite ambitious scientific objectives, set challenging requirements for the satellite design. The paper gives a fast overview of the payloads complement and of the mission-constrained design drivers, including cost minimization, risk reduction, and AIT flexibility. The spacecraft architecture is then outlined, along with an overview of the key subsystems and trade-offs. Some details are given of a Moon gravitometric experiment based on a mother-daughter satellite configuration with the daughter being a subsatellite released from the MAGIA satellite and intended to circle the Moon at a very low altitude. Budgets are appended at the end of the paper showing the key study results.

  11. Status of the Third Miniature Sensor Technology Integration Satellite Mission

    OpenAIRE

    Barnhart, David; Hurtz, Rick; McClelland, Jim; Cellarius, Mark; Meyers, AI

    1994-01-01

    The MSTI-3 satellite is the third in a series established to test, in realistic scenarios, miniature spacecraft and sensor technologies for missile detection and tracking on low-cost, low-earth orbit technology demonstration satellites. Cooperative demonstrations are planned to combine MSTI-provided target track file information, with interceptor technology tests, to fully demonstrate technologies associated with theater missile defense (TMO) targeting. The program is sponsored by the Ballist...

  12. A satellite constellation optimization for a regional GNSS remote sensing mission

    Science.gov (United States)

    Gavili Kilaneh, Narin; Mashhadi Hossainali, Masoud

    2017-04-01

    Due to the recent advances in the Global Navigation Satellite System Remote sensing (GNSS¬R) applications, optimization of a satellite orbit to investigate the Earth's properties seems significant. The comparison of the GNSS direct and reflected signals received by a Low Earth Orbit (LEO) satellite introduces a new technique to remotely sense the Earth. Several GNSS¬R missions including Cyclone Global Navigation Satellite System (CYGNSS) have been proposed for different applications such as the ocean wind speed and height monitoring. The geometric optimization of the satellite orbit before starting the mission is a key step for every space mission. Since satellite constellation design varies depending on the application, we have focused on the required geometric criteria for oceanography applications in a specified region. Here, the total number of specular points, their spatial distribution and the accuracy of their position are assumed to be sufficient for oceanography applications. Gleason's method is used to determine the position of specular points. We considered the 2-D lattice and 3-D lattice theory of flower constellation to survey whether a circular orbit or an elliptical one is suitable to improve the solution. Genetic algorithm is implemented to solve the problem. To check the visibility condition between the LEO and GPS satellites, the satellite initial state is propagated by a variable step size numerical integration method. Constellation orbit parameters achieved by optimization provide a better resolution and precession for the specular points in the study area of this research.

  13. Gravity field modelling and gravimetry

    Directory of Open Access Journals (Sweden)

    Krynski Jan

    2015-12-01

    Full Text Available The summary of research activities concerning gravity field modelling and gravimetric works performed in Poland in the period of 2011-2014 is presented. It contains the results of research on geoid modelling in Poland and other countries, evaluation of global geopotential models, determination of temporal variations of the gravity field with the use of data from satellite gravity space missions, absolute gravity surveys for the maintenance and modernization of the gravity control in Poland and overseas, metrological aspects in gravimetry, maintenance of gravimetric calibration baselines, and investigations of the nontidal gravity changes. The bibliography of the related works is given in references.

  14. Global surface density of water mass variations by using a two-step inversion by cumulating daily satellite gravity information

    Science.gov (United States)

    Ramillien, Guillaume; Frappart, Frédéric; Seoane, Lucia

    2016-04-01

    We propose a new method to produce time series of global maps of surface mass variations by progressive integration of daily geopotential variations measured by orbiting satellites. In the case of the GRACE mission, these geopotential variations can be determined from very accurate inter-satellite K-Band Range Rate (KBRR) measurements of 5-second daily orbits. In particular, the along-track gravity contribution of hydrological mass changes is extracted by removing de-aliasing models for static field, atmosphere, oceans mass variations (including periodical tides), as well as polar movements. Our determination of surface mass sources is composed of two successive dependent Kalman filter stages. The first one consists of reducing the satellite-based potential anomalies by adjusting the longest spatial wavelengths (i.e., low-degree spherical harmonics lower than 2). In the second stage, the residual potential anomalies from the previous stage are used to recover surface mass density changes - in terms of Equivalent-Water Height (EWH) - over a global network of juxtaposed triangular elements. These surface tiles of ~100,000 km x km (or equivalently 330 km by 330 km) are defined to be of equal areas over the terrestrial sphere. However they can be adapted to the local geometry of the surface mass. Our global approach was tested by inverting geopotential data, and successfully applied to estimate time-varying surface mass densities from real GRACE-based residuals. This strategy of combined Kalman filter-type inversions can also be useful for exploring the possibility of improving time and space resolutions for ocean and land studies that would be hopefully brought by future low altitude geodetic missions.

  15. Global thermochemical inversion of seismic waveforms, gravity satellite data, and topography

    Science.gov (United States)

    Fullea, J.; Lebedev, S.; Martinec, Z.

    2016-12-01

    Conventional methods of seismic tomography, topography, gravity and electromagnetic data analysis and geodynamic modelling constrain distributions of seismic velocity, density, electrical conductivity, and viscosity at depth, all depending on temperature and composition of Earth's rocks. However, modelling and interpretation of multiple data provide a multifaceted image of the true thermochemical structure of the Earth that needs to be consistently integrated. A simple combination of gravity, electromagnetic, geodynamics, petrological and seismic models alone is insufficient due to the non-uniqueness and different sensitivities of these models, and the internal consistency relationships that must connect all the intermediate parameters describing the Earth. In fact, global Earth models based on different observables often lead to rather different images of the Earth. A breakthrough in global and consistent imaging of the fine-scale thermochemical hydrous and rheological structure of the Earth's lithosphere and underlying mantle is needed. Thermodynamic and petrological links between seismic velocities, density, electrical conductivity, viscosity, melt, water, temperature, pressure and composition within the Earth can now be modelled accurately using new methods of computational petrology and data from laboratory experiments. The growth of very large terrestrial and satellite geophysical data over the last few years, together with the advancement of petrological and geophysical modelling techniques, now present an opportunity for global, thermochemical and deformation 3D imaging of the lithosphere and underlying upper mantle with unprecedented resolution. Here we present a method for self-consistent joint inversion of multiple data sets, including seismic, satellite gravity and surface topography data, applied to obtain a detailed and robust global thermochemical image of the lithosphere and underlying upper mantle. This project combines state-of-the-art seismic

  16. Limb and gravity-darkening coefficients for the TESS satellite at several metallicities, surface gravities, and microturbulent velocities

    Science.gov (United States)

    Claret, A.

    2017-03-01

    Aims: We present new gravity and limb-darkening coefficients for a wide range of effective temperatures, gravities, metallicities, and microturbulent velocities. These coefficients can be used in many different fields of stellar physics as synthetic light curves of eclipsing binaries and planetary transits, stellar diameters, line profiles in rotating stars, and others. Methods: The limb-darkening coefficients were computed specifically for the photometric system of the space mission tess and were performed by adopting the least-square method. In addition, the linear and bi-parametric coefficients, by adopting the flux conservation method, are also available. On the other hand, to take into account the effects of tidal and rotational distortions, we computed the passband gravity-darkening coefficients y(λ) using a general differential equation in which we consider the effects of convection and of the partial derivative (∂lnI(λ) /∂lng)Teff. Results: To generate the limb-darkening coefficients we adopt two stellar atmosphere models: atlas (plane-parallel) and phoenix (spherical, quasi-spherical, and r-method). The specific intensity distribution was fitted using five approaches: linear, quadratic, square root, logarithmic, and a more general one with four terms. These grids cover together 19 metallicities ranging from 10-5 up to 10+1 solar abundances, 0 ≤ log g ≤ 6.0 and 1500 K ≤Teff ≤ 50 000 K. The calculations of the gravity-darkening coefficients were performed for all plane-parallel ATLAS models. Tables 2-29 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/600/A30

  17. Perspectives &advanced projects for small satellite missions at Carlo Gavazzi Space

    Science.gov (United States)

    Morea, G.; Sabatini, P.

    2004-11-01

    This paper presents the Planned and on-going programs in Carlo Gavazzi Space (CGS) for the next five years. Thanks to the success of the first MITA platform mission, CGS has acquired a consolidated experience in Satellite System Design and of Prime Contractor in Satellite programmes. After four years from launch of first MITA platform from Plesetsk (CSI) several mission concept and satellite program have started and are under developing. The common elements to these program is the low mission cost and short development plan. The first ASI Scientific Small Mission using the MITA platform, AGILE is a Gamma Ray detector aimed to identify Gamma Ray Bursts. The Payload has been developed with the contribution of a large group of Italian Research Centres and Institutes, Carlo Gavazzi Space is also responsible for the overall mission as leader of an Italian Consortium. In the frame of ASI's Earth Observation Programmes, Carlo Gavazzi Space has also successfully concluded the Phase B/C of the HypSEO (HyperSpectral Earth Observer) mission. The Desertsat satellite, devoted to the study of the sand dunes movements and to the assessment of the desertification process, is a joint collaboration with ASI and Egypt. Desertsat is equipped with an Multispectral imager. PALAMEDE, whose peculiar characteristics are two: the first is to use components and technologies not space qualified and therefore by far cheaper than those normally used for space systems, the second is that it is entirely realised by the students of Politecnico.

  18. Satellite-On-A-Chip Feasibility for Distributed Space Missions

    Science.gov (United States)

    2006-07-10

    measure variations in magnetic fields 3 Copyright © 2006 ASME around a spacecraft, perform visual inspection of a spacecraft exterior for signs of damage...Table 5. SpaceChip System Specifications Simple low-resolution Earth observation mission, imagenative problem of low efficiency solar cells on

  19. Gravity Recovery and Interior Laboratory (GRAIL) Mission: Status at the Initiation of the Science Mapping Phase

    Science.gov (United States)

    Zuber, Maria T.; Smith, David E.; Asmar, Sami W.; Alomon; Konopliv, Alexander S.; Lemoine, Frank G.; Melosh, H. Jay; Neumann, Gregory A.; Phillips. Roger J.; Solomon, Sean C.; Watkins, Michael M.; Wieczorek, Mark A.; Williams, James G.

    2012-01-01

    The Gravity Recovery And Interior Laboratory (GRAIL) mission, a component of NASA's Discovery Program, launched successfully from Cape Canaveral Air Force Station on September 10, 2011. The dual spacecraft traversed independent, low-energy trajectories to the Moon via the EL-1 Lagrange point and inserted into elliptical, 11.5-hour polar orbits around the Moon on December 31, 2011, and January 1, 2012. The spacecraft are currently executing a series of maneuvers to circularize their orbits at 55-km mean altitude. Once the mapping orbit is achieved, the spacecraft will undergo additional maneuvers to align them into mapping configuration. The mission is on track to initiate the Science Phase on March 8, 2012.

  20. Advanced Ionospheric Probe scientific mission onboard FORMOSAT-5 satellite

    Directory of Open Access Journals (Sweden)

    Zai-Wun Lin

    2017-01-01

    Full Text Available Advanced Ionospheric Probe (AIP is a piggyback science payload developed by National Central University for FORMOSAT-5 satellite to explore space weather/climate and seismic precursors associated with strong earthquakes. The AIP is an all-in-one plasma sensor that measures ionospheric plasma concentrations, velocities, and temperatures in a time-sharing way and is capable of measuring ionospheric plasma irregularities at a sample rate up to 8192 Hz over a wide range of spatial scales. Electroformed gold grids used in the AIP in theory construct planar electric potential surfaces better than woven grids. Moreover, a plasma injection test performed in the Space Plasma Simulation Chamber has verified that no significant hysteresis is found in current-voltage curves measured by the AIP. It indicates that the AIP can make an accurate measurement of the ionospheric plasma parameters in space. Finally, Ionospheric Plasma and Electrodynamics Instrument (IPEI observations onboard the ROCSAT-1 satellite are applied to show that the scientific objectives of ionospheric space weather/climate and seismo-ionospheric precursors (SIPs of the FORMOSAT-5/AIP can be fulfilled. The observations reveal that ion parameter global distributions are helpful in studying the formation and variation in temperature crests and troughs in the 2200 - 2300 local time sector, as well as SIPs in the density and the velocity over the epicenter area, which are anticipated for the FORMOSAT-5 satellite orbit.

  1. Vertical and Horizontal Analysis of Crustal Structure of Southeastern Mediterranean and the Egyptian Coastal Zone, from Bouguer and Satellite Mission Data

    Science.gov (United States)

    Saleh, Salah

    2016-07-01

    The present Tectonic system of Southeastern Mediterranean is driven by the collision of the African and Eurasian plates, the Arabian Eurasian convergence and the displacement of the Anatolian Aegean microplate, which generally represents the characteristic of lithospheric structure of the region. In the scope of this study, Bouguer and the satellite gravity (satellite altimetry) anomalies of southeastern Mediterranean and North Eastern part of Egypt were used for investigating the lithospheric structures. Second order trend analyses were applied firstly to Bouguer and satellite altimetry data for examining the characteristic of the anomaly. Later, the vertical and horizontal derivatives applications were applied to the same data. Generally, the purpose of the applying derivative methods is determining the vertical and horizontal borders of the structure. According to the results of derivatives maps, the study area could mainly divided into important four tectonic subzones depending on basement and Moho depth maps. These subzones are distributed from south to the north as: Nile delta-northern Sinai zone, north Egyptian coastal zone, Levantine basin zone and northern thrusting (Cyprus and its surroundings) zone. These zones are separated from each other by horizontal tectonic boundaries and/or near-vertical faults that display the block-faulting tectonic style of this belt. Finally, the gravity studies were evaluated together with the seismic activity of the region. Consequently, the geodynamical structure of the region is examined with the previous studies done in the region. Thus, the current study indicates that satellite gravity mission data is a valuable source of data in understanding the tectonic boundary behavior of the studied region and that satellite gravity data is an important modern source of data in the geodynamical studies.

  2. Space Network IP Services (SNIS): An Architecture for Supporting Low Earth Orbiting IP Satellite Missions

    Science.gov (United States)

    Israel, David J.

    2005-01-01

    The NASA Space Network (SN) supports a variety of missions using the Tracking and Data Relay Satellite System (TDRSS), which includes ground stations in White Sands, New Mexico and Guam. A Space Network IP Services (SNIS) architecture is being developed to support future users with requirements for end-to-end Internet Protocol (IP) communications. This architecture will support all IP protocols, including Mobile IP, over TDRSS Single Access, Multiple Access, and Demand Access Radio Frequency (RF) links. This paper will describe this architecture and how it can enable Low Earth Orbiting IP satellite missions.

  3. Satellite Galaxy Velocity Dispersions in the SDSS and Modified Gravity Models

    Directory of Open Access Journals (Sweden)

    John W. Moffat

    2014-05-01

    Full Text Available The Sloan Digital Sky Survey (SDSS provides data on several hundred thousand galaxies. The precise location of these galaxies in the sky, along with information about their luminosities and line-of-sight (Doppler velocities, allows one to construct a three-dimensional map of their location and estimate their line-of-sight velocity dispersion. This information, in principle, allows one to test dynamical gravity models, specifically models of satellite galaxy velocity dispersions near massive hosts. A key difficulty is the separation of true satellites from interlopers. We sidestep this problem by not attempting to derive satellite galaxy velocity dispersions from the data, but instead incorporate an interloper background into the mathematical models and compare the result to the actual data. We find that due to the presence of interlopers, it is not possible to exclude several gravitational theories on the basis of the SDSS data.

  4. Simulation Studies of Satellite Laser CO2 Mission Concepts

    Science.gov (United States)

    Kawa, Stephan Randy; Mao, J.; Abshire, J. B.; Collatz, G. J.; Sun X.; Weaver, C. J.

    2011-01-01

    Results of mission simulation studies are presented for a laser-based atmospheric CO2 sounder. The simulations are based on real-time carbon cycle process modeling and data analysis. The mission concept corresponds to ASCENDS as recommended by the US National Academy of Sciences Decadal Survey. Compared to passive sensors, active (lidar) sensing of CO2 from space has several potentially significant advantages that hold promise to advance CO2 measurement capability in the next decade. Although the precision and accuracy requirements remain at unprecedented levels of stringency, analysis of possible instrument technology indicates that such sensors are more than feasible. Radiative transfer model calculations, an instrument model with representative errors, and a simple retrieval approach complete the cycle from "nature" run to "pseudodata" CO2. Several mission and instrument configuration options are examined, and the sensitivity to key design variables is shown. Examples are also shown of how the resulting pseudo-measurements might be used to address key carbon cycle science questions.

  5. Experiences from ship- and airborne gravity missions within the FAMOS project and onboard the HALO aircraft

    Science.gov (United States)

    Förste, Christoph; Franz, Barthelmes; Svetozar, Petrovic; Biao, Lu; Gunter, Liebsch; Joachim, Schwabe; Jonas, Ågren; Bilker-Koivula, Mirjam; Koivula, Hannu; Ince, Sinem; Scheinert, Mirko

    2017-04-01

    In 2011 GFZ restarted its activities in gravimetry on moving platforms using a Chekan-AM air/ship gravimeter. Since then various gravity missions have been carried out. One special focus of these campaigns is on the improvement of the geoid in the Baltic Sea region within the framework of the ongoing project "Finalising Surveys for the Baltic Motorways of the Sea" (FAMOS). In this context, GFZ has already conducted four campaigns since 2015 together with several European partners around the Baltic Sea under the project management of the Swedish Maritime Administration (SMA). Further two campaigns per year are planned with the GFZ gravimeter till the end of 2020. FAMOS is supported by the European Commission within its Connecting Europe Facility (CET). Another focus is on testing the power and limits of airborne gravimetry onboard the German High Altitude and LOng Range (HALO) research aircraft. An appropriate airborne campaign using this aircraft has been carried out in 2012 over Italy in the framework of the project GEOHALO which was a joint project of several universities and research institutions. The main purpose was to check the performance of the equipment on this aircraft, aiming at the plan to cover the gravity data gap over Antarctica. The presentation gives an overview of these campaigns, summarizes our experiences, especially with respect to processing of the collected data, and shows results from these missions.

  6. Satellite observations of ground water changes in New Mexico

    Science.gov (United States)

    In 2002 NASA launched the Gravity Recovery and Climate Experiment (GRACE) satellite mission. GRACE consists of two satellites with a separation of about 200 km.  By accurately measuring the separation between the twin satellites, the differences in the gravity field can be determined. Monthly observ...

  7. Analysis and numerical modeling of the global free infra-gravity wave climate for the SWOT mission

    Science.gov (United States)

    Ardhuin, Fabrice; Aucan, Jérome; Rawat, Arshad

    2013-04-01

    All sea level variations of the order of 1 cm at scales under 30 km are of great interest for the future Surface Water Ocean Topography (SWOT) satellite mission. That satellite should provide high-resolution maps of the sea surface height for analysis of meso to sub-mesoscale currents, but that will require a filtering of all gravity wave motions in the data. Free infragravity waves (FIGWs) are generated and radiate offshore when swells and/or wind seas and their associated bound infragravity waves impact exposed coastlines. Free infragravity waves have dominant periods comprised between 1 and 10 minutes and horizontal wavelengths of up to tens of kilometers. Given the length scales of the infragravity waves wavelength and amplitude, the infragravity wave field will can a significant fraction the signal measured by the future SWOT mission. In this study, we analyze the data from recovered bottom pressure recorders of the Deep-ocean Assessment and Reporting of Tsunami (DART) program. This analysis includes data spanning several years between 2006 and 2010, from stations at different latitudes in the North and South Pacific, the North Atlantic, the Gulf of Mexico and the Caribbean Sea. We present and discuss the following conclusions: (1) The amplitude of free infragravity waves can reach several centimeters, higher than the precision sought for the SWOT mission. (2) The free infragravity signal is higher in the Eastern North Pacific than in the Western North Pacific, possibly due to smaller incident swell and seas impacting the nearby coastlines. (3) Free infragravity waves are higher in the North Pacific than in the North Atlantic, possibly owing to different average continental shelves configurations in the two basins. (4) There is a clear seasonal cycle at the high latitudes North Atlantic and Pacific stations that is much less pronounced or absent at the tropical stations, consistent with the generation mechanism of free infragravity waves. Our numerical model

  8. Analysis of the global free infra-gravity wave climate for the SWOT mission, and preliminary results of numerical modelling

    Science.gov (United States)

    Rawat, A.; Aucan, J.; Ardhuin, F.

    2012-12-01

    All sea level variations of the order of 1 cm at scales under 30 km are of great interest for the future Surface Water Ocean Topography (SWOT) satellite mission. That satellite should provide high-resolution maps of the sea surface height for analysis of meso to sub-mesoscale currents, but that will require a filtering of all gravity wave motions in the data. Free infragravity waves (FIGWs) are generated and radiate offshore when swells and/or wind seas and their associated bound infragravity waves impact exposed coastlines. Free infragravity waves have dominant periods comprised between 1 and 10 minutes and horizontal wavelengths of up to tens of kilometers. Given the length scales of the infragravity waves wavelength and amplitude, the infragravity wave field will can a significant fraction the signal measured by the future SWOT mission. In this study, we analyze the data from recovered bottom pressure recorders of the Deep-ocean Assessment and Reporting of Tsunami (DART) program. This analysis includes data spanning several years between 2006 and 2010, from stations at different latitudes in the North and South Pacific, the North Atlantic, the Gulf of Mexico and the Caribbean Sea. We present and discuss the following conclusions: (1) The amplitude of free infragravity waves can reach several centimeters, higher than the precision sought for the SWOT mission. (2) The free infragravity signal is higher in the Eastern North Pacific than in the Western North Pacific, possibly due to smaller incident swell and seas impacting the nearby coastlines. (3) Free infragravity waves are higher in the North Pacific than in the North Atlantic, possibly owing to different average continental shelves configurations in the two basins. (4) There is a clear seasonal cycle at the high latitudes North Atlantic and Pacific stations that is much less pronounced or absent at the tropical stations, consistent with the generation mechanism of free infragravity waves. Our numerical model

  9. A new regard on the tectonic map of the Arabian-African region inferred from the satellite gravity analysis

    Science.gov (United States)

    Eppelbaum, Lev; Katz, Youri

    2017-07-01

    Satellite gravimetry is a powerful and reliable tool for regional tectono-geodynamic zonation. The studied region contains intricate geodynamical features (high seismological indicators, active rift systems and collision processes), richest structural arrangement (existence of mosaic blocks of oceanic and continental Earth's crust of various age), and a number of high-amplitude gravity anomalies and complex magnetic pattern. The most hydrocarbon reserves of the world and other important economic deposits occur in this region. Comprehensive analysis of satellite gravity data with application of different approaches was used to develop a sequence of maps specifying crucial properties of the region deep structure. Careful examination of numerous geological sources and their combined examination with satellite gravity (main), magnetic, GPS, seismic, seismological and some other geophysical data enabled to develop a new tectonic map of the Arabian-African region. Integrated analysis of series of gravity map transformations and certain geological indicators allowed to reveal significant geodynamic features of the region.

  10. A test of general relativity using the LARES and LAGEOS satellites and a GRACE Earth gravity model. Measurement of Earth's dragging of inertial frames

    Energy Technology Data Exchange (ETDEWEB)

    Ciufolini, Ignazio [Universita del Salento, Dipartimento Ingegneria dell' Innovazione, Lecce (Italy); Sapienza Universita di Roma, Scuola di Ingegneria Aerospaziale, Rome (Italy); Paolozzi, Antonio; Paris, Claudio [Sapienza Universita di Roma, Scuola di Ingegneria Aerospaziale, Rome (Italy); Museo della Fisica e Centro Studi e Ricerche Enrico Fermi, Rome (Italy); Pavlis, Erricos C. [University of Maryland, Joint Center for Earth Systems Technology (JCET), Baltimore County (United States); Koenig, Rolf [GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Potsdam (Germany); Ries, John [University of Texas at Austin, Center for Space Research, Austin (United States); Gurzadyan, Vahe; Khachatryan, Harutyun; Mirzoyan, Sergey [Alikhanian National Laboratory and Yerevan State University, Center for Cosmology and Astrophysics, Yerevan (Armenia); Matzner, Richard [University of Texas at Austin, Theory Center, Austin (United States); Penrose, Roger [University of Oxford, Mathematical Institute, Oxford (United Kingdom); Sindoni, Giampiero [Sapienza Universita di Roma, DIAEE, Rome (Italy)

    2016-03-15

    We present a test of general relativity, the measurement of the Earth's dragging of inertial frames. Our result is obtained using about 3.5 years of laser-ranged observations of the LARES, LAGEOS, and LAGEOS 2 laser-ranged satellites together with the Earth gravity field model GGM05S produced by the space geodesy mission GRACE. We measure μ = (0.994 ± 0.002) ± 0.05, where μ is the Earth's dragging of inertial frames normalized to its general relativity value, 0.002 is the 1-sigma formal error and 0.05 is our preliminary estimate of systematic error mainly due to the uncertainties in the Earth gravity model GGM05S. Our result is in agreement with the prediction of general relativity. (orig.)

  11. A test of general relativity using the LARES and LAGEOS satellites and a GRACE Earth gravity model: Measurement of Earth's dragging of inertial frames.

    Science.gov (United States)

    Ciufolini, Ignazio; Paolozzi, Antonio; Pavlis, Erricos C; Koenig, Rolf; Ries, John; Gurzadyan, Vahe; Matzner, Richard; Penrose, Roger; Sindoni, Giampiero; Paris, Claudio; Khachatryan, Harutyun; Mirzoyan, Sergey

    2016-01-01

    We present a test of general relativity, the measurement of the Earth's dragging of inertial frames. Our result is obtained using about 3.5 years of laser-ranged observations of the LARES, LAGEOS, and LAGEOS 2 laser-ranged satellites together with the Earth gravity field model GGM05S produced by the space geodesy mission GRACE. We measure [Formula: see text], where [Formula: see text] is the Earth's dragging of inertial frames normalized to its general relativity value, 0.002 is the 1-sigma formal error and 0.05 is our preliminary estimate of systematic error mainly due to the uncertainties in the Earth gravity model GGM05S. Our result is in agreement with the prediction of general relativity.

  12. Lithospheric bending at subduction zones based on depth soundings and satellite gravity

    Science.gov (United States)

    Levitt, Daniel A.; Sandwell, David T.

    1995-01-01

    A global study of trench flexure was performed by simultaneously modeling 117 bathymetric profiles (original depth soundings) and satellite-derived gravity profiles. A thin, elastic plate flexure model was fit to each bathymetry/gravity profile by minimization of the L(sub 1) norm. The six model parameters were regional depth, regional gravity, trench axis location, flexural wavelength, flexural amplitude, and lithospheric density. A regional tilt parameter was not required after correcting for age-related trend using a new high-resolution age map. Estimates of the density parameter confirm that most outer rises are uncompensated. We find that flexural wavelength is not an accurate estimate of plate thickness because of the high curvatures observed at a majority of trenches. As in previous studies, we find that the gravity data favor a longer-wavelength flexure than the bathymetry data. A joint topography-gravity modeling scheme and fit criteria are used to limit acceptable parameter values to models for which topography and gravity yield consistent results. Even after the elastic thicknesses are converted to mechanical thicknesses using the yield strength envelope model, residual scatter obscures the systematic increase of mechanical thickness with age; perhaps this reflects the combination of uncertainties inherent in estimating flexural wavelength, such as extreme inelastic bending and accumulated thermoelastic stress. The bending moment needed to support the trench and outer rise topography increases by a factor of 10 as lithospheric age increases from 20 to 150 Ma; this reflects the increase in saturation bending moment that the lithosphere can maintain. Using a stiff, dry-olivine rheology, we find that the lithosphere of the GDH1 thermal model (Stein and Stein, 1992) is too hot and thin to maintain the observed bending moments. Moreover, the regional depth seaward of the oldest trenches (approximately 150 Ma) exceeds the GDH1 model depths by about 400 m.

  13. Indian remote sensing satellites: Planned missions and future applications

    Science.gov (United States)

    Chandrasekhar, M. G.; Jayaraman, V.; Rao, Mukund

    1996-02-01

    To cater the enhanced user demands, Indian Space Research Organisation is stepping a giant leap forward towards development of the state-of-the-art second generation Indian Remote Sensing Satellites, IRS-1C/1D following the successful design, launch and in-orbit performance of the first generation satellites, IRS-1A/1B. Characterised by improved spatial resolution, extended spectral bands, stereo-viewing and more frequent revisit capability, IRS-1C/1D are expected for launch during the timeframe of 1995-96/8. The IRS-1C and ID, which are identical, will have three major payloads. The Linear Imaging Spectral Scanner (LISS-III) in four spectral bands covering from 0.52 to 1.70 microns will have a spatial resolution of 23m along with a swath of 142 km in the visible and NIR spectral bands and a spatial resolution of 70m along with a swath of 148 km in the SWIR spectral band. The Panchromatic Camera (PAN) with a spectral band of 0.50 to 0.75 microns will have a spatial resolution of information on water stress, pest infestation and vegetation indices to arrive at better agricultural management practices, besides providing enhanced capabilities for arriving solutions for micro-level resource development and generation of digital terrain models. Having marked by the successful launch of IRS-P2 in 1994 through the indigenous development flight of PSLV, India is now poised to launch IRS-P3 satellite with unique payloads in the timeframe of 1995-1996 The IRS-P3 will carry three operational payloads viz., Wide Field Sensor (WiFS), Modular Opto-electronic Scanner (MOS) imaging spectrometer and an X-ray Astronomy payload. These payload mix of sensors will provide further capabilities for application studies related to vegetation dynamics, oceanography and X-ray astronomy. With the launch of these payloads, India will provide more effective and assured data services to the user community beyond the 90's.

  14. Deep and shallow structures in the Arctic region imaged by satellite magnetic and gravity data

    Science.gov (United States)

    Gaina, Carmen; Panet, Isabelle; Shephard, Grace

    2016-07-01

    The last decade has seen an increase in geoscientific data collection, which, together with available and older classified data made publicly available, is contributing to increasing our knowledge about Earth's structure and evolution. Despite this development, there are many gaps in data coverage in remote, hard-to-access regions. Satellite data have the advantage of acquiring measurements steadily and covering the entire globe. From a tectonics point of view, the specific heights of various satellites allow for the identification of moderate to large tectonic features, and can shed light on Earth's lower crust and lithosphere structure. In this contribution I discuss the use of magnetic and gravity models based on satellite data in deciphering the tectonic structure of remote areas. The present day Circum-Arctic region comprises a variety of tectonic settings: from active seafloor spreading in the North Atlantic and Eurasian Basin, and subduction in the North Pacific, to long-lived stable continental platforms in North America and Asia. A series of rifted margins, abandoned rifted areas and presumably extinct oceanic basins fringe these regions. Moreover, rifting- and seafloor spreading-related processes formed many continental splinters and terranes that were transported and docked at higher latitudes. Volcanic provinces of different ages have also been identified, from the Permian-Triassic Siberian traps at ca. 251 Ma to the (presumably) Cretaceous HALIP and smaller Cenozoic provinces in northern Greenland and the Barents Sea. We inspect global lithospheric magnetic data in order to identify the signature of the main volcanic provinces in the High Arctic. One of the most striking features in the Arctic domain is the strong magnetic anomaly close to the North Pole that correlates with a large, igneous oceanic plateau called the Alpha Mendeleev Ridge. The intensity and extent of the magnetic anomalies recorded by aircraft or satellites point towards a very thick

  15. Japanese Global Precipitation Measurement (GPM) mission status and application of satellite-based global rainfall map

    Science.gov (United States)

    Kachi, Misako; Shimizu, Shuji; Kubota, Takuji; Yoshida, Naofumi; Oki, Riko; Kojima, Masahiro; Iguchi, Toshio; Nakamura, Kenji

    2010-05-01

    As accuracy of satellite precipitation estimates improves and observation frequency increases, application of those data to societal benefit areas, such as weather forecasts and flood predictions, is expected, in addition to research of precipitation climatology to analyze precipitation systems. There is, however, limitation on single satellite observation in coverage and frequency. Currently, the Global Precipitation Measurement (GPM) mission is scheduled under international collaboration to fulfill various user requirements that cannot be achieved by the single satellite, like the Tropical Rainfall Measurement Mission (TRMM). The GPM mission is an international mission to achieve high-accurate and high-frequent rainfall observation over a global area. GPM is composed of a TRMM-like non-sun-synchronous orbit satellite (GPM core satellite) and constellation of satellites carrying microwave radiometer instruments. The GPM core satellite carries the Dual-frequency Precipitation Radar (DPR), which is being developed by the Japan Aerospace Exploration Agency (JAXA) and the National Institute of Information and Communications Technology (NICT), and microwave radiometer provided by the National Aeronautics and Space Administration (NASA). Development of DPR instrument is in good progress for scheduled launch in 2013, and DPR Critical Design Review has completed in July - September 2009. Constellation satellites, which carry a microwave imager and/or sounder, are planned to be launched around 2013 by each partner agency for its own purpose, and will contribute to extending coverage and increasing frequency. JAXA's future mission, the Global Change Observation Mission (GCOM) - Water (GCOM-W) satellite will be one of constellation satellites. The first generation of GCOM-W satellite is scheduled to be launched in 2011, and it carries the Advanced Microwave Scanning Radiometer 2 (AMSR2), which is being developed based on the experience of the AMSR-E on EOS Aqua satellite

  16. Tests of daily time variable Earth gravity field solutions for precise orbit determination of altimetry satellites

    Science.gov (United States)

    Rudenko, Sergei; Gruber, Christian

    2016-04-01

    This study makes use of current GFZ monthly and daily gravity field products from 2002 to 2014 based on radial basis functions (RBF) instead of time variable gravity field modeling for precise orbit determination of altimetry satellites. Since some monthly solutions are missing in the GFZ GRACE RL05a solution and in order to reach a better quality for the precise orbit determination, daily generated RBF solutions obtained from Kalman filtered GRACE data processing and interpolated in case of gaps have been used. Moreover, since the geopotential coefficients of low degrees are better determined using SLR observations to geodetic satellites like Lageos, Stella, Starlette and Ajisai than from GRACE observations, these terms are co-estimated in the RBF solutions by using apriori SLR-derived values up to degree and order 4. Precise orbits for altimetry satellites Envisat (2002-2012), Jason-1 (2002-2013) and Jason-2 (2008-2014) are then computed over the given time intervals using this approach and compared with the orbits obtained when using other models such as EIGEN-6S4. An analysis of the root-mean-square values of the observation fits of SLR and DORIS observations and the orbit arcs overlaps will allow us to draw a conclusion on the quality of the RBF solution and to use these new trajectories for sea level trend estimates and geophysical application.

  17. Latitude variability of acoustic-gravity waves in the upper atmosphere based on satellite data

    Science.gov (United States)

    Fedorenko, A. K.; Bespalova, A. V.; Zhuk, I. T.; Kryuchkov, E. I.

    2017-07-01

    Based on satellite measurements, we investigated the properties of acoustic-gravity waves in different geographical areas of the Earth's upper atmosphere. To study wave activity at high latitudes, we used the concentration of neutral particles measured by the low-altitude polar satellite Dynamic Explorer 2 and measurements from the equatorial satellite Atmosphere Explorer-E for analysis of waves at low latitudes. In the range of heights 250-400 km, there are observed latitudinal variations of amplitudes, together with variations in the morphological and spectral properties of acoustic-gravity waves. In the polar regions of thermosphere, the wave amplitudes amount to 3-10% in terms of relative variations of density and do not exceed 3% at low and middle latitudes. At low latitudes, regular fluctuations induced by the solar terminator are clearly seen with a predominant wave mode moving synchronously with terminator. Moreover, at low and middle latitudes, there are observed sporadic local wave packets of small amplitudes (1-2%) that can have origins of various natures. We also investigated the relation between some of the observed wave trains and the earthquakes.

  18. Parallel satellite orbital situational problems solver for space missions design and control

    Science.gov (United States)

    Atanassov, Atanas Marinov

    2016-11-01

    Solving different scientific problems for space applications demands implementation of observations, measurements or realization of active experiments during time intervals in which specific geometric and physical conditions are fulfilled. The solving of situational problems for determination of these time intervals when the satellite instruments work optimally is a very important part of all activities on every stage of preparation and realization of space missions. The elaboration of universal, flexible and robust approach for situation analysis, which is easily portable toward new satellite missions, is significant for reduction of missions' preparation times and costs. Every situation problem could be based on one or more situation conditions. Simultaneously solving different kinds of situation problems based on different number and types of situational conditions, each one of them satisfied on different segments of satellite orbit requires irregular calculations. Three formal approaches are presented. First one is related to situation problems description that allows achieving flexibility in situation problem assembling and presentation in computer memory. The second formal approach is connected with developing of situation problem solver organized as processor that executes specific code for every particular situational condition. The third formal approach is related to solver parallelization utilizing threads and dynamic scheduling based on "pool of threads" abstraction and ensures a good load balance. The developed situation problems solver is intended for incorporation in the frames of multi-physics multi-satellite space mission's design and simulation tools.

  19. Status of the fast mission: Micro-satellite formation flying for technology, science and education

    NARCIS (Netherlands)

    Guo, J.; Maessen, D.C.; Gill, E.K.A.; Moon, S.G.; Zheng, G.

    2009-01-01

    FAST (Formation for Atmospheric Science and Technology demonstration) is a cooperative Dutch Chinese formation flying mission led by Delft University of Technology (TU Delft) in the Netherlands and Tsinghua University in China. It is expected to be the first international micro-satellite formation f

  20. Status of the fast mission: Micro-satellite formation flying for technology, science and education

    NARCIS (Netherlands)

    Guo, J.; Maessen, D.C.; Gill, E.K.A.; Moon, S.G.; Zheng, G.

    2009-01-01

    FAST (Formation for Atmospheric Science and Technology demonstration) is a cooperative Dutch Chinese formation flying mission led by Delft University of Technology (TU Delft) in the Netherlands and Tsinghua University in China. It is expected to be the first international micro-satellite formation

  1. Status of the fast mission: Micro-satellite formation flying for technology, science and education

    NARCIS (Netherlands)

    Guo, J.; Maessen, D.C.; Gill, E.K.A.; Moon, S.G.; Zheng, G.

    2009-01-01

    FAST (Formation for Atmospheric Science and Technology demonstration) is a cooperative Dutch Chinese formation flying mission led by Delft University of Technology (TU Delft) in the Netherlands and Tsinghua University in China. It is expected to be the first international micro-satellite formation f

  2. Versatile Satellite Architecture and Technology: A New Architecture for Low Cost Satellite Missions for Solar-Terrestrial Studies

    Science.gov (United States)

    Cook, T. A.; Chakrabarti, S.; Polidan, R.; Jaeger, T.; Hill, L.

    2011-12-01

    Early in the 20th century, automobiles appeared as extraordinary vehicles - and now they are part of life everywhere. Late in the 20th century, internet and portable phones appeared as innovations - and now omni-present requirements. At mid-century, the first satellites were launched into space - and now 50 years later - "making a satellite" remains in the domain of highly infrequent events. Why do all universities and companies not have their own satellites? Why is the work force capable of doing so remarkably small? Why do highly focused science objectives that require just a glimpse from space never get a chance to fly? Historically, there have been two primary impediments to place an experiment in orbit - high launch costs and the high cost of spacecraft systems and related processes. The first problem appears to have been addressed through the availability of several low-cost (< $10M) commercial launch opportunities. The Versatile Satellite Architecture and Technology (VerSAT) will address the second. Today's space missions are often large, complex and require development times typically a decade from conception to execution. In present risk-averse scenario, the huge expense of these one-of-a-kind mission architecture can only be justified if the technology required to make orders of magnitude gains is flight-proven at the time mission conception. VerSAT will complement these expensive missions which are "too large to fail" and the CUBESATs. A number of Geospace science experiments that could immediately take advantage of VerSAT have been identified. They range from the study of fundamental questions of the "ignorosphere" from a single satellite lasting a few days - a region of space that was probed once about 40 years ago, to a constellation of satellites which will disentangle the space and time ambiguity of the variability of ionospheric structures and their link to the storms in the Sun to long-term studies of the Sun-Earth system. VerSAT is a true

  3. Capturing the fingerprint of Etna volcano activity in gravity and satellite radar data

    Science.gov (United States)

    Negro, Ciro Del; Currenti, Gilda; Solaro, Giuseppe; Greco, Filippo; Pepe, Antonio; Napoli, Rosalba; Pepe, Susi; Casu, Francesco; Sansosti, Eugenio

    2013-01-01

    Long-term and high temporal resolution gravity and deformation data move us toward a better understanding of the behavior of Mt Etna during the June 1995 – December 2011 period in which the volcano exhibited magma charging phases, flank eruptions and summit crater activity. Monthly repeated gravity measurements were coupled with deformation time series using the Differential Synthetic Aperture Radar Interferometry (DInSAR) technique on two sequences of interferograms from ERS/ENVISAT and COSMO-SkyMed satellites. Combining spatiotemporal gravity and DInSAR observations provides the signature of three underlying processes at Etna: (i) magma accumulation in intermediate storage zones, (ii) magmatic intrusions at shallow depth in the South Rift area, and (iii) the seaward sliding of the volcano's eastern flank. Here we demonstrate the strength of the complementary gravity and DInSAR analysis in discerning among different processes and, thus, in detecting deep magma uprising in months to years before the onset of a new Etna eruption. PMID:24169569

  4. Conceptual Design of a Communications Relay Satellite for a Lunar Sample Return Mission

    Science.gov (United States)

    Brunner, Christopher W.

    2005-01-01

    In 2003, NASA solicited proposals for a robotic exploration of the lunar surface. Submissions were requested for a lunar sample return mission from the South Pole-Aitken Basin. The basin is of interest because it is thought to contain some of the oldest accessible rocks on the lunar surface. A mission is under study that will land a spacecraft in the basin, collect a sample of rock fragments, and return the sample to Earth. Because the Aitken Basin is on the far side of the Moon, the lander will require a communications relay satellite (CRS) to maintain contact with the Earth during its surface operation. Design of the CRS's orbit is therefore critical. This paper describes a mission design which includes potential transfer and mission orbits, required changes in velocity, orbital parameters, and mission dates. Several different low lunar polar orbits are examined to compare their availability to the lander versus the distance over which they must communicate. In addition, polar orbits are compared to a halo orbit about the Earth-Moon L2 point, which would permit continuous communication at a cost of increased fuel requirements and longer transmission distances. This thesis also examines some general parameters of the spacecraft systems for the mission under study. Mission requirements for the lander dictate the eventual choice of mission orbit. This mission could be the first step in a period of renewed lunar exploration and eventual human landings.

  5. Launch mission summary and terminal countdown, Delta 153 Satellite Business Systems satellite (SBS-A)

    Science.gov (United States)

    1980-01-01

    A brief summary of the launch vehicle, spacecraft, and mission is contained. Information relative to launch windows, vehicle telemetry coverage, realtime data flow, telemetry coverage by station, selected trajectory information, and a brief sequence of flight events is also included.

  6. Satellite traces, range spread-F occurrence, and gravity wave propagation at the southern anomaly crest

    Energy Technology Data Exchange (ETDEWEB)

    Cabrera, M.A. [Universidad Tecnologica Nacional, Tucuman (Argentina). CIASUR, Facultad Regional Tucuman; Universidad Nacional de Tucuman (Argentina). Lab. de Ionosfera; Pezzopane, M.; Zuccheretti, E. [Istituto Nazionale di Geofisica e Vulcanologia, Rome (Italy); Ezquer, R.G. [Universidad Tecnologica Nacional, Tucuman (Argentina). CIASUR, Facultad Regional Tucuman; Universidad Nacional de Tucuman (Argentina). Lab. de Ionosfera; Consejo Nacional de Investigaciones Cientificas y Tecnicas, Buenos Aires (Argentina)

    2010-07-01

    Range spread-F (RSF) and occurrence of ''satellite'' traces prior to RSF onset were studied at the southern peak of the ionospheric equatorial anomaly (EA). Ionograms recorded in September 2007 at the new ionospheric station of Tucuman, Argentina (26.9 S, 294.6 E, dip latitude 15.5 S), by the Advanced Ionospheric Sounder (AIS) developed at the Istituto Nazionale di Geofisica e Vulcanologia (INGV), were considered. Satellite traces (STs) are confirmed to be a necessary precursor to the appearance of an RSF trace on the ionograms. Moreover, an analysis of isoheight contours of electron density seems to suggest a relationship between RSF occurrence and gravity wave (GW) propagation. (orig.)

  7. Long-term groundwater variations in Northwest India from satellite gravity measurements

    Science.gov (United States)

    Chen, Jianli; Li, Jin; Zhang, Zizhan; Ni, Shengnan

    2014-05-01

    Satellite gravity data from the Gravity Recovery and Climate Experiment (GRACE) provides quantitative measures of terrestrial water storage (TWS) change at large spatial scales. Combining GRACE-observed TWS changes and model estimates of water storage changes in soil and snow at the surface offers a means for measuring groundwater storage change. In this study, we re-assess long-term groundwater storage variation in the Northwest India (NWI) region using an extended record of GRACE time-variable gravity measurements, and a fully unconstrained global forward modeling method. Our new assessments based on the GRACE release-5 (RL05) gravity solutions indicate that during the 10 year period January 2003 to December 2012, the NWI groundwater depletion remains pronounced, especially during the first 5 years (01/2003-12/2007). The newly estimated depletion rates are ~ 20.4 ± 7.1 Gigatonne (Gt)/yr averaged over the 10 year period, and 29.4 ± 8.4 Gt/yr during the first 5 years. The yearly groundwater storage changes in the NWI region are strongly correlated with yearly precipitation anomalies. In 2009, the driest season of the decade, the groundwater depletion reaches nearly 80 Gt, while in the two relatively wet seasons, 2008 and 2011, the groundwater storages even see net increases of about 24 and 35 Gt, respectively. The estimated mean groundwater depletion rates for the first 5 years are significantly higher than previous assessments. The larger depletion rates may reflect the benefits from improved data quality of GRACE RL05 gravity solutions, and improved data processing method, which can more effectively reduce leakage error in GRACE estimates. Our analysis indicates that the neighboring Punjab Province of Pakistan (especially Northern Punjab) apparently also experiences significant groundwater depletion during the same period, which has partly contributed to the new regional groundwater depletion estimates.

  8. The Initial Flight Calibration of the Gyroscopes for the Relativity Mission, Gravity Probe B

    Science.gov (United States)

    Buchman, S.; Bencze, W. J.; Brumley, R. W.; Muhlfelder, B.

