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Sample records for cassini radar experiment

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

    OpenAIRE

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

    2003-01-01

    International audience Simulations of Titan's atmospheric transmission and surface reflectivity have been developed in order to estimate how Titan's atmosphere and surface properties could affect performances of the Cassini radar experiment. In this paper we present a selection of models for Titan's haze, vertical rain distribution, and surface composition implemented in our simulations. We collected dielectric constant values for the Cassini radar wavelength ($\\sim 2.2$ cm) for materials ...

  2. Ground Processing of Cassini RADAR Imagery of Titan

    OpenAIRE

    Stiles, Bryan W.; Gim, Yonggyu; Hamilton, Gary; Hensley, Scott; Johnson, William T. K.; Shimada, Joanne; West, Richard D.; Callahan, Phil

    2006-01-01

    The Cassini RADAR instrument onboard the Cassini Orbiter is currently collecting SAR Imagery of the surface of Saturn's largest moon, Titan. This paper describes the ground processing of Cassini SAR data. We focus upon the unusual features of the data and how these features impact the processing. We exhibit a data dependent mechanism we have implemented for eliminating artifacts due to attitude and ephemeris knowledge error. Finally we describe how we trade-off SAR ...

  3. Constraints on Titan rotation from Cassini radar

    Science.gov (United States)

    Bills, B. G.; Stiles, B. W.; Kirk, R. L.

    2014-12-01

    We give an update on efforts to model the rotation of Titan, subject to constraints from Cassini radar observations. The data we are currently using includes 670 tie-points, each of which is a pair of inertial positions of a single surface point, relative to the center of mass of Titan, and the corresponding pair of observation times. The positional accuracy is of order 1 km, in each Cartesian component. A reasonably good fit to the observations is obtained with a simple model which has a fixed spin pole and a rotation rate which is a sum of a constant value and a single sinusoidal oscillation. A better fit is obtained if we insist that Titan should behave as a synchronous rotator, in the dynamical sense of keeping its axis of least inertia oriented toward Saturn. At the level of accuracy required to fit the Cassini radar data, synchronous rotation is notably different than having a uniform rate of rotation. In this case, we need to model time variations in the orbital mean longitude, which is the longitude of periapse, plus the mean anomaly. That angle varies on a wide range of times scales, including Titan's periapse precession period (703 years), Saturn's heliocentric orbital period (29.47 years), perturbations from relatively large satellites Iapetus (79.3 days), and a 4:3 mean motion resonant interaction with Hyperion (640 and 6850 days), and a linear increase at Titan's mean orbital period (15.9455 day). Our rotation model for Titan has 4 free parameters. Two of them specify the orientation of the fixed spin pole, and the other two are the effective free libration period and viscous damping time. Our dynamical model includes a damped forced longitudinal libration, in which gravitational torques attempt to align the axis of least inertia with the instantaneous direction to Saturn. For a rigid tri-axial body, with Titan's moments of inertia, the free oscillation period for longitudinal librations would be 850 days. For a decoupled elastic shell, the effective

  4. Mountains on Titan observed by Cassini Radar

    Science.gov (United States)

    Radebaugh, J.; Lorenz, R.D.; Kirk, R.L.; Lunine, J.I.; Stofan, E.R.; Lopes, R.M.C.; Wall, S.D.

    2007-01-01

    The Cassini Titan Radar mapper has observed elevated blocks and ridge-forming block chains on Saturn's moon Titan demonstrating high topography we term "mountains." Summit flanks measured from the T3 (February 2005) and T8 (October 2005) flybys have a mean maximum slope of 37?? and total elevations up to 1930 m as derived from a shape-from-shading model corrected for the probable effects of image resolution. Mountain peak morphologies and surrounding, diffuse blankets give evidence that erosion has acted upon these features, perhaps in the form of fluvial runoff. Possible formation mechanisms for these mountains include crustal compressional tectonism and upthrusting of blocks, extensional tectonism and formation of horst-and-graben, deposition as blocks of impact ejecta, or dissection and erosion of a preexisting layer of material. All above processes may be at work, given the diversity of geology evident across Titan's surface. Comparisons of mountain and blanket volumes and erosion rate estimates for Titan provide a typical mountain age as young as 20-100 million years. ?? 2007 Elsevier Inc. All rights reserved.

  5. The First Year of Cassini RADAR Observations of Titan

    Science.gov (United States)

    Elachi, C.; Lorenz, R. D.

    2005-12-01

    Titan`s atmosphere is essentially transparent to Radar, making it an ideal technique to study Titan`s surface. Cassini`s Titan Radar Mapper operates as a passive radiometer, scatterometer, altimeter, and synthetic aperture radar (SAR). Here we review data from four fly-bys in the first year of Cassini`s tour (Ta: October 2004, T3: February 2005, T7: September 2005, and T8: October 2005.) Early SAR images from Ta and T3 (showing Cat scratches`, arrays of linear dark features seem most likely to be Aeolian. Radar provides unique topographic information on Titan`s landscape e.g. the depth of the 80km crater observed in T3 can be geometrically determined to be around 1300m deep. Despite the shallow large-scale slopes indicated in altimetry to date, many small hills are seen in T3. Scatterometry and radiometry maps provide large-scale classification of surface types and polarization and incidence angle coverage being assembled will constrain dielectric and scattering properties of the surface. Judging from the TA/T3 diversity, we expect further variations in the types and distribution of surface materials and geologic features in T7, which spans a wide range of Southern latitudes. T8 SAR will cover a near-equatorial dark region, including the landing site of the Huygens probe.

  6. An Overview of Cassini Radar Mapper Observations of Titan

    Science.gov (United States)

    Wall, S.; Elachi, C.; Cassini RADAR Science Team

    2005-08-01

    The CassiniRadar Mapper imaged the surface of TItan in Ku-band (wavelength = 2.17 cm) on February 14, 2005, more than doubling the coverage obtained in October 2004. The new (T3) flyby collected a 420-km long synthetic-aperture radar (SAR) swath, varying in width from 200 to 500km, and larger-scale radiometry and scatterometry. Data from both passes show that fluvial, impact and volcanic processes are clearly all at work. Evidence will be presented and discussed for each, including a large (440km) impact basin, a smaller (80km) crater with an ejecta blanket, a volcanic construct with flows, and a set of SAR-bright braided and sinuous drainage channels. Recurring patches of subparallel SAR-dark linear features, dubbed ``cat scratches", are tentatively identified as aeolian. A greater diversity of landforms was observed on the T3 flyby than on the previous (Ta) pass. Based on the small number of impact craters detected, the surface thus far imaged by radar is very young compared with those of other Saturnian satellites. The Cassini Project is a joint endeavor of the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA), and the Italian Space Agency (ASI). Cassini is managed by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.

  7. Dunes on Titan observed by Cassini Radar

    Science.gov (United States)

    Radebaugh, J.; Lorenz, R.D.; Lunine, J.I.; Wall, S.D.; Boubin, G.; Reffet, E.; Kirk, R.L.; Lopes, R.M.; Stofan, E.R.; Soderblom, L.; Allison, M.; Janssen, M.; Paillou, P.; Callahan, P.; Spencer, C.; The Cassini Radar Team

    2008-01-01

    Thousands of longitudinal dunes have recently been discovered by the Titan Radar Mapper on the surface of Titan. These are found mainly within ??30?? of the equator in optically-, near-infrared-, and radar-dark regions, indicating a strong proportion of organics, and cover well over 5% of Titan's surface. Their longitudinal duneform, interactions with topography, and correlation with other aeolian forms indicate a single, dominant wind direction aligned with the dune axis plus lesser, off-axis or seasonally alternating winds. Global compilations of dune orientations reveal the mean wind direction is dominantly eastwards, with regional and local variations where winds are diverted around topographically high features, such as mountain blocks or broad landforms. Global winds may carry sediments from high latitude regions to equatorial regions, where relatively drier conditions prevail, and the particles are reworked into dunes, perhaps on timescales of thousands to tens of thousands of years. On Titan, adequate sediment supply, sufficient wind, and the absence of sediment carriage and trapping by fluids are the dominant factors in the presence of dunes. ?? 2007 Elsevier Inc. All rights reserved.

  8. The tectonics of Titan: Global structural mapping from Cassini RADAR

    Science.gov (United States)

    Liu, Zac Yung-Chun; Radebaugh, Jani; Harris, Ron A.; Christiansen, Eric H.; Neish, Catherine D.; Kirk, Randolph L.; Lorenz, Ralph D.

    2016-05-01

    The Cassini RADAR mapper has imaged elevated mountain ridge belts on Titan with a linear-to-arcuate morphology indicative of a tectonic origin. Systematic geomorphologic mapping of the ridges in Synthetic Aperture RADAR (SAR) images reveals that the orientation of ridges is globally E-W and the ridges are more common near the equator than the poles. Comparison with a global topographic map reveals the equatorial ridges are found to lie preferentially at higher-than-average elevations. We conclude the most reasonable formation scenario for Titan's ridges is that contractional tectonism built the ridges and thickened the icy lithosphere near the equator, causing regional uplift. The combination of global and regional tectonic events, likely contractional in nature, followed by erosion, aeolian activity, and enhanced sedimentation at mid-to-high latitudes, would have led to regional infilling and perhaps covering of some mountain features, thus shaping Titan's tectonic landforms and surface morphology into what we see today.

  9. Cassini RADAR at Titan : Latest Results through T65

    Science.gov (United States)

    Lorenz, Ralph D.; T. H. E. Cassini-Radar-Team

    2010-05-01

    The Cassini RADAR investigation continues to yield novel insights into the surface of Titan. T64 (December 2009) acquired SAR over Ligeia Mare and other north polar terrain : these recent data are being studied to search for changes since this area was observed in 2007. The T64 image indicates a class of terrain features not seen widely before. T65 (acquired but not yet processed at the abstract deadline) features new observations of Ontario Lacus, where seasonal changes have already been hinted at in comparisons between radar observations (T57,T58) in summer 2009 and earlier optical observations. Accumulating topography data (notably T55-T61, considerably enhancing the coverage of the deep southern hemisphere) also enables new insights, for example into Titan's hypsogram, which will be compared with other bodies. The hypsogram is remarkably narrow compared with the terrestrial planets. It is unimodal overall, although the possibility of local bimodality will be explored.

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

    Science.gov (United States)

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

    2015-05-01

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

  11. Fluvial channels on Titan: Initial Cassini RADAR observations

    Science.gov (United States)

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

    2008-01-01

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

  12. 10 years of observation of Titan's lakes with the Cassini RADAR Radiometer

    OpenAIRE

    Le Gall, Alice; Janssen, Michael A.; Veyssière, Gaëlle; Encrenaz, Pierre; Lunine, Jonathan I.; Hayes, Alexander G.; Lorenz, Ralph D.

    2014-01-01

    International audience Since 2004, the Cassini RADAR Mapper has been exploring at a wavelength of 2.2-cm Saturn's moon Titan, the only planetary body besides Earth whose surface presently exhibits significant accumulations of liquids in the forms of lakes and seas. In its passive, or radiometry; mode of operation, the Cassini RADAR Radiometer measures the microwave thermal emission from the surface. Doing so, it provides unique insight into properties such as physical temperature, overall ...

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

    Science.gov (United States)

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

    2008-01-01

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

  14. Cassini Solstice Mission Maneuver Experience: Year One

    Science.gov (United States)

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

    2011-01-01

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

  15. Cassini Solstice Mission Maneuver Experience: Year Three

    Science.gov (United States)

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

    2013-01-01

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

  16. Cassini Solstice Mission Maneuver Experience: Year Two

    Science.gov (United States)

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

    2012-01-01

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

  17. Titan's surface from the Cassini RADAR radiometry data during SAR mode

    Science.gov (United States)

    Paganelli, F.; Janssen, M.A.; Lopes, R.M.; Stofan, E.; Wall, S.D.; Lorenz, R.D.; Lunine, J.I.; Kirk, R.L.; Roth, L.; Elachi, C.

    2008-01-01

    We present initial results on the calibration and interpretation of the high-resolution radiometry data acquired during the Synthetic Aperture Radar (SAR) mode (SAR-radiometry) of the Cassini Radar Mapper during its first five flybys of Saturn's moon Titan. We construct maps of the brightness temperature at the 2-cm wavelength coincident with SAR swath imaging. A preliminary radiometry calibration shows that brightness temperature in these maps varies from 64 to 89 K. Surface features and physical properties derived from the SAR-radiometry maps and SAR imaging are strongly correlated; in general, we find that surface features with high radar reflectivity are associated with radiometrically cold regions, while surface features with low radar reflectivity correlate with radiometrically warm regions. We examined scatterplots of the normalized radar cross-section ??0 versus brightness temperature, outlining signatures that characterize various terrains and surface features. The results indicate that volume scattering is important in many areas of Titan's surface, particularly Xanadu, while other areas exhibit complex brightness temperature variations consistent with variable slopes or surface material and compositional properties. ?? 2007.

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

    Science.gov (United States)

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

    2016-04-01

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

  19. Titan's surface from Cassini RADAR SAR and high resolution radiometry data of the first five flybys

    Science.gov (United States)

    Paganelli, F.; Janssen, M.A.; Stiles, B.; West, R.; Lorenz, R.D.; Lunine, J.I.; Wall, S.D.; Callahan, P.; Lopes, R.M.; Stofan, E.; Kirk, R.L.; Johnson, W.T.K.; Roth, L.; Elachi, C.; The Radar Team

    2007-01-01

    The first five Titan flybys with Cassini's Synthetic Aperture RADAR (SAR) and radiometer are examined with emphasis on the calibration and interpretation of the high-resolution radiometry data acquired during the SAR mode (SAR-radiometry). Maps of the 2-cm wavelength brightness temperature are obtained coincident with the SAR swath imaging, with spatial resolution approaching 6 km. A preliminary calibration shows that brightness temperature in these maps varies from 64 to 89 K. Surface features and physical properties derived from the SAR-radiometry maps and SAR imaging are strongly correlated; in general, we find that surface features with high radar reflectivity are associated with radiometrically cold regions, while surface features with low radar reflectivity correlate with radiometrically warm regions. We examined scatterplots of the normalized radar cross-section ??0 versus brightness temperature, finding differing signatures that characterize various terrains and surface features. Implications for the physical and compositional properties of these features are discussed. The results indicate that volume scattering is important in many areas of Titan's surface, particularly Xanadu, while other areas exhibit complex brightness temperature variations consistent with variable slopes or surface material and compositional properties. ?? 2007 Elsevier Inc.

  20. Cassini Scientist for a Day: a tactile experience

    Science.gov (United States)

    Canas, L.; Altobelli, N.

    2012-09-01

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

  1. RADAR performance experiments

    Science.gov (United States)

    Leroux, C.; Bertin, F.; Mounir, H.

    1991-01-01

    Theoretical studies and experimental results obtained at Coulommiers airport showed the capability of Proust radar to detect wind shears, in clear air condition as well as in presence of clouds or rain. Several examples are presented: in a blocking highs situation an atmospheric wave system at the Brunt-Vaisala frequency can be clearly distinguished; in a situation of clouds without rain the limit between clear air and clouds can be easily seen; and a windshear associated with a gust front in rainy conditions is shown. A comparison of 30 cm clear air radar Proust and 5 cm weather Doppler radar Ronsard will allow to select the best candidate for wind shear detection, taking into account the low sensibility to ground clutter of Ronsard radar.

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

    Science.gov (United States)

    Burk, Thomas A.

    2012-01-01

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

  3. Mapping and interpretation of Sinlap crater on Titan using Cassini VIMS and RADAR data

    Science.gov (United States)

    Le, Mouelic S.; Paillou, P.; Janssen, M.A.; Barnes, J.W.; Rodriguez, S.; Sotin, C.; Brown, R.H.; Baines, K.H.; Buratti, B.J.; Clark, R.N.; Crapeau, M.; Encrenaz, P.J.; Jaumann, R.; Geudtner, D.; Paganelli, F.; Soderblom, L.; Tobie, G.; Wall, S.

    2008-01-01

    Only a few impact craters have been unambiguously detected on Titan by the Cassini-Huygens mission. Among these, Sinlap is the only one that has been observed both by the RADAR and VIMS instruments. This paper describes observations at centimeter and infrared wavelengths which provide complementary information about the composition, topography, and surface roughness. Several units appear in VIMS false color composites of band ratios in the Sinlap area, suggesting compositional heterogeneities. A bright pixel possibly related to a central peak does not show significant spectral variations, indicating either that the impact site was vertically homogeneous, or that this area has been recovered by homogeneous deposits. Both VIMS ratio images and dielectric constant measurements suggest the presence of an area enriched in water ice around the main ejecta blanket. Since the Ku-band SAR may see subsurface structures at the meter scale, the difference between infrared and SAR observations can be explained by the presence of a thin layer transparent to the radar. An analogy with terrestrial craters in Libya supports this interpretation. Finally, a tentative model describes the geological history of this area prior, during, and after the impact. It involves mainly the creation of ballistic ejecta and an expanding plume of vapor triggered by the impact, followed by the redeposition of icy spherules recondensed from this vapor plume blown downwind. Subsequent evolution is then driven by erosional processes and aeolian deposition. Copyright 2008 by the American Geophysical Union.

  4. Cryovolcanic features on Titan's surface as revealed by the Cassini Titan Radar Mapper

    Science.gov (United States)

    Lopes, R.M.C.; Mitchell, K.L.; Stofan, E.R.; Lunine, J.I.; Lorenz, R.; Paganelli, F.; Kirk, R.L.; Wood, C.A.; Wall, S.D.; Robshaw, L.E.; Fortes, A.D.; Neish, C.D.; Radebaugh, J.; Reffet, E.; Ostro, S.J.; Elachi, C.; Allison, M.D.; Anderson, Y.; Boehmer, R.; Boubin, G.; Callahan, P.; Encrenaz, P.; Flamini, E.; Francescetti, G.; Gim, Y.; Hamilton, G.; Hensley, S.; Janssen, M.A.; Johnson, W.T.K.; Kelleher, K.; Muhleman, D.O.; Ori, G.; Orosei, R.; Picardi, G.; Posa, F.; Roth, L.E.; Seu, R.; Shaffer, S.; Soderblom, L.A.; Stiles, B.; Vetrella, S.; West, R.D.; Wye, L.; Zebker, H.A.

    2007-01-01

    The Cassini Titan Radar Mapper obtained Synthetic Aperture Radar images of Titan's surface during four fly-bys during the mission's first year. These images show that Titan's surface is very complex geologically, showing evidence of major planetary geologic processes, including cryovolcanism. This paper discusses the variety of cryovolcanic features identified from SAR images, their possible origin, and their geologic context. The features which we identify as cryovolcanic in origin include a large (180 km diameter) volcanic construct (dome or shield), several extensive flows, and three calderas which appear to be the source of flows. The composition of the cryomagma on Titan is still unknown, but constraints on rheological properties can be estimated using flow thickness. Rheological properties of one flow were estimated and appear inconsistent with ammonia-water slurries, and possibly more consistent with ammonia-water-methanol slurries. The extent of cryovolcanism on Titan is still not known, as only a small fraction of the surface has been imaged at sufficient resolution. Energetic considerations suggest that cryovolcanism may have been a dominant process in the resurfacing of Titan. ?? 2006 Elsevier Inc.

  5. Modelling the nongravitational acceleration during Cassini's gravitation experiments

    OpenAIRE

    Bertolami, O.; Francisco, F.; Gil, P. J. S.; Páramos, J.

    2014-01-01

    In this paper we present a computation of the thermally generated acceleration of the Cassini probe during its solar conjunction experiment, obtained from a model of the spacecraft. We build a thermal model of the vehicle and perform a Monte Carlo simulation to find a thermal acceleration with a main component of $(3.01 \\pm 0.33) \\times 10^{-9} {\\rm m/s^2}$. This result is in close agreement with the estimates of this effect performed through Doppler data analysis.

  6. Saturns Thermal Emission at 2.2-cm Wavelength as Imaged by the Cassini RADAR Radiometer

    Science.gov (United States)

    Janssen, M. A.; Ingersoll, A. P.; Allison, M. D.; Gulkis, S.; Laraia, A. L.; Baines, K. H.; Edgington, S. G.; Anderson, Y. Z.; Kelleher, K.; Oyafuso, F. A.

    2013-01-01

    We present well-calibrated, high-resolution maps of Saturn's thermal emission at 2.2-cm wavelength obtained by the Cassini RADAR radiometer through the Prime and Equinox Cassini missions, a period covering approximately 6 years. The absolute brightness temperature calibration of 2% achieved is more than twice better than for all previous microwave observations reported for Saturn, and the spatial resolution and sensitivity achieved each represent nearly an order of magnitude improvement. The brightness temperature of Saturn in the microwave region depends on the distribution of ammonia, which our radiative transfer modeling shows is the only significant source of absorption in Saturn's atmosphere at 2.2-cm wavelength. At this wavelength the thermal emission comes from just below and within the ammonia cloud-forming region, and yields information about atmospheric circulations and ammonia cloud-forming processes. The maps are presented as residuals compared to a fully saturated model atmosphere in hydrostatic equilibrium. Bright regions in these maps are readily interpreted as due to depletion of ammonia vapor in, and, for very bright regions, below the ammonia saturation region. Features seen include the following: a narrow equatorial band near full saturation surrounded by bands out to about 10deg planetographic latitude that demonstrate highly variable ammonia depletion in longitude; narrow bands of depletion at -35deg latitude; occasional large oval features with depleted ammonia around -45deg latitude; and the 2010-2011 storm, with extensive saturated and depleted areas as it stretched halfway around the planet in the northern hemisphere. Comparison of the maps over time indicates a high degree of stability outside a few latitudes that contain active regions.