    The Relativity Mission, Gravity Probe B (GP-B), uses four redundant high precision gyroscopes for measuring the relativistic precessions of the frame of reference in a 640 km polar orbit. The two precessions to be measured are predicted in General Relativity to be the geodetic effect, 6.6 arcsec/year, and the frame dragging effect, 0.042 arcsec/year. The principal performance requirement for the gyroscopes is an accuracy capability of better than 0.3 marcsec/year. Results from more than 120,000 hours of gyroscope operation, testing on simulators, and analysis indicate that the residual Newtonian drift will be about 0.05 marcsec/year for a supported gyroscope and 0.01 marcsec/year for an unsupported gyroscope in a fully inertial orbit. Further disturbance reduction is achievable by optimizing the preload suspension voltage using measured flight parameters. Consistent with the presently scheduled launch of the Gravity Probe on April 17 2004, preliminary results from the initial testing, calibration, and spin-up of the gyroscopes will be presented.

  9. Implementation and Test of the Automatic Flight Dynamics Operations for Geostationary Satellite Mission

    Science.gov (United States)

    Park, Sangwook; Lee, Young-Ran; Hwang, Yoola; Javier Santiago Noguero Galilea

    2009-12-01

    This paper describes the Flight Dynamics Automation (FDA) system for COMS Flight Dynamics System (FDS) and its test result in terms of the performance of the automation jobs. FDA controls the flight dynamics functions such as orbit determination, orbit prediction, event prediction, and fuel accounting. The designed FDA is independent from the specific characteristics which are defined by spacecraft manufacturer or specific satellite missions. Therefore, FDA could easily links its autonomous job control functions to any satellite mission control system with some interface modification. By adding autonomous system along with flight dynamics system, it decreases the operator’s tedious and repeated jobs but increase the usability and reliability of the system. Therefore, FDA is used to improve the completeness of whole mission control system’s quality. The FDA is applied to the real flight dynamics system of a geostationary satellite, COMS and the experimental test is performed. The experimental result shows the stability and reliability of the mission control operations through the automatic job control.

  10. Coseismic and post-seismic signatures of the Sumatra 2004 December and 2005 March earthquakes in GRACE satellite gravity

    Science.gov (United States)

    Panet, I.; Mikhailov, V.; Diament, M.; Pollitz, F.; King, G.; de Viron, O.; Holschneider, M.; Biancale, R.; Lemoine, J.-M.

    2007-01-01

    The GRACE satellite mission has been measuring the Earth's gravity field and its temporal variations since 2002 April. Although these variations are mainly due to mass transfer within the geofluid envelops, they also result from mass displacements associated with phenomena including glacial isostatic adjustment and earthquakes. However, these last contributions are difficult to isolate because of the presence of noise and of geofluid signals, and because of GRACE's coarse spatial resolution (>400 km half-wavelength). In this paper, we show that a wavelet analysis on the sphere helps to retrieve earthquake signatures from GRACE geoid products. Using a wavelet analysis of GRACE geoids products, we show that the geoid variations caused by the 2004 December (Mw = 9.2) and 2005 March (Mw = 8.7) Sumatra earthquakes can be detected. At GRACE resolution, the 2004 December earthquake produced a strong coseismic decrease of the gravity field in the Andaman Sea, followed by relaxation in the area affected by both the Andaman 2004 and the Nias 2005 earthquakes. We find two characteristic timescales for the relaxation, with a fast variation occurring in the vicinity of the Central Andaman ridge. We discuss our coseismic observations in terms of density changes of crustal and upper-mantle rocks, and of the vertical displacements in the Andaman Sea. We interpret the post-seismic signal in terms of the viscoelastic response of the Earth's mantle. The transient component of the relaxation may indicate the presence of hot, viscous material beneath the active Central Andaman Basin. ?? 2007 The Authors Journal compilation ?? 2007 RAS.

  11. Trajectory Design to Mitigate Risk on the Transiting Exoplanet Survey Satellite (TESS) Mission

    Science.gov (United States)

    Dichmann, Donald

    2016-01-01

    The Transiting Exoplanet Survey Satellite (TESS) will employ a highly eccentric Earth orbit, in 2:1 lunar resonance, reached with a lunar flyby preceded by 3.5 phasing loops. The TESS mission has limited propellant and several orbit constraints. Based on analysis and simulation, we have designed the phasing loops to reduce delta-V and to mitigate risk due to maneuver execution errors. We have automated the trajectory design process and use distributed processing to generate and to optimize nominal trajectories, check constraint satisfaction, and finally model the effects of maneuver errors to identify trajectories that best meet the mission requirements.

  12. High-resolution Local Gravity Model of the South Pole of the Moon from GRAIL Extended Mission Data

    Science.gov (United States)

    Goossens, Sander Johannes; Sabaka, Terence J.; Nicholas, Joseph B.; Lemoine, Frank G.; Rowlands, David D.; Mazarico, Erwan; Neumann, Gregory A.; Smith, David E.; Zuber, Maria T.

    2014-01-01

    We estimated a high-resolution local gravity field model over the south pole of the Moon using data from the Gravity Recovery and Interior Laboratory's extended mission. Our solution consists of adjustments with respect to a global model expressed in spherical harmonics. The adjustments are expressed as gridded gravity anomalies with a resolution of 1/6deg by 1/6deg (equivalent to that of a degree and order 1080 model in spherical harmonics), covering a cap over the south pole with a radius of 40deg. The gravity anomalies have been estimated from a short-arc analysis using only Ka-band range-rate (KBRR) data over the area of interest. We apply a neighbor-smoothing constraint to our solution. Our local model removes striping present in the global model; it reduces the misfit to the KBRR data and improves correlations with topography to higher degrees than current global models.

  13. Novel low cost standardized Nano-Satellite structure bus for LEO missions

    Science.gov (United States)

    Anubhav, T.; Sarwesh, P.; Narayan, V.; Varma, P. A.; Prasad, R. A.; Loganathan, M.; Rao, D. N.; Sriram, S.; Venkatesh, M.

    This paper focuses on SRMSAT STRUCTURE BUS which is a standardized Nano-Satellite structure bus. It provides a standard platform for a wide variety of missions in LEO and can be realized in a very short developmental period. The bus was designed and developed for SRMSAT, the SRM University (Sri Ramaswamy Memorial University) student Nano-Satellite, by the undergraduate students and faculty of SRM University in collaboration with Indian Space Research Organization (ISRO). The bus can support payloads up to a mass of 20kg. SRMSAT STRUCTURE BUS has a mass of around 6 kg and dimensions 280mm × 280mm × 280mm with an available volume of 11000 cc. Vibration Testing of the bus has been performed upto 6.7 gRMS. This makes the satellite capable of being launched by any launch vehicle in the world. An innovative PCB mounting design has been introduced in this structure bus which facilitates mounting of a maximum 7 PCB trays independently, each tray capable of holding a 250 mm2 PCB. Structural analysis of SRMSAT STRUCTURE BUS was done using NX Nastran. The boundary conditions for each analysis were defined based on the loading conditions as specified by the launcher, PSLV (Polar Satellite Launch Vehicle). Optimization of each individual component was performed by maintaining a minimum threshold between the local frequencies of the component and global frequencies of the entire satellite. Static, Modal, Harmonic and Random Vibration analysis of the structure bus was performed. This paper also describes the methodology followed in the static and dynamic analysis of the structure bus to finalize the design. The results have been tested and validated at ISRO Satellite Centre, Bangalore with around 90% accuracy and the structure has been certified as a standard structure bus for Nano-satellite missions. In terms of expandability, this structure bus is capable of accommodating deployable solar panels. Also, the payload mounting is not only restricted to th- bottom deck but can

  14. Satellite Constellations for Space Weather and Ionospheric Studies: Overview of the COSMIC and COSMIC-2 Missions

    Science.gov (United States)

    Schreiner, W. S.; Pedatella, N. M.; Weiss, J.

    2016-12-01

    Measurements from constellations of low Earth orbiting (LEO) satellites are proving highly useful for ionospheric science and space weather studies. The Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC), a joint US/Taiwan mission launched in April 2006, is a six micro-satellite constellation carrying Global Positioning System (GPS) radio occultation (RO) receivers. COSMIC has collected a large amount of useful data from these scientific payloads and is still currently collecting up to 1,000 RO measurement events per day on average. The GPS RO dual-frequency L-band phase and amplitude measurements can be used to observe absolute Total Electron Content (TEC) and scintillation on lines of sight between the LEO and GPS satellites, and electron density profiles via the RO method. The large number and complete global and local time coverage of COSMIC data are allowing scientists to observe ionospheric and plasmaspheric phenomena that are difficult to see with other instruments. The success of COSMIC has prompted U.S. agencies and Taiwan to execute a COSMIC follow-on mission (called COSMIC-2) that will put twelve satellites with GNSS (Global Navigation Satellite System) RO payloads into orbit on two launches in the 2017-20 time frame. The first launch in 2017 will place six satellites in a 520-km altitude 24 deg inclination orbit, which is ideal for low latitude ionospheric research and space weather forecasting. The planned second launch (not currently funded) places six additional satellites in a 750 km 72 deg inclination orbit to provide global coverage and increased sampling density. COSMIC-2 will make use of an advanced radio occultation receiver with an innovative beam-forming antenna design, and is expected to produce at least 10,000 high-quality atmospheric and ionospheric profiles per day from GPS and GLONASS signals to support operational weather prediction, climate monitoring, and space weather forecasting. Each COSMIC-2 spacecraft

  15. SPOT satellite family: Past, present, and future of the operations in the mission and control center

    Science.gov (United States)

    Philippe, Pacholczyk

    1993-01-01

    SPOT sun-synchronous remote sensing satellites are operated by CNES since February 1986. Today, the SPOT mission and control center (CCM) operates SPOT1, SPOT2, and is ready to operate SPOT3. During these seven years, the way to operate changed and the CCM, initially designed for the control of one satellite, has been modified and upgraded to support these new operating modes. All these events have shown the performances and the limits of the system. A new generation of satellite (SPOT4) will continue the remote sensing mission during the second half of the 90's. Its design takes into account the experience of the first generation and supports several improvements. A new generation of control center (CMP) has been developed and improves the efficiency, quality, and reliability of the operations. The CMP is designed for operating two satellites at the same time during launching, in-orbit testing, and operating phases. It supports several automatic procedures and improves data retrieval and reporting.

  16. Global gravity field models from the GPS positions of CHAMP, GRACE and GOCE satellites

    Science.gov (United States)

    Bezděk, A.; Sebera, J.; Klokočník, J.; Kostelecký, J.

    2012-04-01

    The aim of our work is to generate Earth's gravity field models from the GPS positions of low Earth orbiters. We will present our inversion method and numerical results based on the real-world data of CHAMP, GRACE and GOCE satellites. The presented inversion method is based on Newton's second law of motion, which relates the observed acceleration of the satellite with the forces acting on it. The vector of the observed acceleration is obtained through a numerical second-derivative filter applied to the time series of the kinematic positions. Forces other than those due to the geopotential are either modelled (lunisolar perturbations, tides) or provided by the onboard measurements (nongravitational perturbations). Then the observation equations are formulated using the gradient of the spherical harmonic expansion of the geopotential. From this linear system the harmonic coefficients are directly obtained. We do not use any a priori gravity field model. Although the basic scheme of the acceleration approach is straightforward, the implementation details play a crucial role in obtaining reasonable results. The numerical derivative of noisy data (here the GPS positions) strongly amplifies the high frequency noise and creates autocorrelation in the observation errors. We successfully solve both of these problems by using the generalized least squares method, which defines a linear transformation of the observation equations. In the transformed variables the errors become uncorrelated, so the ordinary least squares estimation may be used to find the regression parameters with correct estimates of their uncertainties. The digital filter of the second derivative is an approximation to the analytical operation. We will show how different the results might be depending on the particular choice of the parameters defining the filter. Another problem is the correlation of the errors in the GPS positions. Here we use the tools from time series analysis. The systematic behaviour

  17. Improved Traceability of a Small Satellite Mission Concept to Requirements Using Model Based System Engineering

    Science.gov (United States)

    Reil, Robin L.

    2014-01-01

    Model Based Systems Engineering (MBSE) has recently been gaining significant support as a means to improve the "traditional" document-based systems engineering (DBSE) approach to engineering complex systems. In the spacecraft design domain, there are many perceived and propose benefits of an MBSE approach, but little analysis has been presented to determine the tangible benefits of such an approach (e.g. time and cost saved, increased product quality). This paper presents direct examples of how developing a small satellite system model can improve traceability of the mission concept to its requirements. A comparison of the processes and approaches for MBSE and DBSE is made using the NASA Ames Research Center SporeSat CubeSat mission as a case study. A model of the SporeSat mission is built using the Systems Modeling Language standard and No Magic's MagicDraw modeling tool. The model incorporates mission concept and requirement information from the mission's original DBSE design efforts. Active dependency relationships are modeled to demonstrate the completeness and consistency of the requirements to the mission concept. Anecdotal information and process-duration metrics are presented for both the MBSE and original DBSE design efforts of SporeSat.

  18. Towards the Development of a Global, Satellite-based, Terrestrial Snow Mission Planning Tool

    Science.gov (United States)

    Forman, Bart; Kumar, Sujay; Le Moigne, Jacqueline; Nag, Sreeja

    2017-01-01

    A global, satellite-based, terrestrial snow mission planning tool is proposed to help inform experimental mission design with relevance to snow depth and snow water equivalent (SWE). The idea leverages the capabilities of NASAs Land Information System (LIS) and the Tradespace Analysis Tool for Constellations (TAT C) to harness the information content of Earth science mission data across a suite of hypothetical sensor designs, orbital configurations, data assimilation algorithms, and optimization and uncertainty techniques, including cost estimates and risk assessments of each hypothetical orbital configuration.One objective the proposed observing system simulation experiment (OSSE) is to assess the complementary or perhaps contradictory information content derived from the simultaneous collection of passive microwave (radiometer), active microwave (radar), and LIDAR observations from space-based platforms. The integrated system will enable a true end-to-end OSSE that can help quantify the value of observations based on their utility towards both scientific research and applications as well as to better guide future mission design. Science and mission planning questions addressed as part of this concept include:1. What observational records are needed (in space and time) to maximize terrestrial snow experimental utility?2. How might observations be coordinated (in space and time) to maximize utility? 3. What is the additional utility associated with an additional observation?4. How can future mission costs being minimized while ensuring Science requirements are fulfilled?

  19. Iodine Propulsion Advantages for Low Cost Mission Applications and the Iodine Satellite (ISAT) Technology Demonstration

    Science.gov (United States)

    Dankanich, John W.; Schumacher, Daniel M.

    2015-01-01

    The NASA Marshall Space Flight Center Science and Technology Office is continuously exploring technology options to increase performance or reduce cost and risk to future NASA missions including science and exploration. Electric propulsion is a prevalent technology known to reduce mission costs by reduction in launch costs and spacecraft mass through increased post launch propulsion performance. The exploration of alternative propellants for electric propulsion continues to be of interest to the community. Iodine testing has demonstrated comparable performance to xenon. However, iodine has a higher storage density resulting in higher ?V capability for volume constrained systems. Iodine's unique properties also allow for unpressurized storage yet sublimation with minimal power requirements to produce required gas flow rates. These characteristics make iodine an ideal propellant for secondary spacecraft. A range of mission have been evaluated with a focus on low-cost applications. Results highlight the potential for significant cost reduction over state of the art. Based on the potential, NASA has been developing the iodine Satellite for a near-term iodine Hall propulsion technology demonstration. Mission applications and progress of the iodine Satellite project are presented.

  20. PRIMA Platform capability for satellite missions in LEO and MEO (SAR, Optical, GNSS, TLC, etc.)

    Science.gov (United States)

    Logue, T.; L'Abbate, M.

    2016-12-01

    PRIMA (Piattaforma Riconfigurabile Italiana Multi Applicativa) is a multi-mission 3-axis stabilized Platform developed by Thales Alenia Space Italia under ASI contract.PRIMA is designed to operate for a wide variety of applications from LEO, MEO up to GEO and for different classes of satellites Platform Family. It has an extensive heritage in flight heritage (LEO and MEO Satellites already fully operational) in which it has successfully demonstrated the flexibility of use, low management costs and the ability to adapt to changing operational conditions.The flexibility and modularity of PRIMA provides unique capability to satisfy different Payload design and mission requirements, thanks to the utilization of recurrent adaptable modules (Service Module-SVM, Propulsion Module-PPM, Payload Module-PLM) to obtain mission dependent configuration. PRIMA product line development is continuously progressing, and is based on state of art technology, modular architecture and an Integrated Avionics. The aim is to maintain and extent multi-mission capabilities to operate in different environments (LEO to GEO) with different payloads (SAR, Optical, GNSS, TLC, etc.). The design is compatible with a wide range of European and US equipment suppliers, thus maximising cooperation opportunity. Evolution activities are mainly focused on the following areas: Structure: to enable Spacecraft configurations for multiple launch; Thermal Control: to guarantee thermal limits for new missions, more demanding in terms of environment and payload; Electrical: to cope with higher power demand (e.g. electrical propulsion, wide range of payloads, etc.) considering orbital environment (e.g. lighting condition); Avionics : AOCS solutions optimized on mission (LEO observation driven by agility and pointing, agility not a driver for GEO). Use of sensors and actuators tailored for specific mission and related environments. Optimised Propulsion control. Data Handling, SW and FDIR mission customization

  1. Enhanced Gravity Tractor Derived from the Asteroid Redirect Mission for Deflecting Hypothetical Asteroid 2017 PDC

    Science.gov (United States)

    Mazanek, Daniel D.; Reeves, David M.; Abell, Paul A.; Shen, Haijun; Qu, Min

    2017-01-01

    The Asteroid Redirect Mission (ARM) concept would robotically visit a hazardous-size near-Earth asteroid (NEA) with a rendezvous spacecraft, collect a multi-ton boulder and regolith samples from its surface, demonstrate an innovative planetary defense technique known as the Enhanced Gravity Tractor (EGT), and return the asteroidal material to a stable orbit around the Moon, allowing astronauts to explore the returned material in the mid-2020s. Launch of the robotic vehicle to rendezvous with the ARM reference target, NEA (341843) 2008 EV5, would occur in late 2021 [1,2]. The robotic segment of the ARM concept uses a 40 kW Solar Electric Propulsion (SEP) system with a specific impulse (Isp) of 2600 s, and would provide the first ever demonstration of the EGT technique on a hazardous-size asteroid and validate one method of collecting mass in-situ. The power, propellant, and thrust capability of the ARM robotic spacecraft can be scaled from a 40 kW system to 150 kW and 300 kW, which represent a likely future power level progression. The gravity tractor technique uses the gravitational attraction of a station-keeping spacecraft with the asteroid to provide a velocity change and gradually alter the trajectory of the asteroid. EGT utilizes a spacecraft with a high-efficiency propulsion system, such as Solar Electric Propulsion (SEP), along with mass collected in-situ to augment the mass of the spacecraft, thereby increasing the gravitational force between the objects [3]. As long as the spacecraft has sufficient thrust and propellant capability, the EGT force is only limited by the amount of in-situ mass collected and can be increased several orders of magnitude compared to the traditional gravity tractor technique in which only the spacecraft mass is used to generate the gravitational attraction force. This increase in available force greatly reduces the required deflection time. The collected material can be a single boulder, multiple boulders, regolith, or a

  2. ``Bimodal'' Nuclear Thermal Rocket (BNTR) Propulsion for an Artificial Gravity HOPE Mission to Callisto

    Science.gov (United States)

    Borowski, Stanley K.; McGuire, Melissa L.; Mason, Lee M.; Gilland, James H.; Packard, Thomas W.

    2003-01-01

    This paper summarizes the results of a year long, multi-center NASA study which examined the viability of nuclear fission propulsion systems for Human Outer Planet Exploration (HOPE). The HOPE mission assumes a crew of six is sent to Callisto. Jupiter's outermost large moon, to establish a surface base and propellant production facility. The Asgard asteroid formation, a region potentially rich in water-ice, is selected as the landing site. High thrust BNTR propulsion is used to transport the crew from the Earth-Moon L1 staging node to Callisto then back to Earth in less than 5 years. Cargo and LH2 ``return'' propellant for the piloted Callisto transfer vehicle (PCTV) is pre-deployed at the moon (before the crew's departure) using low thrust, high power, nuclear electric propulsion (NEP) cargo and tanker vehicles powered by hydrogen magnetoplasmadynamic (MPD) thrusters. The PCTV is powered by three 25 klbf BNTR engines which also produce 50 kWe of power for crew life support and spacecraft operational needs. To counter the debilitating effects of long duration space flight (~855 days out and ~836 days back) under ``0-gE'' conditions, the PCTV generates an artificial gravity environment of ``1-gE'' via rotation of the vehicle about its center-of-mass at a rate of ~4 rpm. After ~123 days at Callisto, the ``refueled'' PCTV leaves orbit for the trip home. Direct capsule re-entry of the crew at mission end is assumed. Dynamic Brayton power conversion and high temperature uranium dioxide (UO2) in tungsten metal ``cermet'' fuel is used in both the BNTR and NEP vehicles to maximize hardware commonality. Technology performance levels and vehicle characteristics are presented, and requirements for PCTV reusability are also discussed.

  3. Smoothing impact of isostatic crustal thickness models on local integral inversion of satellite gravity gradiometry data

    Science.gov (United States)

    Eshagh, Mehdi; Bagherbandi, Mohammad

    2011-10-01

    The effects of topographic masses on satellite gradiometric data are large and in order to reduce the magnitude of these effects some compensation mechanisms should be considered. Here we use the isostatic hypotheses of Airy-Heiskanen and the recent Vening Meinesz-Moritz for compensating these effects and to smooth the data prior to their downward continuation to gravity anomaly. The second-order partial derivatives of extended Stokes' formula are used for the continuations over a topographically rough territory like Persia. The inversions are performed and compared based on two schemes of the remove-compute-restore technique and direct downward continuation. Numerical results show that the topographic-isostatic effect based on Vening Meinesz-Mortiz's hypothesis smoothes the data better than that based on Airy-Heiskanen's hypothesis. Also the quality of inversions of the smoothed data by this mechanism is twice better than that of the nonsmoothed ones.

  4. Europa Jupiter System Mission (EJSM): Exploration Of The Jovian System And Its Icy Satellites

    Science.gov (United States)

    Grasset, Olivier; Pappalardo, R.; Greeley, R.; Blanc, M.; Dougherty, M.; Bunce, E.; Lebreton, J.; Prockter, L.; Senske, D.; EJSM Joint Science Definition Team

    2009-09-01

    The Europa Jupiter System Mission (EJSM) would be an international mission with the overall theme of investigating the emergence of habitable worlds around gas giants. Its goals are to (1) Determine whether the Jupiter system harbors habitable worlds and (2) Characterize the processes that are operating within the Jupiter system. NASA and ESA have concluded a detailed joint study of a mission to Europa, Ganymede, and the Jupiter system with orbiters developed by NASA and ESA (future contributions by JAXA and Russia are also possible). The baseline EJSM architecture consists of two primary elements operating in the Jovian system: the NASA-led Jupiter Europa Orbiter (JEO), and the ESA-led Jupiter Ganymede Orbiter (JGO). JEO and JGO would execute an intricately choreographed exploration of the Jupiter System before settling into orbit around Europa and Ganymede, respectively. EJSM would directly address themes concerning the origin and evolution of satellite systems and water-rich environments in icy satellites. The potential habitability of the ocean-bearing moons Europa and Ganymede would be investigated, by characterizing the geophysical, compositional, geological, and external processes that affect these icy worlds. EJSM would also investigate Io and Callisto, Jupiter's atmosphere, and the Jovian magnetosphere. By understanding the Jupiter system and unraveling its history, the formation and evolution of gas giant planets and their satellites would be better known. Most important, EJSM would shed new light on the potential for the emergence of life in the celestial neighborhood and beyond. The EJSM architecture provides opportunities for coordinated synergistic observations by JEO and JGO of the Jupiter and Ganymede magnetospheres, the volcanoes and torus of Io, the atmosphere of Jupiter, and comparative planetology of icy satellites. Each spacecraft would conduct both synergistic dual-spacecraft investigations and "stand-alone” measurements.

  5. Bathymetry Prediction in Shallow Water by the Satellite Altimetry-Derived Gravity Anomalies

    Science.gov (United States)

    Kim, Kwang Bae; Yun, Hong Sik

    2017-04-01

    The satellite altimetry-derived free-air gravity anomalies (SAFAGAs) are correlated with undulations of crustal density variations under the seafloor. In this study, shipborne bathymetry from the Korea Rural Community Corporation (KRC) and the SAFAGAs from Scripps Institution of Oceanography were combined to predict bathymetry in shallow water. Density contrast of 5.0 g/cm3 estimated by the check points method of the gravity-geologic method (GGM) between seawater and the seafloor topographic mass was applied to predict bathymetry in shallow water areas outside of the Saemangeum Seawall located on the southwest coast of the Korean peninsula. Bathymetry predicted by the GGM was compared with depth measurements on the shipborne locations to analyze the bathymetry accuracy. The root mean square error (RMSE) of the differences of bathymetry between GGM and KRC on the KRC shipborne tracks in shallow water around the Saemangeum Seawall is 0.55 m. The topographic effects in off-tracks extracted from SAFAGAs in the GGM can be effectively utilized to predict bathymetry by combining with shipborne depth data in shallow water where shipborne depth data are limited. In addition, bathymetry and the SAFAGAs have a linear correlation in the 20 160 km wavelength. The coherency analysis was performed by computing the cross-spectral coherence between satellite altimetry derived bathymetry and the SAFAGAs. Acknowledgement This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2016R1A6A3A11931032).

  6. Pi-Sat: A Low Cost Small Satellite and Distributed Spacecraft Mission System Test Platform

    Science.gov (United States)

    Cudmore, Alan

    2015-01-01

    Current technology and budget trends indicate a shift in satellite architectures from large, expensive single satellite missions, to small, low cost distributed spacecraft missions. At the center of this shift is the SmallSatCubesat architecture. The primary goal of the Pi-Sat project is to create a low cost, and easy to use Distributed Spacecraft Mission (DSM) test bed to facilitate the research and development of next-generation DSM technologies and concepts. This test bed also serves as a realistic software development platform for Small Satellite and Cubesat architectures. The Pi-Sat is based on the popular $35 Raspberry Pi single board computer featuring a 700Mhz ARM processor, 512MB of RAM, a flash memory card, and a wealth of IO options. The Raspberry Pi runs the Linux operating system and can easily run Code 582s Core Flight System flight software architecture. The low cost and high availability of the Raspberry Pi make it an ideal platform for a Distributed Spacecraft Mission and Cubesat software development. The Pi-Sat models currently include a Pi-Sat 1U Cube, a Pi-Sat Wireless Node, and a Pi-Sat Cubesat processor card.The Pi-Sat project takes advantage of many popular trends in the Maker community including low cost electronics, 3d printing, and rapid prototyping in order to provide a realistic platform for flight software testing, training, and technology development. The Pi-Sat has also provided fantastic hands on training opportunities for NASA summer interns and Pathways students.

  7. Experimental techniques for gyroscope performance enhancement for the Gravity Probe B relativity mission

    Science.gov (United States)

    Buchman, Saps; Everitt, Francis; Parkinson, Brad; Turneaure, John; MacKeiser; Taber, Mike; Bardas, Doron; Lockhart, Jim; Muhlfelder, Barry; Mester, John; Xiao, Yueming; Gutt, Gregory; Gill, Dale; Brumley, Robert; Di Donna, Brian

    1996-11-01

    The Gravity Probe B relativity mission experiment is designed to measure the frame dragging and geodetic relativistic precessions in a 650 km polar orbit. We describe some of the advanced experimental techniques used to achieve the required gyroscope accuracy of between 0.05 and 0264-9381/13/11A/026/img1. The subjects discussed are: (i) the development of high-precision gyroscopes with drift rates of less than 0264-9381/13/11A/026/img2, (ii) a low-temperature bake-out procedure resulting in a helium pressure of less than 0264-9381/13/11A/026/img3 at 2.5 K, (iii) a read-out system using DC SQUID magnetometers with a noise figure of 0264-9381/13/11A/026/img4 at 5 mHz and (iv) AC and DC magnetic shielding techniques which produce an AC attenuation factor in excess of 0264-9381/13/11A/026/img5 and a residual DC field of less than 0264-9381/13/11A/026/img6.

  8. Satellite gravity measurement monitoring terrestrial water storage change and drought in the continental United States

    Science.gov (United States)

    Yi, Hang; Wen, Lianxing

    2016-01-01

    We use satellite gravity measurements in the Gravity Recovery and Climate Experiment (GRACE) to estimate terrestrial water storage (TWS) change in the continental United States (US) from 2003 to 2012, and establish a GRACE-based Hydrological Drought Index (GHDI) for drought monitoring. GRACE-inferred TWS exhibits opposite patterns between north and south of the continental US from 2003 to 2012, with the equivalent water thickness increasing from -4.0 to 9.4 cm in the north and decreasing from 4.1 to -6.7 cm in the south. The equivalent water thickness also decreases by -5.1 cm in the middle south in 2006. GHDI is established to represent the extent of GRACE-inferred TWS anomaly departing from its historical average and is calibrated to resemble traditional Palmer Hydrological Drought Index (PHDI) in the continental US. GHDI exhibits good correlations with PHDI in the continental US, indicating its feasibility for drought monitoring. Since GHDI is GRACE-based and has minimal dependence of hydrological parameters on the ground, it can be extended for global drought monitoring, particularly useful for the countries that lack sufficient hydrological monitoring infrastructures on the ground.

  9. Improving GOCE cross-track gravity gradients

    Science.gov (United States)

    Siemes, Christian

    2017-07-01

    The GOCE gravity gradiometer measured highly accurate gravity gradients along the orbit during GOCE's mission lifetime from March 17, 2009, to November 11, 2013. These measurements contain unique information on the gravity field at a spatial resolution of 80 km half wavelength, which is not provided to the same accuracy level by any other satellite mission now and in the foreseeable future. Unfortunately, the gravity gradient in cross-track direction is heavily perturbed in the regions around the geomagnetic poles. We show in this paper that the perturbing effect can be modeled accurately as a quadratic function of the non-gravitational acceleration of the satellite in cross-track direction. Most importantly, we can remove the perturbation from the cross-track gravity gradient to a great extent, which significantly improves the accuracy of the latter and offers opportunities for better scientific exploitation of the GOCE gravity gradient data set.

  10. The determination of Mercury's gravity field and rotational state with the mission BepiColombo

    Science.gov (United States)

    Iess, L.; Asmar, S. W.; Milani, A.; Tortora, P.; Iafolla, V.

    Gravity field and rotational state provide accurate constraints to geophysical models of planetary interiors and have been therefore a major source of information on the internal structure of solar system bodies. Their determination is particularly important for Mercury, whose interior is the least known among terrestrial planets. Today, planetary gravity fields are best investigated by means of microwave Doppler tracking of orbiting spacecraft. In order to attain precise measurements the radio link (involving a carrier transmitted from ground to the spacecraft and retransmitted back to ground) must preserve the highest phase stability and coherence at each intervening stage. Electronic noise from ground and onboard instrumentation must be minimized and propagation noise (due to plasma and troposphere) must be kept to a minimum. This is especially important for phase instabilities induced by interplanetary plasma and solar corona, which have been the main limitation in past gravity experiments with planetary probes. Both forthcoming space missions to Mercury (NASA's Messenger and ESA's Bepi- Colombo) host radio science investigations devoted to geodesy and geophysics. While Messenger's experiment exploits the onboard telecommunication system, based upon a X-band radio link (7.1-8.4 GHz), the experiment MORE (Mercury Orbiter Radioscience Experiment) of BepiColombo makes use of a Ka-band radio link (32-34 GHz) enabled by dedicated onboard and ground hardware. The use of a Ka-band link in combination with the standard telecommunication system allows a complete cancellation of the plasma noise and two-way range rate measurements as accurate as 3 micron/s over time scales of 1000 s, independently of the solar elongation angle. The radio instrumentation includes also a wide-band ranging system (WBRS, using a 20 MHz tone) with a target two-way accuracy of 20 cm. The ranging system will be used to determine Mercury's orbit in the solar system, carrying out accurate tests

  11. Sentinel Convoy: Synergetic Earth Observation with Satellites Flying in Formation with European Operational Missions

    Science.gov (United States)

    Regan, Amanda; Silvestrin, Pierluigi; Fernandez, Diego

    2016-08-01

    The successful launch of Sentinel-1A, Sentinel-1B, Sentinel-2A and Sentinel-3A signify the beginning of the dedicated space segment for the Copernicus Programme, which is the result of the partnership between the European Commission (EC) and the European Space Agency (ESA). These Sentinels are the first of a long-term operational series of Earth Observation (EO) satellites to be launched by Europe that will complement the already well-established series of meteorological missions.For the first time, these missions will provide a continuous and long term European capability for systematic observations of the Earth surface, its oceans and atmosphere to unprecedented accuracies, resolutions, and temporal coverage. If additional cost- effective missions could be flown together with these operational missions (including operational meteorological satellite series such as MetOp (Second Generation - SG) then the possibilities for meeting new Earth science and application objectives could be far- reaching e.g. fulfilling observational gaps, synergistic measurements of Earth system processes, etc. To explore this potential, the ESA initiated three exploratory paper studies (known as the EO-Convoy studies). The aim of these studies is two fold: Firstly, to identify scientific and operational objectives and needs that would benefit from additional in-orbit support. Secondly, to identify and develop a number of cost- effective mission concepts that would meet these objectives and needs. Each EO Convoy study is dedicated to a specific theme, namely: Study 1 - Ocean and Ice Applications, Study 2 - Land Applications and Study 3 - Atmospheric Applications.This paper will present the results of the EO-Convoy studies including an overview of the user needs and derived convoy concept descriptions. This paper shall focus on the resulting science benefits. Example convoy concepts to be presented include a passive C-band SAR flying with Sentinel-1 and possible free flying thermal

  12. An Evaluation of Antarctica as a Calibration Target for Passive Microwave Satellite Missions

    Science.gov (United States)

    Kim, Edward

    2012-01-01

    Passive microwave remote sensing at L-band (1.4 GHz) is sensitive to soil moisture and sea surface salinity, both important climate variables. Science studies involving these variables can now take advantage of new satellite L-band observations. The first mission with regular global passive microwave observations at L-band is the European Space Agency's Soil Moisture and Ocean Salinity (SMOS), launched November, 2009. A second mission, NASA's Aquarius, was launched June, 201l. A third mission, NASA's Soil Moisture Active Passive (SMAP) is scheduled to launch in 2014. Together, these three missions may provide a decade-long data record -- provided that they are intercalibrated. The intercalibration is best performed at the radiance (brightness temperature) level, and Antarctica is proving to be a key calibration target. However, Antarctica has thus far not been fully characterized as a potential target. This paper will present evaluations of Antarctica as a microwave calibration target for the above satellite missions. Preliminary analyses have identified likely target areas, such as the vicinity of Dome-C and larger areas within East Antarctica. Physical sources of temporal and spatial variability of polar firn are key to assessing calibration uncertainty. These sources include spatial variability of accumulation rate, compaction, surface characteristics (dunes, micro-topography), wind patterns, and vertical profiles of density and temperature. Using primarily SMOS data, variability is being empirically characterized and attempts are being made to attribute observed variability to physical sources. One expected outcome of these studies is the potential discovery of techniques for remotely sensing--over all of Antarctica--parameters such as surface temperature.

  13. The ECLAIRs micro-satellite mission for gamma-ray burst multi-wavelength observations

    CERN Document Server

    Schanne, S; Barret, D; Basa, S; Boër, M; Casse, F; Cordier, B; Daigne, F; Klotz, A; Limousin, O; Manchanda, R; Mandrou, P; Mereghetti, S; Mochkovitch, R; Paltani, S; Paul, J; Petitjean, P; Pons, R; Ricker, G; Skinner, G K

    2006-01-01

    Gamma-ray bursts (GRB), at least those with a duration longer than a few seconds are the most energetic events in the Universe and occur at cosmological distances. The ECLAIRs micro-satellite, to be launched in 2009, will provide multi-wavelength observations of GRB, to study their astrophysics and to use them as cosmological probes. Furthermore in 2009 ECLAIRs is expected to be the only space borne instrument capable of providing a GRB trigger in near real-time with sufficient localization accuracy for GRB follow-up observations with the powerful ground based spectroscopic telescopes available by then. A "Phase A study" of the ECLAIRs project has recently been launched by the French Space Agency CNES, aiming at a detailed mission design and selection for flight in 2006. The ECLAIRs mission is based on a CNES micro-satellite of the "Myriade" family and dedicated ground-based optical telescopes. The satellite payload combines a 2 sr field-of-view coded aperture mask gamma-camera using 6400 CdTe pixels for GRB ...

  14. The ECLAIRs micro-satellite mission for gamma-ray burst multi-wavelength observations

    Science.gov (United States)

    Schanne, S.; Atteia, J.-L.; Barret, D.; Basa, S.; Boer, M.; Casse, F.; Cordier, B.; Daigne, F.; Klotz, A.; Limousin, O.; Manchanda, R.; Mandrou, P.; Mereghetti, S.; Mochkovitch, R.; Paltani, S.; Paul, J.; Petitjean, P.; Pons, R.; Ricker, G.; Skinner, G.

    2006-11-01

    Gamma-ray bursts (GRB)—at least those with a duration longer than a few seconds—are the most energetic events in the Universe and occur at cosmological distances. The ECLAIRs micro-satellite, to be launched in 2009, will provide multi-wavelength observations of GRB, to study their astrophysics and to use them as cosmological probes. Furthermore, in 2009 ECLAIRs is expected to be the only space-borne instrument capable of providing a GRB trigger in near real-time with sufficient localization accuracy for GRB follow-up observations with the powerful ground-based spectroscopic telescopes available by then. A “Phase A study” of the ECLAIRs project has recently been launched by the French Space Agency CNES, aiming at a detailed mission design and selection for flight in 2006. The ECLAIRs mission is based on a CNES micro-satellite of the “Myriade” family and dedicated ground-based optical telescopes. The satellite payload combines a 2 sr field-of-view coded aperture mask gamma-camera using 6400 CdTe pixels for GRB detection and localization with 10 arcmin precision in the 4 50 keV energy band, together with a soft X-ray camera for onboard position refinement to 1 arcmin. The ground-based optical robotic telescopes will detect the GRB prompt/early afterglow emission and localize the event to arcsec accuracy, for spectroscopic follow-up observations.

  15. Report of the Joint Scientific Mission Definition Team for an infrared astronomical satellite

    Science.gov (United States)

    1976-01-01

    The joint effort is reported of scientists and engineers from the Netherlands, the United Kingdom, and the United States working as a team for the purpose of exploring the possibility of a cooperative venture. The proposed mission builds upon experience gained from the successful Astronomical Netherlands Satellite (ANS). This satellite will be in a polar orbit at an altitude of 900 km. It will carry an 0.6 m diameter telescope cooled with helium to a temperature near 10K. An array of approximately 100 detectors will be used to measure the infrared flux in four wavelength bands centered at 10, 20, 50, and 100 microns. Sources will be located on the sky with positional accuracy of 1/2 arcminute. The instrument should be able to investigate the structure of extended sources with angular scales up to 1.0 deg. The entire sky will be surveyed and the full lifetime of the mission of about one year will be necessary to complete the survey. Special observational programs will also be incorporated into the mission.

  16. Observations of gravity waves from satellite and implications for the wave driving of the SAO

    Science.gov (United States)

    Ern, Manfred; Preusse, Peter; Riese, Martin

    2015-04-01

    The dynamics at low latitudes in the stratosphere and lower mesosphere is governed by an interplay of the quasi-biennial oscillation (QBO) and the semiannual oscillation (SAO) of the zonal wind. It is known that tropical dynamics has significant influence on the atmosphere over a large range of altitudes and latitudes. For example, QBO and SAO effects are seen in the MLT region, and there is a significant influence of the QBO on surface weather and climate in the Northern Hemisphere during winter. Still, global models have large difficulties in simulating a realistic QBO and SAO. One main uncertainty is the wave driving of these oscillations, in particular the driving by gravity waves (GWs). We derive GW temperature variances, GW momentum fluxes and potential GW drag from over three years of High Resolution Dynamics Limb Sounder (HIRDLS) satellite data in the stratopause region. These observations are compared with the SAO driving due to planetary waves, as well as the zonal wind tendencies, both determined from the ECMWF ERA-Interim (ERAI) reanalysis. HIRDLS satellite observations and ERAI support the general assumption that, due to selective filtering of the GW spectrum by the QBO in the stratosphere, GWs mainly contribute to the SAO momentum budget during SAO eastward wind shear. However, during SAO westward wind shear the GW contribution is usually smaller, and the wave driving is dominated by planetary waves, probably of extratropical origin. Still, we find indications in both satellite observations and ERAI that sometimes GW drag is important also during SAO westward wind shear.

  17. Gravity

    CERN Document Server

    Gamow, George

    2003-01-01

    A distinguished physicist and teacher, George Gamow also possessed a special gift for making the intricacies of science accessible to a wide audience. In Gravity, he takes an enlightening look at three of the towering figures of science who unlocked many of the mysteries behind the laws of physics: Galileo, the first to take a close look at the process of free and restricted fall; Newton, originator of the concept of gravity as a universal force; and Einstein, who proposed that gravity is no more than the curvature of the four-dimensional space-time continuum.Graced with the author's own draw

  18. The gravity field and GGOS

    DEFF Research Database (Denmark)

    Forsberg, René; Sideris, M.G.; Shum, C.K.

    2005-01-01

    The gravity field of the earth is a natural element of the Global Geodetic Observing System (GGOS). Gravity field quantities are like spatial geodetic observations of potential very high accuracy, with measurements, currently at part-per-billion (ppb) accuracy, but gravity field quantities are also...... unique as they can be globally represented by harmonic functions (long-wavelength geopotential model primarily from satellite gravity field missions), or based on point sampling (airborne and in situ absolute and superconducting gravimetry). From a GGOS global perspective, one of the main challenges...... is to ensure the consistency of the global and regional geopotential and geoid models, and the temporal changes of the gravity field at large spatial scales. The International Gravity Field Service, an umbrella "level-2" IAG service (incorporating the International Gravity Bureau, International Geoid Service...

  19. Gravity Anomaly Assessment Using Ggms and Airborne Gravity Data Towards Bathymetry Estimation

    Science.gov (United States)

    Tugi, A.; Din, A. H. M.; Omar, K. M.; Mardi, A. S.; Som, Z. A. M.; Omar, A. H.; Yahaya, N. A. Z.; Yazid, N.

    2016-09-01

    The Earth's potential information is important for exploration of the Earth's gravity field. The techniques of measuring the Earth's gravity using the terrestrial and ship borne technique are time consuming and have limitation on the vast area. With the space-based measuring technique, these limitations can be overcome. The satellite gravity missions such as Challenging Mini-satellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), and Gravity-Field and Steady-State Ocean Circulation Explorer Mission (GOCE) has introduced a better way in providing the information on the Earth's gravity field. From these satellite gravity missions, the Global Geopotential Models (GGMs) has been produced from the spherical harmonics coefficient data type. The information of the gravity anomaly can be used to predict the bathymetry because the gravity anomaly and bathymetry have relationships between each other. There are many GGMs that have been published and each of the models gives a different value of the Earth's gravity field information. Therefore, this study is conducted to assess the most reliable GGM for the Malaysian Seas. This study covered the area of the marine area on the South China Sea at Sabah extent. Seven GGMs have been selected from the three satellite gravity missions. The gravity anomalies derived from the GGMs are compared with the airborne gravity anomaly, in order to figure out the correlation (R2) and the root mean square error (RMSE) of the data. From these assessments, the most suitable GGMs for the study area is GOCE model, GO_CONS_GCF_2_TIMR4 with the R2 and RMSE value of 0.7899 and 9.886 mGal, respectively. This selected model will be used in the estimating the bathymetry for Malaysian Seas in future.

  20. GRAVITY ANOMALY ASSESSMENT USING GGMS AND AIRBORNE GRAVITY DATA TOWARDS BATHYMETRY ESTIMATION

    Directory of Open Access Journals (Sweden)

    A. Tugi

    2016-09-01

    Full Text Available The Earth’s potential information is important for exploration of the Earth’s gravity field. The techniques of measuring the Earth’s gravity using the terrestrial and ship borne technique are time consuming and have limitation on the vast area. With the space-based measuring technique, these limitations can be overcome. The satellite gravity missions such as Challenging Mini-satellite Payload (CHAMP, Gravity Recovery and Climate Experiment (GRACE, and Gravity-Field and Steady-State Ocean Circulation Explorer Mission (GOCE has introduced a better way in providing the information on the Earth’s gravity field. From these satellite gravity missions, the Global Geopotential Models (GGMs has been produced from the spherical harmonics coefficient data type. The information of the gravity anomaly can be used to predict the bathymetry because the gravity anomaly and bathymetry have relationships between each other. There are many GGMs that have been published and each of the models gives a different value of the Earth’s gravity field information. Therefore, this study is conducted to assess the most reliable GGM for the Malaysian Seas. This study covered the area of the marine area on the South China Sea at Sabah extent. Seven GGMs have been selected from the three satellite gravity missions. The gravity anomalies derived from the GGMs are compared with the airborne gravity anomaly, in order to figure out the correlation (R2 and the root mean square error (RMSE of the data. From these assessments, the most suitable GGMs for the study area is GOCE model, GO_CONS_GCF_2_TIMR4 with the R2 and RMSE value of 0.7899 and 9.886 mGal, respectively. This selected model will be used in the estimating the bathymetry for Malaysian Seas in future.

  1. Mean Sea Surface (mss) Model Determination for Malaysian Seas Using Multi-Mission Satellite Altimeter

    Science.gov (United States)

    Yahaya, N. A. Z.; Musa, T. A.; Omar, K. M.; Din, A. H. M.; Omar, A. H.; Tugi, A.; Yazid, N. M.; Abdullah, N. M.; Wahab, M. I. A.

    2016-09-01

    The advancement of satellite altimeter technology has generated many evolutions to oceanographic and geophysical studies. A multi-mission satellite altimeter consists with TOPEX, Jason-1 and Jason-2, ERS-2, Envisat-1, CryoSat-2 and Saral are extracted in this study and has been processed using Radar Altimeter Database System (RADS) for the period of January 2005 to December 2015 to produce the sea surface height (hereinafter referred to SSH). The monthly climatology data from SSH is generated and averaged to understand the variation of SSH during monsoon season. Then, SSH data are required to determine the localised and new mean sea surface (MSS). The differences between Localised MSS and DTU13 MSS Global Model is plotted with root mean square error value is 2.217 metres. The localised MSS is important towards several applications for instance, as a reference for sea level variation, bathymetry prediction and derivation of mean dynamic topography.

  2. MEAN SEA SURFACE (MSS MODEL DETERMINATION FOR MALAYSIAN SEAS USING MULTI-MISSION SATELLITE ALTIMETER

    Directory of Open Access Journals (Sweden)

    N. A. Z. Yahaya

    2016-09-01

    Full Text Available The advancement of satellite altimeter technology has generated many evolutions to oceanographic and geophysical studies. A multi-mission satellite altimeter consists with TOPEX, Jason-1 and Jason-2, ERS-2, Envisat-1, CryoSat-2 and Saral are extracted in this study and has been processed using Radar Altimeter Database System (RADS for the period of January 2005 to December 2015 to produce the sea surface height (hereinafter referred to SSH. The monthly climatology data from SSH is generated and averaged to understand the variation of SSH during monsoon season. Then, SSH data are required to determine the localised and new mean sea surface (MSS. The differences between Localised MSS and DTU13 MSS Global Model is plotted with root mean square error value is 2.217 metres. The localised MSS is important towards several applications for instance, as a reference for sea level variation, bathymetry prediction and derivation of mean dynamic topography.

  3. Electromagnetic panel deployment and retraction using the geomagnetic field in LEO satellite missions

    Science.gov (United States)

    Inamori, Takaya; Sugawara, Yoshiki; Satou, Yasutaka

    2015-12-01

    Increasingly, spacecraft are installed with large-area structures that are extended and deployed post-launch. These extensible structures have been applied in several missions for power generation, thermal radiation, and solar propulsion. Here, we propose a deployment and retraction method using the electromagnetic force generated when the geomagnetic field interacts with electric current flowing on extensible panels. The panels are installed on a satellite in low Earth orbit. Specifically, electrical wires placed on the extensible panels generate magnetic moments, which interfere with the geomagnetic field. The resulting repulsive and retraction forces enable panel deployment and retraction. In the proposed method, a satellite realizes structural deployment using simple electrical wires. Furthermore, the satellite can achieve not only deployment but also retraction for avoiding damage from space debris and for agile attitude maneuvers. Moreover, because the proposed method realizes quasi-static deployment and the retraction of panels by electromagnetic forces, low impulsive force is exerted on fragile panels. The electrical wires can also be used to detect the panel deployment and retraction and generate a large magnetic moment for attitude control. The proposed method was assessed in numerical simulations based on multibody dynamics. Simulation results shows that a small cubic satellite with a wire current of 25 AT deployed 4 panels (20 cm × 20 cm) in 500 s and retracted 4 panels in 100 s.

  4. Control of the Soft X-ray Polychromator on the Solar Maximum Mission Satellite

    Science.gov (United States)

    Springer, L. A.; Levay, M.; Gilbreth, C. W.; Finch, M. L.; Bentley, R. D.; Firth, J. G.

    1981-01-01

    The Soft X-ray Polychromator on the Solar Maximum Mission Satellite consists of two largely independent instruments: the Flat Crystal Spectrometer, a highly collimated scanning spectrometer mounted on a raster platform, and the Bent Crystal Spectrometer, a broadly collimated spectrometer providing high time-resolution (128 ms) spectra for the study of rapidly evolving phenomena. Each instrument is controlled by a microcomputer system built around an RCA 1802 microprocessor. This paper presents a discussion of the motivation for using a microprocessor in this application, and the design concepts that were implemented. The effectiveness of the approach as seen after several months of operation will also be discussed.

  5. 20 Years Experience with using Low Cost Launch Opportunities for 20 Small Satellite Missions

    Science.gov (United States)

    Meerman, Maarten; Sweeting, Martin, , Sir

    To realise the full potential of modern low cost mini-micro-nano-satellite missions, regular and affordable launch opportunities are required. It is simply not economic to launch individual satellites of 5-300kg on single dedicated launchers costing typically 15-20M per launch. Whilst there have been periodic 'piggy-back' launches of small satellites on US launchers since the 1960's, these have been infrequent and often experienced significant delays due the vagaries of the main (paying!) payload. In 1989, Arianespace provided a critical catalyst to the microsatellite community when it imaginatively developed the ASAP platform on Ariane-4 providing, for the first time, a standard interface and affordable launch contracts for small payloads up to 50kg. During the 1990's, some 20 small satellites have been successfully launched on the Ariane-4 ASAP ring for international customers carrying out a range of operational, technology demonstration and training missions. However, most of these microsatellite missions seek low Earth orbit and especially sun-synchronous orbits, but the number of primary missions into these orbit has declined since 1996 and with it the availability of useful low cost launch opportunities for microsatellites. Whilst Ariane-5 has an enhanced capacity ASAP, it has yet to be widely used due both to the infrequent launches, higher costs, and the GTO orbit required by the majority of customers. China, Japan and India have also provided occasional secondary launches for small payloads, but not yet on a regular basis. Fortunately, the growing interest and demand for microsatellite missions coincided with the emergence of regular, low cost launch opportunities from the former Soviet Union (FSU) - both as secondary 'piggy-back' missions or as multiple microsatellite payloads on converted military ICBMs. Indeed, the FSU now supplies the only affordable means of launching minisatellites (200-500kg) into LEO as dedicated missions on converted missiles as

  6. CLAIRE: a Canadian Small Satellite Mission for Measurement of Greenhouse Gases

    Science.gov (United States)

    Sloan, James; Grant, Cordell; Germain, Stephane; Durak, Berke; McKeever, Jason; Latendresse, Vincent

    2016-07-01

    CLAIRE, a Canadian mission operated by GHGSat Inc. of Montreal, is the world's first satellite designed to measure greenhouse gas emissions from single targeted industrial facilities. Claire was launched earlier this year into a 500 km polar sun-synchronous orbit selected to provide an acceptable balance between return frequency and spatial resolution. Extensive simulations of oil & gas facilities, power plants, hydro reservoirs and even animal feedlots were used to predict the mission performance. The principal goal is to measure the emission rates of carbon dioxide and methane from selected targets with greater precision and lower cost than ground-based alternatives. CLAIRE will measure sources having surface areas less than 10 x 10 km2 with a spatial resolution better than 50 m, thereby providing industrial site operators and government regulators with the information they need to understand, manage and ultimately to reduce greenhouse gas emissions more economically. The sensor is based on a Fabry-Perot interferometer, coupled with a 2D InGaAs focal plane array operating in the short-wave infrared with a spectral resolution of about 0.1 nm. The patented, high étendue, instrument design provides signal to noise ratios that permit quantification of emission rates with accuracies adequate for most regulatory reporting thresholds. The very high spatial resolution of the density maps produced by the CLAIRE mission resolves plume shapes and emitter locations so that advanced dispersion models can derive accurate emission rates of multiple sources within the field of view. The satellite bus, provided by the University of Toronto's Space Flight Laboratory, is based on the well-characterized NEMO architecture, including hardware that has significant spaceflight heritage. The mission is currently undergoing initial test and validation measurements in preparation for commercial operation later this year.

  7. Evaluating Cloud and Precipitation Processes in Numerical Models using Current and Potential Future Satellite Missions

    Science.gov (United States)

    van den Heever, S. C.; Tao, W. K.; Skofronick Jackson, G.; Tanelli, S.; L'Ecuyer, T. S.; Petersen, W. A.; Kummerow, C. D.

    2015-12-01

    Cloud, aerosol and precipitation processes play a fundamental role in the water and energy cycle. It is critical to accurately represent these microphysical processes in numerical models if we are to better predict cloud and precipitation properties on weather through climate timescales. Much has been learned about cloud properties and precipitation characteristics from NASA satellite missions such as TRMM, CloudSat, and more recently GPM. Furthermore, data from these missions have been successfully utilized in evaluating the microphysical schemes in cloud-resolving models (CRMs) and global models. However, there are still many uncertainties associated with these microphysics schemes. These uncertainties can be attributed, at least in part, to the fact that microphysical processes cannot be directly observed or measured, but instead have to be inferred from those cloud properties that can be measured. Evaluation of microphysical parameterizations are becoming increasingly important as enhanced computational capabilities are facilitating the use of more sophisticated schemes in CRMs, and as future global models are being run on what has traditionally been regarded as cloud-resolving scales using CRM microphysical schemes. In this talk we will demonstrate how TRMM, CloudSat and GPM data have been used to evaluate different aspects of current CRM microphysical schemes, providing examples of where these approaches have been successful. We will also highlight CRM microphysical processes that have not been well evaluated and suggest approaches for addressing such issues. Finally, we will introduce a potential NASA satellite mission, the Cloud and Precipitation Processes Mission (CAPPM), which would facilitate the development and evaluation of different microphysical-dynamical feedbacks in numerical models.

  8. The Rapid Response Radiation Survey (R3S) Mission Using the HISat Conformal Satellite Architecture

    Science.gov (United States)

    Miller, Nathanael

    2015-01-01

    The Rapid Response Radiation Survey (R3S) experiment, designed as a quick turnaround mission to make radiation measurements in LEO, will fly as a hosted payload in partnership with NovaWurks using their Hyper-integrated Satlet (HiSat) architecture. The need for the mission arises as the Nowcast of Atmospheric Ionization Radiation for Aviation Safety (NAIRAS) model moves from a research effort into an operational radiation assessment tool. The data collected by R3S, in addition to the complementary data from a NASA Langley Research Center (LaRC) atmospheric balloon mission entitled Radiation Dosimetry Experiment (RaDX), will validate exposure prediction capabilities of NAIRAS. This paper discusses the development of the R3S experiment as made possible by use of the HiSat architecture. The system design and operational modes of the experiment are described, as well as the experiment interfaces to the HiSat satellite via the user defined adapter (UDA) provided by NovaWurks. This paper outlines the steps taken by the project to execute the R3S mission in the 4 months of design, build, and test. Finally, description of the engineering process is provided, including the use of facilitated rapid/concurrent engineering sessions, the associated documentation, and the review process employed.

  9. Comparison of marine gravity from shipboard and high-density satellite altimetry along the Mid-Atlantic Ridge, 30.5-35.5 deg S

    Science.gov (United States)

    Neumann, Gregory A.; Forsyth, Donald W.; Sandwell, David

    1993-01-01

    We compare new marine gravity fields derived from satellite altimetry with shipboard measurements over a region of more than 120,000 sq km in the central South Atlantic. Newly declassified satellite data were employed to construct free-air anomaly maps on 0.05 degree grids. An extensive gravity and bathymetry data set from four cruises along the Mid-Atlantic Ridge from 30.5-35.5 deg S provides a benchmark for testing the 2D resolution and accuracy of the satellite measurements where their crosstrack spacing is near their widest. The satellite gravity signal is coherent with bathymetry in this region down to wavelengths of 26 km, compared to 12.5 km for shipboard gravity. Residuals between the shipboard and satellite data sets have a roughly normal distribution. The standard deviation of satellite gravity with respect to shipboard measurements is nearly 7 mGal in a region of 140 mGal total variation, whereas the internal standard deviation at crossovers for GPS-navigated shipboard data is 1.8 mGal. The differences between shipboard and satellite data are too large to use satellite gravity to determine crustal thickness variations within a typical ridge segment.

  10. Prediction of bathymetry from satellite altimeter based gravity in the Arabian Sea: Mapping of two unnamed deep seamounts

    Science.gov (United States)

    Jena, B.; Kurian, P. J.; Swain, D.; Tyagi, A.; Ravindra, R.

    2012-06-01

    This work attempts to predict bathymetry from satellite altimeter based gravity in the Arabian Sea. A collocated match-up database (n = 17,016) was created on Multibeam Echosounder (MBES) bathymetry and satellite gravity values (˜1 min spatial resolution) derived from remote sensing satellites. A Radial Basis Function (RBF) based Artificial Neural Network (ANN) model was developed to predict bathymetry from satellite gravity values. The ANN model was trained with variable undersea features such as seamount, knoll, abyssal plain, hill, etc. to familiarize the network with all possible geomorphic features as inputs through learning and the corresponding target outputs. The performance of the predictive model was evaluated by comparing bathymetric values with MBES datasets that were not used during the training and verification steps of the ANN model formulation. The model was then compared with MBES surveyed seamount observations (those were not used during ANN analysis) and global model bathymetry products. Results demonstrate better performance of ANN model compared to global model products for mapping of two unnamed seamounts in the Arabian Sea. These two unnamed seamounts have been predicted, mapped and their morphology is reported for the first time through this work.

  11. Future Satellite Gravimetry and Earth Dynamics

    CERN Document Server

    Flury, Jakob

    2005-01-01

    Currently, a first generation of dedicated satellite missions for the precise mapping of the Earth’s gravity field is in orbit (CHAMP, GRACE, and soon GOCE). The gravity data from these satellite missions provide us with very new information on the dynamics of planet Earth. In particular, on the mass distribution in the Earth’s interior, the entire water cycle (ocean circulation, ice mass balance, continental water masses, and atmosphere), and on changes in the mass distribution. The results are fascinating, but still rough with respect to spatial and temporal resolution. Technical progress in satellite-to-satellite tracking and in gravity gradiometry will allow more detailed results in the future. In this special issue, Earth scientists develop visions of future applications based on follow-on high-precision satellite gravimetry missions.

  12. Atmospheric inertia-gravity waves retrieved from level-2 data of the satellite microwave limb sounder Aura/MLS

    Science.gov (United States)

    Hocke, Klemens; Lainer, Martin; Moreira, Lorena; Hagen, Jonas; Fernandez Vidal, Susana; Schranz, Franziska

    2016-09-01

    The temperature profiles of the satellite experiment Aura/MLS are horizontally spaced by 1.5° or 165 km along the satellite orbit. These level-2 data contain valuable information about horizontal fluctuations in temperature, which are mainly induced by inertia-gravity waves. Wave periods of 2-12 h, horizontal wavelengths of 200-1500 km, and vertical wavelengths of 6-30 km efficiently contribute to the standard deviation of the horizontal temperature fluctuations. The study retrieves and discusses the global distributions of inertia-gravity waves in the stratosphere and mesosphere during July 2015 and January 2016. We find many patterns that were previously present in data of TIMED/SABER, Aura/HIRDLS, and ECMWF analysis. However, it seems that Aura/MLS achieves a higher vertical resolution in the gravity wave maps since the maps are derived from the analysis of horizontal fluctuations along the orbit of the sounding volume. The zonal mean of the inertia-gravity wave distribution shows vertical modulations with scales of 10-20 km. Enhanced wave amplitudes occur in regions of increased zonal wind or in the vicinity of strong wind gradients. Further, we find a banana-like shape of enhanced inertia-gravity waves above the Andes in the winter mesosphere. We find areas of enhanced inertia-gravity wave activity above tropical deep convection zones at 100 hPa (z ˜ 13 km). Finally, we study the temporal evolution of inertia-gravity wave activity at 100 hPa in the African longitude sector from December 2015 to February 2016.

  13. The gravity field and GGOS

    DEFF Research Database (Denmark)

    Forsberg, René; Sideris, M.G.; Shum, C.K.

    2005-01-01

    unique as they can be globally represented by harmonic functions (long-wavelength geopotential model primarily from satellite gravity field missions), or based on point sampling (airborne and in situ absolute and superconducting gravimetry). From a GGOS global perspective, one of the main challenges...

  14. South China Sea crustal thickness and lithosphere thinning from satellite gravity inversion incorporating a lithospheric thermal gravity anomaly correction

    Science.gov (United States)

    Kusznir, Nick; Gozzard, Simon; Alvey, Andy

    2016-04-01

    The distribution of ocean crust and lithosphere within the South China Sea (SCS) are controversial. Sea-floor spreading re-orientation and ridge jumps during the Oligocene-Miocene formation of the South China Sea led to the present complex distribution of oceanic crust, thinned continental crust, micro-continents and volcanic ridges. We determine Moho depth, crustal thickness and continental lithosphere thinning (1- 1/beta) for the South China Sea using a gravity inversion method which incorporates a lithosphere thermal gravity anomaly correction (Chappell & Kusznir, 2008). The gravity inversion method provides a prediction of ocean-continent transition structure and continent-ocean boundary location which is independent of ocean isochron information. A correction is required for the lithosphere thermal gravity anomaly in order to determine Moho depth accurately from gravity inversion; the elevated lithosphere geotherm of the young oceanic and rifted continental margin lithosphere of the South China Sea produces a large lithosphere thermal gravity anomaly which in places exceeds -150 mGal. The gravity anomaly inversion is carried out in the 3D spectral domain (using Parker 1972) to determine 3D Moho geometry and invokes Smith's uniqueness theorem. The gravity anomaly contribution from sediments assumes a compaction controlled sediment density increase with depth. The gravity inversion includes a parameterization of the decompression melting model of White & McKenzie (1999) to predict volcanic addition generated during continental breakup lithosphere thinning and seafloor spreading. Public domain free air gravity anomaly, bathymetry and sediment thickness data are used in this gravity inversion. Using crustal thickness and continental lithosphere thinning factor maps with superimposed shaded-relief free-air gravity anomaly, we improve the determination of pre-breakup rifted margin conjugacy, rift orientation and sea-floor spreading trajectory. SCS conjugate margins

  15. Design of a satellite end-to-end mission performance simulator for imaging spectrometers and its application to the ESA's FLEX/Sentinel-3 tandem mission

    Science.gov (United States)

    Vicent, Jorge; Sabater, Neus; Tenjo, Carolina; Acarreta, Juan R.; Manzano, María.; Rivera, Juan P.; Jurado, Pedro; Franco, Raffaella; Alonso, Luis; Moreno, Jose

    2015-09-01

    The performance analysis of a satellite mission requires specific tools that can simulate the behavior of the platform; its payload; and the acquisition of scientific data from synthetic scenes. These software tools, called End-to-End Mission Performance Simulators (E2ES), are promoted by the European Space Agency (ESA) with the goal of consolidating the instrument and mission requirements as well as optimizing the implemented data processing algorithms. Nevertheless, most developed E2ES are designed for a specific satellite mission and can hardly be adapted to other satellite missions. In the frame of ESA's FLEX mission activities, an E2ES is being developed based on a generic architecture for passive optical missions. FLEX E2ES implements a state-of-the-art synthetic scene generator that is coupled with dedicated algorithms that model the platform and instrument characteristics. This work will describe the flexibility of the FLEX E2ES to simulate complex synthetic scenes with a variety of land cover classes, topography and cloud cover that are observed separately by each instrument (FLORIS, OLCI and SLSTR). The implemented algorithms allows modelling the sensor behavior, i.e. the spectral/spatial resampling of the input scene; the geometry of acquisition; the sensor noises and non-uniformity effects (e.g. stray-light, spectral smile and radiometric noise); and the full retrieval scheme up to Level-2 products. It is expected that the design methodology implemented in FLEX E2ES can be used as baseline for other imaging spectrometer missions and will be further expanded towards a generic E2ES software tool.

  16. 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

  17. A decadal satellite record of gravity wave activity in the lower stratosphere to study polar stratospheric cloud formation

    Science.gov (United States)

    Hoffmann, Lars; Spang, Reinhold; Orr, Andrew; Alexander, M. Joan; Holt, Laura A.; Stein, Olaf

    2017-02-01

    Atmospheric gravity waves yield substantial small-scale temperature fluctuations that can trigger the formation of polar stratospheric clouds (PSCs). This paper introduces a new satellite record of gravity wave activity in the polar lower stratosphere to investigate this process. The record is comprised of observations of the Atmospheric Infrared Sounder (AIRS) aboard NASA's Aqua satellite from January 2003 to December 2012. Gravity wave activity is measured in terms of detrended and noise-corrected 15 µm brightness temperature variances, which are calculated from AIRS channels that are the most sensitive to temperature fluctuations at about 17-32 km of altitude. The analysis of temporal patterns in the data set revealed a strong seasonal cycle in wave activity with wintertime maxima at mid- and high latitudes. The analysis of spatial patterns indicated that orography as well as jet and storm sources are the main causes of the observed waves. Wave activity is closely correlated with 30 hPa zonal winds, which is attributed to the AIRS observational filter. We used the new data set to evaluate explicitly resolved temperature fluctuations due to gravity waves in the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis. It was found that the analysis reproduces orographic and non-orographic wave patterns in the right places, but that wave amplitudes are typically underestimated by a factor of 2-3. Furthermore, in a first survey of joint AIRS and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite observations, nearly 50 gravity-wave-induced PSC formation events were identified. The survey shows that the new AIRS data set can help to better identify such events and more generally highlights the importance of the process for polar ozone chemistry.

  18. Final state predictions for J2 gravity perturbed motion of the Earth’s artificial satellites using Bispherical coordinates

    Directory of Open Access Journals (Sweden)

    M.A. Sharaf

    2013-06-01

    Full Text Available In this paper, initial value problem for dynamical astronomy will be established using Bispherical coordinates. A computational algorithm is developed for the final state predictions for J2 gravity perturbed motion of the Earth’s artificial satellites. This algorithm is important in targeting, rendezvous maneuvers as well for scientific researches. The applications of the algorithm are illustrated by numerical examples of some test orbits of different eccentricities. The numerical results are extremely accurate and efficient.

  19. Groundwater storage changes in the Tibetan Plateau and adjacent areas revealed from GRACE satellite gravity data

    Science.gov (United States)

    Xiang, Longwei; Wang, Hansheng; Steffen, Holger; Wu, Patrick; Jia, Lulu; Jiang, Liming; Shen, Qiang

    2016-09-01

    Understanding groundwater storage (GWS) changes is vital to the utilization and control of water resources in the Tibetan Plateau. However, well level observations are rare in this big area, and reliable hydrology models including GWS are not available. We use hydro-geodesy to quantitate GWS changes in the Tibetan Plateau and surroundings from 2003 to 2009 using a combined analysis of satellite gravity and satellite altimetry data, hydrology models as well as a model of glacial isostatic adjustment (GIA). Release-5 GRACE gravity data are jointly used in a mascon fitting method to estimate the terrestrial water storage (TWS) changes during the period, from which the hydrology contributions and the GIA effects are effectively deducted to give the estimates of GWS changes for 12 selected regions of interest. The hydrology contributions are carefully calculated from glaciers and lakes by ICESat-1 satellite altimetry data, permafrost degradation by an Active-Layer Depth (ALD) model, soil moisture and snow water equivalent by multiple hydrology models, and the GIA effects are calculated with the new ICE-6G_C (VM5a) model. Taking into account the measurement errors and the variability of the models, the uncertainties are rigorously estimated for the TWS changes, the hydrology contributions (including GWS changes) and the GIA effect. For the first time, we show explicitly separated GWS changes in the Tibetan Plateau and adjacent areas except for those to the south of the Himalayas. We find increasing trend rates for eight basins: + 2.46 ± 2.24 Gt/yr for the Jinsha River basin, + 1.77 ± 2.09 Gt/yr for the Nujiang-Lancangjiang Rivers Source Region, + 1.86 ± 1.69 Gt/yr for the Yangtze River Source Region, + 1.14 ± 1.39 Gt/yr for the Yellow River Source Region, + 1.52 ± 0.95 Gt/yr for the Qaidam basin, + 1.66 ± 1.52 Gt/yr for the central Qiangtang Nature Reserve, + 5.37 ± 2.17 Gt/yr for the Upper Indus basin and + 2.77 ± 0.99 Gt/yr for the Aksu River basin. All these

  20. Satellite observations of middle atmosphere gravity wave absolute momentum flux and of its vertical gradient during recent stratospheric warmings

    Science.gov (United States)

    Ern, Manfred; Trinh, Quang Thai; Kaufmann, Martin; Krisch, Isabell; Preusse, Peter; Ungermann, Jörn; Zhu, Yajun; Gille, John C.; Mlynczak, Martin G.; Russell, James M., III; Schwartz, Michael J.; Riese, Martin

    2016-08-01

    Sudden stratospheric warmings (SSWs) are circulation anomalies in the polar region during winter. They mostly occur in the Northern Hemisphere and affect also surface weather and climate. Both planetary waves and gravity waves contribute to the onset and evolution of SSWs. While the role of planetary waves for SSW evolution has been recognized, the effect of gravity waves is still not fully understood, and has not been comprehensively analyzed based on global observations. In particular, information on the gravity wave driving of the background winds during SSWs is still missing.We investigate the boreal winters from 2001/2002 until 2013/2014. Absolute gravity wave momentum fluxes and gravity wave dissipation (potential drag) are estimated from temperature observations of the satellite instruments HIRDLS and SABER. In agreement with previous work, we find that sometimes gravity wave activity is enhanced before or around the central date of major SSWs, particularly during vortex-split events. Often, SSWs are associated with polar-night jet oscillation (PJO) events. For these events, we find that gravity wave activity is strongly suppressed when the wind has reversed from eastward to westward (usually after the central date of a major SSW). In addition, gravity wave potential drag at the bottom of the newly forming eastward-directed jet is remarkably weak, while considerable potential drag at the top of the jet likely contributes to the downward propagation of both the jet and the new elevated stratopause. During PJO events, we also find some indication for poleward propagation of gravity waves. Another striking finding is that obviously localized gravity wave sources, likely mountain waves and jet-generated gravity waves, play an important role during the evolution of SSWs and potentially contribute to the triggering of SSWs by preconditioning the shape of the polar vortex. The distribution of these hot spots is highly variable and strongly depends on the zonal and

  1. Pseudofaults and associated seamounts in the conjugate Arabian and Eastern Somali basins, NW Indian Ocean- New constraints from high-resolution satellite-derived gravity data

    Digital Repository Service at National Institute of Oceanography (India)

    Sreejith, K.M.; Chaubey, A; Mishra, A; Kumar, S.; Rajawat, A

    is characterized by a gravity low and rugged basement. The refined satellite gravity image of the Arabian Basin also revealed three seamounts in close proximity to the pseudofaults, which were not reported earlier. In the Eastern Somali Basin, seamounts are aligned...

  2. Investigation of ice particle habits to be used for ice cloud remote sensing for the GCOM-C satellite mission

    OpenAIRE

    H. Letu; Ishimoto, H.; J. Riedi; T. Y. Nakajima; L. C.-Labonnote; A. J. Baran; T. M. Nagao; M. Skiguchi

    2015-01-01

    Various ice particle habits are investigated in conjunction with inferring the optical properties of ice cloud for the Global Change Observation Mission-Climate (GCOM-C) satellite program. A database of the single-scattering properties of five ice particle habits, namely, plates, columns, droxtals, bullet-rosettes, and Voronoi, is developed. The database is based on the specification of the Second Generation Global Imager (SGLI) sensor onboard the GCOM-C satellite, which is ...

  3. A Collision Avoidance Strategy for a Potential Natural Satellite Around the Asteroid Bennu for the OSIRIS-REx Mission

    Science.gov (United States)

    Mashiku, Alinda; Carpenter, Russell

    2016-01-01

    The cadence of proximity operations for the OSIRIS-REx mission may have an extra induced challenge given the potential of the detection of a natural satellite orbiting the asteroid Bennu. Current ground radar observations for object detection orbiting Bennu show no found objects within bounds of specific size and rotation rates. If a natural satellite is detected during approach, a different proximity operation cadence will need to be implemented as well as a collision avoidance strategy for mission success. A collision avoidance strategy will be analyzed using the Wald Sequential Probability Ratio Test.

  4. A multi-subwaveform parametric retracker of the radar satellite altimetric waveform and recovery of gravity anomalies over coastal oceans

    Institute of Scientific and Technical Information of China (English)

    HWANG; CheinWay

    2010-01-01

    The quality of satellite radar altimetric data is very important in studies of geodesy,geophysics,and oceanography.Over coastal oceans,altimeter waveforms are contaminated by the terrain and physical environments so that the accuracy of altimeter data is lower than that over open oceans.Here we develop a new multi-subwaveform parametric retracker(MSPR) to improve the quality of altimeter data for the recovery of gravity anomaly in coastal oceans.The least squares collocation method is used to recover the residual gravity anomaly over the coastal water from altimetric data.The waveform data records from Geosat/GM around Taiwan Island are practically retracked with MSPR.When compared with the Taiwan geoid height,the results retracked by MSPR are more accurate than those retracked by the well-known β-5-parmeter method and from the geophysical data records(GDRs).The gravity anomalies over Taiwan coastal waters are calculated from the retracked altimeter data with the least squares collocation.When we compared gravity anomalies computed using altimeter GDRs with the ship-borne gravity data over Taiwan coastal ocean,we found that the results from retracked data are more accurate than those from GDRs.

  5. Optimal Trajectory Determination and Mission Design for Asteroid/Deep-Space Exploration via Multibody Gravity Assist Maneuvers

    Directory of Open Access Journals (Sweden)

    Sean Fritz

    2017-01-01

    Full Text Available This paper discusses the creation of a genetic algorithm to locate and optimize interplanetary trajectories using gravity assist maneuvers to improve fuel efficiency of the mission. The algorithm is implemented on two cases: (i a Centaur-class target close to the ecliptic plane and (ii a Centaur-class target with a high inclination to the ecliptic plane. Cases for multiple numbers of flybys (up to three are discussed and compared. It is shown that, for the targets considered here, a single flyby of Jupiter is the most efficient trajectory to either target with the conditions and limitations discussed in this paper. In this paper, we also iterate on possible reasons for certain results seen in the analysis and show how these previously observed behaviors could be present in any trajectory found. The parameters and methods used in the algorithm are explained and justified over multiple real-life interplanetary missions to provide deeper insights into the development choices.

  6. The impact of the new Earth gravity models on the measurement of the Lense-Thirring effect with a new satellite

    CERN Document Server

    Iorio, L

    2005-01-01

    In this paper we investigate the opportunities offered by the new Earth gravity models from the dedicated CHAMP and, especially, GRACE missions to the project of measuring the general relativistic Lense-Thirring effect with a new Earth's artificial satellite. It turns out that it would be possible to abandon the stringent, and expensive, requirements on the orbital geometry of the originally prosed LARES mission (same semimajor axis a=12270 km of the existing LAGEOS and inclination i=70 deg) by inserting the new spacecraft in a relatively low, and cheaper, orbit (a=7500-8000 km, i\\sim 70 deg) and suitably combining its node Omega with those of LAGEOS and LAGEOS II in order to cancel out the first even zonal harmonic coefficients of the multipolar expansion of the terrestrial gravitational potential J_2, J_4 along with their temporal variations. The total systematic error due to the mismodelling in the remaining even zonal harmonics would amount to \\sim 1% and would be insensitive to departures of the inclinat...

  7. Gravity wave driving of the QBO estimated from satellite observations and ERA-Interim

    Science.gov (United States)

    Ern, Manfred; Preusse, Peter; Kalisch, Silvio; Ploeger, Felix; Riese, Martin

    2015-04-01

    The quasi-biennial oscillation (QBO) of the zonal wind in the tropical stratosphere is an important process in atmospheric dynamics. The QBO has effect on atmospheric dynamics over a large range of altitudes and latitudes. Effects of the QBO are found, for example, in the mesosphere, and selective filtering of upward propagating waves plays an important role for the stratopause semiannual oscillation (SAO). The QBO also influences the extratropics and even surface weather and climate. Still, climate models have large difficulties in reproducing a realistic QBO. Atmospheric waves play an important role in the driving of the QBO. Both global scale waves and mesoscale gravity waves (GWs) contribute. We derive GW temperature variances, GW momentum fluxes and potential GW drag from three years of High Resolution Dynamics Limb Sounder (HIRDLS) and from 11 years of Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite data. These observations are compared with the drag that is still missing in the tropical momentum budget of the ECMWF ERA-Interim (ERAI) reanalysis after considering zonal wind tendency, Coriolis force, advection terms, and the drag due to resolved global-scale waves. Being strongly constrained by data assimilation, the meteorological fields of ERAI are quite realistic. Therefore this missing drag can be attributed to small scale GWs not resolved by the model. We find good qualitative agreement between observed GW drag and the missing drag due to waves not resolved in ERAI. During eastward QBO wind shear even the magnitude of observed and ERAI missing drag are in good agreement. During westward shear, however, observed drag is much weaker than the ERAI missing drag. This asymmetry might hint at uncertainties in the advection terms of ERAI. Further, observed GW spectra indicate that QBO-related GW dissipation is mainly due to critical level filtering.

  8. Glacier changes in the Karakoram region mapped by multi-mission satellite imagery

    Directory of Open Access Journals (Sweden)

    M. Rankl

    2013-08-01

    Full Text Available Glaciers in the Karakoram region are known to show stable and advancing terminus positions or surging behavior, which contrasts the worldwide retreat of many mountain glaciers. The present study uses Landsat imagery to derive an updated and extended glacier inventory. Surging and advancing glaciers and their annual termini position changes are mapped in addition. Out of 1334 glaciers, 134 show advancing or surging behavior, with a marked increase since 2000. The length distribution of surging glaciers differs significantly from non-surging glaciers. More than 50% of the advancing/surging glaciers are shorter than 10 km. Besides a regional spatial coverage of ice dynamics, high-resolution SAR data allows to investigate very small and comparably fast flowing glaciers (up to 1.8 m day−1. Such data enables mapping of temporal changes of ice dynamics of individual small surging or advancing glaciers. In a further case study, glacier volume changes of three glaciers around Braldu Glacier are quantified during a surge event comparing digital elevation models from the Shuttle Radar Topography Mission (SRTM and the new TerraSAR-X add-on for Digital Elevation Measurement (TanDEM-X Mission. We recommend regular acquisitions of high resolution (bi-static SAR satellite data and further exploitation of the archives in order to generate an improved database for monitoring changes, and to at least partially compensate for the lack of in-situ and long-term climatological measurements in the Karakoram region.

  9. ‘DEOS CHAMP-01C 70’: a model of the Earth’s gravity field computed from accelerations of the CHAMP satellite

    NARCIS (Netherlands)

    Ditmar, P.G.; Kuznetsov, V.; Van Eck van der Sluis, A.A.; Schrama, E.; Klees, R.

    2005-01-01

    Performance of a recently proposed technique for gravity field modeling has been assessed with data from the CHAMP satellite. The modeling technique is a variant of the acceleration approach. It makes use of the satellite accelerations that are derived from the kinematic orbit with the 3-point

  10. Spaceborne observations of a changing Earth - Contribution from ESÁ s operating and approved satellite missions.

    Science.gov (United States)

    Johannessen, J. A.

    2009-04-01

    , managerial and regulatory activities (i.e. weather forecasting, deforestation, flooding, etc.) essential to the safe exploitation of global resources, conservation of sustainable ecosystems, and the compliance with numerous international treaties and conventions, depend absolutely on continuity of satellite missions to maximise socio-economic and environmental benefits. This presentation will highlight some of the multidisciplinary Earth science achievements and operational applications using ESA satellite missions. It will also address some of the key scientific challenges and need for operational monitoring services in the years to come. It capitalizes on the knowledge and awareness outlined in "The Changing Earth - New scientific challenges for ESÁs Living Planet Programme" issued in 2006 together with updated views and approved plans expressed during ESÁs Earth Sciences Advisory Committee (ESAC) meetings and agreed at the recent User Consultation meeting in January 2009.

  11. A Regional CO2 Observing System Simulation Experiment for the ASCENDS Satellite Mission

    Science.gov (United States)

    Wang, J. S.; Kawa, S. R.; Eluszkiewicz, J.; Baker, D. F.; Mountain, M.; Henderson, J.; Nehrkorn, T.; Zaccheo, T. S.

    2014-01-01

    Top-down estimates of the spatiotemporal variations in emissions and uptake of CO2 will benefit from the increasing measurement density brought by recent and future additions to the suite of in situ and remote CO2 measurement platforms. In particular, the planned NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) satellite mission will provide greater coverage in cloudy regions, at high latitudes, and at night than passive satellite systems, as well as high precision and accuracy. In a novel approach to quantifying the ability of satellite column measurements to constrain CO2 fluxes, we use a portable library of footprints (surface influence functions) generated by the WRF-STILT Lagrangian transport model in a regional Bayesian synthesis inversion. The regional Lagrangian framework is well suited to make use of ASCENDS observations to constrain fluxes at high resolution, in this case at 1 degree latitude x 1 degree longitude and weekly for North America. We consider random measurement errors only, modeled as a function of mission and instrument design specifications along with realistic atmospheric and surface conditions. We find that the ASCENDS observations could potentially reduce flux uncertainties substantially at biome and finer scales. At the 1 degree x 1 degree, weekly scale, the largest uncertainty reductions, on the order of 50 percent, occur where and when there is good coverage by observations with low measurement errors and the a priori uncertainties are large. Uncertainty reductions are smaller for a 1.57 micron candidate wavelength than for a 2.05 micron wavelength, and are smaller for the higher of the two measurement error levels that we consider (1.0 ppm vs. 0.5 ppm clear-sky error at Railroad Valley, Nevada). Uncertainty reductions at the annual, biome scale range from 40 percent to 75 percent across our four instrument design cases, and from 65 percent to 85 percent for the continent as a whole. Our uncertainty

  12. A regional CO2 observing system simulation experiment for the ASCENDS Satellite Mission

    Directory of Open Access Journals (Sweden)

    J. S. Wang

    2014-05-01

    Full Text Available Top-down estimates of the spatiotemporal variations in emissions and uptake of CO2 will benefit from the increasing measurement density brought by recent and future additions to the suite of in situ and remote CO2 measurement platforms. In particular, the planned NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS satellite mission will provide greater coverage in cloudy regions, at high latitudes, and at night than passive satellite systems, as well as high precision and accuracy. In a novel approach to quantifying the ability of satellite column measurements to constrain CO2 fluxes, we use a portable library of footprints (surface influence functions generated by the WRF-STILT Lagrangian transport model in a regional Bayesian synthesis inversion. The regional Lagrangian framework is well suited to make use of ASCENDS observations to constrain fluxes at high resolution, in this case at 1° latitude × 1° longitude and weekly for North America. We consider random measurement errors only, modeled as a function of mission and instrument design specifications along with realistic atmospheric and surface conditions. We find that the ASCENDS observations could potentially reduce flux uncertainties substantially at biome and finer scales. At the 1° × 1°, weekly scale, the largest uncertainty reductions, on the order of 50%, occur where and when there is good coverage by observations with low measurement errors and the a priori uncertainties are large. Uncertainty reductions are smaller for a 1.57 μm candidate wavelength than for a 2.05 μm wavelength, and are smaller for the higher of the two measurement error levels that we consider (1.0 ppm vs. 0.5 ppm clear-sky error at Railroad Valley, Nevada. Uncertainty reductions at the annual, biome scale range from ∼40% to ∼75% across our four instrument design cases, and from ∼65% to ∼85% for the continent as a whole. Our uncertainty reductions at various scales are

  13. Design Concepts for a Small Space-Based GEO Relay Satellite for Missions Between Low Earth and near Earth Orbits

    Science.gov (United States)

    Bhasin, Kul B.; Warner, Joseph D.; Oleson, Steven; Schier, James

    2014-01-01

    The main purpose of the Small Space-Based Geosynchronous Earth orbiting (GEO) satellite is to provide a space link to the user mission spacecraft for relaying data through ground networks to user Mission Control Centers. The Small Space Based Satellite (SSBS) will provide services comparable to those of a NASA Tracking Data Relay Satellite (TDRS) for the same type of links. The SSBS services will keep the user burden the same or lower than for TDRS and will support the same or higher data rates than those currently supported by TDRS. At present, TDRSS provides links and coverage below GEO; however, SSBS links and coverage capability to above GEO missions are being considered for the future, especially for Human Space Flight Missions (HSF). There is also a rising need for the capability to support high data rate links (exceeding 1 Gbps) for imaging applications. The communication payload on the SSBS will provide S/Ka-band single access links to the mission and a Ku-band link to the ground, with an optical communication payload as an option. To design the communication payload, various link budgets were analyzed and many possible operational scenarios examined. To reduce user burden, using a larger-sized antenna than is currently in use by TDRS was considered. Because of the SSBS design size, it was found that a SpaceX Falcon 9 rocket could deliver three SSBSs to GEO. This will greatly reduce the launch costs per satellite. Using electric propulsion was also evaluated versus using chemical propulsion; the power system size and time to orbit for various power systems were also considered. This paper will describe how the SSBS will meet future service requirements, concept of operations, and the design to meet NASA users' needs for below and above GEO missions. These users' needs not only address the observational mission requirements but also possible HSF missions to the year 2030. We will provide the trade-off analysis of the communication payload design in terms of

  14. Global marine gravity field from the ERS-1 and Geosat geodetic mission altimetry

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Knudsen, Per

    1998-01-01

    to a geoid model and crossover adjusted using bias and tilt. Subsequently, sea surface heights were gridded using local collocation in which residual ocean variability was considered. The conversion of the heights into gravity anomalies was carried out using the fast Fourier transform (FFT). In this process...

  15. Investigation on pre-seismic equatorial ionospheric anomaly and its possible association with the gravity wave using satellite measurements

    Science.gov (United States)

    Ryu, K.; Oyama, K. I.; Sun, Y. Y.; Liu, T. J. Y.

    2016-12-01

    Some examples of the equatorial plasma density measured by DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) increased before some large earthquakes are introduced. Previous examples of the pre-seismic equatorial ionization anomalies (EIA) associated with the northern Sumatra earthquake of 2005, Wenchuan earthquake of 2008, Pisco earthquake of 2007, and Kuril Island earthquake of 2007, commonly accompanied conspicuous precursory EIA enhancements distinct from the longitudinal asymmetric variation which is known as a result of ionospheric interaction with the thermospheric tidal modulation generating wave structure in the global ionospheric density profile in the dayside local time. The physical mechanisms of the seismo-ionospheric coupling manifested as the enhanced EIA intensity can be ascribed either to the gravity wave or static electric field generated by the lithosphere-atmosphere-ionosphere coupling, which is still in debate because of lack in confident observational evidences. Molucca sea earthquake of 2007 which accompanied dominant-ever precursory EIA enhancement was selected as a case study to investigate whether the seismo-ionospheric coupling was originated from the gravity wave propagating from the mesosphere to the thermosphere using the SABER satellite data. The gravity wave intensity according to the frequency was derived by applying the s-transform to the atmospheric neutral temperature profile measured by SABER limb-scanning method. The initial analysis results of the ionospheric plasma condition and thermospheric gravity wave derived from DEMETER, CHAMP, and SABER are introduced and the possible association between the physical conditions are discussed.

  16. Applications of acoustic-gravity waves numerical modelling to tsunami signals observed by gravimetry satellites in very low orbit.

    Science.gov (United States)

    Brissaud, Quentin; Garcia, Raphael; Martin, Roland; Komatitsch, Dimitri; Sladen, Anthony

    2016-04-01

    Acoustic and gravity waves propagating in planetary atmospheres have been studied intensively as markers of specific phenomena (tectonic events, explosions) or as contributors to atmosphere dynamics. To get a better understanding of the physics behind these dynamic processes, both acoustic and gravity waves propagation should be modeled in an attenuating and windy 3D atmosphere from the ground all the way to the upper thermosphere. Thus, in order to provide an efficient numerical tool at the regional or global scale we introduce a high-order finite- difference time domain (FDTD) approach that relies on the linearized compressible Navier-Stokes equations with non constant physical parameters (density, viscosities and speed of sound) and background velocities (wind). We present applications of these simulations to the propagation of gravity waves generated by tsunamis for realistic cases for which atmospheric models are extracted from empirical models including 3D variations of atmospheric parameters, and tsunami forcing at the ocean surface is extracted from finite-fault dislocation simulations. We describe the specific difficulties induced by the size of the simulation, the boundary conditions and the spherical geometry and compare the simulation outputs to data gathered by gravimetric satellites crossing gravity waves generated by tsunamis.

  17. The SPectral Ocean Color (SPOC) Small Satellite Mission: From Payload to Ground Station Development and Everything in Between

    Science.gov (United States)

    Bernardes, S.; Cotten, D. L.

    2016-12-01

    This work introduces the mission concept, technologies, and development status for the measuring SPectral Ocean Color (SPOC) small satellite mission, which will use a hyperspectral imager to map sensitive coastal regions and off coast water quality near the state of Georgia and beyond. SPOC is being developed by The University of Georgia's Small Satellite Research Laboratory (SSRL) with funds from NASA's Undergraduate Student Instrument Project (USIP). The project is led by undergraduates from a wide range of backgrounds and supervised by a multidisciplinary team of Principal Investigators. Using optical components, electronics boards, a grating spectrometer, and a CMOS array the students will assemble and integrate the payload components and ensure their compatibility with the other subsystems. In-house development and assembly includes building the hyperspectral imager, as well integrating it into the satellite, and testing of the different subsystems of the satellite. The mission will collect spectral data along a 300 km swath using the grating spectrometer to diffract the incoming radiation into the 440-865 nm spectral range. The resulting images will be 75 km x 300 km in size, have a 120 m spatial resolution, and a spectral resolution of 2 nm, covering 100 spectral bands. The resulting dataset will allow for spectral analysis comparisons with some of NASA's legacy satellites. The work describes the timeline and current progress of the SPOC mission. Focus will be equally distributed to all the different systems of the satellite including their development, testing, and integration. Particular emphasis is given to Attitude Determination and Control System (ADCS), command and data handling (CDH), payload, power generation, S-Band/X-Band transceivers, and the development of ground station capabilities (S-Band/X-Band).

  18. On gravity from SST, geoid from Seasat, and plate age and fracture zones in the Pacific. [Satellite-to-Satellite Tracking

    Science.gov (United States)

    Marsh, B. D.; Marsh, J. G.; Williamson, R. G.

    1984-01-01

    Data from an additional 50 satellite-to-satellite tracking (SST) passes were combined with earlier measurements of the high degree and order (n, m, 12) gravity in the central Pacific. A composite map was produced which shows good agreement with conventional GEM models. Data from the Seasat altimeter was reduced and found to agree well with both the SST and the GEM fields. The maps are dominated especially in the east, by a pattern of roughly east-west anomalies with a transverse wavelength of about 2000 km. Further comparison with regional bathymetric data shows a remarkably close correlation with plate age. Each anomaly band is framed by those major fracture zones having large offsets. The regular spacing of these fractures seems to account for the fabric in the gravity fields. Other anomalies are accounted for by hot spots. The source of part of these anomalies is in the lithosphere itself. The possible plume size and ascent velocity necessary to supply deep mantle material to the upper mantle without complete thermal equilibration is considered. Previously announced in STAR as N84-11559

  19. Density heterogeneity of the North American upper mantle from satellite gravity and a regional crustal model

    DEFF Research Database (Denmark)

    Herceg, Matija; Artemieva, Irina; Thybo, Hans

    2014-01-01

    and by introducing variations into the crustal structure which corresponds to the uncertainty of its resolution by highquality and low-quality seismic models. We examine the propagation of these uncertainties into determinations of lithospheric mantle density. Given a relatively small range of expected density......We present a regional model for the density structure of the North American upper mantle. The residual mantle gravity anomalies are based on gravity data derived from the GOCE geopotential models with crustal correction to the gravity field being calculated from a regional crustal model. We analyze...... how uncertainties and errors in the crustal model propagate from crustal densities to mantle residual gravity anomalies and the density model of the upper mantle. Uncertainties in the residual upper (lithospheric) mantle gravity anomalies result from several sources: (i) uncertainties in the velocity-density...