  7. Compositional and spatial variations in Titan dune and interdune regions from Cassini VIMS and RADAR

    Science.gov (United States)

    Bonnefoy, Léa E.; Hayes, Alexander G.; Hayne, Paul O.; Malaska, Michael J.; Le Gall, Alice; Solomonidou, Anezina; Lucas, Antoine

    2016-05-01

    Dunes cover about 15 % of Titan's visible surface, and represent one of the largest reservoirs of hydrocarbon solids on Titan (Rodriguez, S. et al. [2014]. Icarus 230, 168-179; Lopes, R.M.C. et al. [2016]. Icarus 270, 162-182.). Herein, we use data from the Cassini spacecraft to derive constraints on the compositional and regional variability of Titan's dune and interdune regions by combining spectral information from the Visual and Infrared Mapping Spectrometer (VIMS) and spatial information from Synthetic Aperture RADAR (SAR) data. Using the combined datasets, we extract pure infrared spectra of dune and interdune regions by extrapolating linear correlations between VIMS reflectance and dune area fraction calculated in each VIMS footprint from SAR images. We applied the same method using the Cassini RADAR Radiometer dataset to extract the microwave surface emissivity of the dune and interdune regions. Globally the dune spectra show little variation, but we find that the interdune spectra exhibit several different behaviors. Similarly, we extract from passive radiometry a mean dune emissivity of 0.98 ± 0.01, while interdune emissivity varies from 0.86 to 0.98. We find that the interdune regions are often spectrally similar to other Titan terrain units, namely Caladan Planitia, the Adiri Mountains, and Sinlap crater, while the dunes are spectrally distinct from all terrain units. Around Sinlap crater, the interdune regions correspond to the dark blue VIMS unit: the dunes could be forming on top of the ejecta, or the material corresponding to the blue unit could be depositing preferentially in the interdunes areas. There was one region in the Belet sand sea where we were unable to extract the dune and interdune spectra and emissivities in spite of high-quality data, which we interpret to result from a thick sand cover in the interdune regions, implying inactive or saturated dune fields. However, the fact that we were able to extract distinct dune and interdune

  8. Geologic Features on Titan's Surface as Revealed by the Cassini Titan Radar Mapper

    Science.gov (United States)

    Lopes, R. M.; Stofan, E.; Elachi, C.; Kirk, R.; Lorenz, R.; Lunine, J.; Mitchell, K. L.; Ori, G. G.; Paganelli, F.; Soderblom, L.; Wall, S.; Wood, C.

    2005-12-01

    The Cassini Titan Radar Mapper is one of the prime investigations to explore Titan's surface from orbit. Because of its almost opaque atmosphere, microwave remote sensing contributes uniquely to that investigation. The Titan Radar Mapper operates as a passive radiometer, scatterometer, altimeter, and synthetic aperture radar (SAR). We review the diversity of geologic features revealed using SAR during four fly-bys (Ta: October 2004, T3: February 2005, T7: September 2005, and T8: October 2005) and their context. Early SAR images from Ta and T3 reveal that Titan is very geologically complex (see Elachi et al., 2005, Science 13, 970-4). A variety of landforms and surface units were characterized morphologically and mapped, based on brightness variations, general planform shape and texture. Significant differences were seen in the geology between the Ta swath (centered at ~ 50N, 80W) and the T3 swath (centered at ~ 30N, 70W). The units in the Ta swath appear relatively young and no impact craters could be unambiguously identified. A variety of features which we argue to be cryovolcanic in origin were seen, including extensive flows, paterae, and a circular feature (Ganesa Macula) interpreted as a volcanic dome. We interpret radar-bright braided and sinuous channels and associated deposits to be fluvial in origin. Five distinct units were mapped in Ta, including a dark mottled unit that may represent the presence of surface liquids. The T3 swath displayed many of the same units seen in Ta, except for cryovolcanic features which are absent or indistinct. Among the new features in T3 are a large impact (440 km diameter) basin, a smaller (80 km diameter) crater, and dark lineated streaks, nicknamed "cat scratches" that are thought to be aeolian in origin. The dominant unit in T3 is a bright mottled unit that may contain ubiquitous small (less than 10 km across) topographic features. Groups of material that appear to be hills are more common in the T3 data than Ta. Based on

  9. Disribution and interplay of geologic processes on Titan from Cassini radar data

    Science.gov (United States)

    Lopes, R.M.C.; Stofan, E.R.; Peckyno, R.; Radebaugh, J.; Mitchell, K.L.; Mitri, G.; Wood, C.A.; Kirk, R.L.; Wall, S.D.; Lunine, J.I.; Hayes, A.; Lorenz, R.; Farr, Tom; Wye, L.; Craig, J.; Ollerenshaw, R.J.; Janssen, M.; LeGall, A.; Paganelli, F.; West, R.; Stiles, B.; Callahan, P.; Anderson, Y.; Valora, P.; Soderblom, L.

    2010-01-01

    The Cassini Titan Radar Mapper is providing an unprecedented view of Titan's surface geology. Here we use Synthetic Aperture Radar (SAR) image swaths (Ta-T30) obtained from October 2004 to December 2007 to infer the geologic processes that have shaped Titan's surface. These SAR swaths cover about 20% of the surface, at a spatial resolution ranging from ~350 m to ~2 km. The SAR data are distributed over a wide latitudinal and longitudinal range, enabling some conclusions to be drawn about the global distribution of processes. They reveal a geologically complex surface that has been modified by all the major geologic processes seen on Earth - volcanism, tectonism, impact cratering, and erosion and deposition by fluvial and aeolian activity. In this paper, we map geomorphological units from SAR data and analyze their areal distribution and relative ages of modification in order to infer the geologic evolution of Titan's surface. We find that dunes and hummocky and mountainous terrains are more widespread than lakes, putative cryovolcanic features, mottled plains, and craters and crateriform structures that may be due to impact. Undifferentiated plains are the largest areal unit; their origin is uncertain. In terms of latitudinal distribution, dunes and hummocky and mountainous terrains are located mostly at low latitudes (less than 30 degrees), with no dunes being present above 60 degrees. Channels formed by fluvial activity are present at all latitudes, but lakes are at high latitudes only. Crateriform structures that may have been formed by impact appear to be uniformly distributed with latitude, but the well-preserved impact craters are all located at low latitudes, possibly indicating that more resurfacing has occurred at higher latitudes. Cryovolcanic features are not ubiquitous, and are mostly located between 30 degrees and 60 degrees north. We examine temporal relationships between units wherever possible, and conclude that aeolian and fluvial

  10. Distribution and interplay of geologic processes on Titan from Cassini radar data

    Science.gov (United States)

    Lopes, R.M.C.; Stofan, E.R.; Peckyno, R.; Radebaugh, J.; Mitchell, K.L.; Mitri, G.; Wood, C.A.; Kirk, R.L.; Wall, S.D.; Lunine, J.I.; Hayes, A.; Lorenz, R.; Farr, Tom; Wye, L.; Craig, J.; Ollerenshaw, R.J.; Janssen, M.; LeGall, A.; Paganelli, F.; West, R.; Stiles, B.; Callahan, P.; Anderson, Y.; Valora, P.; Soderblom, L.

    2010-01-01

    The Cassini Titan Radar Mapper is providing an unprecedented view of Titan's surface geology. Here we use Synthetic Aperture Radar (SAR) image swaths (Ta-T30) obtained from October 2004 to December 2007 to infer the geologic processes that have shaped Titan's surface. These SAR swaths cover about 20% of the surface, at a spatial resolution ranging from ???350 m to ???2 km. The SAR data are distributed over a wide latitudinal and longitudinal range, enabling some conclusions to be drawn about the global distribution of processes. They reveal a geologically complex surface that has been modified by all the major geologic processes seen on Earth - volcanism, tectonism, impact cratering, and erosion and deposition by fluvial and aeolian activity. In this paper, we map geomorphological units from SAR data and analyze their areal distribution and relative ages of modification in order to infer the geologic evolution of Titan's surface. We find that dunes and hummocky and mountainous terrains are more widespread than lakes, putative cryovolcanic features, mottled plains, and craters and crateriform structures that may be due to impact. Undifferentiated plains are the largest areal unit; their origin is uncertain. In terms of latitudinal distribution, dunes and hummocky and mountainous terrains are located mostly at low latitudes (less than 30??), with no dunes being present above 60??. Channels formed by fluvial activity are present at all latitudes, but lakes are at high latitudes only. Crateriform structures that may have been formed by impact appear to be uniformly distributed with latitude, but the well-preserved impact craters are all located at low latitudes, possibly indicating that more resurfacing has occurred at higher latitudes. Cryovolcanic features are not ubiquitous, and are mostly located between 30?? and 60?? north. We examine temporal relationships between units wherever possible, and conclude that aeolian and fluvial/pluvial/lacustrine processes are the

  11. Cassini RADAR observations of Ligeia Mare : Radiometric Properties and Stereo Topography

    Science.gov (United States)

    Lorenz, Ralph; Kirk, R.; Stofan, E.; Lunine, J.; Hayes, A.; Stiles, B.; Mitchell, K.; Le Gall, A.; Zebker, H.; Wye, L.; Encrenaz, P.; Aharonson, O.; Lucas, A.; Janssen, M.; Notarnicola, C.; Casarano, D.; Ventura, B.; Cassini RADAR Team

    2012-10-01

    Ligeia Mare is the best-mapped of Titan’s three seas, and has attracted particular interest as the target of the proposed TiME (Titan Mare Explorer) mission. Here we summarize radar observations of this 400km wide feature and its environs from Cassini flybys T25, T28, T29 and T65. As noted in studies of Ontario Lacus (Hayes ref), radar reflectivity can be used with assumptions to assess liquid depth in shallow areas. Most of Ligeia is well below the noise floor of our observations (which varies across the scene - we use the most sensitive central beam where available to pose the tightest sigma-0 constraint) indicating depths likely > 10m, although we delineate some possibly shallow margins to aid in future modeling of tidal currents. In addition, the brightness temperature measured by passive radiometry (Janssen et al., 2009) places a joint constraint on the surface temperature and the emissivity, suggesting an upper limit of 10% on suspended solid material. Combination of SAR imaging from the flybys permits construction of a stereo Digital Elevation Model. This stereo topography is compared with SARtopo measurements and shows a number of 1km high mountains in the surrounding terrain: the peaks of these mountains would be above the horizon as seen from much of Ligeia. The model also places constraints on the watershed of Ligeia and thus on the hydrological balance of precipitation and evaporation. We will also report on further observations of Ligeia planned in the T86 flyby, shortly before the DPS meeting.