  20. Hail detection algorithm for the Global Precipitation Measuring mission core satellite sensors

    Science.gov (United States)

    Mroz, Kamil; Battaglia, Alessandro; Lang, Timothy J.; Tanelli, Simone; Cecil, Daniel J.; Tridon, Frederic

    2017-04-01

    By exploiting an abundant number of extreme storms observed simultaneously by the Global Precipitation Measurement (GPM) mission core satellite's suite of sensors and by the ground-based S-band Next-Generation Radar (NEXRAD) network over continental US, proxies for the identification of hail are developed based on the GPM core satellite observables. The full capabilities of the GPM observatory are tested by analyzing more than twenty observables and adopting the hydrometeor classification based on ground-based polarimetric measurements as truth. The proxies have been tested using the Critical Success Index (CSI) as a verification measure. The hail detection algorithm based on the mean Ku reflectivity in the mixed-phase layer performs the best, out of all considered proxies (CSI of 45%). Outside the Dual frequency Precipitation Radar (DPR) swath, the Polarization Corrected Temperature at 18.7 GHz shows the greatest potential for hail detection among all GMI channels (CSI of 26% at a threshold value of 261 K). When dual variable proxies are considered, the combination involving the mixed-phase reflectivity values at both Ku and Ka-bands outperforms all the other proxies, with a CSI of 49%. The best-performing radar-radiometer algorithm is based on the mixed-phase reflectivity at Ku-band and on the brightness temperature (TB) at 10.7 GHz (CSI of 46%). When only radiometric data are available, the algorithm based on the TBs at 36.6 and 166 GHz is the most efficient, with a CSI of 27.5%.

  1. Post-Decadal White Paper: A Dual-Satellite Dark-Energy/Microlensing NASA-ESA Mission

    CERN Document Server

    Gould, Andrew

    2010-01-01

    A confluence of scientific, financial, and political factors imply that launching two simpler, more narrowly defined dark-energy/microlensing satellites will lead to faster, cheaper, better (and more secure) science than the present EUCLID and WFIRST designs. The two satellites, one led by ESA and the other by NASA, would be explicitly designed to perform complementary functions of a single, dual-satellite dark-energy/microlensing ``mission''. One would be a purely optical wide-field camera, with large format and small pixels, optimized for weak-lensing, which because of its simple design, could be launched by ESA on relatively short timescales. The second would be a purely infrared satellite with marginally-sampled or under-sampled pixels, launched by NASA. Because of budget constraints, this would be launched several years later. The two would complement one another in 3 dark energy experiments (weak lensing, baryon oscillations, supernovae) and also in microlensing planet searches. Signed international agr...

  2. Exploration of the Jovian System by EJSM (Europa Jupiter System Mission): Origin of Jupiter and Evolution of Satellites

    Science.gov (United States)

    Sasaki, Sho; Fujimoto, Masaki; Takashima, Takeshi; Yano, Hajime; Kasaba, Yasumasa; Takahashi, Yukihiro; Kimura, Jun; Okada, Tatsuaki; Kawakatsu, Yasuhiro; Tsuda, Yuichi; Kawaguchi, Jun-Ichiro; Funase, Ryu; Mori, Osamu; Morimoto, Mutsuko; Ikoma, Masahiro; Naganuma, Takeshi; Yamaji, Atsushi; Hussmann, Hauke; Kurita, Kei; Working Group, Jupiter

    EJSM (Europa Jupiter System Mission) is a planned Jovian system mission with three spacecraft aiming at coordinated observations of the Jovian satellites especially Europa and the magnetosphere, atmosphere and interior of Jupiter. It was formerly called "Laplace" mission. In October 2007, it was selected as one of future ESA scientific missions Cosmic Vision (2015-2025). From the beginning, Japanese group is participating in the discussion process of the mission. JAXA will take a role on the magnetosphere spinner JMO (Jupiter Magnetosphere Orbiter). On the other hand, ESA will take charge of JGO (Jupiter Ganymede Orbiter) and NASA will be responsible for JEO (Jupiter Europa Orbiter). In February 2009, EJSM is prioritized as the first candidate of outer planet flagship mission and mission study continues in the course of Cosmic Vision. The expected launch time of EJSM will be expected in 2020. Currently we are seeking a possibility to combine JMO with a proposed solar sail mission of JAXA for Jupiter and one of Trojan asteroids.

  3. Promoting space research and applications in developing countries through small satellite missions

    Science.gov (United States)

    Sweeting, M.

    The high vantage-point of space offers very direct and tangible benefits to developing countries when carefully focused upon their real and particular communications and Earth observation needs. However, until recently, access to space has been effectively restricted to only those countries prepared to invest enormous sums in complex facilities and expensive satellites and launchers: this has placed individual participation in space beyond the sensible grasp of developing countries. However, during the last decade, highly capable and yet inexpensive small satellites have been developed which provide an opportunity for developing countries realistically to acquire and operate their own independent space assets - customized to their particular national needs. Over the last 22 years, the Surrey Space Centre has pioneered, developed and launched 23 nano-micro-minisatellite missions, and has worked in partnership with 12 developing countries to enable them to take their first independent steps into space. Surrey has developed a comprehensive and in-depth space technology know-how transfer and 'hands-on' training programme that uses a collaborative project comprising the design, construction, launch and operation of a microsatellite to acquire an indigenous space capability and create the nucleus of a national space agency and space industry. Using low cost small satellite projects as a focus, developing countries are able to initiate a long term, affordable and sustainable national space programme specifically tailored to their requirements, that is able to access the benefits derived from Earth observation for land use and national security; improved communications services; catalyzing scientific research and indigenous high-technology supporting industries. Perhaps even more important is the long-term benefit to the country provided by stimulating educational and career opportunities for your scientists and engineers and retaining them inside the country rather the

  4. High Power MPD Nuclear Electric Propulsion (NEP) for Artificial Gravity HOPE Missions to Callisto

    Science.gov (United States)

    McGuire, Melissa L.; Borowski, Stanley K.; Mason, Lee M.; Gilland, James

    2003-01-01

    This documents the results of a one-year multi-center NASA study on the prospect of sending humans to Jupiter's moon, Callisto, using an all Nuclear Electric Propulsion (NEP) space transportation system architecture with magnetoplasmadynamic (MPD) thrusters. The fission reactor system utilizes high temperature uranium dioxide (UO2) in tungsten (W) metal matrix cermet fuel and electricity is generated using advanced dynamic Brayton power conversion technology. The mission timeframe assumes on-going human Moon and Mars missions and existing space infrastructure to support launch of cargo and crewed spacecraft to Jupiter in 2041 and 2045, respectively.

  5. Satellite formation design in orbits of high eccentricity for missions with performance criteria specified over a region of interest

    Science.gov (United States)

    Roscoe, Christopher William Thomas

    Several methods are presented for the design of satellite formations for science missions in high-eccentricity reference orbits with quantifiable performance criteria specified throughout only a portion the orbit, called the Region of Interest (RoI). A modified form of the traditional average along-track drift minimization condition is introduced to account for the fact that performance criteria are only specified within the RoI, and a robust formation design algorithm (FDA) is defined to improve performance in the presence of formation initialization errors. Initial differential mean orbital elements are taken as the design variables and the Gim-Alfriend state transition matrix (G-A STM) is used for relative motion propagation. Using mean elements and the G-A STM allows for explicit inclusion of J2 perturbation effects in the design process. The methods are applied to the complete formation design problem of the NASA Magnetospheric Multiscale (MMS) mission and results are verified using the NASA General Mission Analysis Tool (GMAT). Since satellite formations in high-eccentricity orbits will spend long times at high altitude, third-body perturbations are an important design consideration as well. A detailed analytical analysis of third-body perturbation effects on satellite formations is also performed and averaged dynamics are derived for the particular case of the lunar perturbation. Numerical results of the lunar perturbation analysis are obtained for the example application of the MMS mission and verified in GMAT.

  6. CHASER: An Innovative Satellite Mission Concept to Measure the Effects of Aerosols on Clouds and Climate

    Science.gov (United States)

    Renno, N.; Williams, E.; Rosenfeld, D.; Fischer, D.; Fischer, J.; Kremic, T.; Agrawal, A.; Andreae, M.; Bierbaum, R.; Blakeslee, R.; Boerner, A.; Bowles, N.; Christian, H.; Dunion, J.; Horvath, A.; Huang, X.; Khain, A.; Kinne, S.; Lemos, M.-C.; Penner, J.

    2012-04-01

    The formation of cloud droplets on aerosol particles, technically known as the activation of cloud condensation nuclei (CCN), is the fundamental process driving the interactions of aerosols with clouds and precipitation. Knowledge of these interactions is foundational to our understanding of weather and climate. The Intergovernmental Panel on Climate Change (IPCC) and the Decadal Survey (NRC 2007) indicate that the uncertainty in how clouds adjust to aerosol perturbations dominates the uncertainty in the overall quantification of the radiative forcing attributable to human activities. The Clouds, Hazards, and Aerosols Survey for Earth Researchers (CHASER) mission concept responds to the IPCC and Decadal Survey concerns by studying the activation of CCN and their interactions with clouds and storms. CHASER proposes to revolutionize our understanding of the interactions of aerosols with clouds by making the first global measurements of the fundamental physical entity linking them: activated cloud condensation nuclei. The CHASER mission was conceptualized to measure all quantities necessary for determining the interactions of aerosols with clouds and storms. Measurements by current satellites allow the determination of crude profiles of cloud particle size but not of the activated CCN that seed them. CHASER uses a new technique (Freud et al. 2011; Rosenfeld et al. 2012) and high-heritage instruments to produce the first global maps of activated CCN and the properties of the clouds associated with them. CHASER measures the CCN concentration and cloud thermodynamic forcing simultaneously, allowing their effects to be distinguished. Changes in the behavior of a group of weather systems in which only one of the quantities varies (a partial derivative of the intensity with the desirable quantity) allow the determination of each effect statistically. The high uncertainties of current climate predictions limit their much-needed use in decision-making. CHASER mitigates this

  7. Sensitivity and foreground modelling for large-scale CMB B-mode polarization satellite missions

    CERN Document Server

    Remazeilles, M; Eriksen, H K K; Wehus, I K

    2015-01-01

    Measurements of large-scale B-mode polarization in the cosmic microwave background (CMB) are a fundamental goal of current and future CMB experiments. However, because of the much higher instrumental sensitivity, CMB experiments will be more sensitive to any imperfect modelling of the Galactic foreground polarization in the estimation of the primordial B-mode signal. We compare the sensitivity to B-modes for different concepts of CMB satellite missions (LiteBIRD, COrE, COrE+, PRISM, EPIC, PIXIE) in the presence of Galactic foregrounds that are either correctly or incorrectly modelled. We quantify the impact on the tensor-to-scalar parameter of imperfect foreground modelling in the component separation process. Using Bayesian parametric fitting and Gibbs sampling, we perform the separation of the CMB and the Galactic foreground B-mode polarization. The resulting CMB B-mode power spectrum is used to compute the likelihood distribution of the tensor-to-scalar ratio. We focus the analysis to the very large angula...

  8. Propulsion System Testing for the Iodine Satellite (iSAT) Demonstration Mission

    Science.gov (United States)

    Polzin, Kurt A.; Kamhawi, Hani

    2015-01-01

    CUBESATS are relatively new spacecraft platforms that are typically deployed from a launch vehicle as a secondary payload, providing low-cost access to space for a wide range of end-users. These satellites are comprised of building blocks having dimensions of 10x10x10 cm cu and a mass of 1.33 kg (a 1-U size). While providing low-cost access to space, a major operational limitation is the lack of a propulsion system that can fit within a CubeSat and is capable of executing high delta v maneuvers. This makes it difficult to use CubeSats on missions requiring certain types of maneuvers (i.e. formation flying, spacecraft rendezvous). Recently, work has been performed investigating the use of iodine as a propellant for Hall-effect thrusters (HETs) 2 that could subsequently be used to provide a high specific impulse path to CubeSat propulsion. 3, 4 Iodine stores as a dense solid at very low pressures, making it acceptable as a propellant on a secondary payload. It has exceptionally high ?Isp (density times specific impulse), making it an enabling technology for small satellite near-term applications and providing the potential for systems-level advantages over mid-term high power electric propulsion options. Iodine flow can also be thermally regulated, subliming at relatively low temperature (less than 100 C) to yield I2 vapor at or below 50 torr. At low power, the measured performance of an iodine-fed HET is very similar to that of a state-of-the-art xenon-fed thruster. Just as importantly, the current-voltage discharge characteristics of low power iodine-fed and xenon-fed thrusters are remarkably similar, potentially reducing development and qualifications costs by making it possible to use an already-qualified xenon-HET PPU in an iodine-fed system. Finally, a cold surface can be installed in a vacuum test chamber on which expended iodine propellant can deposit. In addition, the temperature doesn't have to be extremely cold to maintain a low vapor pressure in the

  9. 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.

  10. An Evaluation of Antarctica as a Calibration Target for Passive Microwave Satellite Missions with Climate Data Record Applications

    Science.gov (United States)

    Kim, E. J.

    2011-12-01

    surface salinity, both important climate variables. Science studies involving these variables can now take advantage of new satellite L-band observations. The first mission with regular global passive microwave observations at L-band is the European Space Agency's Soil Moisture and Ocean Salinity (SMOS), launched November, 2009. A second mission, NASA's Aquarius, was launched June, 2011. A third mission, NASA's Soil Moisture Active Passive (SMAP) is scheduled to launch in 2014. Together, these three missions may provide a decade-long data record-provided that they are intercalibrated. The intercalibration is best performed at the radiance (brightness temperature) level, and Antarctica is proving to be a key calibration target. However, Antarctica has thus far not been fully characterized as a potential target. This paper will present evaluations of Antarctica as a microwave calibration target for the above satellite missions. Preliminary analyses have identified likely target areas, such as the vicinity of Dome-C and larger areas within East Antarctica. Physical sources of temporal and spatial variability of polar firn are key to assessing calibration uncertainty. These sources include spatial variability of accumulation rate, compaction, surface characteristics (dunes, micro-topography), wind patterns, and vertical profiles of density and temperature. Using primarily SMOS data, variability is being empirically characterized and attempts are being made to attribute observed variability to physical sources. One expected outcome of these studies is the potential discovery of techniques for remotely sensing--over all of Antarctica-parameters such as surface temperature.

  11. The orbits of the uranian satellites and rings, the gravity field of the uranian system, and the orientation of the pole of Uranus

    Energy Technology Data Exchange (ETDEWEB)

    Jacobson, R. A., E-mail: robert.jacobson@jpl.nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099 (United States)

    2014-11-01

    French et al. determined the orbits of the Uranian rings, the orientation of the pole of Uranus, and the gravity harmonics of Uranus from Earth-based and Voyager ring occultations. Jacobson et al. determined the orbits of the Uranian satellites and the masses of Uranus and its satellites from Earth-based astrometry and observations acquired with the Voyager 2 spacecraft; they used the gravity harmonics and pole from French et al. Jacobson and Rush reconstructed the Voyager 2 trajectory and redetermined the Uranian system gravity parameters, satellite orbits, and ring orbits in a combined analysis of the data used previously augmented with additional Earth-based astrometry. Here we report on an extension of that work that incorporates additional astrometry and ring occultations together with improved data processing techniques.

  12. Evaluating the hydrological consistency of evaporation products using satellite-based gravity and rainfall data

    Science.gov (United States)

    López, Oliver; Houborg, Rasmus; McCabe, Matthew Francis

    2017-01-01

    Advances in space-based observations have provided the capacity to develop regional- to global-scale estimates of evaporation, offering insights into this key component of the hydrological cycle. However, the evaluation of large-scale evaporation retrievals is not a straightforward task. While a number of studies have intercompared a range of these evaporation products by examining the variance amongst them, or by comparison of pixel-scale retrievals against ground-based observations, there is a need to explore more appropriate techniques to comprehensively evaluate remote-sensing-based estimates. One possible approach is to establish the level of product agreement between related hydrological components: for instance, how well do evaporation patterns and response match with precipitation or water storage changes? To assess the suitability of this consistency-based approach for evaluating evaporation products, we focused our investigation on four globally distributed basins in arid and semi-arid environments, comprising the Colorado River basin, Niger River basin, Aral Sea basin, and Lake Eyre basin. In an effort to assess retrieval quality, three satellite-based global evaporation products based on different methodologies and input data, including CSIRO-PML, the MODIS Global Evapotranspiration product (MOD16), and Global Land Evaporation: the Amsterdam Methodology (GLEAM), were evaluated against rainfall data from the Global Precipitation Climatology Project (GPCP) along with Gravity Recovery and Climate Experiment (GRACE) water storage anomalies. To ensure a fair comparison, we evaluated consistency using a degree correlation approach after transforming both evaporation and precipitation data into spherical harmonics. Overall we found no persistent hydrological consistency in these dryland environments. Indeed, the degree correlation showed oscillating values between periods of low and high water storage changes, with a phase difference of about 2-3 months

  13. A method to develop mission critical data processing systems for satellite based instruments. The spinning mode case

    CERN Document Server

    Lazzarotto, Francesco; Costa, Enrico; Del Monte, Ettore; Di Persio, Giuseppe; Donnarumma, Immacolata; Evangelista, Yuri; Feroci, Marco; Pacciani, Luigi; Rubini, Alda; Soffitta, Paolo

    2011-01-01

    Modern satellite based experiments are often very complex real-time systems, composed by flight and ground segments, that have challenging resource related constraints, in terms of size, weight, power, requirements for real-time response, fault tolerance, and specialized input/output hardware-software, and they must be certified to high levels of assurance. Hardware-software data processing systems have to be responsive to system degradation and to changes in the data acquisition modes, and actions have to be taken to change the organization of the mission operations. A big research & develop effort in a team composed by scientists and technologists can lead to produce software systems able to optimize the hardware to reach very high levels of performance or to pull degraded hardware to maintain satisfactory features. We'll show real-life examples describing a system, processing the data of a X-Ray detector on satellite-based mission in spinning mode.

  14. A close examination of under-actuated attitude control subsystem design for future satellite missions' life extension

    Science.gov (United States)

    Lam, Quang M.; Barkana, Itzhak

    2014-12-01

    Satellite mission life, maintained and prolonged beyond its typical norm of their expectancy, are primarily dictated by the state of health of its Reaction Wheel Assembly (RWA), especially for commercial GEO satellites since torquer bars are no longer applicable while thruster assistant is unacceptable due to pointing accuracy impact during jet firing. The RWA is the primary set of actuators (as compared to thrusters for orbit maintenance and maneuvering) mainly responsible for the satellite mission for accurately and precisely pointing its payloads to the right targets to conduct its mission operations. The RWA consisting of either a set of four in pyramid or three in orthogonal is the primary set of actuators to allow the satellite to achieve accurate and precise pointing of the satellite payloads towards the desired targets. Future space missions will be required to achieve much longer lives and are currently perceived by the GEO satellite community as an "expected norm" of 20 years or longer. Driven by customers' demands/goals and competitive market have challenged Attitude Control Subsystems (ACS) engineers to develop better ACS algorithms to address such an emerging need. There are two main directions to design satellite's under-actuated control subsystem: (1) Attitude Feedback with Zero Momentum Principle and (2) Attitude Control by Angular Velocity Tracking via Small Time Local Controllability concept. Successful applications of these control laws have been largely demonstrated via simulation for the rest to rest case. Limited accuracy and oscillatory behaviors are observed in three axes for non-zero wheel momentum while realistic loss of a wheel scenario (i.e., fully actuated to under-actuated) has not been closely examined! This study revisits the under-actuated control design with detailed set ups of multiple scenarios reflecting real life operating conditions which have put current under-actuated control laws mentioned earlier into a re-evaluation mode

  15. Simultaneous Antarctic Gravity Wave Observations in PMCs from the AIM Satellite and PMSE Observations from PANSY Radar

    Science.gov (United States)

    Buzanowicz, M. E.; Yue, J.; Russell, J. M., III; Sato, K.; Kohma, M.; Nakamura, T.

    2015-12-01

    Polar mesospheric clouds (PMCs) are high-altitude ice clouds that form in the cold summer mesopause region due to adiabatic cooling caused by an upwelling induced by the global meridional circulation, which is driven by gravity wave dissipation and forcing. Polar mesospheric summer echoes (PMSEs) are strong coherent echoes also observed in the polar summer mesosphere and are considered to be related to ionization and the small-scale structure associated with PMCs, with their origins thought to be strongly related. The peak PMSE height can be located slightly below the summer mesopause temperature minimum but above the PMC altitude. Upward propagating atmospheric gravity waves (AGWs) are usually considered to be the cause of the wave patterns seen in PMCs. Monitoring PMCs and PMSEs will provide important tools in detecting climate change in the upper atmosphere and a better understanding of the earth-climate system. The science goal I plan to accomplish is to investigate the possibility of a connection between gravity wave perturbation characteristics in PMCs from the AIM (Aeronomy of Ice in the Mesosphere) satellite and PMSE structures observed by PANSY (program of the Antarctic Syowa MST/IS radar). Data from the CIPS instrument onboard AIM, PANSY, and AIRS (Atmospheric Infrared Sounder) will be used. AIM provides a two-dimensional horizontal view of the atmosphere dynamics embedded in PMCs, while PANSY provides a vertical view of PMSEs and gravity waves with high temporal resolution. The combination of AIM and PANSY will provide a three-dimensional view of the atmosphere, AGWs, PMCs and PMSEs. AIRS provides information about AGWs in the stratosphere. Wave analysis of the Fast Fourier Transform or a wavelet analysis will be used to complete the science goal. AIRS will be used to examine how lower atmosphere meteorology may impact the PMC and PMSE structures.

  16. Aero-gravity Assisted Manoeuvers within Preliminary Interplanetary Mission Design: a Multi-objective Evolutive Algorithm Approach

    Science.gov (United States)

    Povoleri, A.; Lavagna, M.; Finzi, A. E.

    The paper presents a new approach to deal with the preliminary space mission analysis design of particularly complex trajectories focused on interplanetary targets. According to an optimisation approach, a multi-objective strategy is selected on a mixed continuous and discrete state variables domain in order to deal with possible multi-gravity assist manoeuvres (GAM) as further degrees of freedom of the problem, in terms of both number and planets sequence selection to minimize both the ?v expense and the time trip time span. A further added value to the proposed algorithm stays in that, according to planets having an atmosphere, aero-gravity assist manoeuvres (AGAM) are considered too within the overall mission design optimisation, and the consequent optimal control problem related to the aerodynamic angles history, is solved. According to the target planet different capture strategies are managed by the algorithm, the aerocapture manoeuvre too, whenever possible (e.g. Venus, Mars target planets). In order not to be trapped in local solution the Evolutionary Algorithms (EAs) have been selected to solve such a complex problem. Simulations and comparison with already designed space missions showed the ability of the proposed architecture in correctly selecting both the sequences and the planets type of either GAMs or AGAMs to optimise the selected criteria vector, in a multidisciplinary environment, switching on the optimal control problem whenever the atmospheric interaction is involved in the optimisation by the search process. Symbols δ = semi-angular deviation for GAM between the v∞ -, v∞ + inoutcoming vectors [rad] φ = Angular deviation for AGAM between the v∞ -, v∞ + inoutcoming vectors [rad] ρ = Atmospheric density [kgm-3 ] γ = Flight path angle [rad] µ = Bank angle [rad] δ?ttransf j = j-th heliocentric transfer time variation with respect to the linked conics solution ?|v∞| = Relative velocity losses because of drag [ms-1 ] ωI = i

  17. Robust guide-star tracking algorithm proposed for Gravity Probe-B relativity mission

    Science.gov (United States)

    Gwo, Dz-Hung

    1997-09-01

    The gravity probe-B cryogenic star-tracking telescope provides the inertial pointing reference, as established by a distant guide star, with milli-arc-second resolution for the NASA/Stanford relatively gyroscope experiment. The star image of the f/27 Cassegrainian telescope is split onto two focal planes by a 50/50 intensity splitter, with each resultant image further divided by a roof prism reflector to generate the quadrant pointing information within few arc-seconds about the guide-star direction. Conventionally, the quadrant pointing information can be derived through the difference- and-sum algorithm. In this article, an alternative simple, yet robust algorithm is proposed and compared with the conventional one in the following aspects: (1) requirements on near perfect star-image division, (2) optimization in selecting null direction, (3) compensation of null-direction drift due to differential aging of photon detectors, (4) operational definitions of response sensitivity, linearity, and linear range of motion measurement, (5) robustness in system redundancy in terms of options in single-detector pointing per axis.

  18. Analysis and Design of Asteroid Retrieval Missions Using Luni-Solar Gravity Assists

    Science.gov (United States)

    Chen, Hongru

    2016-07-01

    This paper will present the utilization of lunar and solar gravity assists for retrieving asteroids into lunar orbits. The Sun-perturbed Moon-to-Moon transfers can change the relative velocity to the Moon (v_∞). This strategy can be utilized to decrease the v_∞ with respect to Moon for libration orbit insertion. It is desirable to find a multiple lunar swingby sequence to reach a sufficiently low v_∞. The paper discusses several types of Moon-to-Moon transfers and establishes a database for all types. The database is used for choosing patchable Moon-to-Moon arcs. The mismatch between two consecutive arcs is made up by impulsive Δv. The optimization routine will be developed to optimize the correction Δv. Computing the required Δv for different insertion conditions (energy and direction) will reveal the relationship between the retrievable mass and retrievable energy of asteroids. The result can also serve as a database in the optimization of the total Δv of the insertion (from heliocentric orbit to Sun-Earth Hill's region) phase and retrieval phase, in the manner of dynamic programming.

  19. 最小二乘法求解三类卫星重力梯度边值问题%Solving Three Types of Satellite Gravity Gradient Boundary Value Problems by Least-Squares

    Institute of Scientific and Technical Information of China (English)

    徐新禹; 李建成; 邹贤才; 褚永海

    2007-01-01

    The principle and method for solving three types of satellite gravity gradient boundary value problems by least-squares are discussed in detail. Also, kernel function expressions of the least-squares solution of three geodetic boundary value problems with the observations {Γzz},{Γxz,Γyz} and {Γzz -Γyy,2Γxy} are presented. From the results of recovering gravity field using simulated gravity gradient tensor data, we can draw a conclusion that satellite gravity gradient integral formulas derived from least-squares are valid and rigorous for recovering the gravity field.

  20. A contrastive study on the influences of radial and three-dimensional satellite gravity gradiometry on the accuracy of the Earth's gravitational field recovery

    Institute of Scientific and Technical Information of China (English)

    Zheng Wei; Hsu Hou-Tse; Zhong Min; Yun Mei-Juan

    2012-01-01

    The accuracy of the Earth's gravitational field measured from the gravity field and steady-state ocean circulation explorer (GOCE),up to 250 degrees,influenced by the radial gravity gradient Vzz and three-dimensional gravity gradient Vij from the satellite gravity gradiometry (SGG) are contrastively demonstrated based on the analytical error model and numerical simulation,respectively.Firstly,the new analytical error model of the cumulative geoid height,influenced by the radial gravity gradient Vzz and three-dimensional gravity gradient Vij are established,respectively.In 250 degrees,the GOCE cumulative geoid height error measured by the radial gravity gradient Vzz is about 21/2 times higher than that measured by the three-dimensional gravity gradient Vij. Secondly,the Earth's gravitational field from GOCE completely up to 250 degrees is recovered using the radial gravity gradient Vzz and three-dimensional gravity gradient Vij by numerical simulation,respectively.The study results show that when the measurement errorof the gravity gradient is 3 × 10-12/s2,the cumulative geoid height errors using the radial gravity gradient Vzz and three-dimensional gravity gradient Vij are 12.319 cm and 9.295 cm at 250 degrees,respectively.The accuracy of the cumulative geoid height using the three-dimensional gravity gradient Vij is improved by 30%-40% on average compared with that using the radial gravity gradient Vzz in 250 degrees.Finally,by mutual verification of the analytical error model and numerical simulation,the orders of magnitude from the accuracies of the Earth's gravitational field recovery make no substantial differences based on the radial and three-dimensional gravity gradients,respectively.Therefore,it is feasible to develop in advance a radial cold-atom interferometric gradiometer with a measurement accuracy of 10-13/s2-10-15/s2 for precisely producing the next-generation GOCE Follow-On Earth gravity field model with a high spatial resolution.

  1. Deriving the DTU15 Global high resolution marine gravity field from satellite altimetry

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Knudsen, Per

    Data from the Cryosat-2 (369 days repeat mission) as well as Jason-1 end-of-life mission are the first new “geodetic mission” data sets released in nearly 2 decades since the ERS-1 and Geosat geodetic missions were conducted in the early 90’th and late 80’th. Besides providing high quality sea...... surface height observations, the Cryosat-2 has now completed its fifth cycle of 369 days. This opens for new ways of using “pseudo” repeat Geodetic mission data, by averaging or other means of analysisOne further advantage of the Cryosat-2 is its ability of provide new accurate sea surface height...... data using a reduced parameter system in combination with empirical retracking of the SAR and SAR-In data in particularly high latitude regions....

  2. Modeling of Present-Day Atmosphere and Ocean Non-Tidal De-Aliasing Errors for Future Gravity Mission Simulations

    Science.gov (United States)

    Bergmann-Wolf, I.; Dobslaw, H.; Mayer-Gürr, T.

    2015-12-01

    A realistically perturbed synthetic de-aliasing model consistent with the updated Earth System Model of the European Space Agency (Dobslaw et al., 2015) is now available for the years 1995 -- 2006. The data-set contains realizations of (i) errors at large spatial scales assessed individually for periods between 10 -- 30, 3 -- 10, and 1 -- 3 days, the S1 atmospheric tide, and sub-diurnal periods; (ii) errors at small spatial scales typically not covered by global models of atmosphere and ocean variability; and (iii) errors due to physical processes not represented in currently available de-aliasing products. The error magnitudes for each of the different frequency bands are derived from a small ensemble of four atmospheric and oceanic models. In order to demonstrate the plausibility of the error magnitudes chosen, we perform a variance component estimation based on daily GRACE normal equations from the ITSG-Grace2014 global gravity field series recently published by the University of Graz. All 12 years of the error model are used to calculate empirical error variance-covariance matrices describing the systematic dependencies of the errors both in time and in space individually for five continental and four oceanic regions, and daily GRACE normal equations are subsequently employed to obtain pre-factors for each of those matrices. For the largest spatial scales up to d/o = 40 and periods longer than 24 h, errors prepared for the updated ESM are found to be largely consistent with noise of a similar stochastic character contained in present-day GRACE solutions. Differences and similarities identified for all of the nine regions considered will be discussed in detail during the presentation.Dobslaw, H., I. Bergmann-Wolf, R. Dill, E. Forootan, V. Klemann, J. Kusche, and I. Sasgen (2015), The updated ESA Earth System Model for future gravity mission simulation studies, J. Geod., doi:10.1007/s00190-014-0787-8.

  3. Modeling tectonic heat flow and source rock maturity in the Rub' Al-Khali Basin (Saudi Arabia), with the help of GOCE satellite gravity data

    NARCIS (Netherlands)

    Abdul Fattah, R.; Meekes, S.; Bouman, J.; Ebbing, J.; Haagmans, R.

    2014-01-01

    A 3D basin modeling study was carried out to reconstruct the regional heat flow and source rock maturity in the Rub'al-Khali basin. Gravity gradient data from the GOCE satellite were used to model deep structures, such as the Moho interface. Tectonic heat flow was modeled using the GOCE-based Moho i

  4. GRACE Gravity Satellite Observations of Terrestrial Water Storage Changes for Drought Characterization in the Arid Land of Northwestern China

    Directory of Open Access Journals (Sweden)

    Yanping Cao

    2015-01-01

    Full Text Available Drought is a complex natural hazard which can have negative effects on agriculture, economy, and human life. In this paper, the primary goal is to explore the application of the Gravity Recovery and Climate Experiment (GRACE gravity satellite data for the quantitative investigation of the recent drought dynamic over the arid land of northwestern China, a region with scarce hydrological and meteorological observation datasets. The spatiotemporal characteristics of terrestrial water storage changes (TWSC were first evaluated based on the GRACE satellite data, and then validated against hydrological model simulations and precipitation data. A drought index, the total storage deficit index (TSDI, was derived on the basis of GRACE-recovered TWSC. The spatiotemporal distributions of drought events from 2003 to 2012 in the study region were obtained using the GRACE-derived TSDI. Results derived from TSDI time series indicated that, apart from four short-term (three months drought events, the study region experienced a severe long-term drought from May 2008 to December 2009. As shown in the spatial distribution of TSDI-derived drought conditions, this long-term drought mainly concentrated in the northwestern area of the entire region, where the terrestrial water storage was in heavy deficit. These drought characteristics, which were detected by TSDI, were consistent with local news reports and other researchers’ results. Furthermore, a comparison between TSDI and Standardized Precipitation Index (SPI implied that GRACE TSDI was a more reliable integrated drought indicator (monitoring agricultural and hydrological drought in terms of considering total terrestrial water storages for large regions. The GRACE-derived TSDI can therefore be used to characterize and monitor large-scale droughts in the arid regions, being of special value for areas with scarce observations.

  5. Refinements in the Combined Adjustment of Satellite Altimetry and Gravity Anomaly Data

    Science.gov (United States)

    1977-07-12

    of the areas covered by the GEOS-3 satellite when compared with the earlier reported results of the AFGL computer program SARRA ^(Short Arc Reduc...in the partial derivatives may be illustrated as follows. A small set of satellite altimetry data was adjusted by the AFGL program SARRA (Short Arc...1 l+2^(a/rf 2^(C cos mX + S sin mX)P ( sine ) n^2v m=0 nm nm nm i + h u>2r0r 3 co326/(kM) , (4.1) which yields dr (r0/r oo n )^n(a

  6. Estimation of mass change trends in the Earth’s system on the basis of GRACE satellite data, with application to Greenland

    NARCIS (Netherlands)

    Siemes, C.; Ditmar, P.; Riva, E.M.; Slobbe, D.C.; Liu, X.L.; Farahani, H.

    2012-01-01

    The Gravity Recovery and Climate Experiment (GRACE) satellite mission measures the Earth’s gravity field since March 2002. We propose a new filtering procedure for post-processing GRACE-based monthly gravity field solutions provided in the form of spherical harmonic coefficients. The procedure is tu

  7. Utilizing low-cost 3U single-sensor satellites for intelligence, surveillance, and reconnaissance mission capabilities

    Science.gov (United States)

    Huang, Philip M.; Knuth, Andrew A.; Garrison-Darrin, Margaret A.

    2012-06-01

    Leveraging low cost launch carriers for small satellites with the functionality required for DoD and intelligence missions realizes a hidden potential capability. The Multi-Mission Bus Demonstration (MBD) is a Johns Hopkins University Applied Physics Laboratory (JHU/APL) program to demonstrate military operational relevance in a 3U CubeSat form factor. The MBD spacecraft caters to mission versatility and responsive launch capabilities with a standardized bus and interchangeable payload interface design. MBD embraced the challenge of building two space vehicles on an extremely aggressive timeline and demanding budget, causing the development team to evaluate every step of the process to maximize efforts with minimal manpower and cost. MBD is providing a classified DoD payload capability that is truly operationally relevant and may revolutionize the mission area. As a single instrument or payload satellite, also called a SensorSat, MBD is a spacecraft of realizable ISR benefits including effective remote sensing, simplified engineering design and program requirements, and reduced time to launch, all yielding an appealing cost per unit. The SensorSat has potential to detect sufficient information that will act as a complementary component to tactical commanders in heightening battlefield awareness. Recent advancements in technology has put capabilities such as precision navigation, communication intelligence, signal intelligence, tactical warning, environmental intelligence, and a wide variety of ground imaging, at the tip of culmination in a small, economical package. This paper reviews the high functionality of the MBD spacecraft in the miniaturized footprint of 10 cm by 10 cm by 30cm which allows the mission to leverage inexpensive launch opportunities.

  8. An Evaluation of Antarctica as a Calibration Target for Passive Microwave Satellite Missions with Climate Data Record Applications

    Science.gov (United States)

    Kim, Edward

    2011-01-01

    Passive microwave remote sensing at L-band (1.4 GHz) is sensitive to soil moisture and sea surface salinity, both important climate variables. Science studies involving these variables can now take advantage of new satellite L-band observations. The first mission with regular global passive microwave observations at L-band is the European Space Agency's Soil Moisture and Ocean Salinity (SMOS), launched November, 2009. A second mission, NASA's Aquarius, was launched June, 201 I. A third mission, NASA's Soil Moisture Active Passive (SMAP) is scheduled to launch in 2014. Together, these three missions may provide a decade-long data record-provided that they are intercalibrated. The intercalibration is best performed at the radiance (brightness temperature) level, and Antarctica is proving to be a key calibration target. However, Antarctica has thus far not been fully characterized as a potential target. This paper will present evaluations of Antarctica as a microwave calibration target for the above satellite missions. Preliminary analyses have identified likely target areas, such as the vicinity of Dome-C and larger areas within East Antarctica. Physical sources of temporal and spatial variability of polar firn are key to assessing calibration uncertainty. These sources include spatial variability of accumulation rate, compaction, surface characteristics (dunes, micro-topography), wind patterns, and vertical profiles of density and temperature. Using primarily SMOS data, variability is being empirically characterized and attempts are being made to attribute observed variability to physical sources. One expected outcome of these studies is the potential discovery of techniques for remotely sensing--over all of Antarctica-parameters such as surface temperature.

  9. Gradients from GOCE reveal gravity changes before Pisagua Mw=8.2 and Iquique Mw=7.7 large megathrust earthquakes

    OpenAIRE

    Alvarez, O; Nacif, S.; S. Spagnotto; A. Folguera; Gimenez, M.; Chlieh, Mohamed; C. Braitenberg

    2015-01-01

    Considerable improvements in the measurement of the Earth gravity field from GOCE satellite mission have provided global gravity field models with homogeneous coverage, high precision and good spatial resolution. In particular, the vertical gravity gradient (Tzz), in comparison to the classic Bouguer anomaly, defines more accurately superficial mass heterogeneities. Moreover, the correction of these satellite-derived data from the effect of Earth topographic masses by means of new techniques ...

  10. Expansion of the South China Sea basin: Constraints from magnetic anomaly stripes, sea floor topography, satellite gravity and submarine geothermics

    Directory of Open Access Journals (Sweden)

    Xuezhong Yu

    2017-01-01

    Full Text Available The widely distributed E–W-trending magnetic anomaly stripes in the central basin and the N–E-trending magnetic anomaly stripes in the southwest sub-basin provide the most important evidence for Neogene expansion of the South China Sea. The expansion mechanism remains, however, controversial because of the lack of direct drilling data, non-systematic marine magnetic survey data, and irregular magnetic anomaly stripes with two obvious directions. For example, researchers have inferred different ages and episodes of expansion for the central basin and southwest sub-basin. Major controversy centers on the order of basinal expansion and the mechanism of expansion for the entire South China Sea basin. This study attempts to constrain these problems from a comprehensive analysis of the seafloor topography, magnetic anomaly stripes, regional aeromagnetic data, satellite gravity, and submarine geothermics. The mapped seafloor terrain shows that the central basin is a north-south rectangle that is relatively shallow with many seamounts, whereas the southwest sub-basin is wide in northeast, gradually narrows to the southwest, and is relatively deeper with fewer seamounts. Many magnetic anomaly stripes are present in the central basin with variable dimensions and directions that are dominantly EW-trending, followed by the NE-, NW- and NS-trending. Conversely such stripes are few in the southwest sub-basin and mainly NE-trending. Regional magnetic data suggest that the NW-trending Ailaoshan-Red River fault extends into the South China Sea, links with the central fault zone in the South China Sea, which extends further southward to Reed Tablemount. Satellite gravity data show that both the central basin and southwest sub-basin are composed of oceanic crust. The Changlong seamount is particularly visible in the southwest sub-basin and extends eastward to the Zhenbei seamount. Also a low gravity anomaly zone coincides with the central fault zone in the sub

  11. Preliminary interpretation of satellite gravity and magnetic anomalies in the region of the Philippine Sea Plate

    Science.gov (United States)

    Chen, C.; Hu, Z.; Du, J.; Wang, Q.

    2011-12-01

    The Philippine Sea, situated in the northwestern Pacific, is one of the largest marginal seas on the Earth. Analysis of the Philippine Sea's intraplate fault tectonic systems and lithosphere's density and magnetism structures has a significant contribution to understanding not only the dynamic principles of subduction and convergence zones but also effect of plate subduction on back-arc area. It is also important to have cognizance for structure evolution of the ocean crust, the tension and extending progress of marginal sea basins and the mechanisms of geodynamics. Meanwhile, it can be a significant approach for researching the evolution of the East China Sea and the South China Sea. Using high-precision gravity forwarding method based on spatial domain in spherical coordinate, we have calculated the Bouguer gravity disturbance (BGD) in the Philippine Sea based on the ETOPO1 1 arc-minute topography & bathymetry data and the gravity field model EIGEN-6C. After removing the gravity effect of the sediments and deep abnormal materials, we make spherical cap harmonic analysis of the residual anomaly and obtain the topography of Moho and apparent-density's distribution of our study area by alternate iteration inversion method. Then, we calculate the distributions of the study area's magnetic anomalies based on the Earth magnetic model NGDC720, reduce to the pole of the study area's magnetic anomalies by the equivalent source method based on spherical prism magnetic forwarding, inverse the processed magnetic anomalies with spherical cap harmonic analysis to obtain the topography of Curie surface and the apparent magnetic susceptibility distribution. Finally, we divide the Philippine Sea block into tectonic units and derive the faults distributions through the analysis of gravity magnetic anomalies' linear characteristics. The results show that West Philippine Basin is divided by Central Basin Ridge into two block units, the tectonic trend of the north block is south

  12. Updated Hungarian Gravity Field Solution Based on Fifth Generation GOCE Gravity Field Models

    Science.gov (United States)

    Toth, Gyula; Foldvary, Lorant

    2015-03-01

    With the completion of the ESA's GOCE satellite's mission fifth generation gravity field models are available from the ESA's GOCE High Processing Facility. Our contribution is an updated gravity field solution for Hungary using the latest DIR R05 GOCE gravity field model. The solution methodology is least squares gravity field parameter estimation using Spherical Radial Base Functions (SRBF). Regional datasets include deflections of the vertical (DOV), gravity anomalies and quasigeoid heights by GPS/levelling. The GOCE DIR R05 model has been combined with the EGM20008 model and has been evaluated in comparison with the EGM2008 and EIGEN-6C3stat models to assess the performance of our regional gravity field solution.

  13. Assessing GOCE Gravity Models using Altimetry and In-situ Ocean Current Observation

    DEFF Research Database (Denmark)

    Knudsen, Per; Andersen, Ole Baltazar; Honecker, Johanna

    The Gravity and steady state Ocean Circulation Explorer (GOCE) satellite mission measures Earth's gravity field with an unprecedented accuracy at short spatial scales. Previous results have demonstrated a significant advance in our ability to determine the ocean's general circulation. The improved...... gravity models provided by the GOCE mission have enhanced the resolution and sharpened the boundaries of those features and the associated geostrophic surface currents reveal improvements for all of the ocean's current systems. In this study, a series of 23 newer gravity models including observations from...

  14. The Delta low-inclination satellite concept, an opportunity to enhance the science return of the Swarm mission

    DEFF Research Database (Denmark)

    Hulot, Gauthier; Leger, Jean-Michel; Olsen, Nils;

    of these data, however, would be possible if a fourth “Delta” satellite were to be launched soon enough to join the constellation at a similar altitude but much lower inclination orbit (such as 60°). Such a satellite would provide less geographical coverage but a much faster mapping of all local times over...... and investigation efforts are now hampered by the still limited local time coverage provided by this constellation. This affects our ability to accurately characterize time changes in the ionospheric and magnetospheric field contributions, and to model the electrical conductivity of the Earth’s mantle. It also...... these latitudes. In this presentation we will present the rational for such a Delta mission and discuss the benefit it would bring....

  15. Life Science Research in Outer Space: New Platform Technologies for Low-Cost, Autonomous Small Satellite Missions

    Science.gov (United States)

    Ricco, Antonio J.; Parra, Macarena P.; Niesel, David; McGinnis, Michael; Ehrenfreund, Pascale; Nicholson, Wayne; Mancinelli, Rocco; Piccini, Matthew E.; Beasley, Christopher C.; Timucin, Linda R.; Ricks, Robert D.; McIntyre, Michael J.; Squires, David; Yost, Bruce D.; Hines, John W.

    2009-01-01

    We develop integrated instruments and platforms suitable for economical, frequent space access for autonomous life science experiments and processes in outer space. The technologies represented by three of our recent free-flyer small-satellite missions are the basis of a rapidly growing toolbox of miniaturized biologically/biochemically-oriented instrumentation now enabling a new generation of in-situ space experiments. Autonomous small satellites ( 1 50 kg) are less expensive to develop and build than fullsize spacecraft and not subject to the comparatively high costs and scheduling challenges of human-tended experimentation on the International Space Station, Space Shuttle, and comparable platforms. A growing number of commercial, government, military, and civilian space launches now carry small secondary science payloads at far lower cost than dedicated missions; the number of opportunities is particularly large for so-called cube-sat and multicube satellites in the 1 10 kg range. The recent explosion in nano-, micro-, and miniature technologies, spanning fields from telecommunications to materials to bio/chemical analysis, enables development of remarkably capable autonomous miniaturized instruments to accomplish remote biological experimentation. High-throughput drug discovery, point-of-care medical diagnostics, and genetic analysis are applications driving rapid progress in autonomous bioanalytical technology. Three of our recent missions exemplify the development of miniaturized analytical payload instrumentation: GeneSat-1 (launched: December 2006), PharmaSat (launched: May 2009), and O/OREOS (organism/organics exposure to orbital stresses; scheduled launch: May 2010). We will highlight the overall architecture and integration of fluidic, optical, sensor, thermal, and electronic technologies and subsystems to support and monitor the growth of microorganisms in culture in these small autonomous space satellites, including real-time tracking of their culture

  16. Relative humidity distribution from SAPHIR experiment on board Megha-Tropiques satellite mission: Comparison with global radiosonde and other satellite and reanalysis data sets

    Science.gov (United States)

    Venkat Ratnam, M.; Basha, Ghouse; Krishna Murthy, B. V.; Jayaraman, A.