  12. Titan’s mid-latitude surface regions with Cassini VIMS and RADAR

    Science.gov (United States)

    Solomonidou, Anezina; Lopes, Rosaly M. C.; Coustenis, Athena; Malaska, Michael; Rodriguez, Sebastien; Maltagliati, Luca; Drossart, Pierre; Janssen, Michael; Lawrence, Kenneth; Jaumann, Ralf; Sohl, Frank; Stephan, Katrin; Brown, Robert H.; Bratsolis, Emmanuel; Matsoukas, Christos

    2015-11-01

    The Cassini-Huygens mission instruments have revealed Titan to have a complex and dynamic atmosphere and surface. Data from the remote sensing instruments have shown the presence of diverse surface terrains in terms of morphology and composition, suggesting both exogenic and endogenic processes [1]. We define both the surface and atmospheric contributions in the VIMS spectro-imaging data by use of a radiative transfer code in the near-IR range [2]. To complement this dataset, the Cassini RADAR instrument provides additional information on the surface morphology, from which valuable geological interpretations can be obtained [3]. We examine the origin of key Titan terrains, covering the mid-latitude zones extending from 50ºN to 50ºS. The different geological terrains we investigate include: mountains, plains, labyrinths, craters, dune fields, and possible cryovolcanic and/or evaporite features. We have found that the labyrinth terrains and the undifferentiated plains seem to consist of a very similar if not the same material, while the different types of plains show compositional variations [3]. The processes most likely linked to their formation are aeolian, fluvial, sedimentary, lacustrine, in addition to the deposition of atmospheric products though the process of photolysis and sedimentation of organics. We show that temporal variations of surface albedo exist for two of the candidate cryovolcanic regions. The surface albedo variations together with the presence of volcanic-like morphological features suggest that the active regions are possibly related to the deep interior, possibly via cryovolcanism processes (with important implications for the satellite’s astrobiological potential) as also indicated by new interior structure models of Titan and corresponding calculations of the spatial pattern of maximum tidal stresses [4]. However, an explanation attributed to exogenic processes is also possible [5]. We will report on results from our most recent

  13. Constrains on the nature of Titan's surface from Cassini/VIMS and RADAR

    Science.gov (United States)

    Solomonidou, Anezina; Coustenis, Athena; Lopes, Rosaly; Rodriguez, Sebastien; Drossart, Pierre; Schmitt, Bernard; Philippe, Sylvain; Malaska, Michael; Janssen, Michael; Maltagliati, Luca; Lawrence, Kenneth; Jaumann, Ralf; Sohl, Frank; Stephan, Katrin; Brown, Robert; Bratsolis, Emannuel; Matsoukas, Christos

    2016-04-01

    Cassini remote-sensing instruments for more than 10 years now and in situ by the Huygens instruments back in 2005. For the surface, the presence of diverse terrains in terms of morphology and composition suggest both exogenic and endogenic processes to be at play. In this study, we investigate the surface and atmospheric contributions from the Visual and Infrared Mapping Spectrometer (VIMS) spectro-imaging data by use of a radiative transfer code in the near-IR range and the RADAR/SAR data for the distinction of geomorphological units. We focus here on those units identified in Lopes et al. (2010, 2015) [1; 2] and Malaska et al. (2015) [3]: mountains, plains, labyrinths, dune fields, and the areas previously suggested to have experienced change such as the possible cryovolcanic and evaporite features (Barnes et al. 2013; Solomonidou et al. 2014; 2015) [4; 5; 6]. With the use of a recently updated radiative transfer code, we evaluate the atmospheric contribution and extract the pure surface albedo information for each region of interest. The extracted albedo shapes and values are then tested against spectra of constituents that are considered to be the best Titan candidate materials, including a very recent library of Titan ice spectra [7]. We find that many of the units show compositional variations while units of significant geomorphological differences seem to consist of very similar materials, which help us provide implications on their endogenic or exogenic origin. Preliminary results on the chemical composition of the regions that have shown temporal changes are also presented. References: [1] Lopes, R.M.C., et al.: Icarus, 205, 540-558, 2010; [2] Lopes, R.M.C., et al.: Icarus, in press; [3] Malaska, M., et al. : Icarus, submitted; [4] Barnes, J., et al.: Planetary Science, 2:1, 2013; [5] Solomonidou, A., et al.: JGR, 119, 1729-1747, 2014; [6] Solomonidou, A., et al.: Icarus, in press; [7] Schmitt, B., et al.: GhoSST datacase (ghosst.osug.fr).

  14. The geology of Hotei Regio, Titan: Correlation of Cassini VIMS and RADAR

    Science.gov (United States)

    Soderblom, L.A.; Brown, R.H.; Soderblom, J.M.; Barnes, J.W.; Kirk, R.L.; Sotin, C.; Jaumann, R.; MacKinnon, D.J.; Mackowski, D.W.; Baines, K.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.

    2009-01-01

    Joint Cassini VIMS and RADAR SAR data of ???700-km-wide Hotei Regio reveal a rich collection of geological features that correlate between the two sets of images. The degree of correlation is greater than anywhere else seen on Titan. Central to Hotei Regio is a basin filled with cryovolcanic flows that are anomalously bright in VIMS data (in particular at 5 ??m) and quite variable in roughness in SAR. The edges of the flows are dark in SAR data and appear to overrun a VIMS-bright substrate. SAR-stereo topography shows the flows to be viscous, 100-200 m thick. On its southern edge the basin is ringed by higher (???1 km) mountainous terrain. The mountains show mixed texture in SAR data: some regions are extremely rough, exhibit low and spectrally neutral albedo in VIMS data and may be partly coated with darker hydrocarbons. Around the southern margin of Hotei Regio, the SAR image shows several large, dendritic, radar-bright channels that flow down from the mountainous terrain and terminate in dark blue patches, seen in VIMS images, whose infrared color is consistent with enrichment in water ice. The patches are in depressions that we interpret to be filled with fluvial deposits eroded and transported by liquid methane in the channels. In the VIMS images the dark blue patches are encased in a latticework of lighter bands that we suggest to demark a set of circumferential and radial fault systems bounding structural depressions. Conceivably the circular features are tectonic structures that are remnant from an ancient impact structure. We suggest that impact-generated structures may have simply served as zones of weakness; no direct causal connection, such as impact-induced volcanism, is implied. We also speculate that two large dark features lying on the northern margin of Hotei Regio could be calderas. In summary the preservation of such a broad suite of VIMS infrared color variations and the detailed correlation with features in the SAR image and SAR topography

  15. A Three-Dimensional View of Titan's Surface Features from Cassini RADAR Stereogrammetry

    Science.gov (United States)

    Kirk, R. L.; Howington-Kraus, E.; Redding, B. L.; Becker, T. L.; Lee, E. M.; Stiles, B. W.; Hensley, S.; Hayes, A.; Lopes, R. M.; Lorenz, R. D.; Mitchell, K. L.; Radebaugh, J.; Paganelli, F.; Soderblom, L. A.; Stofan, E. R.; Wood, C. A.; Wall, S. D.; Cassini RADAR Team

    2008-12-01

    As of the end of its four-year Prime Mission, Cassini has obtained 300-1500 m resolution synthetic aperture radar images of the surface of Titan during 19 flybys. The elongated image swaths overlap extensively, and ~2% of the surface has now been imaged two or more times. The majority of image pairs have different viewing directions, and thus contain stereo parallax that encodes information about Titan's surface relief over distances of ~1 km and greater. As we have previously reported, the first step toward extracting quantitative topographic information was the development of rigorous "sensor models" that allowed the stereo systems previously used at the USGS and JPL to map Venus with Magellan images to be used for Titan mapping. The second major step toward extensive topomapping of Titan has been the reprocessing of the RADAR images based on an improved model of the satellite's rotation. Whereas the original images (except for a few pairs obtained at similar orbital phase, some of which we have mapped previously) were offset by as much as 30 km, the new versions align much better. The remaining misalignments, typically adjustment of the spacecraft trajectories before mapping, which also ensures that the stereo digital topographic models (DTMs) are made consistent with altimetry and SAR topography profiles. The useful stereo coverage now available includes a much larger portion of Titan's north polar lake country than we previously presented, a continuous traverse of high resolution data from the lakes to mid-southern latitudes, and widely distributed smaller areas. A remaining challenge is that many pairs of images are illuminated from opposite sides or from near-perpendicular directions, which can make image matching more difficult. We find that the high-contrast polarizing display of the stereo workstation at USGS provides a much clearer view of these unfavorably illuminated pairs than (for example) anaglyphs, and lets us supplement automatic image matching

  16. Constraining Depths and Wave Heights for Titan's lakes with Cassini RADAR Data

    Science.gov (United States)

    Wye, L.; Zebker, H. A.; Hayes, A. G.; Lorenz, R. D.; Notarnicola, C.; Ventura, B.; Casarano, D.; Cassini RADAR Team

    2010-12-01

    Hayes et al. (JGR 2010) observed that the Cassini synthetic aperture radar (SAR) imaging magnitudes collected in Titan flybys T57 (22-June-2009) and T58 (8-July-2009) over Titan’s Ontario Lacus vary exponentially with distance from the lake shore, as expected if there is a deepening liquid layer that is attenuating the reflection from a roughened bottom. They deduced near-shore slopes at 13 locations around the lake perimeter. Previously, at the 2010 DPS meeting, we applied a similar model to the real-aperture radar data collected on Titan flyby T65 (12-January-2010) to obtain complete depth profiles across the entire width and length of Ontario Lacus, thereby constraining its maximum depths. The real-aperture reduction provides longer integration times, thus reducing the noise in the data. Consequently, we can detect bottom reflections from greater depths farther out into the lake. This improvement in signal-to-noise comes at the expense of resolution. We assume that the variation in backscatter across the lake is due largely to changes in depth, although changes in the lake bottom roughness or changes in the concentration of suspended scatterers would also affect the perceived backscatter. In this paper, we add the T57 and T58 data to our T65 Ontario Lacus analysis to more completely evaluate the subsurface topography across the lake. The shape of the lakebed may have implications for the lake geology. We also extend the bathymetry model to the northern lakes. While we map the depths of Ontario Lacus to be not much greater than several times the two-way absorption length (1.2 m for the assumed dielectric properties), the subsurface reflection in the northern lakes quickly extinguishes as the radar beam moves away from the shore, suggesting the lake floor to be at much greater depths. Only in Jingpo Lacus and Ligeia Mare do we find detectable subsurface structure away from the shore. Assuming dielectric properties similar to those deduced by Hayes et al. for

  17. Geomorphological significance of Ontario Lacus on Titan: Integrated interpretation of Cassini VIMS, ISS and RADAR data and comparison with the Etosha Pan (Namibia)

    OpenAIRE

    Cornet, T.; Bourgeois, Olivier; Le Mouélic, Stéphane; Rodriguez, S.; Lopez Gonzalez, Téodolina; Tobie, Gabriel; Fleurant, Cyril; Sotin, C.; Barnes, J.W.; Brown, R. H.; Baines, K. H.; Buratti, Bonnie J.; Clark, R. N.; Buratti, B.J.; Nicholson, P. D.