    2013-09-01

    For better understanding the life cycle of the convective systems and their interactions with the environment, a joint Indo-French satellite mission named Megha-Tropiques has been launched in October 2011 in a low-inclination (20°) orbit. In the present study, we show the first results on the comparison of relative humidity (RH) obtained using a six-channel microwave sounder, covering from surface to 100 hPa, from one of the payloads SAPHIR (Sounder for Atmospheric Profiling of Humidity in the Inter-tropical Regions). The RH observations from SAPHIR illustrated the numerous scales of variability in the atmosphere both vertically and horizontally. As a part of its validation, we compare SAPHIR RH with simultaneous observations from a network of radiosondes distributed across the world (±30° latitude), other satellites (Atmospheric Infrared Sounder, Infrared Atmospheric Sounder Interferometer, Constellation Observation System for Meteorology Ionosphere and Climate (COSMIC)), and various reanalysis (National Center for Environmental Prediction (NCEP), European Center for Medium-Range Weather Forecasts reanalysis (ERA)-Interim, Modern-Era Retrospective Analysis for Research and Application (MERRA)) products. Being at a low inclination, SAPHIR is able to show better global coverage when compared to any other existing satellites in the tropical region where some important weather processes take place. A very good correlation is noticed with the RH obtained from a global radiosonde network particularly in the altitude range corresponding to 850-250 hPa, thus providing a valuable data set for investigating the convective processes. In the case of satellite data sets, SAPHIR RH is well comparable with COSMIC RH. Among the reanalysis products, NCEP shows less difference with SAPHIR followed by ERA-Interim, and the MERRA products show large differences in the middle and upper troposphere.

  17. Pseudofaults and associated seamounts in the conjugate Arabian and Eastern Somali basins, NW Indian Ocean - New constraints from high-resolution satellite-derived gravity data

    Science.gov (United States)

    Sreejith, K. M.; Chaubey, A. K.; Mishra, Akhil; Kumar, Shravan; Rajawat, A. S.

    2016-12-01

    Marine gravity data derived from satellite altimeters are effective tools in mapping fine-scale tectonic features of the ocean basins such as pseudofaults, fracture zones and seamounts, particularly when the ocean basins are carpeted with thick sediments. We use high-resolution satellite-generated gravity and seismic reflection data to map boundaries of pseudofaults and transferred crust related to the Paleocene spreading ridge propagation in the Arabian and its conjugate Eastern Somali basins. The study has provided refinement in the position of previously reported pseudofaults and their spatial extensions in the conjugate basins. It is observed that the transferred crustal block bounded by inner pseudofault and failed spreading ridge is characterized by a gravity low and rugged basement. The refined satellite gravity image of the Arabian Basin also revealed three seamounts in close proximity to the pseudofaults, which were not reported earlier. In the Eastern Somali Basin, seamounts are aligned along NE-SW direction forming ∼300 km long seamount chain. Admittance analysis and Flexural model studies indicated that the seamount chain is isostatically compensated locally with Effective Elastic Thickness (Te) of 3-4 km. Based on the present results and published plate tectonic models, we interpret that the seamounts in the Arabian Basin are formed by spreading ridge propagation and are associated with pseudofaults, whereas the seamount chain in the Eastern Somali Basin might have probably originated due to melting and upwelling of upper mantle heterogeneities in advance of migrating/propagating paleo Carlsberg Ridge.

  18. The Rapid Response Radiation Survey (R3S) Mission Using the HiSat Conformal Satellite Architecture

    Science.gov (United States)

    Miller, Nathanael A.; Norman, Ryan B.; Soto, Hector L.; Stewart, Victor A.; Jones, Mark L.; Kowalski, Matthew C.; Ben Shabat, Adam; Gough, Kerry M.; Stavely, Rebecca L.; Shim, Alex C.; hide

    2015-01-01

    The Rapid Response Radiation Survey (R3S) experiment, designed as a quick turnaround mission to make radiation measurements in Low Earth Orbit (LEO), will fly as a hosted payload in partnership with NovaWurks using their Hyper-integrated Satlet (HISat) architecture. The need for the mission arises as the Nowcast of Atmospheric Ionization Radiation for Aviation Safety (NAIRAS) model moves from a research effort into an operational radiation assessment tool. Currently, airline professionals are the second largest demographic of radiation workers and to date their radiation exposure is undocumented in the USA. The NAIRAS model seeks to fill this information gap. The data collected by R3S, in addition to the complementary data from a NASA Langley Research Center (LaRC) atmospheric balloon mission entitled Radiation Dosimetry Experiment (RaD-X), will validate exposure prediction capabilities of NAIRAS. The R3S mission collects total dose and radiation spectrum measurements using a Teledyne µDosimeter and a Liulin-6SA2 LED spectrometer. These two radiation sensors provide a cross correlated radiometric measurement in combination with the Honeywell HMR2300 Smart Digital Magnetometer. The magnetometer assesses the Earth's magnetic field in the LEO environment and allows radiation dose to be mapped as a function of the Earth's magnetic shielding. R3S is also unique in that the radiation sensors will be exposed on the outer surface of the spacecraft, possibly making this the first measurements of the LEO radiation environment with bare sensors. Viability of R3S as an extremely fast turnaround mission is due, in part, to the nature of the robust, well-defined interfaces of the conformal satellite HiSat Architecture. The HiSat architecture, which was developed with the support of the Defense Advanced Research Projects Agency's (DARPA's) Phoenix Program, enabled the R3S system to advance from the first concept to delivery of preliminary design review (PDR) level documents in

  19. Innovative Applications of DoD Propulsion Technology for Low-Cost Satellite Missions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We are proposing to leverage the Missile Defense Agency investments in high-performance propulsion systems for low-cost space missions with large Dv requirements,...

  20. Innovative Applications of DOD Propulsion Technology for Low-Cost Satellite Missions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We are proposing to leverage the Missile Defense Agency investments in high-performance propulsion systems for low-cost space missions with large Dv requirements,...

  1. Satellite observations of atmosphere-ionosphere vertical coupling by gravity waves

    Science.gov (United States)

    Trinh, Thai; Ern, Manfred; Preusse, Peter; Riese, Martin

    2017-04-01

    The Earth's thermosphere/ionosphere (T/I) is strongly influenced by various processes from above as well as from below. One of the most important processes from below is vertical coupling by atmospheric waves. Among these waves, gravity waves (GWs) excited in the lower atmosphere, mainly in the troposphere and tropopause region, are likely essential for the mean state of the T/I system. The penetration of GWs into the T/I system is however not well understood in modeling as well as observations. In this work, we analyze the correlation between different GW parameters at lower altitudes (below 90 km) and GW induced perturbations in the T/I. At lower altitudes, GW parameters are derived from temperature observations of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). In the T/I, GW induced perturbations of neutral density measured by Gravity field and Ocean Circulation Explorer (GOCE) and CHAllenging Minisatellite Payload (CHAMP) are analyzed. Interestingly, we find positive correlations between the spatial distributions at low altitudes (i.e. below 90km) and the spatial distributions of GW-induced density fluctuations in the T/I (at 200km and above), which suggests that many waves seen in the T/I have their origins in the troposphere or lower stratosphere. It is also indicated that mountain waves generated near the Andes and Antarctic Peninsula propagate up to the T/I. Strong positive correlations between GW perturbations in the T/I and GW parameters at 30 km are mainly found at mid latitudes, which may be an indicator of propagation of convectively generated GWs. Increase of correlation starting from 70 km in many cases shows that filtering of the GW distribution by the background atmosphere is very important. Processes that are likely involved are GW dissipation, generation of secondary GWs, as well as horizontal propagation of GWs. Limitations of our method and of the observations are also discussed.

  2. Propagation of Rainfall Products uncertainties in hydrological applications : Studies in the framework of the Megha-Tropiques Satellite Mission

    Science.gov (United States)

    Gosset, M.; Roca, R.

    2012-04-01

    The use of satellite based rainfall in research or operational Hydrological application is becoming more and more frequent. This is specially true in the Tropics where ground based gages (or radar) network are generally scarce and generally degrading. The new French-Indian satellite Mission Megha-Tropiques (MT) dedicated to the water and energy budget in the tropical atmosphere will contribute to a better monitoring of rainfall in the inter-tropical zone. As part of this mission, research is developed on the use of MT rainfall products for hydrological research or operational application such as flood monitoring. A key issue for such applications is how to account for rainfall products biases and uncertainties, and how to propagate them in the end user models ? Another important question is how to chose the best space-time resolution for the rainfall forcing, given that both model performances and rain-product uncertainties are resolution dependent. This talk will present on going investigations and perspectives on this subject, with examples from the Megha_tropiques Ground validation sites. Several sensitivity studies have been carried out in the Oueme Basin in Benin, West Africa, one the instrumented basin that will be used for MT products direct and hydrological validation.

  3. It's All Gravity

    Science.gov (United States)

    Murad, P. A.

    2003-01-01

    Newtonian gravitation adequately predicts planet and satellite motion. Gravitational anomalies and the wish to travel at relativistic speeds, however, imply that gravity should be integrated within a unification framework that may include electricity and magnetism. Thus, new theories are needed that predict currently accepted phenomenon as well as anomalies to prepare the necessary groundwork for experimental validation needed for advanced technology propulsion schemes and far-term missions. A primary deficiency is that we are obviously limited within the confines of our own solar system and a different gravity model may be applicable elsewhere in the cosmos. The model proposed here follows previous ideas proposed by Murad, Dyatlov, and Jefimenko for a universal gravitation model with an intrinsic radial force term coupled with angular momentum. Including angular momentum may explain several spin symmetries seen in some anomalous gyroscopic experiments and throughout the universe regarding planets that orbit around the sun: moons that orbit larger planetary bodies: and the rotation about each planetary axis.

  4. Global-scale Observations of the Limb and Disk (GOLD) Mission: Science from Geostationary Orbit on-board a Commercial Communications Satellite

    Science.gov (United States)

    Eastes, R.; Deaver, T.; Krywonos, A.; Lankton, M. R.; McClintock, W. E.; Pang, R.

    2011-12-01

    Geostationary orbits are ideal for many science investigations of the Earth system on global scales. These orbits allow continuous observations of the same geographic region, enabling spatial and temporal changes to be distinguished and eliminating the ambiguity inherent to observations from low Earth orbit (LEO). Just as observations from geostationary orbit have revolutionized our understanding of changes in the troposphere, they will dramatically improve our understanding of the space environment at higher altitudes. However, geostationary orbits are infrequently used for science missions because of high costs. Geostationary satellites are large, typically weighing tons. Consequently, devoting an entire satellite to a science mission requires a large financial commitment, both for the spacecraft itself and for sufficient science instrumentation to justify a dedicated spacecraft. Furthermore, the small number of geostationary satellites produced for scientific missions increases the costs of each satellite. For these reasons, it is attractive to consider flying scientific instruments on satellites operated by commercial companies, some of whom have fleets of ~40 satellites. However, scientists' lack of understanding of the capabilities of commercial spacecraft as well as commercial companies' concerns about risks to their primary mission have impeded the cooperation necessary for the shared use of a spacecraft. Working with a commercial partner, the GOLD mission has successfully overcome these issues. Our experience indicates that there are numerous benefits to flying on commercial communications satellites (e.g., it is possible to downlink large amounts of data) and the costs are low if the experimental requirements adequately match the capabilities and available resources of the host spacecraft. Consequently, affordable access to geostationary orbit aboard a communications satellite now appears possible for science payloads.

  5. 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.

    2010-04-01

    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 μm, 1.822 μm and 3.547 μm, 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

  6. The GALILEO GALILEI small-satellite mission with FEEP thrusters (G G)

    Energy Technology Data Exchange (ETDEWEB)

    Nobili, A. M.; Bramanti, D.; Catastini, G. [Pisa, Univ. (Italy). Dipt. di Matematica. Gruppo di Meccanica Spaziale

    1997-09-01

    The Equivalence Principle, formulated by Einstein generalizing Galileo`s and Newton`s work, is a fundamental principle of modern physics. As such it should be tested as accurately as possible. Its most direct consequence, namely the Universality of Free Fall, can be tested in space, in a low Earth orbit, the crucial advantage being that the driving signal is about three orders of magnitude stronger than on Earth. GALILEO GALILEI (G G) is a small space mission designed for such a high-accuracy test. At the time of print, G G has been selected by ASI (Agenzia Spaziale Italiana) as a candidate for the next small Italian mission. Ground tests of the proposed apparatus now indicate that an accuracy of 1 part in 10{sup 17} is within the reach of this small mission.

  7. The GALILEO GALILEI small-satellite mission with FEEP thrusters (GG).

    Science.gov (United States)

    Nobili, A. M.; Bramanti, D.; Catastini, G.

    1997-10-01

    The Equivalence Principle, formulated by Einstein generalizing Galileo's and Newton's work, is a fundamental principle of modern physics. As such it should be tested as accurately as possible. Its most direct consequence, namely the universality of free fall, can be tested in space in a low Earth orbit, the crucial advantage being that the driving signal is about three orders of magnitude stronger than on Earth. GALILEO GALILEI (GG) is a small space mission designed for such a high-accuracy test. GG has been selected by ASI (Agenzia Spaziale Italiana) as a candidate for the next small Italian mission. Ground tests of the proposed apparatus now indicate that an accuracy of 1 part in 1017 is within the reach of this small mission.

  8. Satellite Formation Flight Results from Phase 1 of the Magnetospheric Multiscale Mission

    Science.gov (United States)

    Williams, Trevor; Ottenstein, Neil; Palmer, Eric; Godine, Dominic

    2017-01-01

    This paper describes the underlying dynamics of formation flying in a high-eccentricity orbit such as that of the Magnetospheric Multiscale mission. The GPS-based results used for MMS navigation are summarized, as well as the procedures that are used to design the maneuvers used to place the spacecraft into a tetrahedron formation and then maintain it. The details of how to carry out these maneuvers are then discussed. Finally, the numerical results that have been obtained concerning formation flying for the MMS mission to date (e.g. tetrahedron sizes flown, maneuver execution error, fuel usage, etc.) are presented in detail.

  9. A case study of the energy dissipation of the gravity wave field based on satellite altimeter measurements

    Science.gov (United States)

    Huang, N. E.; Parsons, C. L.; Long, S. R.; Bliven, L. F.

    1983-01-01

    Wave breaking is proposed as the primary energy dissipation mechanism for the gravity wave field. The energy dissipation rate is calculated based on the statistical model proposed by Longuet-Higgins (1969) with a modification of the breaking criterion incorporating the surface stress according to Phillips and Banner (1974). From this modified model, an analytic expression is found for the wave attenuation rate and the half-life time of the wave field which depend only on the significant slope of the wave field and the ratio of friction velocity to initial wave phase velocity. These expressions explain why the freshly generated wave field does not last long, but why swells are capable of propagating long distances without substantial change in energy density. It is shown that breaking is many orders of magnitude more effective in dissipating wave energy than the molecular viscosity, if the significant slope is higher than 0.01. Limited observational data from satellite and laboratory are used to compare with the analytic results, and show good agreement.

  10. Long Range River Discharge Forecasting Using the Gravity Recovery and Climate Experiment (GRACE) Satellite to Predict Conditions for Endemic Cholera

    Science.gov (United States)

    Jutla, A.; Akanda, A. S.; Colwell, R. R.

    2014-12-01

    Prediction of conditions of an impending disease outbreak remains a challenge but is achievable if the associated and appropriate large scale hydroclimatic process can be estimated in advance. Outbreaks of diarrheal diseases such as cholera, are related to episodic seasonal variability in river discharge in the regions where water and sanitation infrastructure are inadequate and insufficient. However, forecasting river discharge, few months in advance, remains elusive where cholera outbreaks are frequent, probably due to non-availability of geophysical data as well as transboundary water stresses. Here, we show that satellite derived water storage from Gravity Recovery and Climate Experiment Forecasting (GRACE) sensors can provide reliable estimates on river discharge atleast two months in advance over regional scales. Bayesian regression models predicted flooding and drought conditions, a prerequisite for cholera outbreaks, in Bengal Delta with an overall accuracy of 70% for upto 60 days in advance without using any other ancillary ground based data. Forecasting of river discharge will have significant impacts on planning and designing intervention strategies for potential cholera outbreaks in the coastal regions where the disease remain endemic and often fatal.

  11. Measuring the Value of Earth Observation Information with the Gravity Research and Climate Experiment (GRACE) Satellite

    Science.gov (United States)

    Bernknopf, R.; Kuwayama, Y.; Brookshire, D.; Macauley, M.; Zaitchik, B.; Pesko, S.; Vail, P.

    2014-12-01

    Determining how much to invest in earth observation technology depends in part on the value of information (VOI) that can be derived from the observations. We design a framework and then evaluate the value-in-use of the NASA Gravity Research and Climate Experiment (GRACE) for regional water use and reliability in the presence of drought. As a technology that allows measurement of water storage, the GRACE Data Assimilation System (DAS) provides information that is qualitatively different from that generated by other water data sources. It provides a global, reproducible grid of changes in surface and subsurface water resources on a frequent and regular basis. Major damages from recent events such as the 2012 Midwest drought and the ongoing drought in California motivate the need to understand the VOI from remotely sensed data such as that derived from GRACE DAS. Our conceptual framework models a dynamic risk management problem in agriculture. We base the framework on information from stakeholders and subject experts. The economic case for GRACE DAS involves providing better water availability information. In the model, individuals have a "willingness to pay" (wtp) for GRACE DAS - essentially, wtp is an expression of savings in reduced agricultural input costs and for costs that are influenced by regional policy decisions. Our hypothesis is that improvements in decision making can be achieved with GRACE DAS measurements of water storage relative to data collected from groundwater monitoring wells and soil moisture monitors that would be relied on in the absence of GRACE DAS. The VOI is estimated as a comparison of outcomes. The California wine grape industry has features that allow it to be a good case study and a basis for extrapolation to other economic sectors. We model water use in this sector as a sequential decision highlighting the attributes of GRACE DAS input as information for within-season production decisions as well as for longer-term water reliability.

  12. Aircraft data collection in support of NASA's earth observing satellite missions

    Science.gov (United States)

    NASA's Earth observing missions have been providing global information on soil moisture, vegetation, and precipitation that is crucial for hydrological and agricultural applications. For example, accurate soil moisture information is a key component in land surface and agricultural models used for w...

  13. Finite Difference Simulations of Acoustic and Gravity Wave Propagation in Mars Atmosphere: Applications to INSIGHT NASA Mission and Mars Microphone Experiments

    Science.gov (United States)

    Garcia, R.; Brissaud, Q.; Martin, R.; Rolland, L. M.; Komatitsch, D.

    2015-12-01

    A simulation tool of acoustic and gravity wave propagation through finite differences is applied to the case of Mars atmosphere.The details of the code and its validation for Earth atmosphere are presented in session SA003.The simulations include the modeling of both acoustic and gravity waves in the same run, an effects of exponential density decrease, winds and attenuation.The application to Mars requires the inclusion of a specific attenuation effect related to the relaxation induced by vibrational modes of carbon dioxide molecules.Two different applications are presented demonstrating the ability of the simulation tool to work at very different scale length and frequencies.First the propagation of acoustic and gravity waves due to a bolide explosion in the atmosphere of Mars are simulated.This case has a direct application to the atmospheric pressure and seismic measurements that will be performed by INSIGHT NASA discovery mission next year.Then, we also present simulations of sound wave propagation on a scale of meters that can be used to infer the feasability microphone measurements for future Mars missions.

  14. Precise Relative Orbit Determination of Twin GRACE Satellites

    Institute of Scientific and Technical Information of China (English)

    ZHAO Qile; HU Zhigang; GUO Jing; LI Min; GE Maorong

    2010-01-01

    When formation flying spacecrafts are used as platform to gain earth oriented observation, precise baselines between these spacecrafts are always essential. Gravity recovery and climate experiment (GRACE) mission is aimed at mapping the global gravity field and its variation. Accurate baseline of GRACE satellites is necessary for the gravity field modeling. The determination of kinematic and reduced dynamic relative orbits of twin satellites has been studied in this paper, and an accuracy of 2 mm for dynamic relative orbits and 5 mm for kinematic ones can be obtained, whereby most of the double difference onboard GPS ambiguities are resolved.

  15. CSR Gravity Field Data Products

    Science.gov (United States)

    Bettadpur, Srinivas

    2014-05-01

    The joint NASA/DLR GRACE mission has successfully operated for nearly 12 years, and has provided a remarkable record of global mass flux due to a large variety of geophysical and climate processes at various spatio-temporal scales. The University of Texas Center for Space Research (CSR) hosts the mission PI, and is responsible for delivery of operational (presently denoted as Release-05 or RL05) gravity field data products. In addition, CSR generates and distributes a variety of other gravity field data products, including products generated from the use of satellite laser ranging data. This poster will provide an overview of all these data products, their relative quality, potential applications, and future plans for their development and delivery.

  16. How can present and future satellite missions support scientific studies that address ocean acidification?

    Science.gov (United States)

    Salisbury, Joseph; Vandemark, Douglas; Jonsson, Bror; Balch, William; Chakraborty, Sumit; Lohrenz, Steven; Chapron, Bertrand; Hales, Burke; Mannino, Antonio; Mathis, Jeremy T.; Reul, Nicolas; Signorini, Sergio; Wanninkhof, Rik; Yates, Kimberly K.

    2016-01-01

    Space-based observations offer unique capabilities for studying spatial and temporal dynamics of the upper ocean inorganic carbon cycle and, in turn, supporting research tied to ocean acidification (OA). Satellite sensors measuring sea surface temperature, color, salinity, wind, waves, currents, and sea level enable a fuller understanding of a range of physical, chemical, and biological phenomena that drive regional OA dynamics as well as the potentially varied impacts of carbon cycle change on a broad range of ecosystems. Here, we update and expand on previous work that addresses the benefits of space-based assets for OA and carbonate system studies. Carbonate chemistry and the key processes controlling surface ocean OA variability are reviewed. Synthesis of present satellite data streams and their utility in this arena are discussed, as are opportunities on the horizon for using new satellite sensors with increased spectral, temporal, and/or spatial resolution. We outline applications that include the ability to track the biochemically dynamic nature of water masses, to map coral reefs at higher resolution, to discern functional phytoplankton groups and their relationships to acid perturbations, and to track processes that contribute to acid variation near the land-ocean interface.

  17. Continuation of the mission NINA: Nina-2 experiment on MITA satellite

    Science.gov (United States)

    Casolino, Marco

    NINA-2 is a silicon detector cosmic ray telescope to be launched on board the Italian satellite MITA by the end of 1999. Its physics objectives are to study - for a period of at least 3 years - the cosmic ray component for nuclei from Hydrogen to Iron in the energy range between 10 and 200 MeV/n. Furthermore, the segmented nature of the silicon strip detector will allow the detection outside the containment of particles up to 1 GeV/n. As the satellite will be placed in 87.3 degrees sun-synchronous polar orbit around the Earth, it will be able to detect particle of solar and galactic nature, studying long and short term transient phenomena such as solar modulation effects - as we move toward solar maximum - and the composition of solar flares. The interaction of the Sun with Earth's magnetosphere will also be observed. The characteristics of MITA on board computer system allowed a very fast hardware and software integration between the scientific payload and the satellite, optimising the device observational capabilities.

  18. Towards an Autonomous Turbidimeter Network for Multi-Mission Ocean Colour Satellite Data Validation Activities

    Science.gov (United States)

    Dogliotti, A. I.; Nechad, B.; Ruddick, K. G.; Gossn, J. I.

    2016-08-01

    Satellite-based optical sensors such as MODIS/Aqua, Sentinel-2, Sentinel-3, Landsat-8, Pléiades, SABIA/Mar, PROBA-V , etc. can be used to map turbidity and suspended particulate matter in coastal, estuarine and inland waters as support for water quality monitoring, sediment transport applications such as dredging and fisheries science. However, data quality is a critical problem and in situ data must be gathered from a wide range of test sites in order to provide validation for the diverse range of conditions that can be encountered all over the world. In this context, a network to validate satellite turbidity products called TURBINET is proposed with the goal to establish a long-term (autonomous) international network of collaboration and data-sharing. Joint measurements of turbidity, reflectance and in-water side/back-scattering have been performed in Belgium and Argentina in 2015. Instrument comparisons showed that comparable values could be retrieved using different sensors and field measurements were used to validate a Pléiades high resolution image (2m). The results presented in this work demonstrate the feasibility and usefulness of setting up a network to validate satellite turbidity products.

  19. 低轨卫星精密定轨中重力场模型误差的补偿%Reducing Influence of Gravity Model Error in Precise Orbit Determination of Low Earth Orbit Satellites

    Institute of Scientific and Technical Information of China (English)

    郭金来; 胡敏; 赵齐乐; 郭道玉

    2007-01-01

    Based on the orbit integration and orbit fitting method, the influence of the characters of the gravity model, with different precisions, on the movement of low Earth orbit satellites was studied. The way and the effect of absorbing the influence of gravity model error on CHAMP and GRACE satellite orbits, using linear and periodical empirical acceleration models and the so-called "pseudo-stochastic pulses" model, were also analyzed.

  20. A Nano-satellite Mission to Study Charged Particle Precipitation from the Van Allen Radiation Belts caused due to Seismo-Electromagnetic Emissions

    CERN Document Server

    Sivadas, Nithin; Kannapan, Deepti; Yalamarthy, Ananth Saran; Dhiman, Ankit; Bhagoji, Arjun; Shankar, Athreya; Prasad, Nitin; Ramachandran, Harishankar; Koilpillai, R David

    2014-01-01

    In the past decade, several attempts have been made to study the effects of seismo-electromagnetic emissions - an earthquake precursor, on the ionosphere and the radiation belts. The IIT Madras nano-satellite (IITMSAT) mission is designed to make sensitive measurements of charged particle fluxes in a Low Earth Orbit to study the nature of charged particle precipitation from the Van Allen radiation belts caused due to such emissions. With the Space-based Proton Electron Energy Detector on-board a single nano-satellite, the mission will attempt to gather statistically significant data to verify possible correlations with seismo-electromagnetic emissions before major earthquakes.

  1. Design of a Low-Cost Single-Board Computer System for Use In Low-Earth Orbit Small Satellite Missions

    OpenAIRE

    Milani, Dino

    1996-01-01

    A single-board computer system created specifically to meet the demands of a new generation of small satellite missions is being designed, built and tested by students at the University of New Hampshire. The Satellite Single-Board Computer (SSBC) is an Intel 80C186 based system that is qualified for explicit use in low-earth orbit missions. The SSBC serves as a low-cost, high-quality alternative to commercially available systems which are usually very costly and designed for much harsher spac...

  2. A CubeSat Mission for Mapping Spot Beams of Geostationary Communications Satellites

    Science.gov (United States)

    2015-03-26

    spot beam mapping CubeSats. The Dynamic Ionosphere CubeSat Experiment ( DICE ) mission, Launched in 2011 was tasked with “mapping geomagnetic storm...ADCS components, computing hardware, power hardware, wire harnessing, and any structural or thermal mitigation components. Future work with position...drawnow % force draw so that there is something to maximize on the next line... set(jFrame,’Maximized’,true) % maximize it via the javahandle

  3. Numerical modeling and remote sensing of global water management systems: Applications for land surface modeling, satellite missions, and sustainable water resources

    Science.gov (United States)

    Solander, Kurt C.

    The ability to accurately quantify water storages and fluxes in water management systems through observations or models is of increasing importance due to the expected impacts from climate change and population growth worldwide. Here, I describe three innovative techniques developed to better understand this problem. First, a model was created to represent reservoir storage and outflow with the objective of integration into a Land Surface Model (LSM) to simulate the impacts of reservoir management on the climate system. Given this goal, storage capacity represented the lone model input required that is not already available to an LSM user. Model parameterization was linked to air temperature to allow future simulations to adapt to a changing climate, making it the first such model to mimic the potential response of a reservoir operator to climate change. Second, spatial and temporal error properties of future NASA Surface Water and Ocean Topography (SWOT) satellite reservoir operations were quantified. This work invoked the use of the SWOTsim instrument simulator, which was run over a number of synthetic and actual reservoirs so the resulting error properties could be extrapolated to the global scale. The results provide eventual users of SWOT data with a blueprint of expected reservoir error properties so such characteristics can be determined a priori for a reservoir given knowledge about its topology and anticipated repeat orbit pass over its location. Finally, data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission was used in conjunction with in-situ water use records to evaluate sustainable water use at the two-digit HUC basin scale over the contiguous United States. Results indicate that the least sustainable water management region is centered in the southwest, where consumptive water use exceeded water availability by over 100% on average for some of these basins. This work represents the first attempt at evaluating sustainable

  4. Digital-beamforming array antenna technologies for future ocean-observing satellite missions

    DEFF Research Database (Denmark)

    Iupikov, Oleg A.; Ivashina, Marianna V.; Cappellin, Cecilia

    2016-01-01

    Existing passive microwave radiometers that are used for ocean observations are limited in spatial resolution and geographic coverage, due to the limitations of traditional antenna technologies using mechanically-scanning reflectors and horn-type feeds. Future ocean observation missions call...... for new solutions, such as digitally-beamforming array feeds (DBAFs) as well as stationary and more complex reflectors. Our studies demonstrate that DBAFs can overcome the physically fundamental limitations of traditional horn feeds, and are capable of meeting all the challenging requirements for the next...

  5. Remote Sensing of Grassland Biophysical Parameters in the Context of the Sentinel-2 Satellite Mission

    Directory of Open Access Journals (Sweden)

    Karolina Sakowska

    2016-01-01

    Full Text Available This study investigates the potential of the Sentinel-2 satellite for monitoring the seasonal changes in grassland total canopy chlorophyll content (CCC, fraction of photosynthetically active radiation absorbed by the vegetation canopy (FAPAR, and fraction of photosynthetically active radiation absorbed only by its photosynthesizing components (GFAPAR. Reflectance observations were collected on a continuous basis during growing seasons by means of a newly developed ASD-WhiteRef system. Two models using Sentinel-2 simulated data (linear regression-vegetation indices (VIs approach and multiple regression (MR reflectance approach were tested to estimate vegetation biophysical parameters. To assess whether the use of full solar spectrum reflectance data is able to provide an added value in CCC and GFAPAR estimation accuracy, a third model based on partial least squares regression (PLSR and the ASD-WhiteRef reflectance data was tested. The results showed that FAPAR remained quite stable during the reproduction and senescence stages, and no significant relationships between FAPAR and VIs were found. On the other hand, GFAPAR showed clearer seasonal trends. The comparison of the three models revealed no significant differences in the accuracies of CCC and GFAPAR predictions and demonstrated a strong contribution of SWIR bands to the explained variability of investigated parameters. The promising results highlight the potential of the Sentinel-2 satellite for retrieving biophysical parameters from space.

  6. The Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS mission: design, execution, and first results

    Directory of Open Access Journals (Sweden)

    D. J. Jacob

    2010-06-01

    Full Text Available The NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS mission was conducted in two 3-week deployments based in Alaska (April 2008 and western Canada (June–July 2008. Its goal was to better understand the factors driving current changes in Arctic atmospheric composition and climate, including (1 influx of mid-latitude pollution, (2 boreal forest fires, (3 aerosol radiative forcing, and (4 chemical processes. The June–July deployment was preceded by one week of flights over California (ARCTAS-CARB focused on (1 improving state emission inventories for greenhouse gases and aerosols, (2 providing observations to test and improve models of ozone and aerosol pollution. ARCTAS involved three aircraft: a DC-8 with a detailed chemical payload, a P-3 with an extensive aerosol and radiometric payload, and a B-200 with aerosol remote sensing instrumentation. The aircraft data augmented satellite observations of Arctic atmospheric composition, in particular from the NASA A-Train. The spring phase (ARCTAS-A revealed pervasive Asian pollution throughout the Arctic as well as significant European pollution below 2 km. Unusually large Siberian fires in April 2008 caused high concentrations of carbonaceous aerosols and also affected ozone. Satellite observations of BrO column hotspots were found not to be related to Arctic boundary layer events but instead to tropopause depressions, suggesting the presence of elevated inorganic bromine (5–10 pptv in the lower stratosphere. Fresh fire plumes from Canada and California sampled during the summer phase (ARCTAS-B indicated low NOx emission factors from the fires, rapid conversion of NOx to PAN, no significant secondary aerosol production, and no significant ozone enhancements except when mixed with urban pollution.

  7. Concept of a small satellite for sub-MeV and MeV all sky survey: the CAST mission

    Science.gov (United States)

    Nakazawa, Kazuhiro; Takahashi, Tadayuki; Ichinohe, Yuto; Takeda, Shin'ichiro; Tajima, Hiroyasu; Kamae, Tuneyoshi; Kokubun, Motohide; Takashima, Takeshi; Tashiro, Makoto; Tamagawa, Toru; Terada, Yukikatsu; Nomachi, Masaharu; Fukazawa, Yasushi; Makishima, Kazuo; Mizuno, Tsunefumi; Mitani, Takefumi; Yoshimitsu, Tetsuo; Watanabe, Shin

    2012-09-01

    MeV and sub-MeV energy band from ~200 keV to ~2 MeV contains rich information of high-energy phenomena in the universe. The CAST (Compton Telescope for Astro and Solar Terrestrial) mission is planned to be launched at the end of 2010s, and aims at providing all-sky map in this energy-band for the first time. It is made of a semiconductor Compton telescope utilizing Si as a scatterer and CdTe as an absorber. CAST provides allsky sub-MeV polarization map for the first time, as well. The Compton telescope technology is based on the design used in the Soft Gamma-ray Detector (SGD) onboard ASTRO-H, characterized by its tightly stacked semiconductor layers to obtain high Compton reconstruction efficiency. The CAST mission is currently planned as a candidate for the small scientific satellite series in ISAS/JAXA, weighting about 500 kg in total. Scalable detector design enables us to consider other options as well. Scientific outcome of CAST is wide. It will provide new information from high-energy sources, such as AGN and/or its jets, supernova remnants, magnetors, blackhole and neutron-star binaries and others. Polarization map will tell us about activities of jets and reflections in these sources, as well. In addition, CAST will simultaneously observe the Sun, and depending on its attitude, the Earth.

  8. The Near Earth Object Surveillance Satellite: Mission status and CCD evolution after 18 months on-orbit

    Science.gov (United States)

    Wallace, B.; Scott, R.; Sale, M.

    2014-09-01

    The Near Earth Object Surveillance Satellite (NEOSSat) is a small telescope equipped microsatellite designed to perform both Space Situational Awareness (SSA) experiments and asteroid detection. NEOSSat was launched on 25 February 2013, however, due to time pressures, NEOSSat was launched with only the minimal software required to keep the spacecraft safe. The time pressure also resulted in the spacecraft undergoing reduced system and environmental testing on the ground. The full software suite, required to obtain imagery and maintain stable pointing, has since been uploaded to the spacecraft. NEOSSat has obtained imagery since June 2013, with the shutter both open and closed, but as of March 2014 has not achieved the fine pointing required to obtain scientifically useful data. The collected imagery is being used to characterize the on-board CCD camera. While gain and dark current values agree with pre-launch values, unexpected artefacts have appeared in the images. Methods for mitigating the artefacts through image processing have been developed, and spacecraft-level fixes are currently being investigated. In addition, damage from high energy particles impacting the CCD has produced hot pixels in imagery. We have been able to measure the evolution of these hot pixels over several months, both in terms of numbers and characteristics; these results will be presented. In addition, early results from the mission (image quality issues and evolution, early imagery examples), as well as the mission status (including fine pointing), will be discussed.

  9. A miniature, low-power scientific fluxgate magnetometer: A stepping-stone to cube-satellite constellation missions

    Science.gov (United States)

    Miles, D. M.; Mann, I. R.; Ciurzynski, M.; Barona, D.; Narod, B. B.; Bennest, J. R.; Pakhotin, I. P.; Kale, A.; Bruner, B.; Nokes, C. D. A.; Cupido, C.; Haluza-DeLay, T.; Elliott, D. G.; Milling, D. K.

    2016-12-01

    Difficulty in making low noise magnetic measurements is a significant challenge to the use of cube-satellite (CubeSat) platforms for scientific constellation class missions to study the magnetosphere. Sufficient resolution is required to resolve three-dimensional spatiotemporal structures of the magnetic field variations accompanying both waves and current systems of the nonuniform plasmas controlling dynamic magnetosphere-ionosphere coupling. This paper describes the design, validation, and test of a flight-ready, miniature, low-mass, low-power, and low-magnetic noise boom-mounted fluxgate magnetometer for CubeSat applications. The miniature instrument achieves a magnetic noise floor of 150-200 pT/√Hz at 1 Hz, consumes 400 mW of power, has a mass of 121 g (sensor and boom), stows on the hull, and deploys on a 60 cm boom from a three-unit CubeSat reducing the noise from the onboard reaction wheel to less than 1.5 nT at the sensor. The instrument's capabilities will be demonstrated and validated in space in late 2016 following the launch of the University of Alberta Ex-Alta 1 CubeSat, part of the QB50 constellation mission. We illustrate the potential scientific returns and utility of using a CubeSats carrying such fluxgate magnetometers to constitute a magnetospheric constellation using example data from the low-Earth orbit European Space Agency Swarm mission. Swarm data reveal significant changes in the spatiotemporal characteristics of the magnetic fields in the coupled magnetosphere-ionosphere system, even when the spacecraft are separated by only approximately 10 s along track and approximately 1.4° in longitude.

  10. Visir-Sat - a Prospective Micro-Satellite Based Multi-Spectral Thermal Mission for Land Applications

    Science.gov (United States)

    Ruecker, G.; Menz, G.; Heinemann, S.; Hartmann, M.; Oertel, D.

    2015-04-01

    Current space-borne thermal infrared satellite systems aimed at land surface remote sensing retain some significant deficiencies, in particular in terms of spatial resolution, spectral coverage, number of imaging bands and temperature-emissivity separation. The proposed VISible-to-thermal IR micro-SATellite (VISIR-SAT) mission addresses many of these limitations, providing multi-spectral imaging data with medium-to-high spatial resolution (80m GSD from 800 km altitude) in the thermal infrared (up to 6 TIR bands, between 8 and 11μm) and in the mid infrared (1 or 2 MIR bands, at 4μm). These MIR/TIR bands will be co-registered with simultaneously acquired high spatial resolution (less than 30 m GSP) visible and near infrared multi-spectral imaging data. To enhance the spatial resolution of the MIR/TIR multi-spectral imagery during daytime, data fusion methods will be applied, such as the Multi-sensor Multi-resolution Technique (MMT), already successfully tested over agricultural terrain. This image processing technique will make generation of Land Surface Temperature (LST) EO products with a spatial resolution of 30 x 30 m2 possible. For high temperature phenomena such as vegetation- and peat-fires, the Fire Disturbance Essential Climate Variables (ECV) "Active fire location" and "Fire Radiative Power" will be retrieved with less than 100 m spatial resolution. Together with the effective fire temperature and the spatial extent even for small fire events the innovative system characteristics of VISIR-SAT go beyond existing and planned IR missions. The comprehensive and physically high-accuracy products from VISIR-SAT (e.g. for fire monitoring) may synergistically complement the high temperature observations of Sentinel-3 SLSTR in a unique way. Additionally, VISIR-SAT offers a very agile sensor system, which will be able to conduct intelligent and flexible pointing of the sensor's line-of-sight with the aim to provide global coverage of cloud free imagery every 5

  11. TYCHO: Demonstrator and operational satellite mission to Earth-Moon-Libration point EML-4 for communication relay provision as a service

    Science.gov (United States)

    Hornig, Andreas; Homeister, Maren

    2015-03-01

    In the current wake of mission plans to the Moon and to Earth-Moon Libration points (EML) by several agencies and organizations, TYCHO identifies the key role of telecommunication provision for the future path of lunar exploration. It demonstrates an interesting extension to existing communication methods to the Moon and beyond by combining innovative technology with a next frontier location and the commercial space communication sector. It is evident that all communication systems will rely on direct communication to Earth ground stations. In case of EML-2 missions around HALO orbits or bases on the far side of the Moon, it has to be extended by communication links via relay stations. The innovative approach is that TYCHO provides this relay communication to those out-of-sight lunar missions as a service. TYCHO will establish a new infrastructure for future missions and even create a new market for add-on relay services. The TMA-0 satellite is TYCHO's first phase and a proposed demonstrator mission to the Earth-Moon Libration point EML-4. It demonstrates relay services needed for automated exploratory and manned missions (Moon bases) on the rim (>90°E and >90°W) and far side surface, to lunar orbits and even to EML-2 halo orbits (satellites and space stations). Its main advantage is the permanent availability of communication coverage. This will provide full access to scientific and telemetry data and furthermore to crucial medical monitoring and safety. The communication subsystem is a platform for conventional communication but also a test-bed for optical communication with high data-rate LASER links to serve the future needs of manned bases and periodic burst data-transfer from lunar poles. The operational TMA-1 satellite is a stand-alone mission integrated into existing space communication networks to provide open communication service to external lunar missions. Therefore the long-time stable libration points EML-4 and -5 are selected to guarantee an

  12. Technology development of the Space Transportation System mission and terrestrial applications of satellite technology

    Science.gov (United States)

    1981-01-01

    The Space Transportation System (STS) is discussed, including the launch processing system, the thermal protection subsystem, meteorological research, sound supression water system, rotating service structure, improved hypergol or removal systems, fiber optics research, precision positioning, remote controlled solid rocket booster nozzle plugs, ground operations for Centaur orbital transfer vehicle, parachute drying, STS hazardous waste disposal and recycle, toxic waste technology and control concepts, fast analytical densitometry study, shuttle inventory management system, operational intercommunications system improvement, and protective garment ensemble. Terrestrial applications are also covered, including LANDSAT applications to water resources, satellite freeze forecast system, application of ground penetrating radar to soil survey, turtle tracking, evaluating computer drawn ground cover maps, sparkless load pulsar, and coupling a microcomputer and computing integrator with a gas chromatograph.

  13. Efficient estimation algorithms for a satellite-aided search and rescue mission

    Science.gov (United States)

    Argentiero, P.; Garza-Robles, R.

    1977-01-01

    It has been suggested to establish a search and rescue orbiting satellite system as a means for locating distress signals from downed aircraft, small boats, and overland expeditions. Emissions from Emergency Locator Transmitters (ELT), now available in most U.S. aircraft are to be utilized in the positioning procedure. A description is presented of a set of Doppler navigation algorithms for extracting ELT position coordinates from Doppler data. The algorithms have been programmed for a small computing machine and the resulting system has successfully processed both real and simulated Doppler data. A software system for solving the Doppler navigation problem must include an orbit propagator, a first guess algorithm, and an algorithm for estimating longitude and latitude from Doppler data. Each of these components is considered.

  14. Computational mission analysis and conceptual system design for super low altitude satellite

    Institute of Scientific and Technical Information of China (English)

    Ming Xu; Jinlong Wang; Nan Zhou

    2014-01-01

    This paper deals with system engineering and design methodology for super low altitude satel ites in the view of the com-putational mission analysis. Due to the slight advance of imaging instruments, such as the focus of camera and the image element of charge coupled device (CCD), it is an innovative and economical way to improve the camera’s resolution to enforce the satel ite to fly on the lower altitude orbit. DFH-3, the mature satel ite bus de-veloped by Chinese Academy of Space Technology, is employed to define the mass and power budgets for the computational mis-sion analysis and the detailed engineering design for super low altitude satel ites. An effective iterative algorithm is proposed to solve the ergodic representation of feasible mass and power bud-gets at the flight altitude under constraints. Besides, boundaries of mass or power exist for every altitude, where the upper boundary is derived from the maximum power, while the minimum thrust force holds the lower boundary before the power reaching the initial value. What’s more, an analytical algorithm is employed to numerical y investigate the coverage percentage over the altitude, so that the nominal altitude could be selected from al the feasi-ble altitudes based on both the mass and power budgets and the repetitive ground traces. The local time at the descending node is chosen for the nominal sun-synchronous orbit based on the average evaluation function. After determining the key orbital ele-ments based on the computational mission analysis, the detailed engineering design on the configuration and other subsystems, like power, telemetry telecontrol and communication (TT&C), and attitude determination and control system (ADCS), is performed based on the benchmark bus, besides, some improvements to the bus are also implemented to accommodate the flight at a super low altitude. Two operation strategies, drag-free closed-loop mode and on/off open-loop mode, are presented to maintain the satel

  15. Artificial Gravity

    CERN Document Server

    Clément, Gilles

    2007-01-01

    Protecting the health, safety, and performance of exploration-class mission crews against the physiological deconditioning resulting from long-term weightlessness during transit and long-term reduced gravity during surface operations will require effective, multi-system countermeasures. Artificial gravity, which would replace terrestrial gravity with inertial forces generated by rotating the transit vehicle or by short-radius human centrifuge devices within the transit vehicle or surface habitat, has long been considered a potential solution. However, despite its attractiveness as an efficient

  16. Validation of MPI-ESM Decadal Hindcast Experiments with Terrestrial Water Storage Variations as Observed by the GRACE Satellite Mission

    Directory of Open Access Journals (Sweden)

    Liangjing Zhang

    2016-12-01

    Full Text Available Time-variations in the gravity field as observed by the GRACE mission provide for the first time quantitative estimates of the terrestrial water storage (TWS at monthly resolution over one decade (2002–2011. TWS from GRACE is applied here to validate three different ensemble sets of decadal hindcasts performed with the coupled climate model MPI-ESM within the German research project MiKlip. Those experiments differ in terms of the applied low (LR and medium (MR spatial resolution configuration of MPI-ESM, as well as by the applied ensemble initialization strategy, where ocean-only (b0 is replaced by atmosphere and ocean (b1 anomaly initialization. Moderately positive skill scores of the initialized hindcasts are obtained both with respect to the zero anomaly forecast and the uninitialized projections in particular for lead year 1 in moderate to high latitudes of the Northern Hemisphere. Skill scores gradually increase when moving from b0-LR to b1-LR, and less prominent also for b1-LR to b1-MR, thereby documenting improvements of the MPI-ESM decadal climate prediction system during the most recent years.