    2012-01-01

    Ontario Lacus is the largest lake of the whole southern hemisphere of Titan, Saturn's major moon. It has been imaged twice by each of the Cassini imaging systems (Imaging Science Subsystem (ISS) in 2004 and 2005, Visual and Infrared Mapping Spectrometer (VIMS) in 2007 and 2009 and Radar in 2009 and 2010). In this study, we take advantage of each imaging dataset to establish a global survey of Ontario Lacus' environment from 2005 to 2010. We perform a geomorphological mapping and interpretatio...

  18. Constraining the physical properties of Titan's empty lake basins using nadir and off-nadir Cassini RADAR backscatter

    Science.gov (United States)

    Michaelides, R. J.; Hayes, A. G.; Mastrogiuseppe, M.; Zebker, H. A.; Farr, T. G.; Malaska, M. J.; Poggiali, V.; Mullen, J. P.

    2016-05-01

    We use repeat synthetic aperture radar (SAR) observations and complementary altimetry passes acquired by the Cassini spacecraft to study the scattering properties of Titan's empty lake basins. The best-fit coefficients from fitting SAR data to a quasi-specular plus diffuse backscatter model suggest that the bright basin floors have a higher dielectric constant, but similar facet-scale rms surface facet slopes, to surrounding terrain. Waveform analysis of altimetry returns reveals that nadir backscatter returns from basin floors are greater than nadir backscatter returns from basin surroundings and have narrower pulse widths. This suggests that floor deposits are structurally distinct from their surroundings, consistent with the interpretation that some of these basins may be filled with evaporitic and/or sedimentary deposits. Basin floor deposits also express a larger diffuse component to their backscatter, which is likely due to variations in subsurface structure or an increase in roughness at the wavelength scale (Hayes, A.G. et al. [2008]. Geophys. Res. Lett. 35, 9). We generate a high-resolution altimetry radargram of the T30 altimetry pass over an empty lake basin, with which we place geometric constraints on the basin's slopes, rim heights, and depth. Finally, the importance of these backscatter observations and geometric measurements for basin formation mechanisms is briefly discussed.

  19. On the two approaches to the data analysis of the Cassini interplanetary relativity experiment

    OpenAIRE

    Kopeikin, Sergei

    2009-01-01

    We compare two theoretical approaches to the data analysis of the Cassini relativity experiment based on the Doppler tracking and the time delay technique that were published correspondingly by Kopeikin et al in Phys. Lett. A 367, 276 (2007) and by Bertotti et al in Class. Quant. Grav. 25, 045013 (2008). Bertotti et al believed that they found a discrepancy with our paper and claimed that our analysis was erroneous. The present paper elucidates, however, that the discrepancy is illusory and d...

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

    Science.gov (United States)

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

    2014-01-01

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

  1. Correlations between Cassini VIMS spectra and RADAR SAR images: Implications for Titan's surface composition and the character of the Huygens Probe Landing Site

    Science.gov (United States)

    Soderblom, L.A.; Kirk, R.L.; Lunine, J.I.; Anderson, J.A.; Baines, K.H.; Barnes, J.W.; Barrett, J.M.; Brown, R.H.; Buratti, B.J.; Clark, R.N.; Cruikshank, D.P.; Elachi, C.; Janssen, M.A.; Jaumann, R.; Karkoschka, E.; Le Mouélic, Stéphane; Lopes, R.M.; Lorenz, R.D.; McCord, T.B.; Nicholson, P.D.; Radebaugh, J.; Rizk, B.; Sotin, C.; Stofan, E.R.; Sucharski, T.L.; Tomasko, M.G.; Wall, S.D.

    2007-01-01

    Titan's vast equatorial fields of RADAR-dark longitudinal dunes seen in Cassini RADAR synthetic aperture images correlate with one of two dark surface units discriminated as "brown" and "blue" in Visible and Infrared Mapping Spectrometer (VIMS) color composites of short-wavelength infrared spectral cubes (RGB as 2.0, 1.6, 1.3 ??m). In such composites bluer materials exhibit higher reflectance at 1.3 ??m and lower at 1.6 and 2.0 ??m. The dark brown unit is highly correlated with the RADAR-dark dunes. The dark brown unit shows less evidence of water ice suggesting that the saltating grains of the dunes are largely composed of hydrocarbons and/or nitriles. In general, the bright units also show less evidence of absorption due to water ice and are inferred to consist of deposits of bright fine precipitating tholin aerosol dust. Some set of chemical/mechanical processes may be converting the bright fine-grained aerosol deposits into the dark saltating hydrocarbon and/or nitrile grains. Alternatively the dark dune materials may be derived from a different type of air aerosol photochemical product than are the bright materials. In our model, both the bright aerosol and dark hydrocarbon dune deposits mantle the VIMS dark blue water ice-rich substrate. We postulate that the bright mantles are effectively invisible (transparent) in RADAR synthetic aperture radar (SAR) images leading to lack of correlation in the RADAR images with optically bright mantling units. RADAR images mostly show only dark dunes and the water ice substrate that varies in roughness, fracturing, and porosity. If the rate of deposition of bright aerosol is 0.001-0.01 ??m/yr, the surface would be coated (to optical instruments) in hundreds-to-thousands of years unless cleansing processes are active. The dark dunes must be mobile on this very short timescale to prevent the accumulation of bright coatings. Huygens landed in a region of the VIMS bright and dark blue materials and about 30 km south of the

  2. Titan's surface at 2.18-cm wavelength imaged by the Cassini RADAR radiometer: Results and interpretations through the first ten years of observation

    Science.gov (United States)

    Janssen, M. A.; Le Gall, A.; Lopes, R. M.; Lorenz, R. D.; Malaska, M. J.; Hayes, A. G.; Neish, C. D.; Solomonidou, A.; Mitchell, K. L.; Radebaugh, J.; Keihm, S. J.; Choukroun, M.; Leyrat, C.; Encrenaz, P. J.; Mastrogiuseppe, M.

    2016-05-01

    A comprehensive calibration and mapping of the thermal microwave emission from Titan's surface is reported based on radiometric data obtained at 2.18-cm wavelength by the passive radiometer included in the Cassini RADAR instrument. Compared to previous work, the present results incorporate the much larger data set obtained in the approximately ten years following Saturn Orbit Insertion. Brightness temperature data including polarization were accumulated by segments in Titan passes from Ta (October 2004) through T98 (February 2014). The observational segments were analyzed to produce a mosaic of effective dielectric constant based on the measurement of thermal polarization covering 76% of the surface, and brightness temperature at normal incidence covering Titan's entire surface. As part of the mosaicking process we also solved for the seasonal variation of physical temperature with latitude, which we found to be smaller by a factor of 0.87 ± 0.05 in relative amplitude compared to that reported in the thermal infrared by Cassini's Composite Infrared Spectrometer (CIRS). We used the equatorial temperature obtained by the Huygens probe and the seasonal dependence with latitude from CIRS to convert the brightness mosaic to absolute emissivity, from which we could infer global thermophysical properties of the surface in combination with the dielectric mosaic. We see strong evidence for subsurface (volume) scattering as a dominant cause of the radar reflectivity in bright regions, and elsewhere a surface composition consistent with the slow deposition and processing of organic compounds from the atmosphere. The presence of water ice in the near subsurface is strongly indicated by the high degree of volume scattering observed in radar-bright regions (e.g., Hummocky/mountainous terrains) constituting ∼10% of Titan's surface. A thermal analysis allowed us to infer a mean 2.18-cm emission depth in the range 40-100 cm for the dominant radar-dark terrains (the remainder of

  3. Looking at some equatorial regions on Titan using Cassini/VIMS and RADAR data: a case for changes in surface properties

    Science.gov (United States)

    Solomonidou, Anezina; Coustenis, Athena; Lopes, Rosaly; Hirtzig, Mathieu; Bratsolis, Emmanuel; Drossart, Pierre; Le Mouélic, Stephane; Rodriguez, Sebastien; Jaumann, Ralf; Stephan, Katrin; Bampasidis, Georgios; Sotin, Christophe; Brown, Robert

    2014-05-01

    Titan, Saturn's largest moon, has a complex, dynamic and -in some aspects- Earth-like atmosphere and surface. Data from the remote sensing instruments on board Cassini, particularly VIMS and the RADAR, have shown the presence of diverse terrains on the surface, suggesting exogenic and endogenic processes [1;2;3]. In this research we focus on some equatorial regions that have been identified as possibly subject to changes, having particular spectral properties and possibly being the strongest cryovolcanic candidate regions, that is: Sotra Patera, Hotei Regio and Tui Regio [1,4,5]. We use VIMS data, to which we apply a state-of-the-art Principal Component Analysis (PCA) and radiative transfer methods [4;7] with updated parameterization for the spectroscopic data and infer the surface albedos of all of these regions, that we interpret in terms of possible surface composition and morphology combining with information from RADAR data. Indeed, by including despeckled SAR images we identify geomorphological units and investigate spatial and temporal geological relationships [6]. This combination provides us with implications on the surface composition of different units. By looking at evolution with time, we find that two of these regions show albedo changes with time, for Tui Regio from 2005-2009 (darkening) and Sotra Patera from 2005-2006 (brightening) at all wavelengths, indicating that dynamical processes control the regions, compatible with their complex morphology. In conclusion, we also associate radiometry and topographic data with the compositional information from VIMS to derive constraints on the chemical composition and the geology of the surface and finally the nature of these regions. References: [1] Lopes, R.M.C., et al.: JGR, 118, 416-435; [2] Solomonidou, A., et al.: PSS, 70, 77-104; [3] Moore, J.M., and Howard, A.D.: GRL, 37, L22205, 2010; [4] Solomonidou, A., et al.: submitted(a); [5] Solomonidou, A., et al.: submitted(b); [6] Bratsolis, E., et al.: PSS

  4. Radar imagery from the 1994 Lock Linnhe ship wake experiment

    Energy Technology Data Exchange (ETDEWEB)

    Mullenhoff, C.J.; Lehman, S.K.; Jones, H. [Lawrence Livermore National Lab., CA (United States)] [and others

    1994-11-15

    The 1994 Loch Linnhe radar ocean imaging trials were held from September 4 through September 17. Two ships were used: the R.V. Colonel Templer, and the RMAS Collie. Thorn EMI, Inc., fielded a dual band, dual polarization radar on a hillside overlooking the loch. A primary purpose of the experiment was to obtain highly visible images of ship generated internal waves. Presented here is imagery for a few of the good ship runs, as well as a study of the environment of the visibility of ship generated internal waves.

  5. SAR Experiments Using a Conformal Antenna Array Radar Demonstrator

    Directory of Open Access Journals (Sweden)

    Peter Knott

    2012-01-01

    Full Text Available Conformal antenna arrays have been studied for several years but only few examples of applications in modern radar or communication systems may be found up to date due to technological difficulties. The objective of the “Electronic Radar with Conformal Array Antenna” (ERAKO demonstrator system which has been developed at the Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR is to demonstrate the feasibility of an active electronically scanned antenna for conformal integration into small and medium sized airborne platforms. For practical trials the antenna has been adapted for operation with the Phased Array Multifunctional Imaging Radar (PAMIR system developed at the institute. The antenna in combination with the PAMIR front-end needed to undergo a special calibration procedure for beam forming and imaging post-processing. The present paper describes the design and development of the conformal antenna array of the demonstrator system, its connection to the PAMIR system and results of recently conducted synthetic aperture radar (SAR experiments.

  6. Multifrequency radar imaging of ash plumes: an experiment at Stromboli

    Science.gov (United States)

    Donnadieu, Franck; Freret-Lorgeril, Valentin; Delanoë, Julien; Vinson, Jean-Paul; Peyrin, Frédéric; Hervier, Claude; Caudoux, Christophe; Van Baelen, Joël; Latchimy, Thierry

    2016-04-01

    Volcanic ash emissions in the atmosphere are hazardous to aviation while ash fallout affects people and human activities and may cause damage to infrastructures and economic losses. In the framework of the French Government Laboratory of Excellence ClerVolc initiative, an experiment was carried out on Stromboli volcano (Italy), between 28 September and 4 October 2015. The aim was to retrieve various physical properties of the ash plumes, especially the mass loading parameters which are critical for the modelling of ash dispersal. We used a complementary set of cutting edge techniques recording in different bands of the electromagnetic spectrum. The innovative instrument setup consisted in three radars, hyperspectral thermal infrared and dual-band UV cameras, a mini DOAS-Flyspec and a multigas sensor. A drone equipped with differential GPS was flown near the ash plumes with several sensors including SO2, CO2 and particle counter. We mainly focus on radar measurements of over 200 ash plumes and present some preliminary comparisons at three frequencies. The BASTA Doppler radar at 95 GHz, originally designed for atmospheric studies, was deployed at about 2.2 km in slant distance from the eruptive craters. It was configured to observe volumes above one of the active craters with a spatio-temporal resolution of 12.5 m and 1 s. From the same location, a 1.2 GHz volcano Doppler radar (VOLDORAD) was recording the signature of ballistics and small lapilli at 0.15 s in 60 m-deep volumes. In addition, a commercial 24 GHz micro rain Doppler radar (MRR) simultaneously recorded activity from the Rochette station, at 400 to 650 m from the active craters with a sampling rate of 10 s and a resolution of 25 m. The latter was pointing almost perpendicularly to the other radar beams. Reflectivity factors were measured inside the ash plume above the source vent by the BASTA radar (3 mm wavelength) spanning -9 to +21 dBZ. Fallout could sometimes be tracked during several minutes within

  7. Overview of the Cassini Processing Altimetric Data System

    OpenAIRE

    Martín Isanda, Oriol

    2008-01-01

    Projecte final de carrera reaitzat en col.laboració amb La Sapienza Although the Cassini-Huygens interplanetary mission is a project that covers Saturn, its rings and most of its multiple satellites, in this introduction attention will be focused mainly in the biggest moon of Saturn: Titan, since Cassini Radar, from which Cassini Processing Altimetric Data (PAD) system (on which is based this work) receives science data, has been built especially to study Titan.

  8. Space Debris Radar Experiments at the Medicina VLBI Dish

    Science.gov (United States)

    Pupillo, G.; Montebugnoli, S.; Di Martino, M.; Salerno, E.; Bartolini, M.; Pluchino, S.; Schilliro, F.; Anselmo, L.; Portelli, C.; Konovalenko, A.; Nabatov, A.

    2009-03-01

    In 2007 three space debris detection tests were performed in the framework of a monitoring program carried out by the Istituto Nazionale di Astrofisica - INAF - in collaboration with the Italian Space Agency - ASI. The observations were made by using the bistatic radar technique. The INAF 32 m radiotelescope located at Medicina (Bologna, Italy) was used as receiver whereas the Ukrainian 70 m parabolic antenna located at Evpatoria was utilized as transmitter. The aim of the experiment was to test the sensitivity of the Medicina-Evpatoria radar system in space debris detection, and to validate and optimize the hardware setup. Measurements were mainly carried out on inactive satellites and catalogued space debris. However the search for new fragments in LEO was also performed during the campaign. This paper reports on results of these observations.

  9. Cassini Mission Sequence Subsystem (MSS)

    Science.gov (United States)

    Alland, Robert

    2011-01-01

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

  10. Cassini's Grand Finale

    Science.gov (United States)

    Edgington, Scott G.; Spilker, Linda J.

    2016-07-01

    After more than a decade exploring Saturn and its moons, the Cassini mission is in its closing act. Cassini's last year is an encore performance stuffed with science, including a final plunge into Saturn's atmosphere.

  11. Bollène-2002 Experiment : Radar quantitative precipitation estimation in the Cévennes-Vivarais Region, France

    OpenAIRE

    Delrieu, Guy; Boudevillain, Brice; Nicol, John; CHAPON, Benoît; Kirstetter, Pierre-Emmanuel; Andrieu, Hervé; Faure, D.

    2009-01-01

    The Bollène-2002 Experiment was aimed at developing the use of a radar volume-scanning strategy for conducting radar rainfall estimations in the mountainous regions of France. A developmental radar processing system, called Traitements Régionalisés et Adaptatifs de Données Radar pour l’Hydrologie (Regionalized and Adaptive Radar Data Processing for Hydrological Applications), has been built and several algorithms were specifically produced as part of this project. These algorithms include 1) ...

  12. Signal processing for airborne doppler radar detection of hazardous wind shear as applied to NASA 1991 radar flight experiment data

    Science.gov (United States)

    Baxa, Ernest G., Jr.

    1992-01-01

    Radar data collected during the 1991 NASA flight tests have been selectively analyzed to support research directed at developing both improved as well as new algorithms for detecting hazardous low-altitude windshear. Analysis of aircraft attitude data from several flights indicated that platform stability bandwidths were small compared to the data rate bandwidths which should support an assumption that radar returns can be treated as short time stationary. Various approaches at detection of weather returns in the presence of ground clutter are being investigated. Non-coventional clutter rejection through spectrum mode tracking and classification algorithms is a subject of continuing research. Based upon autoregressive modeling of the radar return time sequence, this approach may offer an alternative to overcome errors in conventional pulse-pair estimates. Adaptive filtering is being evaluated as a means of rejecting clutter with emphasis on low signal-to-clutter ratio situations, particularly in the presence of discrete clutter interference. An analysis of out-of-range clutter returns is included to illustrate effects of ground clutter interference due to range aliasing for aircraft on final approach. Data are presented to indicate how aircraft groundspeed might be corrected from the radar data as well as point to an observed problem of groundspeed estimate bias variation with radar antenna scan angle. A description of how recorded clutter return data are mixed with simulated weather returns is included. This enables the researcher to run controlled experiments to test signal processing algorithms. In the summary research efforts involving improved modelling of radar ground clutter returns and a Bayesian approach at hazard factor estimation are mentioned.

  13. Bistatic radar

    CERN Document Server

    Willis, Nick

    2004-01-01

    Annotation his book is a major extension of a chapter on bistatic radar written by the author for the Radar Handbook, 2nd edition, edited by Merrill Skolnik. It provides a history of bistatic systems that points out to potential designers the applications that have worked and the dead-ends not worth pursuing. The text reviews the basic concepts and definitions, and explains the mathematical development of relationships, such as geometry, Ovals of Cassini, dynamic range, isorange and isodoppler contours, target doppler, and clutter doppler spread.Key Features * All development and analysis are

  14. Multistatic Wireless Fidelity Network Based Radar – Results of the Chrcynno Experiment

    Directory of Open Access Journals (Sweden)

    S. Rzewuski

    2014-04-01

    Full Text Available This paper presents the theory and experimental result of passive radar using WIFI transmitters as illuminators of opportunity. As a result of experiments conducted on 17th August 2013 at airfield Chrcynno a Cessna C208 airplane was detected and tracked using multistatic passive radar system based on low power signal from WIFI network nodes, which were acting as non cooperative illuminators of opportunity. In the experiment 3 wireless access points were communicating with each other and illuminating the radar scene (airfield. The direct reference and reflected (surveillance signals have been acquired and processed using specially developed algorithm presented in the paper. After signal processing using Passive Coherent Location methods target has been detected. This paper describes in details the algorithms and the results of the experiment for the multistatic passive radar based on the WIFI signal.

  15. Experiment in Onboard Synthetic Aperture Radar Data Processing

    Science.gov (United States)

    Holland, Matthew

    2011-01-01

    Single event upsets (SEUs) are a threat to any computing system running on hardware that has not been physically radiation hardened. In addition to mandating the use of performance-limited, hardened heritage equipment, prior techniques for dealing with the SEU problem often involved hardware-based error detection and correction (EDAC). With limited computing resources, software- based EDAC, or any more elaborate recovery methods, were often not feasible. Synthetic aperture radars (SARs), when operated in the space environment, are interesting due to their relevance to NASAs objectives, but problematic in the sense of producing prodigious amounts of raw data. Prior implementations of the SAR data processing algorithm have been too slow, too computationally intensive, and require too much application memory for onboard execution to be a realistic option when using the type of heritage processing technology described above. This standard C-language implementation of SAR data processing is distributed over many cores of a Tilera Multicore Processor, and employs novel Radiation Hardening by Software (RHBS) techniques designed to protect the component processes (one per core) and their shared application memory from the sort of SEUs expected in the space environment. The source code includes calls to Tilera APIs, and a specialized Tilera compiler is required to produce a Tilera executable. The compiled application reads input data describing the position and orientation of a radar platform, as well as its radar-burst data, over time and writes out processed data in a form that is useful for analysis of the radar observations.