  17. Magnetometer Data in the Classroom as a part of the NASA THEMIS Satellite Mission

    Science.gov (United States)

    Peticolas, L. M.; Bean, J.; Walker, A.

    2011-12-01

    The NASA-funded THEMIS mission was designed to determine the onset time and location of magnetic substorms of Earth's space environment, a prerequisite to understanding space weather. THEMIS is an acronym for Time History of Events and Macroscale Interactions during Substorms. he Geomagnetic Event Observation Network by Students (GEONS) project was the flagship, formal education component of the E/PO program. With the placement of magnetometers in the proximity of rural schools throughout the country, middle and high school teachers along with their students benefited from the opportunity to work with 'real-time' data and participated in hands-on space science activities. Particular attention was paid to placing the magnetometer stations at schools in rural communities whose students were traditionally underserved and underrepresented in the sciences. The project offered to the teachers of these students long-term professional development opportunities that centered around THEMIS-related space science and the magnetometer data. The THEMIS E/PO final evaluation report for the main phase of the THEMIS mission covered the period from 2003-2009, describing the impact of this program such as this program placed magnetometers sites at 13 rural, underserved schools/communities, two-fifths of which are on tribal lands; and provided intensive professional development for 20 teachers from 2004 through 2009. A core group of eight teachers estimated reaching more than 2,720 students with THEMIS-related materials/ideas. 75% of these students are minorities in science. Core teachers provided evidence of the project's positive impact on students' attitudes toward science and their choices for courses that position them for STEM-related careers. Core teachers reported sharing THEMIS-related materials/ideas with 275 colleagues. The NewsHour with Jim Lehrer featured the Petersburg, Alaska site potentially reaching more than 5 million viewers in two airings, according to Nielsen

  18. Recent dynamics of alpine lakes on the endorheic Changtang Plateau from multi-mission satellite data

    Science.gov (United States)

    Yang, Kehan; Yao, Fangfang; Wang, Jida; Luo, Jiancheng; Shen, Zhanfeng; Wang, Chao; Song, Chunqiao

    2017-09-01

    Monitoring of the alpine lakes on the endorheic Changtang Plateau is vitally important in understanding climate impacts on hydrological cycle. Existing studies have revealed an accelerated lake expansion on the Changtang Plateau during the 2000s compared with prior decades. However, the partial hiatus of recent Landsat archive affected the continuation of understanding the lake changes in the recent decade. Here we synergistically used imagery from Landsat and Huanjing satellites to enable a detailed monitoring of lake area dynamics on the Changtang Plateau. Our results present that lakes on the Changtang Plateau continued to expand at a rapid rate of 340.79 km2 yr-1 (1.06% yr-1, p variations of the selected 24 large lakes fluctuated within 0.22-2.46% (in coefficient of variation) for glacier-fed lakes and 0.17-2.36% for non-glacier-fed lakes. Most of these lakes expanded during the unfrozen period (from May/June to October) and reached to their maximum extents in September or October. By spatially associating our revealed lake changes with climate variables, we observed that the recent lake expansion is more related to precipitation than to temperature, although future efforts are needed for a more comprehensive picture of the lake changing mechanisms.

  19. The scientific basis for a satellite mission to retrieve CCN concentrations and their impacts on convective clouds

    Directory of Open Access Journals (Sweden)

    D. Rosenfeld

    2012-02-01

    Full Text Available The cloud -mediated radiative forcing is widely recognized as the main source of uncertainty in our knowledge of the anthropogenic climate forcing and in our understanding of climate sensitivity. Current outstanding challenges are (1 global measurements of cloud condensation nuclei (CCN in the cloudy boundary layer from space, and, (2 disentangling the effects of aerosols from the thermodynamic and meteorological effects on the clouds. Here we present a new concept for a way to overcome these two challenges, using relatively simple passive satellite measurements in the visible and IR. The idea is to use the clouds themselves as natural CCN chambers by retrieving simultaneously the number of activated aerosols at cloud base, Na, and the cloud base updraft speed. The Na is obtained by analyzing the distribution of cloud drop effective radius in convective elements as a function distance above cloud base. The cloud base updraft velocities are estimated by double stereoscopic viewing and tracking of the evolution of cloud surface features just above cloud base. In order to resolve the vertical dimension of the clouds, the field of view will be 100 m for the microphysical retrievals, and 50 m for the stereoscopic measurements. The viewing geometry will be 30 degrees off nadir eastward, with the Sun in the back at 30 degrees off zenith westward, which requires a Sun synchronous orbit at 14:00 LST. Having measured simultaneously the thermodynamic environment, the vertical motions of the clouds, their microstructure and the CCN concentration will allow separating the dynamic from the CCN effects. This concept is being applied in the proposed satellite mission named Clouds, Hazards and Aerosols Survey for Earth Researchers (CHASER.

  20. The scientific basis for a satellite mission to retrieve CCN concentrations and their impacts on convective clouds

    Directory of Open Access Journals (Sweden)

    D. Rosenfeld

    2012-08-01

    Full Text Available The cloud-mediated aerosol radiative forcing is widely recognized as the main source of uncertainty in our knowledge of the anthropogenic forcing on climate. The current challenges for improving our understanding are (1 global measurements of cloud condensation nuclei (CCN in the cloudy boundary layer from space, and (2 disentangling the effects of aerosols from the thermodynamic and meteorological effects on the clouds. Here, we present a new conceptual framework to help us overcome these two challenges, using relatively simple passive satellite measurements in the visible and infared (IR. The idea is to use the clouds themselves as natural CCN chambers by retrieving simultaneously the number of activated aerosols at cloud base, Na, and the cloud base updraft speed. The Na is obtained by analyzing the distribution of cloud drop effective radius in convective elements as a function of distance above cloud base. The cloud base updraft velocities are estimated by double stereoscopic viewing and tracking of the evolution of cloud surface features just above cloud base. In order to resolve the vertical dimension of the clouds, the field of view will be 100 m for the microphysical retrievals, and 50 m for the stereoscopic measurements. The viewing geometry will be eastward and 30 degrees off nadir, with the Sun in the back at 30 degrees off zenith westward, requiring a Sun-synchronous orbit at 14 LST. Measuring simultaneously the thermodynamic environment, the vertical motions of the clouds, their microstructure and the CCN concentration will allow separating the dynamics from the CCN effects. This concept is being applied in the proposed satellite mission named Clouds, Hazards and Aerosols Survey for Earth Researchers (CHASER.

  1. The Surface Water and Ocean Topography Satellite Mission - An Assessment of Swath Altimetry Measurements of River Hydrodynamics

    Science.gov (United States)

    Wilson, Matthew D.; Durand, Michael; Alsdorf, Douglas; Chul-Jung, Hahn; Andreadis, Konstantinos M.; Lee, Hyongki

    2012-01-01

    The Surface Water and Ocean Topography (SWOT) satellite mission, scheduled for launch in 2020 with development commencing in 2015, will provide a step-change improvement in the measurement of terrestrial surface water storage and dynamics. In particular, it will provide the first, routine two-dimensional measurements of water surface elevations, which will allow for the estimation of river and floodplain flows via the water surface slope. In this paper, we characterize the measurements which may be obtained from SWOT and illustrate how they may be used to derive estimates of river discharge. In particular, we show (i) the spatia-temporal sampling scheme of SWOT, (ii) the errors which maybe expected in swath altimetry measurements of the terrestrial surface water, and (iii) the impacts such errors may have on estimates of water surface slope and river discharge, We illustrate this through a "virtual mission" study for a approximately 300 km reach of the central Amazon river, using a hydraulic model to provide water surface elevations according to the SWOT spatia-temporal sampling scheme (orbit with 78 degree inclination, 22 day repeat and 140 km swath width) to which errors were added based on a two-dimension height error spectrum derived from the SWOT design requirements. Water surface elevation measurements for the Amazon mainstem as may be observed by SWOT were thereby obtained. Using these measurements, estimates of river slope and discharge were derived and compared to those which may be obtained without error, and those obtained directly from the hydraulic model. It was found that discharge can be reproduced highly accurately from the water height, without knowledge of the detailed channel bathymetry using a modified Manning's equation, if friction, depth, width and slope are known. Increasing reach length was found to be an effective method to reduce systematic height error in SWOT measurements.

  2. Tidal Models In A New Era of Satellite Gravimetry

    Science.gov (United States)

    Ray, Richard D.; Rowlings, David D.; Edbert, G. D.; Chao, Benjamin F. (Technical Monitor)

    2002-01-01

    The high precision gravity measurements to be made by recently launched (and recently approved) satellites place new demands on models of Earth, atmospheric, and oceanic tides. The latter is the most problematic. The ocean tides induce variations in the Earth's geoid by amounts that far exceed the new satellite sensitivities, and tidal models must be used to correct for this. Two methods are used here to determine the standard errors in current ocean tide models. At long wavelengths these errors exceed the sensitivity of the GRACE mission. Tidal errors will not prevent the new satellite missions from improving our knowledge of the geopotential by orders of magnitude, but the errors may well contaminate GRACE estimates of temporal variations in gravity. Solar tides are especially problematic because of their long alias periods. The satellite data may be used to improve tidal models once a sufficiently long time series is obtained. Improvements in the long-wavelength components of lunar tides are especially promising.

  3. Solidification under zero gravity: A Long Duration Exposure Facility (LDEF) experiment for an early space shuttle mission

    Science.gov (United States)

    Bailey, J. A.; Whitfield, J. K.

    1976-01-01

    The preliminary design of two series of simple experiments the objectives of which are to determine the effect of an absence of gravity on (1) the general morphology of the structure, (2) location of ullage space, and (3) magnitude of surface tension driven convection, during the solidification of several metallic and nonmetallic systems is described. Details of the investigative approach, experimental procedure, experimental hardware, data reduction and analysis, and anticipated results are given.

  4. A global mean dynamic topography and ocean circulation estimation using a preliminary GOCE gravity model

    DEFF Research Database (Denmark)

    Knudsen, Per; Bingham, R.; Andersen, Ole Baltazar

    2011-01-01

    The Gravity and steady-state Ocean Circulation Explorer (GOCE) satellite mission measures Earth’s gravity field with an unprecedented accuracy at short spatial scales. In doing so, it promises to significantly advance our ability to determine the ocean’s general circulation. In this study......, an initial gravity model from GOCE, based on just 2 months of data, is combined with the recent DTU10MSS mean sea surface to construct a global mean dynamic topography (MDT) model. The GOCE MDT clearly displays the gross features of the ocean’s steady-state circulation. More significantly, the improved...... gravity model provided by the GOCE mission has enhanced the resolution and sharpened the boundaries of those features compared with earlier satellite only solutions. Calculation of the geostrophic surface currents from the MDT reveals improvements for all of the ocean’s major current systems. In the North...

  5. Measuring the Change in Water Table with Gravity Methods - a Controlled Experiment

    DEFF Research Database (Denmark)

    Lund, S; Christiansen, Lars; Andersen, O. B.;

    2009-01-01

    Gravity changes linearly with the change in soil water content. With the GRACE satellite mission the interest for ground-based gravity methods in hydrology has gained new attention. Time-lapse gravity data have the potential to constrain hydrological model parameters in a calibration scheme...... in water content, a controlled experiment was set up in 30 m by 20 m basin. The water table was lowered 0.69 m within 1½ hours and the corresponding gravity signal measured using two different approaches: a time series measurements at one location and a gravity network measurement including four points....... Both where in agreement with the calculated maximum theoretical gravity change of 27*10^-8 m/s^2. Uncertainties on the change in gravity in the network measurements where 4*10^-8 m/s^2 (one standard deviation). This corresponds to an infinite horizontal slab of water with a thickness of 0.1 m. The time...

  6. REDUCTION AND GRIDDED PROCESSING OF SATELLITE GRAVITY GRADIENT DATA%卫星重力梯度数据的归算与格网化处理

    Institute of Scientific and Technical Information of China (English)

    钟波; 刘华亮; 罗志才; 李振海

    2011-01-01

    Satellite gravity gradient data reduction and gridding are indispensable steps for recovering the Earth' s gravity field with space-wise method. The second-order radial correction formula for gravity gradient data reduction is given, and the results show that the use of high-precision reference gravity field model can effectively reduce the reduction errors. The gridding accuracy and applicability of weighted average method, Shepard surface fitting and least squares collocation method are compared. As a test, the radial gravity gradient data that added with different types of noises are gridded with the above three gridding methods. The results show that the LSC method has obvious advantages compared with the weighted average and Shepard surface fitting methods, and it can be used for high-accuracy Earth' s gravity field recovery, so the LSC method is recommended for GOCE gravity gradient data gridded processing.%给出引力梯度数据归算的二阶径向改正公式,计算结果表明选用高精度参考重力场模型可以有效控制归算误差的影响.比较加权平均法、Shepard曲面拟合法和最小二乘配置法用于卫星重力梯度数据格网化处理的精度和适用性,采用不同噪声背景的径向引力梯度数据进行格网化处理,计算结果表明:最小二乘配置法相比加权平均法和Shepard曲面拟合法具有明显优势,其格网化精度可满足高精度重力场恢复的需要,建议在实际计算中采用最小二乘配置法进行格网化处理.

  7. Data use investigations for applications Explorer Mission A (Heat Capacity Mapping Mission): HCMM's role in studies of the urban heat island, Great Lakes thermal phenomena and radiometric calibration of satellite data. [Buffalo, Syracuse, and Rochester New York and Lake Ontario

    Science.gov (United States)

    Schott, J. R. (Principal Investigator); Schimminger, E. W.

    1981-01-01

    The utility of data from NASA'a heat capacity mapping mission satellite for studies of the urban heat island, thermal phenomena in large lakes and radiometric calibration of satellite sensors was assessed. The data were found to be of significant value in all cases. Using HCMM data, the existence and microstructure of the heat island can be observed and associated with land cover within the urban complex. The formation and development of the thermal bar in the Great Lakes can be observed and quantitatively mapped using HCMM data. In addition, the thermal patterns observed can be associated with water quality variations observed both from other remote sensing platforms and in situ. The imaging radiometer on-board the HCMM satellite is shown to be calibratible to within about 1.1 C of actual surface temperatures. These findings, as well as the analytical procedures used in studying the HCMM data, are included.

  8. Comparison of gridded multi-mission and along-track mono-mission satellite altimetry wave heights with in situ near-shore buoy data.

    Digital Repository Service at National Institute of Oceanography (India)

    Shanas, P.R.; SanilKumar, V.; Hithin, N.K.

    The applicability of altimeter data for the coastal region is examined by comparing the gridded multi-mission and along-track mono-mission significant wave height (SWH) data with the in situ buoy measurements at four stations off the east and west...

  9. Assimilation of satellite data to optimize large-scale hydrological model parameters: a case study for the SWOT mission

    Science.gov (United States)

    Pedinotti, V.; Boone, A.; Ricci, S.; Biancamaria, S.; Mognard, N.

    2014-11-01

    During the last few decades, satellite measurements have been widely used to study the continental water cycle, especially in regions where in situ measurements are not readily available. The future Surface Water and Ocean Topography (SWOT) satellite mission will deliver maps of water surface elevation (WSE) with an unprecedented resolution and provide observation of rivers wider than 100 m and water surface areas greater than approximately 250 x 250 m over continental surfaces between 78° S and 78° N. This study aims to investigate the potential of SWOT data for parameter optimization for large-scale river routing models. The method consists in applying a data assimilation approach, the extended Kalman filter (EKF) algorithm, to correct the Manning roughness coefficients of the ISBA (Interactions between Soil, Biosphere, and Atmosphere)-TRIP (Total Runoff Integrating Pathways) continental hydrologic system. Parameters such as the Manning coefficient, used within such models to describe water basin characteristics, are generally derived from geomorphological relationships, which leads to significant errors at reach and large scales. The current study focuses on the Niger Basin, a transboundary river. Since the SWOT observations are not available yet and also to assess the proposed assimilation method, the study is carried out under the framework of an observing system simulation experiment (OSSE). It is assumed that modeling errors are only due to uncertainties in the Manning coefficient. The true Manning coefficients are then supposed to be known and are used to generate synthetic SWOT observations over the period 2002-2003. The impact of the assimilation system on the Niger Basin hydrological cycle is then quantified. The optimization of the Manning coefficient using the EKF (extended Kalman filter) algorithm over an 18-month period led to a significant improvement of the river water levels. The relative bias of the water level is globally improved (a 30

  10. Validation of ERS-1 and high-resolution satellite gravity with in-situ shipborne gravity over the Indian offshore regions: Accuracies and implications to subsurface modeling

    Digital Repository Service at National Institute of Oceanography (India)

    Chatterjee, S.; Bhattacharyya, R.; Michael, L.; Krishna, K.S.; Majumdar, T.J.

    has emerged as a powerful reconnaissance tool for exploration of sedimentary basins on both the Indian continental margins and in deep-water regions (Biswas 1982; Majumdar et al. 1998). With the advent of more and more altimetric missions... useful tool for exploration of the ocean basins as against the tedious geophysical ship cruises. For the prevailing security restrictions, latitudinal/longitudinal markings have been omitted in Figs. 8–11. Acknowledgements The authors are very much...

  11. GRAIL gravity field determination using the Celestial Mechanics Approach - status report

    Science.gov (United States)

    Bertone, S.; Arnold, D.; Jäggi, A.; Beutler, G.; Mervart, L.

    2015-10-01

    The NASA mission GRAIL (Gravity Recovery And Interior Laboratory [1]) inherits its concept from the GRACE (Gravity Recovery And Climate Experiment)mission to determine the gravity field of the Moon. The use of inter-satellite Ka-band range-rate (KBRR) observations enables data aquisition even when the spacecraft are not tracked from the Earth [2]. The data allows for a highly accurate estimation of the lunar gravity field on both sides of the Moon, which is crucial to improve the understanding of its internal structure and thermal evolution. In this presentation we dis- cuss our latest GRAIL-based lunar gravity fields generated with the Celestial Mechanics Approach using the Bernese Software.

  12. Preliminary trajectory design for a solar polar observatory using SEP and multiple gravity assists

    NARCIS (Netherlands)

    Corpaccioli, L.; Noomen, R.; De Smet, S.; Parker, J.S.; Herman, J.F.C.

    2015-01-01

    Satellite solar observatories have always been of central importance to heliophysics; while there have been numerous such missions, the solar poles have been extremely under-observed. This paper proposes to use low-thrust as well as multiple gravity assists to reach the enormous energies required ob

  13. Ocean contribution to seismic gravity changes: the sea level equation for seismic perturbations revisited

    NARCIS (Netherlands)

    Broerse, D.B.T.; Riva, R.E.M.; Vermeersen, B.

    2014-01-01

    During megathrust earthquakes, great ruptures are accompanied by large scale mass redistribution inside the solid Earth and by ocean mass redistribution due to bathymetry changes. These large scale mass displacements can be detected using the monthly gravity maps of the GRACE satellite mission. In r

  14. Preliminary trajectory design for a solar polar observatory using SEP and multiple gravity assists

    NARCIS (Netherlands)

    Corpaccioli, L.; Noomen, R.; De Smet, S.; Parker, J.S.; Herman, J.F.C.

    2015-01-01

    Satellite solar observatories have always been of central importance to heliophysics; while there have been numerous such missions, the solar poles have been extremely under-observed. This paper proposes to use low-thrust as well as multiple gravity assists to reach the enormous energies required ob

  15. Ocean contribution to seismic gravity changes: the sea level equation for seismic perturbations revisited

    NARCIS (Netherlands)

    Broerse, D.B.T.; Riva, R.E.M.; Vermeersen, B.

    2014-01-01

    During megathrust earthquakes, great ruptures are accompanied by large scale mass redistribution inside the solid Earth and by ocean mass redistribution due to bathymetry changes. These large scale mass displacements can be detected using the monthly gravity maps of the GRACE satellite mission. In

  16. Assimilation of satellite data to optimize large scale hydrological model parameters: a case study for the SWOT mission

    Directory of Open Access Journals (Sweden)

    V. Pedinotti

    2014-04-01

    Full Text Available During the last few decades, satellite measurements have been widely used to study the continental water cycle, especially in regions where in situ measurements are not readily available. The future Surface Water and Ocean Topography (SWOT satellite mission will deliver maps of water surface elevation (WSE with an unprecedented resolution and provide observation of rivers wider than 100 m and water surface areas greater than approximately 250 m × 250 m over continental surfaces between 78° S and 78° N. This study aims to investigate the potential of SWOT data for parameter optimization for large scale river routing models which are typically employed in Land Surface Models (LSM for global scale applications. The method consists in applying a data assimilation approach, the Extended Kalman Filter (EKF algorithm, to correct the Manning roughness coefficients of the ISBA-TRIP Continental Hydrologic System. Indeed, parameters such as the Manning coefficient, used within such models to describe water basin characteristics, are generally derived from geomorphological relationships, which might have locally significant errors. The current study focuses on the Niger basin, a trans-boundary river, which is the main source of fresh water for all the riparian countries. In addition, geopolitical issues in this region can restrict the exchange of hydrological data, so that SWOT should help improve this situation by making hydrological data freely available. In a previous study, the model was first evaluated against in-situ and satellite derived data sets within the framework of the international African Monsoon Multi-disciplinary Analysis (AMMA project. Since the SWOT observations are not available yet and also to assess the proposed assimilation method, the study is carried out under the framework of an Observing System Simulation Experiment (OSSE. It is assumed that modeling errors are only due to uncertainties in the Manning coefficient. The true

  17. Assimilation of satellite data to optimize large scale hydrological model parameters: a case study for the SWOT mission

    Science.gov (United States)

    Pedinotti, V.; Boone, A.; Ricci, S.; Biancamaria, S.; Mognard, N.

    2014-04-01

    During the last few decades, satellite measurements have been widely used to study the continental water cycle, especially in regions where in situ measurements are not readily available. The future Surface Water and Ocean Topography (SWOT) satellite mission will deliver maps of water surface elevation (WSE) with an unprecedented resolution and provide observation of rivers wider than 100 m and water surface areas greater than approximately 250 m × 250 m over continental surfaces between 78° S and 78° N. This study aims to investigate the potential of SWOT data for parameter optimization for large scale river routing models which are typically employed in Land Surface Models (LSM) for global scale applications. The method consists in applying a data assimilation approach, the Extended Kalman Filter (EKF) algorithm, to correct the Manning roughness coefficients of the ISBA-TRIP Continental Hydrologic System. Indeed, parameters such as the Manning coefficient, used within such models to describe water basin characteristics, are generally derived from geomorphological relationships, which might have locally significant errors. The current study focuses on the Niger basin, a trans-boundary river, which is the main source of fresh water for all the riparian countries. In addition, geopolitical issues in this region can restrict the exchange of hydrological data, so that SWOT should help improve this situation by making hydrological data freely available. In a previous study, the model was first evaluated against in-situ and satellite derived data sets within the framework of the international African Monsoon Multi-disciplinary Analysis (AMMA) project. Since the SWOT observations are not available yet and also to assess the proposed assimilation method, the study is carried out under the framework of an Observing System Simulation Experiment (OSSE). It is assumed that modeling errors are only due to uncertainties in the Manning coefficient. The true Manning

  18. Investigation of ice particle habits to be used for ice cloud remote sensing for the GCOM-C satellite mission

    Science.gov (United States)

    Letu, Husi; Ishimoto, Hiroshi; Riedi, Jerome; Nakajima, Takashi Y.; -Labonnote, Laurent C.; Baran, Anthony J.; Nagao, Takashi M.; Sekiguchi, Miho

    2016-09-01

    In this study, various ice particle habits are investigated in conjunction with inferring the optical properties of ice clouds for use in the Global Change Observation Mission-Climate (GCOM-C) satellite programme. We develop a database of the single-scattering properties of five ice habit models: plates, columns, droxtals, bullet rosettes, and Voronoi. The database is based on the specification of the Second Generation Global Imager (SGLI) sensor on board the GCOM-C satellite, which is scheduled to be launched in 2017 by the Japan Aerospace Exploration Agency. A combination of the finite-difference time-domain method, the geometric optics integral equation technique, and the geometric optics method is applied to compute the single-scattering properties of the selected ice particle habits at 36 wavelengths, from the visible to the infrared spectral regions. This covers the SGLI channels for the size parameter, which is defined as a single-particle radius of an equivalent volume sphere, ranging between 6 and 9000 µm. The database includes the extinction efficiency, absorption efficiency, average geometrical cross section, single-scattering albedo, asymmetry factor, size parameter of a volume-equivalent sphere, maximum distance from the centre of mass, particle volume, and six nonzero elements of the scattering phase matrix. The characteristics of calculated extinction efficiency, single-scattering albedo, and asymmetry factor of the five ice particle habits are compared. Furthermore, size-integrated bulk scattering properties for the five ice particle habit models are calculated from the single-scattering database and microphysical data. Using the five ice particle habit models, the optical thickness and spherical albedo of ice clouds are retrieved from the Polarization and Directionality of the Earth's Reflectances-3 (POLDER-3) measurements, recorded on board the Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a

  19. Model of the Availability of Satellite Navigational Systems Asg-Eupos and Rtk Services in Poland

    Science.gov (United States)

    Oszczak, Bartlomiej; Maciejczyk, Olga

    Geodetic precision gravity field satellite missions are to determine Earth gravity field with a high spatial resolution and accuracy. In order to carry out a successful gravity field stallite mission non-gravitational forces acting upon the spacecraft need to be either compensated or measured and thereafter corrected as they distort the actual gravity signal. These non-gravitational forces can be detected and determined by an onboard accelerometer. However, in many cases not only non-gravitational effects are detected, but also noise signals which are self-induced by the satellites onboard instruments. This study shall give a brief overview about the effects acting upon geodetic precision space laboratories, that ought to be regarded in order to realise a smooth functioning of a gravity field mission. Abstract In this study the focus will be upon the GRACE (Gravity Recovery And Climate Experiment) gravity field satellite mission, concerning the impacts that onboard instruments used for attitude and orbit control as well as thermal control have onto the accelerometer and what impact this can have onto the gravity field determined by the GRACE twin satellites. As the GRACE twin satellites can only operate successfully if they are maintained in the same orbit and in a certrain orientation to each other, the Attitude and Orbit Control System (AOCS) is mandatory. This AOCS determines whether the onboard cold-gas thrusters, which are used for both orbit and attitude recovery, are fired and also the duration of the firing event. Moreover, the AOCS controls the three onboard magnetic torquers, which only can be used for attitude restorage. The acceleration disturbances induced by instruments for attitude and orbit restorage can be as high as 20 nm/s2 due to magnetic torquer activity and 0.6 µm/s2 due to thruster firing events.

  20. A global water cycle reanalysis (2003-2012) merging satellite gravimetry and altimetry observations with a hydrological multi-model ensemble

    NARCIS (Netherlands)

    van Dijk, A. I. J. M.; Renzullo, L. J.; Wada, Y.|info:eu-repo/dai/nl/341387819; Tregoning, P.

    2014-01-01

    We present a global water cycle reanalysis that merges water balance estimates derived from the Gravity Recovery And Climate Experiment (GRACE) satellite mission, satellite water level altimetry and off-line estimates from several hydrological models. Error estimates for the sequential data

  1. A global water cycle reanalysis (2003-2012) merging satellite gravimetry and altimetry observations with a hydrological multi-model ensemble

    NARCIS (Netherlands)

    van Dijk, A. I. J. M.; Renzullo, L. J.; Wada, Y.; Tregoning, P.

    2014-01-01

    We present a global water cycle reanalysis that merges water balance estimates derived from the Gravity Recovery And Climate Experiment (GRACE) satellite mission, satellite water level altimetry and off-line estimates from several hydrological models. Error estimates for the sequential data assimila

  2. A global mean ocean circulation estimation using goce gravity models - the DTU12MDT mean dynamic topography model

    DEFF Research Database (Denmark)

    Knudsen, Per; Andersen, Ole Baltazar

    2012-01-01

    The Gravity and Ocean Circulation Experiment - GOCE satellite mission measure the Earth gravity field with unprecedented accuracy leading to substantial improvements in the modelling of the ocean circulation and transport. In this study of the performance of GOCE, a newer gravity model have been...... have been improved significantly compared to results obtained using pre-GOCE gravity field models. The results of this study show that geostrophic surface currents associated with the mean circulation have been further improved and that currents having speeds down to 5 cm/s have been recovered....

  3. CHAMP gravity field recovery using the energy balance approach

    Directory of Open Access Journals (Sweden)

    Ch. Gerlach

    2003-01-01

    Full Text Available Since the early days of satellite geodesy energy balance based methods for gravity field determination have been considered. If non-conservative forces are known the Hamiltonian along the orbit is a constant of the motion. Thus the gravity field can be determined if position and velocity of the satellite are known and accelerometer measurements are available to model the non-conservative part. CHAMP is the first satellite that provides the user with those three kinds of data nearly continuously. Numerical investigations using real CHAMP data are presented to show the feasibility of the method. Using a semi-analytical approach the gravity field can be determined efficiently by a 2D-Fourier method. Those fast computations also give way to application of the method not only to a full gravity field recovery but also, e.g. for quick-look and validation of SST observations for satellite missions like CHAMP, GRACE or GOCE. The method can also be used for estimation of accelerometer calibration parameters.Key words. gravity field, energy balance, Jacobi-integral, non-conservative forces, accelerometer calibration, CHAMP

  4. Tectonics of the Bay of Bengal: New insights from satellite-gravity and ship-borne geophysical data

    Digital Repository Service at National Institute of Oceanography (India)

    Subrahmanyam, C.; Thakur, N.K.; Rao, T.G.; Khanna, R.; Ramana, M.V.; Subrahmanyam, V.

    the Rajmahal and Sylhet Traps and volcanics in the Bengal and Mahanadi basins, almost on the scale of the Deccan volcanic province along the west coast, can be envisaged taking into account the occurrences of intrusive rocks around the age of 117 Ma. Gravity...

  5. Constraints on Covariant Horava-Lifshitz Gravity from frame-dragging experiment

    Energy Technology Data Exchange (ETDEWEB)

    Radicella, Ninfa; Lambiase, Gaetano; Parisi, Luca; Vilasi, Gaetano, E-mail: ninfa.radicella@sa.infn.it, E-mail: lambiase@sa.infn.it, E-mail: parisi@sa.infn.it, E-mail: vilasi@sa.infn.it [Dipartimento di Fisica ' ' E.R. Caianiello" , Università di Salerno, Via Giovanni Paolo II 132, 84081 Fisciano (Italy)

    2014-12-01

    The effects of Horava-Lifshitz corrections to the gravito-magnetic field are analyzed. Solutions in the weak field, slow motion limit, referring to the motion of a satellite around the Earth are considered. The post-newtonian paradigm is used to evaluate constraints on the Horava-Lifshitz parameter space from current satellite and terrestrial experiments data. In particular, we focus on GRAVITY PROBE B, LAGEOS and the more recent LARES mission, as well as a forthcoming terrestrial project, GINGER.

  6. Constraints on Covariant Horava-Lifshitz Gravity from frame-dragging experiment

    CERN Document Server

    Radicella, Ninfa; Parisi, Luca; Vilasi, Gaetano

    2014-01-01

    The effects of Horava-Lifshitz corrections to the gravito-magnetic field are analyzed. Solutions in the weak field, slow motion limit, referring to the motion of a satellite around the Earth are considered. The post-newtonian paradigm is used to evaluate constraints on the Horava-Lifshitz parameter space from current satellite and terrestrial experiments data. In particular, we focus on GRAVITY PROBE B, LAGEOS and the more recent LARES mission, as well as a forthcoming terrestrial project, GINGER.

  7. Fine orbit tuning to increase the accuracy of the gravity-field modelling

    Science.gov (United States)

    Bezdek, A.; Klokocnik, J.; Kostelecky, J.; Floberghagen, R.; Sebera, J.

    2010-12-01

    Fine orbit tuning will be presented as a tool to enhance the accuracy of the gravity-field parameters based on the data from satellite missions around the Earth or other planetary bodies. A slight variation in the satellite altitude of a few hundred metres or kilometres may dramatically change the pattern and density of the groundtracks, thus leading to a significant difference in the quality of the derived gravity-field parameters. This aspect is important not only to missions dedicated to the gravity-field mapping, but it can be applied to any planetary mission, whose orbital data may yield useful information on the particular gravity field. The geometry of satellite groundtracks is closely connected with the term orbital resonance or repeat orbit, which was intensively studied by the satellite geodesy community since the 1970s. In a systematic way, fine orbit tuning was first applied to altimetry missions for oceanographic purposes in the early 1990s, when it became clear that small changes in the satellite altitude might substantially influence the utility of the data from the onboard instruments. The monthly geopotential solutions from the GRACE mission (in orbit since 2002) displayed apparently worse precision in August-September 2004, which was later found to be caused by a sparser groundtrack pattern due to the passage of the GRACE satellites through the 61/4 orbit resonance. The lessons learned from GRACE were applied by ESA to its gravity field mission GOCE (in orbit since 2009). Here, the situation is different, as the GOCE onboard thrusters are capable of maintaining the satellite at a constant altitude. In order to fully use the measurement potential of the first space gradiometer ever flown, in the GOCE mission planning the influence of orbit geometry was taken into account, and a minimum 2-month repeat period for the orbit was specified. We analysed several orbital configurations of GOCE, as possible candidates for the gravity mapping phases. We

  8. Satellite Control Laboratory

    DEFF Research Database (Denmark)

    Wisniewski, Rafal; Bak, Thomas

    2001-01-01

    The Satellite Laboratory at the Department of Control Engineering of Aalborg University (SatLab) is a dynamic motion facility designed for analysis and test of micro spacecraft. A unique feature of the laboratory is that it provides a completely gravity-free environment. A test spacecraft...... is suspended on an air bearing, and rotates freely in 3 degrees of freedom. In order to avoid any influence of the gravitational force the centre of mass of the satellite is placed in the geometric centre of the air bearing by an automatic balancing system. The test spacecraft is equipped with a three...... of the laboratory is to conduct dynamic tests of the control and attitude determination algorithms during nominal operation and in abnormal conditions. Further it is intended to use SatLab for validation of various algorithms for fault detection, accommodation and supervisory control. Different mission objectives...

  9. Developments in Lunar Gravity Field Recovery Within the Project GRAZIL

    Science.gov (United States)

    Wirnsberger, Harald; Klinger, Beate; Krauss, Sandro; Mayer-Gürr, Torsten

    2016-10-01

    The project GRAZIL addresses the highly accurate recovery of the lunar gravity field using intersatellite Ka-band ranging (KBR) measurements collected by the Lunar Gravity Ranging System (LGRS) of the Gravity Recovery And Interior Laboratory (GRAIL) mission. Dynamic precise orbit determination is an indispensable task in order to recover the lunar gravity field based on LGRS measurements. The concept of variational equations is adopted to determine the orbit of the two GRAIL satellites based on radio science data. In this contribution we focus on the S-band two-way Doppler data collected by the Deep Space Network.As far as lunar gravity field recovery is concerned, we apply an integral equation approach using short orbital arcs. In this contribution we demonstrate the progress of Graz lunar gravity field models (GrazLGM) from the beginning, till the end of the projet GRAZIL. For the latest GrazLGM version special attention is given to the refinement of our processing strategy in conjunction with an increase of the spectral resolution. Furthermore, we present the first GrazLGM based on KBR observations during the primary and the extended mission phase. Our results are validated against state of the art lunar gravity field models computed at NASA-GSFC and NASA-JPL.

  10. A Ground-Based Study on Extruder Standoff Distance for the 3D Printing in Zero Gravity Technology Demonstration Mission

    Science.gov (United States)

    Prater, T. J.; Bean, Q. A.; Werkheiser, N. J.; Beshears, R. D.; Rolin, T. D.; Rabenberg, E. M.; Soohoo, H. A.; Ledbetter, F. E., III; Bell, S. C.

    2017-01-01

    Analysis of phase I specimens produced as part of the 3D printing in zero G technology demonstration mission exhibited some differences in structure and performance for specimens printed onboard the International Space Station (ISS) and specimens produced on the ground with the same printer prior to its launch. This study uses the engineering test unit for the printer, identical to the unit on ISS, to conduct a ground-based investigation of the impact of the distance between the extruder tip and the build tray on material outcomes. This standoff distance was not held constant for the phase I flight prints and is hypothesized to be a major source of the material variability observed in the phase I data set.

  11. High-Resolution Gravity and Time-Varying Gravity Field Recovery using GRACE and CHAMP

    Science.gov (United States)

    Shum, C. K.

    2002-01-01

    This progress report summarizes the research work conducted under NASA's Solid Earth and Natural Hazards Program 1998 (SENH98) entitled High Resolution Gravity and Time Varying Gravity Field Recovery Using GRACE (Gravity Recovery and Climate Experiment) and CHAMP (Challenging Mini-satellite Package for Geophysical Research and Applications), which included a no-cost extension time period. The investigation has conducted pilot studies to use the simulated GRACE and CHAMP data and other in situ and space geodetic observable, satellite altimeter data, and ocean mass variation data to study the dynamic processes of the Earth which affect climate change. Results from this investigation include: (1) a new method to use the energy approach for expressing gravity mission data as in situ measurements with the possibility to enhance the spatial resolution of the gravity signal; (2) the method was tested using CHAMP and validated with the development of a mean gravity field model using CHAMP data, (3) elaborate simulation to quantify errors of tides and atmosphere and to recover hydrological and oceanic signals using GRACE, results show that there are significant aliasing effect and errors being amplified in the GRACE resonant geopotential and it is not trivial to remove these errors, and (4) quantification of oceanic and ice sheet mass changes in a geophysical constraint study to assess their contributions to global sea level change, while the results improved significant over the use of previous studies using only the SLR (Satellite Laser Ranging)-determined zonal gravity change data, the constraint could be further improved with additional information on mantle rheology, PGR (Post-Glacial Rebound) and ice loading history. A list of relevant presentations and publications is attached, along with a summary of the SENH investigation generated in 2000.

  12. Multi-scale gravity field modeling in space and time

    Science.gov (United States)

    Wang, Shuo; Panet, Isabelle; Ramillien, Guillaume; Guilloux, Frédéric

    2016-04-01

    The Earth constantly deforms as it undergoes dynamic phenomena, such as earthquakes, post-glacial rebound and water displacement in its fluid envelopes. These processes have different spatial and temporal scales and are accompanied by mass displacements, which create temporal variations of the gravity field. Since 2002, the GRACE satellite missions provide an unprecedented view of the gravity field spatial and temporal variations. Gravity models built from these satellite data are essential to study the Earth's dynamic processes (Tapley et al., 2004). Up to present, time variations of the gravity field are often modelled using spatial spherical harmonics functions averaged over a fixed period, as 10 days or 1 month. This approach is well suited for modeling global phenomena. To better estimate gravity related to local and/or transient processes, such as earthquakes or floods, and adapt the temporal resolution of the model to its spatial resolution, we propose to model the gravity field using localized functions in space and time. For that, we build a model of the gravity field in space and time with a four-dimensional wavelet basis, well localized in space and time. First we design the 4D basis, then, we study the inverse problem to model the gravity field from the potential differences between the twin GRACE satellites, and its regularization using prior knowledge on the water cycle. Our demonstration of surface water mass signals decomposition in time and space is based on the use of synthetic along-track gravitational potential data. We test the developed approach on one year of 4D gravity modeling and compare the reconstructed water heights to those of the input hydrological model. Perspectives of this work is to apply the approach on real GRACE data, addressing the challenge of a realistic noise, to better describe and understand physical processus with high temporal resolution/low spatial resolution or the contrary.

  13. Application of satellite gravity information fusion to refine regional quasi-geoid%卫星重力信息融合及区域似大地水准面精化应用

    Institute of Scientific and Technical Information of China (English)

    宋雷; 陈晓华; 胡伍生; 王德宝; 王牧龙

    2013-01-01

    为改善地面重力数据缺乏区域似大地水准面的精度和分辨率,提出利用神经网络融合卫星重力信息应用于似大地水准面精化的方法,通过融合不同时期CHAMP卫星数据计算的重力场模型和GPS/水准数据中区域重力场信息,进行区域似大地水准面精化并进行精度统计,结果表明:融合卫星重力信息将区域似大地水准面模型的精度由0.4702 m提高至0.2038 m,验证了神经网络技术融合卫星重力信息并应用于区域似大地水准面精化是有效的.%In order to improve the precision and resolution of quasi-geoid in the region of lacking ground gravity data, the method of satellite gravity information fusion using neural network to refine regional quasi-geoid is proposed.The regional quasi-geoid is refined by fusing the gravity informa-tion of CHAMP ( challenging mini-satellite payload ) gravity field models at different periods and GPS/leveling, and then the precision of quasi-geoid is estimated.The results show that the satellite gravity information fusion can improve the precision of regional quasi-geoid from 0.470 2 m to 0.203 8 m, which verify that satellite gravity information fusion using neural network to refine re-gional quasi-geoid is effective.

  14. The GRADIO spaceborne gravity gradiometer: Development and accommodation

    Science.gov (United States)

    Bernard, A.

    1989-06-01

    The European ARISTOTELES mission aims at the determination of the Earth's gravity field at short wavelength with a global coverage. Gravity gradient measurements will be achieved during six months by the GRADIO instrument onboard a dedicated satellite in a near dawn-dusk sun-synchronous orbit at an altitude of 200 km. The objective is an accuracy of better than 5 mgals for gravity anomalies, at ground level for blocks of 1 x 1 deg. According to present knowledge of the potential, the recovery of higher spherical harmonics (degree and order greater than 30) is of main importance. This leads to focus on the variations of the measured components T(sub ij) of the gravity gradient tensor, at frequencies greater than 5 x 10(exp -3) Hz. The resolution, required for the gradiometer is 10(exp -2) Eotvos (i.e., 10(exp -11)/s squared) with an averaging time of 4 s.

  15. The search and rescue satellite mission - A basis for international cooperation. [in aircraft crash and marine distress

    Science.gov (United States)

    Redisch, W. N.; Trudell, B. J.

    1978-01-01

    The use of geostationary and polar-orbiting satellites to monitor and locate signals of the Emergency Locator Transmitter (ELT) and Emergency Position Indicating Radio Beacon (EPIB) of general aviation aircraft and inspected marine vessels respectively is described. The joint U.S. Canada/France SARSAT demonstration program will require a minimum of four minutes of mutual visibility of distress transmitter, local user terminal and satellite to obtain a location by Doppler tracking. The program consisting of placing instrumentation on-board three of the Tiros-N series of NOAA operational satellites is attracting interest also from other countries including the USSR, Norway, Australia, and Japan.

  16. SeaWiFS Technical Report Series. Volume 42; Satellite Primary Productivity Data and Algorithm Development: A Science Plan for Mission to Planet Earth

    Science.gov (United States)

    Falkowski, Paul G.; Behrenfeld, Michael J.; Esaias, Wayne E.; Balch, William; Campbell, Janet W.; Iverson, Richard L.; Kiefer, Dale A.; Morel, Andre; Yoder, James A.; Hooker, Stanford B. (Editor); Firestone, Elaine R. (Editor)

    1998-01-01

    Two issues regarding primary productivity, as it pertains to the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Program and the National Aeronautics and Space Administration (NASA) Mission to Planet Earth (MTPE) are presented in this volume. Chapter 1 describes the development of a science plan for deriving primary production for the world ocean using satellite measurements, by the Ocean Primary Productivity Working Group (OPPWG). Chapter 2 presents discussions by the same group, of algorithm classification, algorithm parameterization and data availability, algorithm testing and validation, and the benefits of a consensus primary productivity algorithm.

  17. Superconducting gravity gradiometer and a test of inverse square law

    Science.gov (United States)

    Moody, M. V.; Paik, Ho Jung

    1989-01-01

    The equivalence principle prohibits the distinction of gravity from acceleration by a local measurement. However, by making a differential measurement of acceleration over a baseline, platform accelerations can be cancelled and gravity gradients detected. In an in-line superconducting gravity gradiometer, this differencing is accomplished with two spring-mass accelerometers in which the proof masses are confined to motion in a single degree of freedom and are coupled together by superconducting circuits. Platform motions appear as common mode accelerations and are cancelled by adjusting the ratio of two persistent currents in the sensing circuit. The sensing circuit is connected to a commercial SQUID amplifier to sense changes in the persistent currents generated by differential accelerations, i.e., gravity gradients. A three-axis gravity gradiometer is formed by mounting six accelerometers on the faces of a precision cube, with the accelerometers on opposite faces of the cube forming one of three in-line gradiometers. A dedicated satellite mission for mapping the earth's gravity field is an important one. Additional scientific goals are a test of the inverse square law to a part in 10(exp 10) at 100 km, and a test of the Lense-Thirring effect by detecting the relativistic gravity magnetic terms in the gravity gradient tensor for the earth.

  18. Small is Beautiful — Technology Trends in the Satellite Industry and Their Implications for Planetary Science Missions

    Science.gov (United States)

    Freeman, A.

    2017-02-01

    It’s an exciting time in the space business - new technologies being developed under the ‘NewSpace’ umbrella have some profound implications for planetary science missions over the next three decades.

  19. Gravity field recovery in the framework of a Geodesy and Time Reference in Space (GETRIS)

    Science.gov (United States)

    Hauk, Markus; Schlicht, Anja; Pail, Roland; Murböck, Michael

    2017-04-01

    The study ;Geodesy and Time Reference in Space; (GETRIS), funded by European Space Agency (ESA), evaluates the potential and opportunities coming along with a global space-borne infrastructure for data transfer, clock synchronization and ranging. Gravity field recovery could be one of the first beneficiary applications of such an infrastructure. This paper analyzes and evaluates the two-way high-low satellite-to-satellite-tracking as a novel method and as a long-term perspective for the determination of the Earth's gravitational field, using it as a synergy of one-way high-low combined with low-low satellite-to-satellite-tracking, in order to generate adequate de-aliasing products. First planned as a constellation of geostationary satellites, it turned out, that an integration of European Union Global Navigation Satellite System (Galileo) satellites (equipped with inter-Galileo links) into a Geostationary Earth Orbit (GEO) constellation would extend the capability of such a mission constellation remarkably. We report about simulations of different Galileo and Low Earth Orbiter (LEO) satellite constellations, computed using time variable geophysical background models, to determine temporal changes in the Earth's gravitational field. Our work aims at an error analysis of this new satellite/instrument scenario by investigating the impact of different error sources. Compared to a low-low satellite-to-satellite-tracking mission, results show reduced temporal aliasing errors due to a more isotropic error behavior caused by an improved observation geometry, predominantly in near-radial direction within the inter-satellite-links, as well as the potential of an improved gravity recovery with higher spatial and temporal resolution. The major error contributors of temporal gravity retrieval are aliasing errors due to undersampling of high frequency signals (mainly atmosphere, ocean and ocean tides). In this context, we investigate adequate methods to reduce these errors. We

  20. 月球重力场环境对月球卫星轨道影响分析%The effect of lunar gravity environment on lunar satellite orbit

    Institute of Scientific and Technical Information of China (English)

    童科伟; 李文清; 刘伟; 高朝辉; 王俊峰

    2012-01-01

    文章分析了月球复杂的重力场环境对月球卫星轨道运行的影响。通过月球卫星冻结轨道与地球卫星冻结轨道的对比分析,结果表明月球重力场存在较大异常,并由此引起月球卫星轨道发生较大漂移。另外,月球冻结轨道在带谐项影响下还存在中等周期的漂移,仅简单考虑带谐项系数无法求得完美的月球冻结系数。由于月球重力场异常对绕月卫星的影响与地球轨道卫星情况相比存在很大差异,因此月球轨道卫星的长期运行与控制策略的设计必须充分考虑此影响%The effect of lunar gravity environment on the lunar satellite orbit is analyzed. The differences between the frozen orbit for lunar and earth satellites are compared first. It is shown that the lunar gravity anomaly is responsible for a large drift to the lunar satellite orbit, the lunar tesseral harmonics are responsible for a moderate period drift to the lunar frozen orbit. Because the effect of lunar gravity anomaly on lunar satellites is quite different from the case for the earth, so for the long-term orbit operation and control for lunar satellites, a different strategy must be adopted than the traditional methods designed for the earth satellite orbit.

  1. Determination of the Earth gravity Field Parameters in Persian Gulf and Oman Sea with the Satellite Altimetry Data

    Science.gov (United States)

    Emadi, S. R.; Najafi-Alamardi, M.; Toosi, K. N.; Sedighi, M.; Nankali, H. R.

    2006-07-01

    Satellite altimetry provides continuous, accur ate, and homogenous data ser ies in marine areas .Th e Sea Surf ace Heigh ts (SSH) ex tracted from altimetry data w as used in a method sear ching for the least squares of the sea surface topography to simultaneously d etermine the geoidal height and the sea surface topography as well in the Persian Gulf and the Oman sea. This is contrary to th e methods wh ich r equire the knowledge of one parameter to estimate the other. The North and East componen ts of the deflections of vertical w ere also estimated by differentiating the der ived geoid al heights in the corresponding directions, and finally the free- air grav ity anomalies w ere computed utilizing the inverse V ening- Meinesz integral.

  2. Application of Satellite Gravimetry for Water Resource Vulnerability Assessment

    Science.gov (United States)

    Rodell, Matthew

    2012-01-01

    The force of Earth's gravity field varies in proportion to the amount of mass near the surface. Spatial and temporal variations in the gravity field can be measured via their effects on the orbits of satellites. The Gravity Recovery and Climate Experiment (GRACE) is the first satellite mission dedicated to monitoring temporal variations in the gravity field. The monthly gravity anomaly maps that have been delivered by GRACE since 2002 are being used to infer changes in terrestrial water storage (the sum of groundwater, soil moisture, surface waters, and snow and ice), which are the primary source of gravity variability on monthly to decadal timescales after atmospheric and oceanic circulation effects have been removed. Other remote sensing techniques are unable to detect water below the first few centimeters of the land surface. Conventional ground based techniques can be used to monitor terrestrial water storage, but groundwater, soil moisture, and snow observation networks are sparse in most of the world, and the countries that do collect such data rarely are willing to share them. Thus GRACE is unique in its ability to provide global data on variations in the availability of fresh water, which is both vital to life on land and vulnerable to climate variability and mismanagement. This chapter describes the unique and challenging aspects of GRACE terrestrial water storage data, examples of how the data have been used for research and applications related to fresh water vulnerability and change, and prospects for continued contributions of satellite gravimetry to water resources science and policy.

  3. Terrestrial Gravity Fluctuations

    Science.gov (United States)

    Harms, Jan

    2015-12-01

    Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW) detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10-23 Hz-1/2 above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of

  4. Terrestrial Gravity Fluctuations.

    Science.gov (United States)

    Harms, Jan

    2015-01-01

    Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW) detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10(-23) Hz(-1/2) above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of

  5. Terrestrial Gravity Fluctuations

    Directory of Open Access Journals (Sweden)

    Jan Harms

    2015-12-01

    Full Text Available Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10^–23 Hz^–1/2 above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our

  6. Recent developments in high-resolution global altimetric gravity field modeling

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Knudsen, Per; Berry, P. A .M.

    2010-01-01

    older gravity fields show accuracy improvement of the order of 20-40% due to a combination of retracking, enhanced processing, and the use of the new EGM2008 geoid model. In coastal and polar regions, accuracy improved in many places by 40-50% (or more) compared with older global marine gravity fields.......In recent years, dedicated effort has been made to improve high-resolution global marine gravity fields. One new global field is the Danish National Space Center (DNSC) 1-minute grid called DNSC08GRA, released in 2008. DNSC08GRA was derived from double-retracked satellite altimetry, mainly from...... the ERS-1 geodetic mission data, augmented with new retracked GEOSAT data which have significantly enhanced the range and hence the gravity field accuracy. DNSC08GRA is the first high-resolution global gravity field to cover the entire Arctic Ocean all the way to the North Pole. Comparisons with other...

  7. Application of Gravity Gradients in the Process of GOCE Orbit Determination

    Directory of Open Access Journals (Sweden)

    Bobojć Andrzej

    2016-04-01

    Full Text Available The possibility of improving the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE mission satellite orbit using gravity gradient observations was investigated. The orbit improvement is performed by a dedicated software package, called the Orbital Computation System (OCS, which is based on the classical least squares method. The corrections to the initial satellite state vector components are estimated in an iterative process, using dynamic models describing gravitational perturbations. An important component implemented in the OCS package is the 8th order Cowell numerical integration procedure, which directly generates the satellite orbit. Taking into account the real and simulated GOCE gravity gradients, different variants of the solution of the orbit improvement process were obtained. The improved orbits were compared to the GOCE reference orbits (Precise Science Orbits for the GOCE satellite provided by the European Space Agency using the root mean squares (RMS of the differences between the satellite positions in these orbits. The comparison between the improved orbits and the reference orbits was performed with respect to the inertial reference frame (IRF at J2000.0 epoch. The RMS values for the solutions based on the real gravity gradient measurements are at a level of hundreds of kilometers and more. This means that orbit improvement using the real gravity gradients is ineffective. However, all solutions using simulated gravity gradients have RMS values below the threshold determined by the RMS values for the computed orbits (without the improvement. The most promising results were achieved when short orbital arcs with lengths up to tens of minutes were improved. For these short arcs, the RMS values reach the level of centimeters, which is close to the accuracy of the Precise Science Orbit for the GOCE satellite. Additional research has provided requirements for efficient orbit improvement in terms of the accuracy and

  8. Demonstrating soil moisture remote sensing with observations from the UK TechDemoSat-1 satellite mission

    Science.gov (United States)

    Chew, Clara; Shah, Rashmi; Zuffada, Cinzia; Hajj, George; Masters, Dallas; Mannucci, Anthony J.

    2016-04-01

    The ability of spaceborne Global Navigation Satellite System (GNSS) bistatic radar receivers to sense changes in soil moisture is investigated using observations from the low Earth orbiting UK TechDemoSat-1 satellite (TDS-1). Previous studies using receivers on aircraft or towers have shown that ground-reflected GNSS signals are sensitive to changes in soil moisture, though the ability to sense this variable from space has yet to be quantified. Data from TDS-1 show a 7 dB sensitivity of reflected signals to temporal changes in soil moisture. If the effects of surface roughness and vegetation on the reflected signals can be quantified, spaceborne GNSS bistatic radar receivers could provide soil moisture on relatively small spatial and temporal scales.

  9. Simulation of free fall and resonances in the GOCE mission

    OpenAIRE

    A. Bezděk; J. Klokočník; J. Kostelecký; R. Floberghagen; C. Gruber

    2009-01-01

    Abstract GOCE, ESA's first Earth gravity mission, is currently to be launched early in 2009 into a sun-synchronous orbit. Using the full-scale numerical propagator, we investigated the satellite's free fall from the initial injection altitude of 280km down to the first measurement phase altitude (at 264km). During this decay phase the satellite will pass below the 16:1 resonance (268.4km). The effect of this resonance, together with the uncertainty in the solar activity prediction,...

  10. Analysis of the Lunar Gravity Field by Using GL0660B Model and Its Effect on Lunar Satellite Orbit%月球重力场模型GL0660B特征分析及其对绕月卫星轨道的影响

    Institute of Scientific and Technical Information of China (English)

    黄昆学; 常晓涛; 朱广彬; 李武东

    2016-01-01

    The lunar gravity field provides a way to research moon’s evolution and probes the interior structure of the moon.It is an important factor influencing the lunar satellite precise orbit determination as well.The new lunar gravity model GL0660B from GRAIL mission dramatically improves the gravity spectrum and spectral ranges.Using the model GL0660B,it can be computed that the corresponding degree-wise RMS and correlation of topography,with which the quality of model GL0660B can be analyzed.Then different characters of the lunar gravity field comparing with other lunar gravity fields are analyzed. Besides,gravity anomaly distribution figures at different height of the models are given,and the character and difference of the lunar gravity models at different height are compared.In addition,lunar satellite orbit revolutionary at different height are modeled by GEODYN.The result shows that the trend of lunar satellite eccentricity changes is a complex and long cycle of change trend.It is different affected by the perturbation of the mascons of different height,which causes different changes of apolune,perilune and eccentricity.%月球重力场可用来研究月球演化过程和内部结构,是影响绕月卫星精密定轨的重要因素。基于GRAIL任务数据解算的GL0660B重力场模型,极大提高了月球重力场空间频谱信号的强度和范围。本文首先通过计算相应重力场的阶方差和地形相关性分析,对GL0660B模型进行了精度分析;其次,利用GL0660B模型和其他几个月球重力场模型进行比较,对月球重力场的特征进行了分析;然后通过绘制GL0660B模型和 LP150Q模型在月球外部不同高度处的重力异常图,分析比较了月球重力场模型在不同高度上所反映的月球重力场的特征和差异;最后,利用 GEODYN 软件模拟计算了不同高度卫星的轨道变化。可以看出绕月卫星离心率随时间的变化,以及周期性变化趋势,而且

  11. Simulation of whistler waves excited in the presence of a cold plasma cloud - Implications for the CRRES mission. [Combined Release and Radiation Effects Satellite

    Science.gov (United States)

    Pritchett, P. L.; Schriver, D.; Ashour-Abdalla, M.

    1991-01-01

    A one-dimensional electromagnetic particle simulation model is constructed to study the excitation of whistler waves in the presence of a cold plasma cloud for conditions representative of those after the release of lithium in the inner plasma sheet during the Combined Release and Radiation Effect Satellite mission. The results indicate that a standing-wave pattern with discrete wave frequencies is formed within the cloud. The magnetic wave amplitude inside the cloud, which is limited by quasi-linear diffusion, is of the order of several nanoteslas. Assuming a magnetospheric loss cone of 5 deg, the observed pitch angle diffusion produced by the whistler waves is sufficient to put the electrons on strong diffusion.

  12. Satellite Control Laboratory

    DEFF Research Database (Denmark)

    Wisniewski, Rafal; Bak, Thomas

    2001-01-01

    The Satellite Laboratory at the Department of Control Engineering of Aalborg University (SatLab) is a dynamic motion facility designed for analysis and test of micro spacecraft. A unique feature of the laboratory is that it provides a completely gravity-free environment. A test spacecraft...... of the laboratory is to conduct dynamic tests of the control and attitude determination algorithms during nominal operation and in abnormal conditions. Further it is intended to use SatLab for validation of various algorithms for fault detection, accommodation and supervisory control. Different mission objectives...... can be implemented in the laboratory, e.g. three-axis attitude control, slew manoeuvres, spins stabilization using magnetic actuation and/or reaction wheels. The spacecraft attitude can be determined applying magnetometer measurements...

  13. Neptune's small satellites

    Science.gov (United States)

    Thomas, P.

    1992-04-01

    The small satellites of Neptune and other planets discovered during the Voyager 2 mission are discussed in terms of their composition and relationship to the planetary systems. The satellite Proteus is described in terms of its orbit, five other satellites are described, and they are compared to ther small satellites and systems. Neptune's satellites are hypothesized to be related to the ring system, and the satellite Galatea is related to the confinement of the rings.

  14. OMV mission simulator

    Science.gov (United States)

    Cok, Keith E.

    1989-01-01

    The Orbital Maneuvering Vehicle (OMV) will be remotely piloted during rendezvous, docking, or proximity operations with target spacecraft from a ground control console (GCC). The real-time mission simulator and graphics being used to design a console pilot-machine interface are discussed. A real-time orbital dynamics simulator drives the visual displays. The dynamics simulator includes a J2 oblate earth gravity model and a generalized 1962 rotating atmospheric and drag model. The simulator also provides a variable-length communication delay to represent use of the Tracking and Data Relay Satellite System (TDRSS) and NASA Communications (NASCOM). Input parameter files determine the graphics display. This feature allows rapid prototyping since displays can be easily modified from pilot recommendations. A series of pilot reviews are being held to determine an effective pilot-machine interface. Pilots fly missions with nominal to 3-sigma dispersions in translational or rotational axes. Console dimensions, switch type and layout, hand controllers, and graphic interfaces are evaluated by the pilots and the GCC simulator is modified for subsequent runs. Initial results indicate a pilot preference for analog versus digital displays and for two 3-degree-of-freedom hand controllers.

  15. The potential of ground gravity measurements to validate GRACE data

    Directory of Open Access Journals (Sweden)

    D. Crossley

    2003-01-01

    Full Text Available New satellite missions are returning high precision, time-varying, satellite measurements of the Earth’s gravity field. The GRACE mission is now in its calibration/- validation phase and first results of the gravity field solutions are imminent. We consider here the possibility of external validation using data from the superconducting gravimeters in the European sub-array of the Global Geodynamics Project (GGP as ‘ground truth’ for comparison with GRACE. This is a pilot study in which we use 14 months of 1-hour data from the beginning of GGP (1 July 1997 to 30 August 1998, when the Potsdam instrument was relocated to South Africa. There are 7 stations clustered in west central Europe, and one station, Metsahovi in Finland. We remove local tides, polar motion, local and global air pressure, and instrument drift and then decimate to 6-hour samples. We see large variations in the time series of 5–10µgal between even some neighboring stations, but there are also common features that correlate well over the 427-day period. The 8 stations are used to interpolate a minimum curvature (gridded surface that extends over the geographical region. This surface shows time and spatial coherency at the level of 2– 4µgal over the first half of the data and 1–2µgal over the latter half. The mean value of the surface clearly shows a rise in European gravity of about 3µgal over the first 150 days and a fairly constant value for the rest of the data. The accuracy of this mean is estimated at 1µgal, which compares favorably with GRACE predictions for wavelengths of 500 km or less. Preliminary studies of hydrology loading over Western Europe shows the difficulty of correlating the local hydrology, which can be highly variable, with large-scale gravity variations.Key words. GRACE, satellite gravity, superconducting gravimeter, GGP, ground truth

  16. From Satellites to Rings: The Diversity of the Saturnian System Ices in the VIS-NIR at the End of Cassini-VIMS Nominal Mission

    Science.gov (United States)

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

    2008-09-01

    After four years of nominal mission, VIMS has observed the whole 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 whole dataset available at june 2008 which consists of about 1500 full-disk observations of the moons as well as several radial mosaics of the ring system. The most important spectrophotometric indicators (I/F continua, VIS spectral slopes, water and carbon dioxide IR bands strengths and positions) are calculated for each observation in order to identify the disk-integrated compositional units of the satellites, the distribution of water ice respect to "contaminants” abundances and typical regolith grain properties for both satellites and rings. These quantities are varying between the almost pure water ice surfaces of Enceladus and Calypso to the organic and carbon dioxide rich Hyperion, Iapetus and Phoebe. Some significant differences are detected in the VIS colors of co-orbital moons Epimetheus and Janus, with the first very red and therefore similar to Hyperion while the last is more "neutral” these results could help to decipher the origins and evolutional story of these two moons. The water ice band strengths of the A-B rings are the most intense of the Saturnian system denoting a minimal presence of "contaminants” which can be estimated thanks to the 350-520 nm spectral slope. Finally we compare these spectral parameters with some TNOs and outer solar system objects (1995UG5, 90377-Sedna, 1996TO66, Pholus, Triton, Charon, Oberon, Titania) to search for possible analogies. This research was possible thanks to the support of the Italian Space Agency (ASI).

  17. A Novel Satellite Mission Concept for Upper Air Water Vapour, Aerosol and Cloud Observations Using Integrated Path Differential Absorption LiDAR Limb Sounding

    Directory of Open Access Journals (Sweden)

    Claudia Weitnauer

    2012-03-01

    Full Text Available We propose a new satellite mission to deliver high quality measurements of upper air water vapour. The concept centres around a LiDAR in limb sounding by occultation geometry, designed to operate as a very long path system for differential absorption measurements. We present a preliminary performance analysis with a system sized to send 75 mJ pulses at 25 Hz at four wavelengths close to 935 nm, to up to 5 microsatellites in a counter-rotating orbit, carrying retroreflectors characterized by a reflected beam divergence of roughly twice the emitted laser beam divergence of 15 µrad. This provides water vapour profiles with a vertical sampling of 110 m; preliminary calculations suggest that the system could detect concentrations of less than 5 ppm. A secondary payload of a fairly conventional medium resolution multispectral radiometer allows wide-swath cloud and aerosol imaging. The total weight and power of the system are estimated at 3 tons and 2,700 W respectively. This novel concept presents significant challenges, including the performance of the lasers in space, the tracking between the main spacecraft and the retroreflectors, the refractive effects of turbulence, and the design of the telescopes to achieve a high signal-to-noise ratio for the high precision measurements. The mission concept was conceived at the Alpbach Summer School 2010.

  18. Oceanic Weather Decision Support for Unmanned Global Hawk Science Missions into Hurricanes with Tailored Satellite Derived Products

    Science.gov (United States)

    Feltz, Wayne; Griffin, Sarah; Velden, Christopher; Zipser, Ed; Cecil, Daniel; Braun, Scott

    2017-04-01

    The purpose of this presentation is to identify in-flight hazards to high-altitude aircraft, namely the Global Hawk. The Global Hawk was used during Septembers 2012-2016 as part of two NASA funded Hurricane Sentinel-3 field campaigns to over-fly hurricanes in the Atlantic Ocean. This talk identifies the cause of severe turbulence experienced over Hurricane Emily (2005) and how a combination of NOAA funded GOES-R algorithm derived cloud top heights/tropical overshooting tops using GOES-13/SEVIRI imager radiances, and lightning information are used to identify areas of potential turbulence for near real-time navigation decision support. Several examples will demonstrate how the Global Hawk pilots remotely received and used real-time satellite derived cloud and lightning detection information to keep the aircraft safely above clouds and avoid regions of potential turbulence.

  19. Radial and tangential gravity rates from GRACE in areas of glacial isostatic adjustment

    Science.gov (United States)

    van der Wal, Wouter; Kurtenbach, Enrico; Kusche, Jürgen; Vermeersen, Bert

    2011-11-01

    In areas dominated by Glacial Isostatic Adjustment (GIA), the free-air gravity anomaly rate can be converted to uplift rate to good approximation by using a simple spectral relation. We provide quantitative comparisons between gravity rates derived from monthly gravity field solutions (GFZ Potsdam, CSR Texas, IGG Bonn) from the Gravity Recovery and Climate Experiment (GRACE) satellite mission with uplift rates measured by GPS in these areas. The band-limited gravity data from the GRACE satellite mission can be brought to very good agreement with the point data from GPS by using scaling factors derived from a GIA model (the root-mean-square of differences is 0.55 mm yr-1 for a maximum uplift rate signal of 10 mm yr-1). The root-mean-square of the differences between GRACE derived uplift rates and GPS derived uplift rates decreases with increasing GRACE time period to a level below the uncertainty that is expected from GRACE observations, GPS measurements and the conversion from gravity rate to uplift rate. With the current length of time-series (more than 8 yr) applying filters and a hydrology correction to the GRACE data does not reduce the root-mean-square of differences significantly. The smallest root-mean-square was obtained with the GFZ solution in Fennoscandia and with the CSR solution in North America. With radial gravity rates in excellent agreement with GPS uplift rates, more information on the GIA process can be extracted from GRACE gravity field solutions in the form of tangential gravity rates, which are equivalent to a rate of change in the deflection of the vertical scaled by the magnitude of gravity rate vector. Tangential gravity rates derived from GRACE point towards the centre of the previously glaciated area, and are largest in a location close to the centre of the former ice sheet. Forward modelling showed that present day tangential gravity rates have maximum sensitivity between the centre and edge of the former ice sheet, while radial gravity

  20. A New Class of Advanced Accuracy Satellite Instrumentation (AASI) for the CLARREO Mission: Interferometer Test-bed Tradestudies and Selection

    Science.gov (United States)

    Taylor, J. K.; Revercomb, H. E.; Grandmont, F. J.; Buijs, H.; Gero, P. J.; Best, F. A.; Tobin, D. C.; Knuteson, R. O.; Laporte, D. D.

    2009-12-01

    NASA has selected CLARREO (Climate Absolute Radiance and Refractivity Observatory), a climate mission recommended by the 2007 Decadal Survey of the US National Research Council, as a potential new start in 2010. CLARREO will measure spectrally resolved radiance from the earth and atmospheric bending of GPS signals related to atmospheric structure (refractivity) as benchmark measurements of long-term climate change trends. CLARREO will provide more complete spectral and time-of-day coverage and will fly basic physical standards to eliminate the need to assume on-board reference stability. Therefore, the spectral radiances from this mission will also serve as benchmarks to propagate a highly accurate calibration to other space-borne IR instruments. Technology development and risk reduction for the CLARREO mission is being conducted at the Space Science and Engineering Center at the University of Wisconsin-Madison. The objective of this work is to develop and demonstrate the technology necessary to measure IR spectrally resolved radiances (3 - 50 micrometers) with ultra high accuracy (model forecasts. The proposed work (University of Wisconsin-Madison and Harvard University) was selected for the 2007 NASA Instrument Incubator Program (IIP) and will develop four primary technologies to assure SI traceability on-orbit and demonstrate the ultra high accuracy measurement capability required for CLARREO: (1) On-orbit Absolute Radiance Standard (OARS), a high emissivity blackbody source that uses multiple miniature phase-change cells to provide a revolutionary on-orbit standard with absolute temperature accuracy proven over a wide range of temperatures, (2) On-orbit Cavity Emissivity Modules (OCEMs), providing a source (quantum cascade laser, QCL, or “Heated Halo”) to measure any change in the cavity emissivity of the OARS, (3) On-orbit Spectral Response Module (OSRM), a source for spectral response measurements using a nearly monochromatic QCL source configured to

  1. Topographic/isostatic evaluation of new-generation GOCE gravity field models

    Science.gov (United States)

    Hirt, C.; Kuhn, M.; Featherstone, W. E.; GöTtl, F.

    2012-05-01

    We use gravity implied by the Earth's rock-equivalent topography (RET) and modeled isostatic compensation masses to evaluate the new global gravity field models (GGMs) from European Space Agency (ESA)'s Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite gravimetry mission. The topography is now reasonably well-known over most of the Earth's landmasses, and also where conventional GGM evaluation is prohibitive due to the lack (or unavailability) of ground-truth gravity data. We construct a spherical harmonic representation of Earth's RET to derive band-limited topography-implied gravity, and test the somewhat simplistic Airy/Heiskanen and Pratt/Hayford hypotheses of isostatic compensation, but which did not improve the agreement between gravity from the uncompensated RET and GOCE. The third-generation GOCE GGMs (based on 12 months of space gravimetry) resolve the Earth's gravity field effectively up to spherical harmonic degree ˜200-220 (˜90-100 km resolution). Such scales could not be resolved from satellites before GOCE. From the three different GOCE processing philosophies currently in use by ESA, the time-wise and direct approaches exhibit the highest sensitivity to short-scale gravity recovery, being better than the space-wise approach. Our topography-implied gravity comparisons bring evidence of improvements from GOCE to gravity field knowledge over the Himalayas, Africa, the Andes, Papua New Guinea and Antarctic regions. In attenuated form, GOCE captures topography-implied gravity signals up to degree ˜250 (˜80 km resolution), suggesting that other signals (originating, e.g., from the crust-mantle boundary and buried loads) are captured as well, which might now improve our knowledge on the Earth's lithosphere structure at previously unresolved spatial scales.

  2. Arctic sea level change over the past 2 decades from GRACE gradiometry and multi-mission satellite altimetry

    DEFF Research Database (Denmark)

    Andersen, O. B.; Stenseng, L.; Sørensen, C. S.

    2014-01-01

    gradiometer observations from the ESA GOCE mission, we are now able to derive a mean dynamic topography of the Arctic Ocean with unprecedented accuracy to constrain the Arctic Ocean circulation controlling sea level variations in the Arctic. We present both a new estimation of the mean ocean circulation......The Arctic is still an extremely challenging region for theuse of remote sensing for sea level studies. Despite the availability of 20 years of altimetry, only very limited sea level observations exist in the interior of the Arctic Ocean. However, with Cryosat-2 SAR altimetry the situation...... is changing and through development of tailored retrackers dealing with presence of sea ice within the radar footprint, we can now develop sea surface height and its variation in most of the Arctic Ocean. We have processed 3 years of Cryosat-2 data quantified as either Lead or Ocean data within the Cryosat-2...

  3. Satellite mission Aeronomy of Ice in the Mesosphere (AIM) partners with formal and informal education programs to study clouds on the edge of space

    Science.gov (United States)

    Robinson, D. Q.; Maggi, B. H.

    2004-12-01

    The satellite-based research mission "Aeronomy of Ice In the Mesosphere" (AIM), has developed an exciting partnership of formal and informal education programs that will connect students and the public to the unique scientific aspects of the mission. The AIM satellite mission is dedicated to providing a scientific basis for understanding why Polar Mesospheric Clouds (PMCs) form and vary. PMCs are sometimes known as Noctilucent Clouds (NLCs) or "night shinning" clouds because of their visibility at dawn and dusk. The visible manifestation of PMCs provides a unique opportunity for Education and Public Outreach. The AIM outreach programs will utilize the beautiful images of "clouds on the edge of space" as a tool to motivate students and the public to increase their knowledge and understanding about issues surrounding changes in our atmosphere. In an effort to provide formal and informal outreach opportunities worldwide, AIM has developed a partnership with the GLOBE program. GLOBE is a network of schools, science centers, and clubs from over 105 countries where participants collect scientific data according to precise protocols and enter the data into a central database allowing both scientists and students to utilize the data. The collaboration between AIM and GLOBE will involve participants in collecting and utilizing NLC data worldwide. This partnership will provide a mechanism for sustaining AIM education opportunities for both formal and informal education venues in the future. Included in the formal education component of AIM outreach is the implementation of two educator workshops that will establish partnerships between the mission and classrooms nationwide. The educator workshops will be held in Alaska due to the optimal location for viewing NLCs. Participants attending the workshops will be chosen from a national pool allowing teachers working with students in southern latitudes an opportunity to experience the excitement of working with data that can only

  4. 面向新任务插入的电子侦察卫星任务规划方法%Mission Planning for Electronic Reconnaissance Satellites Oriented the Insertion of the New Missions

    Institute of Scientific and Technical Information of China (English)

    祝江汉; 黄维; 李建军; 王迪

    2011-01-01

    This paper builds up dynamic Constraint Satisfied Problem (CSP) with two-level optimization objective, puts forward a dynamic insertion algorithm based on heuristic rules focusing on the arrival of the new missions with objective to maximize the sum of tasks planned and minimize the changes of the initial reconnaissance plans after the all or some of new mission insertion. At last, it gives an example of the electronic reconnaissance satellites to validate the model and algorithm. The result shows that the algorithm is able to satisfy the require that the variety of original scheme is as small as possible, after inserting new tasks, also validate the model and algorithm. It makes sense in continuing the research and solving the practical problems.%针对电子侦察卫星在执行初始侦察计划的过程中新任务动态到达的情况,以最大化完成任务优先级之和,并使新任务到达后,对原侦察计划调整最小为目标,建立了具有两级优化目标的动态约束满足模型,提出了一种基于启发式规则的动态插入算法,最后通过仿真实例,对模型和算法进行了验证,实验结果表明算法一定程度上能够满足卫星新任务插入后使得原始方案变化尽可能小的要求,也验证了该模型和算法的合理性,同时对开展后续的研究和解决实际问题具有一定现实启发意义.

  5. Separating climate-induced mass transfers and instrumental effects from tectonic signal in repeated absolute gravity measurements

    Science.gov (United States)

    Van Camp, M.; Viron, O.; Avouac, J. P.

    2016-05-01

    We estimate the signature of the climate-induced mass transfers in repeated absolute gravity measurements based on satellite gravimetric measurements from the Gravity Recovery and Climate Experiment (GRACE) mission. We show results at the globe scale and compare them with repeated absolute gravity (AG) time behavior in three zones where AG surveys have been published: Northwestern Europe, Canada, and Tibet. For 10 yearly campaigns, the uncertainties affecting the determination of a linear gravity rate of change range 3-4 nm/s2/a in most cases, in the absence of instrumental artifacts. The results are consistent with what is observed for long-term repeated campaigns. We also discuss the possible artifact that can result from using short AG survey to determine the tectonic effects in a zone of high hydrological variability. We call into question the tectonic interpretation of several gravity changes reported from stations in Tibet, in particular the variation observed prior to the 2015 Gorkha earthquake.

  6. Commentary to "LARES successfully launched in orbit: Satellite and mission description" by A. Paolozzi and I. Ciufolini

    CERN Document Server

    Iorio, Lorenzo

    2014-01-01

    We comment on some statements in a recent paper by Paolozzi and Ciufolini concerning certain remarks raised by us on the realistic accuracy obtainable in testing the general relativistic Lense-Thirring effect in the gravitational field of the Earth with the newly launched LARES satellite together with the LAGEOS and LAGEOS II spacecraft in orbit for a long time. The orbital configuration of LARES is different from that of the originally proposed LAGEOS-3. Indeed, while the latter one should have been launched to the same altitude of LAGEOS (i.e. about $h_{\\rm L}=5890$ km) in an orbital plane displaced by $180$ deg with respect to that of LAGEOS ($I_{\\rm L}=110$ deg, $I_{\\rm L3}=70$ deg), LARES currently moves at a much smaller altitude (about $h_{\\rm LR}=1440$ km) and at a slightly different inclination ($I_{\\rm LR} = 69.5$ deg). As independently pointed out in the literature by different authors, the overall accuracy of a LARES-LAGEOS-LAGEOS II Lense-Thirring test may be unfavorably \\textcolor{black}{impacte...

  7. Polar gravity fields from GOCE and airborne gravity

    DEFF Research Database (Denmark)

    Forsberg, René; Olesen, Arne Vestergaard; Yidiz, Hasan

    2011-01-01

    Airborne gravity, together with high-quality surface data and ocean satellite altimetric gravity, may supplement GOCE to make consistent, accurate high resolution global gravity field models. In the polar regions, the special challenge of the GOCE polar gap make the error characteristics...... of combination models especially sensitive to the correct merging of satellite and surface data. We outline comparisons of GOCE to recent airborne gravity surveys in both the Arctic and the Antarctic. The comparison is done to new 8-month GOCE solutions, as well as to a collocation prediction from GOCE gradients...... in Antarctica. It is shown how the enhanced gravity field solutions improve the determination of ocean dynamic topography in both the Arctic and in across the Drake Passage. For the interior of Antarctica, major airborne gravity programs are currently being carried out, and there is an urgent need...

  8. GRACE Orbit and Gravity Field Recovery at GFZ Potsdam - First Experiences and Perspectives

    Science.gov (United States)

    Reigber, C.; Flechtner, F.; Koenig, R.; Meyer, U.; Neumayer, K.; Schmidt, R.; Schwintzer, P.; Zhu, S.

    2002-12-01

    Since the launch of the two GRACE satellites on March 17, 2002, both satellites follow each other in a distance of about 220 km in an almost polar, circular and 500 km high orbit. For orbit and long-wavelength gravity field recovery the GRACE mission concept follows CHAMP's configuration, i.e., GPS satellite-to-satellite tracking and accelerometry on each of the two satellites. The essentially new element is the K-band microwave link measuring the relative distance of one satellite with respect to the other in both directions with an ultra-high precision (few æm). To fully exploit this high precision, the requirements on the performance and precision of the accelerometers to measure non-gravitational orbit perturbations are one order of magnitude more stringent than on CHAMP. The goal of GRACE is a distinct progress in global gravity field recovery from space with respect to accuracy and spatial as well as temporal resolution. First experiences of the GFZ project team with the instrument and sensor performance on the GRACE satellites, the parametrization of the data in precise orbit determination and first tentative gravity field solutions are discussed and compared with CHAMP related results. GRACE data processing at GFZ Potsdam is part of the GRACE level-2 product generation and validation, which is shared with UTEX/CSR and NASA/JPL. On level-1, GFZ Potsdam is responsible for providing high frequency atmosphere and ocean mass variation models to avoid alias effects in GRACE's envisaged sequence of monthly gravity field solutions. Gravity de-aliasing products quality will be discussed.

  9. Variations of geoid undulations from satellite data of GRACE for Israel and surrounding countries

    Science.gov (United States)

    Kostelecky, Jan; Klokocnik, Jaroslav; Bezdek, Ales

    2017-04-01

    Since 2002, the US-German GRACE satellite mission (Gravity Recovery and Climate Experiment) has been providing a precise survey of the Earth's time-variable gravity field, with unprecedented temporal and spatial sampling. GRACE time-variable gravity field is a tool for measuring temporal and spatial variations of the mass redistribution within the Earth system. Time variability of the gravity field is presented here as "monthly gravity field models" of the geoid undulations. We show their regional variations in Israel and surrounding countries which have seasonal and secular character, connected with desiccation of underground water in the area. During 13 year interval of the data from GRACE, the secular decrease of the level of the waters in this area became evident. This result supports warnings coming from other data and points to the existence of a great danger not only for this area.

  10. 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

  11. Status of GRAIL Gravity Field Determination Using the Celestial Mechanics Approach

    Science.gov (United States)

    Arnold, Daniel; Beutler, Gerhard; Jäggi, Adrian; Bock, Heike; Mervart, Leos; Meyer, Ulrich; Bertone, Stefano

    To determine the gravity field of the Moon, the NASA mission GRAIL (Gravity Recovery And Interior Laboratory) inherits its concept from the Earth orbiting GRACE (Gravity Recovery and Climate Experiment) mission. The use of ultra-precise inter-satellite Ka-band ranging observations enables data acquisition even when the spacecraft are not tracked from the Earth. The data allows for a highly accurate estimation of the lunar gravity field with unprecedented resolution on both sides of the Moon, which is crucial to improve the understanding of its internal structure and thermal evolution. In this presentation we discuss GRAIL-based lunar gravity fields generated with the Celestial Mechanics Approach. Ka-band range-rate (KBRR) observations and position data (GNI1B products) are used to solve for the lunar gravity field parameters in a generalized orbit determination problem. Apart from normalized spherical harmonic coefficients up to degrees n≤ 200, also arc- and satellite-specific parameters, like initial state vectors and pseudo-stochastic pulses, are set up as common parameters for all measurement types. The latter shall compensate for imperfect models of non-gravitational accelerations, e.g., caused by solar radiation pressure. In addition, especially for the data of the primary mission phase, it is essential to estimate time bias parameters for the KBRR observations. We compare our results from the nominal mission phase with the official Level 2 gravity field models first released in October 2013. Our results demonstrate that the lunar gravity field can be recovered with a high quality by adapting the Celestial Mechanics Approach, even when using pre-GRAIL or pre-SELENE gravity field models as a priori fields and when replacing sophisticated models of non-gravitational accelerations by appropriately spaced and constrained pseudo-stochastic pulses. Yet, the usage of preprocessed position data as pseudo observations is not fully satisfying and is potentially

  12. Satellite Attitude Control System Simulator

    Directory of Open Access Journals (Sweden)

    G.T. Conti

    2008-01-01

    Full Text Available Future space missions will involve satellites with great autonomy and stringent pointing precision, requiring of the Attitude Control Systems (ACS with better performance than before, which is function of the control algorithms implemented on board computers. The difficulties for developing experimental ACS test is to obtain zero gravity and torque free conditions similar to the SCA operate in space. However, prototypes for control algorithms experimental verification are fundamental for space mission success. This paper presents the parameters estimation such as inertia matrix and position of mass centre of a Satellite Attitude Control System Simulator (SACSS, using algorithms based on least square regression and least square recursive methods. Simulations have shown that both methods have estimated the system parameters with small error. However, the least square recursive methods have performance more adequate for the SACSS objectives. The SACSS platform model will be used to do experimental verification of fundamental aspects of the satellite attitude dynamics and design of different attitude control algorithm.

  13. Study on Multi-scale Temporal Gravity Field in the Eastern Margin of Tibetan Plateau Based on Satellite Gravity%基于卫星重力的青藏高原东缘多尺度时变重力场研究

    Institute of Scientific and Technical Information of China (English)

    姜永涛; 张永志; 王帅; 刘国仕

    2014-01-01

    In this paper,we calculate annual satellite gravity changes in the eastern margin of the Tibetan Plateau from 2003 to 2012 by using the Gravity Recovery and Climate Experiment (GRACE)time-variable gravity field models with decorrelated filtering.By contraposing the three strong earthquakes that occurred recently in this region,including the Wenchuan MS8.0,Yushu MS 7.1,and Ya’an MS 7.0 earthquakes,we analyze the changes in satellite gravity field features re-lated to the strong earthquakes with the annual gravity changes before and after each earthquake. For analyzing the relationship between these earthquakes and the gravity change mode in detail, we also caculate the monthly gravity change for the Wenchuan MS 8.0 and Yushu MS 7.1 earth-quakes.Moreover,we use the recently relesed weekly GRACE gravity models to caculate the point-wise gravity change near Longmenshan fault for the Wenchuan MS 8.0 earthquake.The re-gional annual differentiated dynamic gravity changes image indicates that all three earthquakes oc-curred in a period of small gravity change,which means a small migration of crust-mantle material occurred according to the mantle convection theory.The same feature is indicated in the regional annual cumulative dynamic gravity changes image.These gravity changes likely indicate a medi-um-short term earthquake precursor.In the monthly differentiated dynamic gravity changes im-age,the gravity change mode shows significant changes in both the Wenchuan MS 8.0 earthquake and the Yushu MS 7.1 earthquake,which indicates that the gravity gradient change direction al-tered from perpendicular to the plane of a fault to parallel.These change in the gravity change mode may confirm the theory of post-earthquake potential field restoration.The nine points of the weekly gravity change sequences in Longmenshan fault area that occurred during 2008 indicate that a nearly nine-week contrary gravity change trend occurred between the eastern and western areas of the fault

  14. Propagation of Satelite Rainfall Products uncertainties in hydrological applications : Examples in West-Africa in the framework of the Megha-Tropiques Satellite Mission

    Science.gov (United States)

    Casse, C.; Gosset, M.; Peugeot, C.; Boone, A.; Pedinotti, V.

    2013-12-01

    The use of satellite based rainfall in research or operational Hydrological application is becoming more and more frequent. This is specially true in the Tropics where ground based gauge (or radar) network are generally scarce and often degrading. Member of the GPM constellation, the new French-Indian satellite Mission Megha-Tropiques (MT) dedicated to the water and energy budget in the tropical atmosphere contributes to a better monitoring of rainfall in the inter-tropical zone. As part of this mission, research is developed on the use of MT rainfall products for hydrological research or operational application such as flood monitoring. A key issue for such applications is how to account for rainfall products biases and uncertainties, and how to propagate them in the end user models ? Another important question is how to choose the best space-time resolution for the rainfall forcing, given that both model performances and rain-product uncertainties are resolution dependent. This talk will present on going investigations and perspectives on this subject, with examples from the Megha_tropiques Ground validation sites in West Africa. The CNRM model Surfex-ISBA/TRIP has been set up to simulate the hydrological behavior of the Niger River. This modeling set up is being used to study the predictability of Niger Floods events in the city of Niamey and the performances of satellite rainfall products as forcing for such predictions. One of the interesting feature of the Niger outflow in Niamey is its double peak : a first peak attributed to 'local' rainfall falling in small to medium size basins situated in the region of Niamey, and a second peak linked to the rainfall falling in the upper par of the river, and slowly propagating through the river towards Niamey. The performances of rainfall products are found to differ between the wetter/upper part of the basin, and the local/sahelian areas. Both academic tests with artificially biased or 'perturbed' rainfield and actual

  15. Merging aerosol optical depth data from multiple satellite missions to view agricultural biomass burning in Central and East China

    Directory of Open Access Journals (Sweden)

    Y. Xue

    2012-04-01

    Full Text Available Agricultural biomass burning (ABB in Central and East China occurs every year from May to October and peaks in June. The biomass burning event in June 2007 was very strong. During the period from 26 May to 16 June 2007, ABB occurred mainly in Anhui, Henan, Jiangsu and Shandong provinces. A comprehensive set of aerosol optical depth (AOD data, produced by a merger of AOD product data from the Moderate Resolution Imaging Spectroradiometer (MODIS and the Multiangle Imaging Spectroradiometer (MIRS, is used to study the spatial and temporal distribution of agricultural biomass aerosols in Central and East China combining with ground observations from both AErosol RObotic NETwork (AERONET and China Aerosol Remote Sensing NETwork (CARSNET measurements. We compared merged AOD data with single-sensor single-algorithm AOD data (MODIS Dark Target AOD data, MODIS Deep Blue AOD data, SRAP-MODIS AOD data and MISR AOD data. In this comparison, we found merged AOD products can improve the quality of AOD products from single-sensor single-algorithm data sets by expanding the spatial coverage of the study area and keeping the statistical confidence in AOD parameters. There existed high correlation (0.8479 between the merged AOD data and AERONET measurements. Our merged AOD data make use of synergetic information conveyed in all of the available satellite data. The merged AOD data were used for the analysis of the biomass burning event from 26 May to 16 June 2007 together with meteorological data. The merged AOD products and the ground observations from China suggest that biomass burning in Central and East China has had great impact on AOD over China. Influenced by this ABB, the highest AOD value in Beijing on 12 June 2007 reached 5.71.

  16. Merging aerosol optical depth data from multiple satellite missions to view agricultural biomass burning in Central and East China

    Science.gov (United States)

    Xue, Y.; Xu, H.; Mei, L.; Guang, J.; Guo, J.; Li, Y.; Hou, T.; Li, C.; Yang, L.; He, X.

    2012-04-01

    Agricultural biomass burning (ABB) in Central and East China occurs every year from May to October and peaks in June. The biomass burning event in June 2007 was very strong. During the period from 26 May to 16 June 2007, ABB occurred mainly in Anhui, Henan, Jiangsu and Shandong provinces. A comprehensive set of aerosol optical depth (AOD) data, produced by a merger of AOD product data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Multiangle Imaging Spectroradiometer (MIRS), is used to study the spatial and temporal distribution of agricultural biomass aerosols in Central and East China combining with ground observations from both AErosol RObotic NETwork (AERONET) and China Aerosol Remote Sensing NETwork (CARSNET) measurements. We compared merged AOD data with single-sensor single-algorithm AOD data (MODIS Dark Target AOD data, MODIS Deep Blue AOD data, SRAP-MODIS AOD data and MISR AOD data). In this comparison, we found merged AOD products can improve the quality of AOD products from single-sensor single-algorithm data sets by expanding the spatial coverage of the study area and keeping the statistical confidence in AOD parameters. There existed high correlation (0.8479) between the merged AOD data and AERONET measurements. Our merged AOD data make use of synergetic information conveyed in all of the available satellite data. The merged AOD data were used for the analysis of the biomass burning event from 26 May to 16 June 2007 together with meteorological data. The merged AOD products and the ground observations from China suggest that biomass burning in Central and East China has had great impact on AOD over China. Influenced by this ABB, the highest AOD value in Beijing on 12 June 2007 reached 5.71.

  17. Assessing the Impact of Earth Radiation Pressure Acceleration on Low-Earth Orbit Satellites

    Science.gov (United States)

    Vielberg, Kristin; Forootan, Ehsan; Lück, Christina; Kusche, Jürgen; Börger, Klaus

    2017-04-01

    The orbits of satellites are influenced by several external forces. The main non-gravitational forces besides thermospheric drag, acting on the surface of satellites, are accelerations due to the Earth and Solar Radiation Pres- sure (SRP and ERP, respectively). The sun radiates visible and infrared light reaching the satellite directly, which causes the SRP. Earth also emits and reflects the sunlight back into space, where it acts on satellites. This is known as ERP acceleration. The influence of ERP increases with decreasing distance to the Earth, and for low-earth orbit (LEO) satellites ERP must be taken into account in orbit and gravity computations. Estimating acceler- ations requires knowledge about energy emitted from the Earth, which can be derived from satellite remote sensing data, and also by considering the shape and surface material of a satellite. In this sensitivity study, we assess ERP accelerations based on different input albedo and emission fields and their modelling for the satellite missions Challenging Mini-Satellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE). As input fields, monthly 1°x1° products of Clouds and the Earth's Radiant En- ergy System (CERES), L3 are considered. Albedo and emission models are generated as latitude-dependent, as well as in terms of spherical harmonics. The impact of different albedo and emission models as well as the macro model and the altitude of satellites on ERP accelerations will be discussed.

  18. Evaluation of flat-Earth approximation results for geopotential missions.

    Science.gov (United States)

    Tapley, M. B.

    1997-04-01

    Simplified calculations can approximate the formal uncertainties in estimates of the spherical harmonic coefficients representing the Earth's gravitational potential. The calculations model the Earth locally as a plane, producing errors negligible for wavelengths shorter than the radius of the Earth. Information derived from observations of low altitude polar orbiting satellites is considered. With some constraints, the final model uncertainties derive from a priori gravitational field information, specific orbital elements, and parameters describing instrumentation characteristics. The author demonstrates how to refine the technique to accept inputs from the currently operational Navstar Global Positioning System (GPS) constellation and how to use information from partial tensor gravitational gradiometers. This approach is beneficial when evaluating prospective satellite geodesy missions because the covariance analyses for various mission scenarios can be made efficiently and expeditiously. The author demonstrates the utility of the flat Earth approach by comparing results with those of more elaborate and time consuming calculations performed for the European Space Agency ARISTOTELES proposed geopotential mapping mission, the NASA Gravity Probe B Relativity mission, and the NASA/Center National d'Etudes Spatiales Topographic Ocean Experiment Satellite (TOPEX)/Poseidon mission.