  16. Recent MTI experiments using ARL's synchronous impulse reconstruction (SIRE) radar

    Science.gov (United States)

    Ranney, Kenneth; Martone, Anthony; Nguyen, Lam; Stanton, Brian; Ressler, Marc; Wong, David; Koenig, Francois; Tran, Chi; Kirose, Getachew; Smith, Greg; Kappra, Karl; Sichina, Jeffrey

    2008-04-01

    The Army Research Laboratory (ARL) has recently developed the ground-based synchronous impulse reconstruction (SIRE) radar - a low-frequency radar capable of exploiting both a real antenna array and along-track integration techniques to increase the quality of processed imagery. We have already demonstrated the system's utility by imaging static scenes. In this paper we address the moving target indication (MTI) problem, and we demonstrate the impulse-based system's ability to both detect and locate slowly moving targets. We begin by briefly describing the SIRE system itself as well as the system configuration utilized in collecting the MTI data. Next we discuss the signal processing techniques employed to create the final MTI image. Finally, we present processed imagery illustrating the utility of the proposed method.

  17. An enhanced Planetary Radar Operating Centre (PROC)

    Science.gov (United States)

    Catallo, C.

    2010-12-01

    Planetary exploration by means of radar systems, mainly using GPRs is an important role of Italy and numerous scientific international space programs are carried out jointly with ESA and NASA by Italian Space Agency, the scientific community and the industry. Three experiments under Italian leadership ( designed and manufactured by the Italian industry) provided by ASI within a NASA/ESA/ASI joint venture framework are successfully operating: MARSIS on-board MEX, SHARAD on-board MRO and CASSINI Radar on-board Cassini spacecraft: the missions have been further extended . Three dedicated operational centers, namely SHOC, (Sharad Operating Centre), MOC (Marsis Operating Center) and CASSINI PAD are operating from the missions beginning to support all the scientific communities, institutional customers and experiment teams operation Each center is dedicated to a single instrument management and control, data processing and distribution and even if they had been conceived to operate autonomously and independently one from each other, synergies and overlaps have been envisaged leading to the suggestion of a unified center, the Planetary Radar Processing Center (PROC). In order to harmonize operations either from logistics point of view and from HW/SW capabilities point of view PROC is designed and developed for offering improved functionalities to increase capabilities, mainly in terms of data exchange, comparison, interpretation and exploitation. PROC is, therefore, conceived as the Italian support facility to the scientific community for on-going and future Italian planetary exploration programs, such as Europa-Jupiter System Mission (EJSM) The paper describes how the new PROC is designed and developed, to allow SHOC, MOC and CASSINI PAD to operate as before, and to offer improved functionalities to increase capabilities, mainly in terms of data exchange, comparison, interpretation and exploitation aiding scientists to increase their knowledge in the field of surface

  18. Results From the SHARAD Sounding Radar Experiment at Mars

    Science.gov (United States)

    Phillips, R. J.; Seu, R.; Biccari, D.; Campbell, B. A.; Safaeinili, A.; Plaut, J. J.; Carter, L. M.; Holt, J. W.; Leuschen, C. J.; Smrekar, S. E.; Putzig, N. E.; Orosei, R.; Egan, A. F.; Milkovich, S. M.

    2007-12-01

    The SHARAD radar on the Mars Reconnaissance Orbiter has carried out successful subsurface soundings in a number of locales since operations began in late 2006. NORTH POLAR LAYERED DEPOSITS (NPLD): These consist of a thick (up to 2 km+), layered ice-rich unit (Apl) overlying a basal unit (BU), which differs from APl, principally in its lower albedo but additionally because it is platy and irregular compared to Apl. The circumpolar erg, most prevalent at Olympia Undae, is likely material shed from the BU. SHARAD shows that Apl is divided into a finely-layered upper facies of variable thickness, containing dozens of apparent reflectors that likely under-resolve a more finely layered ice-dust sequence, and a lower facies, typically a kilometer or more thick, which contains a limited number of distinct reflectors. SHARAD shows that BU is up to approximately a kilometer thick under the main lobe of the NPLD and is largely absent beneath the minor lobe (centered on the prime meridian), as was suggested earlier by mapping exposures in chasmata on the periphery of the NPLD. SHARAD does not see a sharp reflector at the base of the BU, likely due to volume scattering within the BU, but its sister radar MARSIS, operating at lower frequencies, does see such an interface and its extension beneath Olympia Undae. SOUTH POLAR LAYERED DEPOSITS (SPLD): SHARAD typically does not penetrate to the base of the SPLD, but maps fine-scale layering within this unit. Dipping layers are truncated at the surface and at depth there is good evidence for angular unconformities in the layers, which are likely tied to surface erosion followed by new episodes of ice and dust deposition. AMAZONIS PLANITIA: This roughly circular lowland north of the hemispheric dichotomy boundary is one of the flattest places on Mars, with a smooth cover of sediment. Younger flow-like features with ridged and platy surface structures occur in southwestern Amazonis. These flows are widely held to be volcanic, but some

  19. A New Generalized Cassini Determinant

    OpenAIRE

    Martinjak, Ivica; Urbiha, Igor

    2015-01-01

    In this paper we extend a notion of Cassini determinant to recently introduced hyperfibonacci sequences. We find $Q$-matrix for the $r$-th generation hyperfibonacci numbers and prove an explicit expression of the Cassini determinant for these sequences.

  20. Cassini's Solstice Mission

    Science.gov (United States)

    Seal, David; Mitchell, Robert

    2010-01-01

    With the recent approval of NASA's flagship Cassini mission for seven more years of continued operations, dozens more Titan, Enceladus and other icy moon flybys await, as well as many occultations and multiple close passages to Saturn. Seasonal change is the principal scientific theme as Cassini extends its survey of the target-rich system over one full half-season, from just after northern winter solstice at arrival back in 2004, to northern summer solstice at the end of mission in 2017. The new seven-year mission extension requires careful propellant management as well as streamlined operations strategies with smaller spacecraft, sequencing and science teams. Cassini's never-before-envisioned end of mission scenario also includes nearly two dozen high-inclination orbits which pass between the rings and the planet allowing thrilling and unique science opportunities before entry into Saturn's atmosphere.

  1. Stochastic simulation experiment to assess radar rainfall retrieval uncertainties associated with attenuation and its correction

    Directory of Open Access Journals (Sweden)

    R. Uijlenhoet

    2008-03-01

    Full Text Available As rainfall constitutes the main source of water for the terrestrial hydrological processes, accurate and reliable measurement and prediction of its spatial and temporal distribution over a wide range of scales is an important goal for hydrology. We investigate the potential of ground-based weather radar to provide such measurements through a theoretical analysis of some of the associated observation uncertainties. A stochastic model of range profiles of raindrop size distributions is employed in a Monte Carlo simulation experiment to investigate the rainfall retrieval uncertainties associated with weather radars operating at X-, C-, and S-band. We focus in particular on the errors and uncertainties associated with rain-induced signal attenuation and its correction for incoherent, non-polarimetric, single-frequency, operational weather radars. The performance of two attenuation correction schemes, the (forward Hitschfeld-Bordan algorithm and the (backward Marzoug-Amayenc algorithm, is analyzed for both moderate (assuming a 50 km path length and intense Mediterranean rainfall (for a 30 km path. A comparison shows that the backward correction algorithm is more stable and accurate than the forward algorithm (with a bias in the order of a few percent for the former, compared to tens of percent for the latter, provided reliable estimates of the total path-integrated attenuation are available. Moreover, the bias and root mean square error associated with each algorithm are quantified as a function of path-averaged rain rate and distance from the radar in order to provide a plausible order of magnitude for the uncertainty in radar-retrieved rain rates for hydrological applications.

  2. The Composition of Titan's Lower Atmosphere and Simple Surface Volatiles as Measured by the Cassini-Huygens Probe Gas Chromatograph Mass Spectrometer Experiment

    Science.gov (United States)

    Niemann, H. B.; Atreya, S. K.; Demick, J. E.; Gautier, D.; Haberman, J. A.; Harpold, D. N.; Kasprzak, W. T.; Lunine, J. I.; Owen, T. C.; Raulin, F.

    2010-01-01

    The Cassini-Huygens Probe Gas Chromatograph Mass Spectrometer (GCMS) determined the composition of the Titan atmosphere from 140km altitude to the surface. After landing, it returned composition data of gases evaporated from the surface. Height profiles of molecular nitrogen (N2), methane (CH4) and molecular hydrogen (H2) were determined. Traces were detected on the surface of evaporating methane, ethane (C2H6), acetylene (C2H2), cyanogen (C2N2) and carbon dioxide (CO2). The methane data showed evidence that methane precipitation occurred recently. The methane mole fraction was (1.48+/-0.09) x 10(exp -2) in the lower stratosphere (139.8 km to 75.5 km) and (5.65+/-0.18) x 10(exp -2) near the surface (6.7 km to the surface). The molecular hydrogen mole fraction was (1.01+/-0.16) x 10(exp -3) in the atmosphere and (9.90+/-0.17) x 10(exp -4) on the surface. Isotope ratios were 167.7+/-0.6 for N-14/N-15 in molecular nitrogen, 91.1+/-1.4 for C-12/C-13 in methane and (1.35+/-0.30) x 10(exp -4) for D/H in molecular hydrogen. The mole fractions of Ar-36 and radiogenic Ar-40 are (2.1+/-0.8) x 10(exp -7) and (3.39 +/-0.12) x 10(exp -5) respectively. Ne-22 has been tentatively identified at a mole fraction of (2.8+/-2.1) x 10(exp -7) Krypton and xenon were below the detection threshold of 1 x 10(exp -8) mole fraction. Science data were not retrieved from the gas chromatograph subsystem as the abundance of the organic trace gases in the atmosphere and on the ground did not reach the detection threshold. Results previously published from the GCMS experiment are superseded by this publication.