  19. Determining the 3D Subsurface Density Structure of Taurus Littrow Valley Using Apollo 17 Gravity Data

    Science.gov (United States)

    Urbancic, N.; Ghent, R.; Stanley, S,; Johnson, C. L.; Carroll, K. A.; Hatch, D.; Williamson, M. C.; Garry, W. B.; Talwani, M.

    2016-01-01

    Surface gravity surveys can detect subsurface density variations that can reveal subsurface geologic features. In 1972, the Apollo 17 (A17) mission conducted the Traverse Gravimeter Experiment (TGE) using a gravimeter that measured the local gravity field near Taurus Littrow Valley (TLV), located on the south-eastern rim of the Serenitatis basin. TLV is hypothesized to be a basaltfilled radial graben resulting from the impact that formed Mare Serenitatis. It is bounded by both the North and South Massifs (NM and SM) as well as other smaller mountains to the East that are thought to be mainly composed of brecciated highland material. The TGE is the first and only successful gravity survey on the surface of the Moon. Other more recent satellite surveys, such as NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission (2011- 2012), have produced the best global gravity field to date (approx. 13km resolution). However, these satellite surveys are not sensitive enough to detect fine-scale (structures. This underscores the value of the data collected at the surface by A17. In the original analysis of the data a 2D forward-modelling approach was used to derive a thickness of the subsurface basalt layer of 1.0 km by assuming a simple flat-faced rectangular geometry and using densities derived from Apollo lunar samples. We are investigating whether modern 3D modelling techniques in combination with high-resolution topographical and image datasets can reveal additional fine-scale subsurface structure in TLV.

  20. Low Gravity Anchoring System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Future sampling missions to the Moon, Mars and Asteroids will likely involve drilling and in-situ analysis from mobile robotic platforms in low gravity. Past...

  1. Ground-based diffusion experiments on liquid Sn-In systems using the shear cell technique of the satellite mission Foton-M1.

    Science.gov (United States)

    Suzuki, Shinsuke; Kraatz, Kurt-Helmut; Frohberg, Günter

    2004-11-01

    This study reported in this paper was aimed at testing the shear cell that was developed for the satellite mission Foton-M1 to measure diffusion coefficients in liquid metals under microgravity (microg)-conditions. Thick Layer diffusion experiments were performed in the system Sn90In10 versus Sn under 1 g-conditions. For this system several microg-diffusion results are available as reference data. This combination provides a low, but sufficiently stable, density layering throughout the entire experiment, which is important to avoid buoyancy-driven convection. The experimental results were corrected for the influences of the shear-induced convection and mixing after the final shearing, both of which are typical for the shear cell technique. As the result, the reproducibility and the reliability of the diffusion coefficients in the ground-based experiments were within the limits of error of microg-data. Based on our results we discuss the necessary conditions to avoid buoyancy-driven convection.

  2. The Europa Clipper Mission Concept

    Science.gov (United States)

    Pappalardo, Robert; Goldstein, Barry; Magner, Thomas; Prockter, Louise; Senske, David; Paczkowski, Brian; Cooke, Brian; Vance, Steve; Wes Patterson, G.; Craft, Kate

    2014-05-01

    A NASA-appointed Science Definition Team (SDT), working closely with a technical team from the Jet Propulsion Laboratory (JPL) and the Applied Physics Laboratory (APL), recently considered options for a future strategic mission to Europa, with the stated science goal: Explore Europa to investigate its habitability. The group considered several mission options, which were fully technically developed, then costed and reviewed by technical review boards and planetary science community groups. There was strong convergence on a favored architecture consisting of a spacecraft in Jupiter orbit making many close flybys of Europa, concentrating on remote sensing to explore the moon. Innovative mission design would use gravitational perturbations of the spacecraft trajectory to permit flybys at a wide variety of latitudes and longitudes, enabling globally distributed regional coverage of the moon's surface, with nominally 45 close flybys at altitudes from 25 to 100 km. We will present the science and reconnaissance goals and objectives, a mission design overview, and the notional spacecraft for this concept, which has become known as the Europa Clipper. The Europa Clipper concept provides a cost-efficient means to explore Europa and investigate its habitability, through understanding the satellite's ice and ocean, composition, and geology. The set of investigations derived from the Europa Clipper science objectives traces to a notional payload for science, consisting of: Ice Penetrating Radar (for sounding of ice-water interfaces within and beneath the ice shell), Topographical Imager (for stereo imaging of the surface), ShortWave Infrared Spectrometer (for surface composition), Neutral Mass Spectrometer (for atmospheric composition), Magnetometer and Langmuir Probes (for inferring the satellite's induction field to characterize an ocean), and Gravity Science (to confirm an ocean).The mission would also include the capability to perform reconnaissance for a future lander

  3. Global Characterization of CO2 Column Retrievals from Shortwave-Infrared Satellite Observations of the Orbiting Carbon Observatory-2 Mission

    Directory of Open Access Journals (Sweden)

    Charles Miller

    2011-02-01

    Full Text Available The global characteristics of retrievals of the column-averaged CO2 dry air mole fraction, XCO2, from shortwave infrared observations has been studied using the expected measurement performance of the NASA Orbiting Carbon Observatory-2 (OCO-2 mission. This study focuses on XCO2 retrieval precision and averaging kernels and their sensitivity to key parameters such as solar zenith angle (SZA, surface pressure, surface type and aerosol optical depth (AOD, for both nadir and sunglint observing modes. Realistic simulations have been carried out and the single sounding retrieval errors for XCO2 have been derived from the formal retrieval error covariance matrix under the assumption that the retrieval has converged to the correct answer and that the forward model can adequately describe the measurement. Thus, the retrieval errors presented in this study represent an estimate of the retrieval precision. For nadir observations, we find single-sounding retrieval errors with values typically less than 1 part per million (ppm over most land surfaces for SZAs less than 70° and up to 2.5 ppm for larger SZAs. Larger errors are found over snow/ice and ocean surfaces due to their low albedo in the spectral regions of the CO2 absorption bands and, for ocean, also in the O2 A band. For sunglint observations, errors over the ocean are significantly smaller than in nadir mode with values in the range of 0.3 to 0.6 ppm for small SZAs which can decrease to values as small as 0.15 for the largest SZAs. The vertical sensitivity of the retrieval that is represented by the column averaging kernel peaks near the surface and exhibits values near unity throughout most of the troposphere for most anticipated scenes. Nadir observations over dark ocean or snow/ice surfaces and observations with large AOD and large SZA show a decreased sensitivity to near-surface CO2. All simulations are carried out for a mid-latitude summer atmospheric profile, a given aerosol type and

  4. Gravity model development for TOPEX/POSEIDON: Joint gravity models 1 and 2

    Science.gov (United States)

    Nerem, R. S.; Lerch, F. J.; Marshall, J. A.; Pavlis, E. C.; Putney, B. H.; Tapley, B. D.; Eanes, R. J.; Ries, J. C.; Schutz, B. E.; Shum, C. K.

    1994-01-01

    The TOPEX/POSEIDON (T/P) prelaunch Joint Gravity Model-1 (JGM-1) and the postlaunch JGM-2 Earth gravitational models have been developed to support precision orbit determination for T/P. Each of these models is complete to degree 70 in spherical harmonics and was computed from a combination of satellite tracking data, satellite altimetry, and surface gravimetry. While improved orbit determination accuracies for T/P have driven the improvements in the models, the models are general in application and also provide an improved geoid for oceanographic computations. The postlaunch model, JGM-2, which includes T/P satellite laser ranging (SLR) and Doppler orbitography and radiopositioning integrated by satellite (DORIS) tracking data, introduces radial orbit errors for T/P that are only 2 cm RMS with the commission errors of the marine geoid for terms to degree 70 being +/- 25 cm. Errors in modeling the nonconservative forces acting on T/P increase the total radial errors to only 3-4 cm root mean square (RMS), a result much better than premission goals. While the orbit accuracy goal for T/P has been far surpassed geoid errors still prevent the absolute determination of the ocean dynamic topography for wavelengths shorter than about 2500 km. Only a dedicated gravitational field satellite mission will likely provide the necessary improvement in the geoid.

  5. Hybrid Atom Electrostatic System for Satellite Geodesy

    Science.gov (United States)

    Zahzam, Nassim; Bidel, Yannick; Bresson, Alexandre; Huynh, Phuong-Anh; Liorzou, Françoise; Lebat, Vincent; Foulon, Bernard; Christophe, Bruno

    2017-04-01

    The subject of this poster comes within the framework of new concepts identification and development for future satellite gravity missions, in continuation of previously launched space missions CHAMP, GRACE, GOCE and ongoing and prospective studies like NGGM, GRACE 2 or E-GRASP. We were here more focused on the inertial sensors that complete the payload of such satellites. The clearly identified instruments for space accelerometry are based on the electrostatic technology developed for many years by ONERA and that offer a high level of performance and a high degree of maturity for space applications. On the other hand, a new generation of sensors based on cold atom interferometry (AI) is emerging and seems very promising in this context. These atomic instruments have already demonstrated on ground impressive results, especially with the development of state-of-the-art gravimeters, and should reach their full potential only in space, where the microgravity environment allows long interaction times. Each of these two types of instruments presents their own advantages which are, for the electrostatic sensors (ES), their demonstrated short term sensitivity and their high TRL, and for AI, amongst others, the absolute nature of the measurement and therefore no need for calibration processes. These two technologies seem in some aspects very complementary and a hybrid sensor bringing together all their assets could be the opportunity to take a big step in this context of gravity space missions. We present here the first experimental association on ground of an electrostatic accelerometer and an atomic accelerometer and underline the interest of calibrating the ES instrument with the AI. Some technical methods using the ES proof-mass as the Raman Mirror seem very promising to remove rotation effects of the satellite on the AI signal. We propose a roadmap to explore further in details and more rigorously this attractive hybridization scheme in order to assess its potential

  6. SELENE: The Moon-Orbiting Observatory Mission

    Science.gov (United States)

    Mizutani, H.; Kato, M.; Sasaki, S.; Iijima, Y.; Tanaka, K.; Takizawa, Y.

    The Moon-orbiting SELENE (Selenological and Engineering Explorer) mission is prepared in Japan for lunar science and technology development. The launch target has been changed from 2005 to 2006 because of the launch failure of H2A rocket in 2003. The spacecraft consists of a main orbiting satellite at about 100 km altitude in the polar orbit and two sub-satellites in the elliptical orbits. The scientific objectives of the mission are; 1) study of the origin and evolution of the Moon, 2) in-situ measurement of the lunar environment, and 3) observation of the solar-terrestrial plasma environment. SELENE carries the instruments for scientific investigation, including mapping of lunar topography and surface composition, measurement of the gravity and magnetic fields, and observation of lunar and solar-terrestrial plasma environment. The total mass of scientific payload is about 300 kg. The mission period will be 1 year. If extra fuel is available, the mission will be extended in a lower orbit around 50 km. The elemental abundances are measured by x-ray and gamma-ray spectrometers. Alpha particles from the radon gas and polonium are detected by an alpha particle spectrometer. The mineralogical abundance is characterized by a multi-band imager. The mineralogical composition is identified by a spectral profiler which is a continuous spectral analyzer. The surface topographic data are obtained by a high resolution terrain camera and a laser altimeter. The inside structure up to 5 km below the lunar surface is observed by the radar sounder experiment using a 5 MHz radio wave. A magnetometer and an electron reflectometer provides data on the lunar surface magnetic field. Doppler tracking of the orbiter via the sub-satellite when the orbiter is in the far side is used to determine the gravity field of the far side. Radio sources on the two sub-satellites are used to conduct differential VLBI observation from the ground stations. The lunar environment of high energy particles

  7. Noise variance estimation and optimal weight determination for GOCE gravity recovery­

    Directory of Open Access Journals (Sweden)

    J. Kusche

    2003-01-01

    Full Text Available In the course of level 2 data processing for the GOCE (Gravity Field and Steady–State Ocean Circulation Explorer satellite mission different streams of level 1b data will be merged in a single solution providing the Earth’s gravity field, but also state-vector parameters and other quantities. A proper weighting of orbit tracking data, gravity gradiometry data and certain a priori information, usually considered as ‘solution constraints’, can be expected as crucial for the solution quality. But the a priori stochastic models, based on pre–mission assessment of the expected instrument behaviour, may be over–optimistic or even too pessimistic since they refer to an unprecedented mission with scientific payload never tested in space. One way to derive an optimal weighting scheme on a statistically sound basis while simultaneously validating the stochastic noise levels of the data is by including variance component estimation as a part of the level 1b to level 2 data analysis process. The idea is that by applying Monte-Carlo techniques this method can be extended to a large-scale problem like GOCE data analysis, using software modules that already exist or are currently under development. The proposed method has been tested using simulated GOCE orbit trajectories as well as gravity gradiometry data corrupted by colored random noise.Key words. GOCE, gravity field modelling, combination solutions, weight estimation, variance component estimation

  8. Development of the high sensitivity GRADIO accelerometers - The Aristoteles gradiometer mission preparation

    Science.gov (United States)

    Bernard, A.; Touboul, P.

    ESA and NASA are preparing the cooperative geopotential mission ARISTOTELES that will combine, for the global and fine recovery of the earth's gravity field, gradiometric measurements on board a dedicated satellite at 200-km altitude and satellite-to-satellite tracking using GPS network. The gradiometer required accuracy is 0.01 Eotvos, leading for the GRADIO ultrasensitive accelerometers composing this instrument to a resolution of 5 x 10 exp -12 per sq ms in the bandwidth (5 x 10 exp -3 Hz, 0.125 Hz) in microgravity conditions. Two laboratory models and a specific test bench have been realized. In spite of the presence of gravity and of the seismic noise, differential tests at a level of better than one nanoG are achieved on ground.

  9. A Transportable Gravity Gradiometer Based on Atom Interferometry

    Science.gov (United States)

    Yu, Nan; Thompson, Robert J.; Kellogg, James R.; Aveline, David C.; Maleki, Lute; Kohel, James M.

    2010-01-01

    A transportable atom interferometer-based gravity gradiometer has been developed at JPL to carry out measurements of Earth's gravity field at ever finer spatial resolutions, and to facilitate high-resolution monitoring of temporal variations in the gravity field from ground- and flight-based platforms. Existing satellite-based gravity missions such as CHAMP and GRACE measure the gravity field via precise monitoring of the motion of the satellites; i.e. the satellites themselves function as test masses. JPL's quantum gravity gradiometer employs a quantum phase measurement technique, similar to that employed in atomic clocks, made possible by recent advances in laser cooling and manipulation of atoms. This measurement technique is based on atomwave interferometry, and individual laser-cooled atoms are used as drag-free test masses. The quantum gravity gradiometer employs two identical atom interferometers as precision accelerometers to measure the difference in gravitational acceleration between two points (Figure 1). By using the same lasers for the manipulation of atoms in both interferometers, the accelerometers have a common reference frame and non-inertial accelerations are effectively rejected as common mode noise in the differential measurement of the gravity gradient. As a result, the dual atom interferometer-based gravity gradiometer allows gravity measurements on a moving platform, while achieving the same long-term stability of the best atomic clocks. In the laboratory-based prototype (Figure 2), the cesium atoms used in each atom interferometer are initially collected and cooled in two separate magneto-optic traps (MOTs). Each MOT, consisting of three orthogonal pairs of counter-propagating laser beams centered on a quadrupole magnetic field, collects up to 10(exp 9) atoms. These atoms are then launched vertically as in an atom fountain by switching off the magnetic field and introducing a slight frequency shift between pairs of lasers to create a moving

  10. Latest developments in lunar gravity field recovery within the project GRAZIL

    Science.gov (United States)

    Krauss, Sandro; Wirnsberger, Harald; Klinger, Beate; Mayer-Gürr, Torsten; Baur, Oliver

    2016-04-01

    The project GRAZIL addresses the highly accurate recovery of the lunar gravity field using intersatellite Ka-band ranging (KBR) measurements collected by the Lunar Gravity Ranging System (LGRS) of the Gravity Recovery And Interior Laboratory (GRAIL) mission. Dynamic precise orbit determination is an indispensable task in order to recover the lunar gravity field based on LGRS measurements. The concept of variational equations is adopted to determine the orbit of the two GRAIL satellites based on radio science data. In this contribution we focus on the S-band two-way Doppler data collected by the Deep Space Network. As far as lunar gravity field recovery is concerned, we apply an integral equation approach using short orbital arcs in the order of one hour. In this contribution special attention is given to the refinement of our processing strategy in conjunction with an increase of the spectral resolution. Based on these considerations we present the latest version of a lunar gravity field model developed in Graz which is based on KBR observations during the primary mission phase (March 1 to May 29, 2012). Our results are validated against GRAIL models computed at NASA-GSFC and NASA-JPL.

  11. High Degree and Order Gravity Fields of the Moon Derived from GRAIL Data

    Science.gov (United States)

    Lemoine, F. G.; Goossens, S. J.; Sabaka, T. J.; Nicholas, J. B.; Mazarico, E.; Rowlands, D. D.; Loomis, B. D.; Chinn, D. S.; Caprette, D. S.; McCarthy, J. J.; Neumann, G. A.; Zuber, M. T.; Smith, D. E.

    2012-01-01

    The Gravity Recovery and Interior Laboratory (GRAIL) spacecraft conducted the mapping of the gravity field of the Moon from March 1, 2012 to May 29, 2012. The twin spacecraft acquired highly precise K Band range-rate (KBRR) intersatellite ranging data and Deep Space Network (DSN) data during this prime mission phase from altitudes of 15 to 75 km above the lunar surface over three lunar months. We have processed these data using the NASA GSFC GEODYN orbit determination and geodetic parameter estimation program, and we have determined gravity fields up to degree and order 420 in spherical harmonics. The new gravity solutions show improved correlations with LOLA-derived topography to high degree and order and resolve many lunar features in the geopotential with a resolution of less than 30 km, including for example the central peak of the crater Tycho. We discuss the methodology used for the processing of the GRAIL data, the quality of the orbit determination on the GRAIL satellites and the derivation of the solutions, and their evaluation with independent data, including Lunar Prospector. We show that with these new GRAIL gravity solutions, we can now fit the low altitude, extended mission Lunar Prospector tracking data better than with any previous gravity model that included the LP data.

  12. De-correlated combination of two low-low Satellite-to-Satellite tracking pairs according to temporal aliasing

    Science.gov (United States)

    Murböck, Michael; Pail, Roland

    2014-05-01

    The monitoring of the temporal changes in the Earth's gravity field is of great scientific and societal importance. Within several days a homogeneous global coverage of gravity observations can be obtained with satellite missions. Temporal aliasing of background model errors into global gravity field models will be one of the largest restrictions in future satellite temporal gravity recovery. The largest errors are due to high-frequent tidal and non-tidal atmospheric and oceanic mass variations. Having a double pair low-low Satellite-to-Satellite tracking (SST) scenario on different inclined orbits reduces temporal aliasing errors significantly. In general temporal aliasing effects for a single (-pair) mission strongly depend on the basic orbital rates (Murböck et al. 2013). These are the rates of the argument of the latitude and of the longitude of the ascending node. This means that the revolution time and the length of one nodal day determine how large the temporal aliasing error effects are for each SH order. The combination of two low-low SST missions based on normal equations requires an adequate weighting of the two components. This weighting shall ensure the full de-correlation of each of the two parts. Therefore it is necessary to take the temporal aliasing errors into account. In this study it is analyzed how this can be done based on the resonance orders of the two orbits. Different levels of approximation are applied to the de-correlation approach. The results of several numerical closed-loop simulations are shown including stochastic modeling of realistic future instrument noise. It is shown that this de-correlation approach is important for maximizing the benefit of a double-pair low-low SST mission for temporal gravity recovery. Murböck M, Pail R, Daras I and Gruber T (2013) Optimal orbits for temporal gravity recovery regarding temporal aliasing. Journal of Geodesy, Springer Berlin Heidelberg, ISSN 0949-7714, DOI 10.1007/s00190-013-0671-y

  13. Ocean calibration approach to correcting for spurious accelerations for data from the GRACE and GRACE Follow-On missions

    CERN Document Server

    Bender, Peter L

    2015-01-01

    The GRACE mission has been providing valuable new information on time variations in the Earth's gravity field since 2002. In addition, the GRACE Follow-On mission is scheduled to be flown soon after the end of life of the GRACE mission in order to minimize the loss of valuable data on the Earth's gravity field changes. In view of the major benefits to hydrology and oceanography, as well as to other fields, it is desirable to investigate the fundamental limits to monitoring the time variations in the Earth's gravity field during GRACE-type missions. A simplified model is presented in this paper for making estimates of the effect of differential spurious accelerations of the satellites during times when four successive revolutions cross the Pacific Ocean. The analysis approach discussed is to make use of changes in the satellite separation observed during passages across low latitude regions of the Pacific and of other oceans to correct for spurious accelerations of the satellites. The low latitude regions of t...

  14. A comment on ''A test of general relativity using the LARES and LAGEOS satellites and a GRACE Earth gravity model'', by I. Ciufolini et al

    Energy Technology Data Exchange (ETDEWEB)

    Iorio, Lorenzo [Ministero dell' Istruzione Univ. della Ricerca (M.I.U.R.), Bari (Italy)

    2017-02-15

    Recently, Ciufolini et al. reported on a test of the general relativistic gravitomagnetic Lense-Thirring effect by analyzing about 3.5 years of laser ranging data to the LAGEOS, LAGEOS II, LARES geodetic satellites orbiting the Earth. By using the GRACE-based GGM05S Earth's global gravity model and a linear combination of the nodes Ω of the three satellites designed to remove the impact of errors in the first two even zonal harmonic coefficients J{sub 2}, J{sub 4} of the multipolar expansion of the Newtonian part of the Earth's gravitational potential, they claimed an overall accuracy of 5% for the Lense-Thirring caused node motion. We show that the scatter in the nominal values of the uncancelled even zonals of degree l = 6, 8, 10 from some of the most recent global gravity models does not yet allow to reach unambiguously and univocally the expected ∼1% level, being large up to

  15. Testing General Relativity and Alternative Theories of Gravity with Space-based Atomic Clocks and Atom Interferometers

    CERN Document Server

    Bondarescu, Ruxandra; Jetzer, Philippe; Angélil, Raymond; Saha, Prasenjit; Lundgren, Andrew

    2015-01-01

    The successful miniaturisation of extremely accurate atomic clocks and atom interferometers invites prospects for satellite missions to perform precision experiments. We discuss the effects predicted by general relativity and alternative theories of gravity that can be detected by a clock, which orbits the Earth. Our experiment relies on the precise tracking of the spacecraft using its observed tick-rate. The spacecraft's reconstructed four-dimensional trajectory will reveal the nature of gravitational perturbations in Earth's gravitational field, potentially differentiating between different theories of gravity. This mission can measure multiple relativistic effects all during the course of a single experiment, and constrain the Parametrized Post-Newtonian Parameters around the Earth. A satellite carrying a clock of fractional timing inaccuracy of $\\Delta f/f \\sim 10^{-16}$ in an elliptic orbit around the Earth would constrain the PPN parameters $|\\beta -1|, |\\gamma-1| \\lesssim 10^{-6}$. We also briefly revi...

  16. The MICROSTAR electrostatic accelerometer for the GRASP Mission

    Science.gov (United States)

    Foulon, Bernard; Christophe, Bruno; Liorzou, Francoise; Huynh, Phuong-Anh; Perrot, Eddy

    2015-04-01

    The Geodetic Reference Antenna in Space (GRASP) is a micro satellite mission concept dedicated to the enhancement of all the space geodetic techniques, and promising revolutionary improvements to the definition of the Terrestrial Reference Frame (TRF). GRASP collocates GPS, SLR, VLBI, and DORIS sensors on a dedicated spacecraft in order to establish precise and stable ties between the key geodetic techniques used to define and disseminate the TRF. GRASP also offers a space-based reference antenna for the present and future Global Navigation Satellite Systems (GNSS). The integration of an ultra sensitive accelerometer at the Center of mass of the satellite can provide not only improvement of the Precise Orbit Determination (POD) by the accurate measurement of the non-gravitational force acting on the surface of the satellite but also by the possibility to calibrate with an accuracy better than 100 µm the change in the position of the Satellite Center of Mass as it is performed in the GRACE mission and to determine the precise motion of the antennas assuming some rigid structure between them and the accelerometer as it is done between the star sensor, the optical cube assembly of satellite laser ranging system and the accelerometer in the GRACE-Follow On mission. The proposed accelerometer is miniaturized version of the electrostatic accelerometers developed for the Earth gravity missions CHAMP, GRACE, GOCE and GRACE-FO. He has 3 sensitive axes thanks to a cubic proof-mass and provides the 3 linear accelerations and the 3 angular accelerations about its 3 orthogonal axes. He is called MICROSTAR and its foreseen performance is a linear acceleration noise lower than 10-11 ms-2/Hz1/2 into a measurement bandwidth between 10-3 Hz and 0.1 Hz.

  17. Simulation of the time-variable gravity field by means of coupled geophysical models

    Directory of Open Access Journals (Sweden)

    Th. Gruber

    2011-07-01

    Full Text Available Time variable gravity fields, reflecting variations of mass distribution in the system Earth is one of the key parameters to understand the changing Earth. Mass variations are caused either by redistribution of mass in, on or above the Earth's surface or by geophysical processes in the Earth's interior. The first set of observations of monthly variations of the Earth gravity field was provided by the US/German GRACE satellite mission beginning in 2002. This mission is still providing valuable information to the science community. However, as GRACE has outlived its expected lifetime, the geoscience community is currently seeking successor missions in order to maintain the long time series of climate change that was begun by GRACE. Several studies on science requirements and technical feasibility have been conducted in the recent years. These studies required a realistic model of the time variable gravity field in order to perform simulation studies on sensitivity of satellites and their instrumentation. This was the primary reason for the European Space Agency (ESA to initiate a study on "Monitoring and Modelling individual Sources of Mass Distribution and Transport in the Earth System by Means of Satellites". The goal of this interdisciplinary study was to create as realistic as possible simulated time variable gravity fields based on coupled geophysical models, which could be used in the simulation processes in a controlled environment. For this purpose global atmosphere, ocean, continental hydrology and ice models were used. The coupling was performed by using consistent forcing throughout the models and by including water flow between the different domains of the Earth system. In addition gravity field changes due to solid Earth processes like continuous glacial isostatic adjustment (GIA and a sudden earthquake with co-seismic and post-seismic signals were modelled. All individual model results were combined and converted to gravity field

  18. Monte Carlo Analysis as a Trajectory Design Driver for the TESS Mission

    Science.gov (United States)

    Nickel, Craig; Lebois, Ryan; Lutz, Stephen; Dichmann, Donald; Parker, Joel

    2016-01-01

    The Transiting Exoplanet Survey Satellite (TESS) will be injected into a highly eccentric Earth orbit and fly 3.5 phasing loops followed by a lunar flyby to enter a mission orbit with lunar 2:1 resonance. Through the phasing loops and mission orbit, the trajectory is significantly affected by lunar and solar gravity. We have developed a trajectory design to achieve the mission orbit and meet mission constraints, including eclipse avoidance and a 30-year geostationary orbit avoidance requirement. A parallelized Monte Carlo simulation was performed to validate the trajectory after injecting common perturbations, including launch dispersions, orbit determination errors, and maneuver execution errors. The Monte Carlo analysis helped identify mission risks and is used in the trajectory selection process.

  19. Analytical solution of perturbed relative motion: an application of satellite formations to geodesy

    Science.gov (United States)

    Wnuk, Edwin

    In the upcoming years, several space missions will be operated using a number of spacecraft flying in formation. Clusters of spacecraft with a carefully designed orbits and optimal formation geometry enable a wide variety of applications ranging from remote sensing to astronomy, geodesy and basic physics. Many of the applications require precise relative navigation and autonomous orbit control of satellites moving in a formation. For many missions a centimeter level of orbit control accuracy is required. The GRACE mission, since its launch in 2002, has been improving the Earth's gravity field model to a very high level of accuracy. This mission is a formation flying one consisting of two satellites moving in coplanar orbits and provides range and range-rate measurements between the satellites in the along-track direction. Future geodetic missions probably will employ alternative architectures using additional satellites and/or performing out-of-plane motion, e.g cartwheel orbits. The paper presents an analytical model of a satellite formation motion that enables propagation of the relative spacecraft motion. The model is based on the analytical theory of satellite relative motion that was presented in the previous our papers (Wnuk and Golebiewska, 2005, 2006). This theory takes into account the influence of the following gravitational perturbation effects: 1) zonal and tesseral harmonic geopotential coefficients up to arbitrary degree and order, 2) Lunar gravity, 3) Sun gravity. Formulas for differential perturbations were derived with any restriction concerning a plane of satellite orbits. They can be applied in both: in plane and out of plane cases. Using this propagator we calculated relative orbits and future relative satellite positions for different types of formations: in plane, out of plane, cartwheel and others. We analyzed the influence of particular parts of perturbation effects and estimated the accuracy of predicted relative spacecrafts positions

  20. Status of the GRACE Follow-On Mission (Invited)

    Science.gov (United States)

    Watkins, M. M.; Flechtner, F.; Tapley, B. D.

    2010-12-01

    NASA has included a GRACE Follow-On mission in its proposed budget for fiscal year 2011. As of the time of this abstract submission (September 2, 2010), although the FY11 NASA budget has not been approved by Congress, we continue to anticipate a new start for the mission in FY11. We also anticipate and welcome a continuation of the GRACE partnership with German colleagues at GFZ and DLR. The proposed mission goal is focused on continuation of the critical global mass flux time series initiated by GRACE, and therefore launching as soon as practical is a high priority. The GRACE mission is well into its extended mission, and we will summarize the latest satellite status and expected lifetime. To minimize the development time of a Follow-On mission while minimizing cost and technical risk, a high inheritance "rebuild" of GRACE is the mission baseline, taking advantage of lessons learned from GRACE. We have conducted a study of the systematic errors from the GRACE thermal control system, the satellite seismicity (particularly the nadir radiator), and the attitude control hardware and software in order to feed forward selected modest cost design improvements which provide high science value to the Follow-On. We have also developed basic plans to incorporate, on a "tech demo" basis, an experimental laser interferometer system derived from technology developed by the Earth Science Technology Office Instrument Incubator program, and in conjunction with German developments led by AEI/U. Hannover. This system could provide important experience and risk reduction for future gravity mapping missions targeted for improved accuracy and spatial resolution. In this talk, we will provide the latest technical and programmatic status of this developing project to continue and extend the successful science from the GRACE mission.

  1. Titan's gravity: An update

    Science.gov (United States)

    Durante, D.; Iess, L.; Racioppa, P.; Armstrong, J. W.; Lunine, J. I.; Stevenson, D. J.; Tortora, P.

    2016-12-01

    Since its arrival at Saturn in 2004, Cassini performed nine flybys devoted to the determination of Titan's gravity field and its tidal variations. The last gravity flyby of the mission (T122) took place on Aug. 10, 2016. We will present an updated gravity solution, based on all available data. These include also an additional flyby (T110, March 2015, primarily devoted to the imaging Titan's north polar lakes) carried out with the low gain antenna. This flyby was particularly valuable because closest approach occurred at high latitude (75°N), over an area not previously sampled. Published gravity results (Iess et al., 2012) indicated that Titan is subject to large eccentricity tides in response to Saturn's time varying forcing field. The magnitude of the response quadrupole field, controlled by the Love number k2, was used to infer the existence of an internal ocean. The new gravity field determination provides a better estimate of k2, to a level of a few percent. In addition to a full 3x3 field, the new solution includes also higher degree and order harmonic coefficients (such as J4) and offers an improved map of gravity anomalies. The updated geoid and its associated uncertainty could be used to refine the gravity-altimetry correlative analysis and for improved interpretation of radar altimetric data.

  2. The ALEXIS mission recovery

    Energy Technology Data Exchange (ETDEWEB)

    Bloch, J.; Armstrong, T.; Dingler, B.; Enemark, D.; Holden, D.; Little, C.; Munson, C.; Priedhorsky, B.; Roussel-Dupre, D.; Smith, B. [Los Alamos National Lab., NM (United States); Warner, R.; Dill, B.; Huffman, G.; McLoughlin, F.; Mills, R.; Miller, R. [AeroAstro, Inc., Herndon, VA (United States)

    1994-03-01

    The authors report the recovery of the ALEXIS small satellite mission. ALEXIS is a 113-kg satellite that carries an ultrasoft x-ray telescope array and a high-speed VHF receiver/digitizer (BLACKBEARD), supported by a miniature spacecraft bus. It was launched by a Pegasus booster on 1993 April 25, but a solar paddle was damaged during powered flight. Initial attempts to contact ALEXIS were unsuccessful. The satellite finally responded in June, and was soon brought under control. Because the magnetometer had failed, the rescue required the development of new attitude control-techniques. The telemetry system has performed nominally. They discuss the procedures used to recover the ALEXIS mission.

  3. Precise Orbit Determination of Earth's Satellites for Climate Change Investigation

    Science.gov (United States)

    Vespe, Francesco

    The tremendous improvement of the gravity field models which we are achieving with the last Earth's satellite missions like, CHAMP, GRACE and GOCE devoted to its recovery could make feasibile the use of precise orbit determination (POD) of Earth satellites as a tool for sensing global changes of some key atmosphere parameters like refractivity and extinction. Such improvements indeed, coupled with the huge number of running Earth's satellites and combinations of their orbital parameters (namely the nodes) in a gravity field free fashion (hereafter GFF) can magnify the solar radiation pressure acting on medium earth orbit satellites :GPS, Etalon and, in near real future GALILEO and its smooth modulation through the Earth's atmosphere (penumbra). We would remind that The GFF technique is able to cancel out with "n" satellite orbital parameters the first n-1 even zonal harmonics of the gravity field. Previously it was demonstrated that the signal we want to detect could in principle emerge from the noise threshold but, more refined models of the atmosphere would be needed to perform a more subtle analysis. So we will re-compute the signal features of penumbra by applying more refined atmospheric models. The analysis will be performed by including in GFF Earth's satellites equipped with DORIS systems (Jason, Spot 2-3-4-5, ENVISAT etc.) other than those ranged with SLR and GPS. The introduction of DORIS tracked satellites indeed will allow to cancel higher and higher order of even zonal harmonics and will make still more favourable the signal to noise budget. The analysis will be performed over a time span of at least few tens of years just to enhance probable climate signatures.

  4. Measurement of the gravitational redshift effect with RadioAstron satellite

    CERN Document Server

    Birukov, A V; Litvinov, D A; Porayko, N K; Rudenko, V N

    2015-01-01

    RadioAstron satellite admits in principle a testing the gravitational redshift effect with an accuracy of better than $10^{-5}$. It would surpass the result of Gravity Probe A mission at least an order of magnitude. However, RadioAstron's communications and frequency transfer systems are not adapted for a direct application of the non relativistic Doppler and troposphere compensation scheme used in the Gravity Probe A experiment. This leads to degradation of the redshift test accuracy approximately to the level 0.01. We discuss the way to overcome this difficulty and present preliminary results based on data obtained during special observing sessions scheduled for testing the new techniques.

  5. A space-time multiscale modelling of Earth's gravity field variations

    Science.gov (United States)

    Wang, Shuo; Panet, Isabelle; Ramillien, Guillaume; Guilloux, Frédéric

    2017-04-01

    The mass distribution within the Earth varies over a wide range of spatial and temporal scales, generating variations in the Earth's gravity field in space and time. These variations are monitored by satellites as the GRACE mission, with a 400 km spatial resolution and 10 days to 1 month temporal resolution. They are expressed in the form of gravity field models, often with a fixed spatial or temporal resolution. The analysis of these models allows us to study the mass transfers within the Earth system. Here, we have developed space-time multi-scale models of the gravity field, in order to optimize the estimation of gravity signals resulting from local processes at different spatial and temporal scales, and to adapt the time resolution of the model to its spatial resolution according to the satellites sampling. For that, we first build a 4D wavelet family combining spatial Poisson wavelets with temporal Haar wavelets. Then, we set-up a regularized inversion of inter-satellites gravity potential differences in a bayesian framework, to estimate the model parameters. To build the prior, we develop a spectral analysis, localized in time and space, of geophysical models of mass transport and associated gravity variations. Finally, we test our approach to the reconstruction of space-time variations of the gravity field due to hydrology. We first consider a global distribution of observations along the orbit, from a simplified synthetic hydrology signal comprising only annual variations at large spatial scales. Then, we consider a regional distribution of observations in Africa, and a larger number of spatial and temporal scales. We test the influence of an imperfect prior and discuss our results.

  6. Possibilities of the regional gravity field recovery from first-, second- and third-order radial derivatives of the disturbing gravitational potential measured on moving platforms

    Science.gov (United States)

    Pitonak, Martin; Sprlak, Michal; Novak, Pavel; Tenzer, Robert

    2016-04-01

    Recently realized gravity-dedicated satellite missions allow for measuring values of scalar, vectorial (Gravity Recovery And Climate Experiment - GRACE) and second-order tensorial (Gravity field and steady-state Ocean Circulation Explorer - GOCE) parameters of the Earth's gravitational potential. Theoretical aspects related to using moving sensors for measuring elements of the third-order gravitational tensor are currently under investigation, e.g., the gravity field-dedicated satellite mission OPTIMA (OPTical Interferometry for global Mass change detection from space) should measure third-order derivatives of the Earth's gravitational potential. This contribution investigates regional recovery of the disturbing gravitational potential on the Earth's surface from satellite and aerial observations of the first-, second- and third-order radial derivatives of the disturbing gravitational potential. Synthetic measurements along a satellite orbit at the altitude of 250 km and along an aircraft track at the altitude of 10 km are synthetized from the global gravitational model EGM2008 and polluted by the Gaussian noise. The process of downward continuation is stabilized by the Tikhonov regularization. Estimated values of the disturbing gravitational potential are compared with the same quantity synthesized directly from EGM2008.

  7. Behaviour of the low degree terms of the Earth gravity field over the last 30 years

    Science.gov (United States)

    Biancale, R.; Lemoine, J.-M.; Reinquin, F.; Deleflie, F.; Ramillien, G.; Gégout, P.

    2012-04-01

    The GRACE mission has revealed since 2002 the recent evolution of the Earth's gravity field with a resolution down to 400 km, equivalent to degree and order 50 in spherical harmonics. Precise orbit computation for altimetric satellites can obviously gain by applying these variations, which are classically given, as in recent EIGEN models, as drifts and periodic terms (yearly and semi-yearly). However extrapolating these variations to pre-GRACE periods, mainly the drifts, can be problematic for orbit computation performances on former altimetric satellites. One option is to analyse older satellite data, in particular SLR data on geodetic satellites, in order to assess the very low degree variations of the gravity field and compare it to the GRACE determination. This can be done over the last 30 years, using for instance the Lageos and Lageos-2, Starlette and Stella satellites. The spherical harmonic degrees that can be accessed in this way are degrees 2 to 4. Additional information on degree 2 can be derived from the analysis of the Earth orientation parameters, pole coordinates and length of day (LOD), which have been observed over a long period with great accuracy by astrometric, satellite geodetic and extra-galactic means. Once corrected for atmospheric and oceanic load and velocity variations, the pole coordinates will principally bring information on the C(2,1) and S(2,1) coefficients, while the LOD will principally be connected with the C(2,0). Combining these two approaches allows a better observation of the temporal evolution of the gravity field over a long time span and a more realistic modelling of it for the precise orbit computation of past altimeter missions.

  8. Gravity-derived High-resolution Moho Model for Greenland

    Science.gov (United States)

    Steffen, R.; Strykowski, G.; Lund, B.

    2016-12-01

    Obtaining knowledge of the depth of the crust-mantle boundary (Mohorovičić discontinuity, Moho) beneath Greenland is important for the understanding of ice mass losses as those estimates depend on earth model parameters. However, the ice sheet on Greenland impedes the access and installation of seismological stations as well as the gathering of reflection and refraction seismic data, making the use of the most common methods to determine the crust-mantle boundary difficult. However, the Moho depth can be estimated also from gravity data through an inversion procedure and such data can, on the contrary, be obtained not only through ground measurements, but also through airborne campaigns as well as from satellite missions. Here, we use the Parker-Oldenburg algorithm together with the most recent EIGEN-6C4 gravity model to estimate the crust-mantle boundary beneath Greenland and surroundings. The available gravity data are corrected for the topographic effect, the gravity effect of sediments and the gravity effect of the ice load induced deformation. The resulting Moho model for Greenland shows maximum depths below east Greenland of up to 55 km and and values less than 20 km offshore east Greenland. The northern part of Greenland has a shallower Moho of only 30 km compared to southern Greenland, indicating a change in the crustal structures and the presence of two different crustal blocks in Greenland. An uncertainty of ±2.5 km is determined for the final model, which has a spatial resolution of 0.1°. The results of the gravity inversion are consistent with previous Moho models determined by seismological and seismic data mainly, where those are available. The comparison to previously estimated models based on older gravity data and using different inversion algorithms shows only small differences.

  9. Length of day and polar motion, with respect to temporal variations of the Earth gravity field

    CERN Document Server

    Bourda, G

    2007-01-01

    The masses distribution inside the Earth governs the behaviour of the rotation axis in the Earth (polar motion), as well as the Earth rotation rate (or equivalently, length of day). This masses distribution can be measured from space owing to artificial satellites, the orbitography of which provides the Earth gravity field determination. Then, the temporal variations of the Earth gravity field can be related to the variations of the Earth Orientation Parameters (EOP) (with the Inertia Tensor). Nowadays, owing to the satellite laser ranging (SLR) technique and to the new gravimetric satellite missions (such as CHAMP or GRACE), the temporal variations of the low degree coefficients of the Earth gravity field (i.e. Stokes coefficients) can be determined. This paper is one of the first study using gravity variations data in the equations already established (e.g. Lambeck 1988) and linking the variations of the length of day and of the C20 Stokes coefficient (or, linking the polar motion and the C21 and S21 coeffi...

  10. Probing Gravity with Next Generation Lunar Laser Ranging

    Science.gov (United States)

    Martini, Manuele; Dell'Agnello, Simone

    Lunar and satellite laser ranging (LLR/SLR) are consolidated techniques which provide a precise, and at the same time, cost-effective method to determine the orbits of the Moon and of satellites equipped with laser retroreflectors with respect to the International Celestial Reference System. We describe the precision tests of general relativity and of new theories of gravity that can be performed with second-generation LLR payloads on the surface of the Moon (NASA/ASI MoonLIGHT project), and with SLR/LLR payloads deployed on spacecraft in the Earth-Moon system. A new wave of lunar exploration and lunar science started in 2007-2008 with the launch of three missions (Chang'e by China, Kaguya by Japan, Chandrayaan by India), missions in preparation (LCROSS, LRO, GRAIL/LADEE by NASA) and other proposed missions (like MAGIA in Italy). This research activity will be greatly enhanced by the future robotic deployment of a lunar geophysics network (LGN) on the surface of the Moon. A scientific concept of the latter is the International Lunar Network (ILN, see http://iln.arc.nasa.gov/). The LLR retroreflector payload developed by a US-Italy team described here and under space qualification at the National Laboratories of Frascati (LNF) is the optimum candidate for the LGN, which will be populated in the future by any lunar landing mission.

  11. Impact of CryoSat-2 for marine gravity field - globally and in the Arctic Ocean

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Stenseng, Lars; Knudsen, Per

    days repeat offered by CryoSat-2 provides denser coverage than older geodetic mission data set like ERS-1. Thirdly, the 92 degree inclination of CryoSat-2 is designed to map more of the Arctic Ocean than previous altimetric satellites. Finally, CryoSat-2 is able to operate in two new modes (SAR and SAR...... GDR data, NOAA LRM data, but also Level1b (LRM, SAR and SAR-in waveforms) data have been analyzed. A suite of eight different empirical retrackers have been developed and investigated for their ability to predict marine gravity in the Arctic Ocean. The impact of the various improvement offered by Cryo......Sat-2 in comparison with conventional satellite altimetry have been studied and quantified both globally but particularly for the Arctic Ocean using a large number of marine and airborne surveys providing “ground truth” marine gravity....

  12. Interest of the MICROSTAR Accelerometer to improve the GRASP Mission.

    Science.gov (United States)

    Perrot, E.; Lebat, V.; Foulon, B.; Christophe, B.; Liorzou, F.; Huynh, P. A.

    2015-12-01

    The Geodetic Reference Antenna in Space (GRASP) is a micro satellite mission concept proposed by JPL to improve the definition of the Terrestrial Reference Frame (TRF). GRASP collocates GPS, SLR, VLBI, and DORIS sensors on a dedicated spacecraft in order to establish precise and stable ties between the key geodetic techniques used to define and disseminate the TRF. GRASP also offers a space-based reference antenna for the present and future Global Navigation Satellite Systems (GNSS). By taking advantage of the new testing possibilities offer by the catapult facility at the ZARM drop tower, the ONERA's space accelerometer team proposes an up-dated version, called MICROSTAR, of its ultra sensitive electrostatic accelerometers which have contributed to the success of the last Earth's gravity missions GRACE and GOCE. Built around a cubic proof-mass, it provides the 3 linear accelerations with a resolution better than 10-11 ms-2/Hz1/2 into a measurement bandwidth between 10-3 Hz and 0.1 Hz and the 3 angular accelerations about its 3 orthogonal axes with 5´10-10 rad.s-2/Hz1/2 resolution. Integrated at the centre of mass of the satellite, MICROSTAR improves the Precise Orbit Determination (POD) by accurate measurement of the non-gravitational force acting on the satellite. It offers also the possibility to calibrate the change in the position of the satellite center of mass with an accuracy better than 100 μm as demonstrated in the GRACE mission. Assuming a sufficiently rigid structure between the antennas and the accelerometer, its data can participate to reach the mission objective of 1 mm precision for the TRF position.

  13. Marine Geoid Undulation Assessment Over South China Sea Using Global Geopotential Models and Airborne Gravity Data

    Science.gov (United States)

    Yazid, N. M.; Din, A. H. M.; Omar, K. M.; Som, Z. A. M.; Omar, A. H.; Yahaya, N. A. Z.; Tugi, A.

    2016-09-01

    Gl