  3. Dynamic experiment design regularization approach to adaptive imaging with array radar/SAR sensor systems.

    Science.gov (United States)

    Shkvarko, Yuriy; Tuxpan, José; Santos, Stewart

    2011-01-01

    We consider a problem of high-resolution array radar/SAR imaging formalized in terms of a nonlinear ill-posed inverse problem of nonparametric estimation of the power spatial spectrum pattern (SSP) of the random wavefield scattered from a remotely sensed scene observed through a kernel signal formation operator and contaminated with random Gaussian noise. First, the Sobolev-type solution space is constructed to specify the class of consistent kernel SSP estimators with the reproducing kernel structures adapted to the metrics in such the solution space. Next, the "model-free" variational analysis (VA)-based image enhancement approach and the "model-based" descriptive experiment design (DEED) regularization paradigm are unified into a new dynamic experiment design (DYED) regularization framework. Application of the proposed DYED framework to the adaptive array radar/SAR imaging problem leads to a class of two-level (DEED-VA) regularized SSP reconstruction techniques that aggregate the kernel adaptive anisotropic windowing with the projections onto convex sets to enforce the consistency and robustness of the overall iterative SSP estimators. We also show how the proposed DYED regularization method may be considered as a generalization of the MVDR, APES and other high-resolution nonparametric adaptive radar sensing techniques. A family of the DYED-related algorithms is constructed and their effectiveness is finally illustrated via numerical simulations. PMID:22163859

  4. Dynamic Experiment Design Regularization Approach to Adaptive Imaging with Array Radar/SAR Sensor Systems

    Directory of Open Access Journals (Sweden)

    Stewart Santos

    2011-04-01

    Full Text Available We consider a problem of high-resolution array radar/SAR imaging formalized in terms of a nonlinear ill-posed inverse problem of nonparametric estimation of the power spatial spectrum pattern (SSP of the random wavefield scattered from a remotely sensed scene observed through a kernel signal formation operator and contaminated with random Gaussian noise. First, the Sobolev-type solution space is constructed to specify the class of consistent kernel SSP estimators with the reproducing kernel structures adapted to the metrics in such the solution space. Next, the “model-free” variational analysis (VA-based image enhancement approach and the “model-based” descriptive experiment design (DEED regularization paradigm are unified into a new dynamic experiment design (DYED regularization framework. Application of the proposed DYED framework to the adaptive array radar/SAR imaging problem leads to a class of two-level (DEED-VA regularized SSP reconstruction techniques that aggregate the kernel adaptive anisotropic windowing with the projections onto convex sets to enforce the consistency and robustness of the overall iterative SSP estimators. We also show how the proposed DYED regularization method may be considered as a generalization of the MVDR, APES and other high-resolution nonparametric adaptive radar sensing techniques. A family of the DYED-related algorithms is constructed and their effectiveness is finally illustrated via numerical simulations.

  5. Saturation and hysteresis effects in ionospheric modification experiments observed by the CUTLASS and EISCAT radars

    Directory of Open Access Journals (Sweden)

    D. M. Wright

    2006-03-01

    Full Text Available The results of high latitude ionospheric modification experiments utilising the EISCAT heating facility at Tromsø are presented. As a result of the interaction between the high power pump waves and upper hybrid waves in the ionosphere, field-aligned electron density irregularities are artificially excited. Observations of these structures with the CUTLASS coherent HF radars and the EISCAT incoherent UHF radar exhibit hysteresis effects as the heater output power is varied. These are explained in terms of the two-stage mechanism which leads to the growth of the irregularities. Experiments which involve preconditioning of the ionosphere also indicate that hysteresis could be exploited to maximise the intensity of the field-aligned irregularities, especially where the available heater power is limited.

    In addition, the saturation of the irregularity amplitude is considered. Although, the rate of irregularity growth becomes less rapid at high heater powers it does not seem to fully saturate, indicating that the amplification would continue beyond the capabilities of the Tromsø heater - currently the most powerful of its kind. It is shown that the CUTLASS radars are sensitive to irregularities produced by very low heater powers (effective radiated powers <4 MW. This fact is discussed from the perspective of a new heating facility, SPEAR, located on Spitzbergen and capable of transmitting high frequency radio waves with an effective radiated power ~10% of that of the Tromsø heater (28MW.

  6. Island based radar and microwave radiometer measurements of stratus cloud parameters during the Atlantic Stratocumulus Transition Experiment (ASTEX)

    Energy Technology Data Exchange (ETDEWEB)

    Frisch, A.S. [Colorado State Univ., Fort Collins, CO (United States); Fairall, C.W.; Snider, J.B. [NOAA Environmental Technology Lab., Boulder, CO (United States); Lenshow, D.H.; Mayer, S.D. [National Center for Atmospheric Research, Boulder, CO (United States)

    1996-04-01

    During the Atlantic Stratocumulus Transition Experiment (ASTEX) in June 1992, simultaneous measurements were made with a vertically pointing cloud sensing radar and a microwave radiometer. The radar measurements are used to estimate stratus cloud drizzle and turbulence parameters. In addition, with the microwave radiometer measurements of reflectivity, we estimated the profiles of cloud liquid water and effective radius. We used radar data for computation of vertical profiles of various drizzle parameters such as droplet concentration, modal radius, and spread. A sample of these results is shown in Figure 1. In addition, in non-drizzle clouds, with the radar and radiometer we can estimate the verticle profiles of stratus cloud parameters such as liquid water concentration and effective radius. This is accomplished by assuming a droplet distribution with droplet number concentration and width constant with height.

  7. Imaging radar observations of Farley Buneman waves during the JOULE II experiment

    Directory of Open Access Journals (Sweden)

    D. L. Hysell

    2008-07-01

    Full Text Available Vector electric fields and associated E×B drifts measured by a sounding rocket in the auroral zone during the NASA JOULE II experiment in January 2007, are compared with coherent scatter spectra measured by a 30 MHz radar imager in a common volume. Radar imaging permits precise collocation of the spectra with the background electric field. The Doppler shifts and spectral widths appear to be governed by the cosine and sine of the convection flow angle, respectively, and also proportional to the presumptive ion acoustic speed. The neutral wind also contributes to the Doppler shifts. These findings are consistent with those from the JOULE I experiment and also with recent numerical simulations of Farley Buneman waves and instabilities carried out by Oppenheim et al. (2008. Simple linear analysis of the waves offers some insights into the spectral moments. A formula relating the spectral width to the flow angle, ion acoustic speed, and other ionospheric parameters is derived.

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

    Science.gov (United States)

    Abbas, Mian M.

    2014-01-01

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

  9. Harmonic motion and Cassini ovals

    OpenAIRE

    Khristo N. Boyadzhiev; Boyadzhiev, Irina A.

    2013-01-01

    We consider a two-dimensional free harmonic oscillator where the initial position is fixed and the initial velocity can change direction. All possible orbits are ellipses and their enveloping curve is an ellipse too. We show that the locus of the foci of all elliptical orbits is a Cassini oval. Depending on the magnitude of the initial velocity we observe all three kinds of Cassini ovals, one of which is the lemniscate of Bernoulli. These Cassini ovals have the same foci as the enveloping ell...

  10. Microcontroller-based binary integrator for millimeter-wave radar experiments

    Science.gov (United States)

    Eskelinen, Pekka; Ruoskanen, Jukka; Peltonen, Jouni

    2010-05-01

    An easily on-site reconfigurable multiple binary integrator for millimeter radar experiments has been constructed of static random access memories, an eight bit microcontroller, and high speed video operational amplifiers. The design uses a raw comparator path and two adjustable m-out-of-n chains in a wired-OR configuration. Standard high speed memories allow the use of pulse widths below 100 ns. For eight pulse repetition intervals it gives a maximum improvement of 6.6 dB for stationary low-level target echoes. The doubled configuration enhances the capability against fluctuating targets. Because of the raw comparator path, also single return pulses of relatively high amplitude are processed.

  11. Polarisation in the auroral red line during coordinated EISCAT Svalbard Radar/optical experiments

    Directory of Open Access Journals (Sweden)

    M. Barthélémy

    2011-06-01

    Full Text Available The polarisation of the atomic oxygen red line in the Earth's thermosphere is observed in different configurations with respect to the magnetic field line at high latitude during several coordinated Incoherent Scatter radar/optical experiment campaigns. When pointing northward with a line-of-sight nearly perpendicular to the magnetic field, we show that, as expected, the polarisation is due to precipitated electrons with characteristic energies of a few hundreds of electron Volts. When pointing toward the zenith or southward with a line-of-sight more parallel to the magnetic field, we show that the polarisation practically disappears. This confirms experimentally the predictions deduced from the recent discovery of the red line polarisation. We show that the polarisation direction is parallel to the magnetic field line during geomagnetic activity intensification and that these results are in agreement with theoretical work.

  12. Using radar tomography, tracer experiments and hydraulic data to characterize fractured rock flow systems

    Science.gov (United States)

    Day-Lewis, Frederick David

    Among the most pressing problems in hydrogeology is describing heterogeneity in fractured rock, where data are typically local and sparse, and permeability varies by orders of magnitude over short distances. This dissertation presents new approaches to characterize fractured rock groundwater flow systems using cross-well radar, tracer, and hydraulic experiments. The methods are demonstrated using data from the U.S. Geological Survey Fractured Rock Hydrology Research Site near Mirror Lake, New Hampshire. One underutilized source of information in characterization of fractured rock is hydraulic connection data. Wells connected by a high-permeability fracture zone tend to exhibit similar hydraulic responses during pumping or drilling. A simulated-annealing algorithm is presented to condition geostatistical simulations to inferred connections. The method is used to generate 3-D realizations of fracture-zone geometry at the Mirror Lake Site. Results indicate the likely extents of specific zones. Flow models based on realizations are calibrated to hydraulic data to estimate the hydraulic parameters of the fracture zones and surrounding bedrock. Another innovative source of information for characterization is time-lapse difference-attenuation radar tomography, which has been used to monitor the migration of electrically conductive saline tracers. A sequential-inversion methodology is presented and demonstrated for a synthetic example. The method uses space-time parameterization and regularization to account for changes in concentration that occur quickly relative to the collection of radar data. The time-lapse tomographic inversion method is applied to data from the Mirror Lake Site. Difference-attenuation tomography indicates the timing and spatial distribution of tracer transport in three planes that form a triangular prism. Tracer migration is focused along a preferential pathway. Comparison of the time-series of tomograms with the outlet tracer data suggests that much

  13. NASA 3D Models: Cassini

    Data.gov (United States)

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

  14. Titan from Cassini-Huygens

    CERN Document Server

    Brown, Robert H; Waite, J. Hunter

    2010-01-01

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

  15. Cassini Tour Atlas Automated Generation

    Science.gov (United States)

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

    2011-01-01

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

  16. The Cassini-Huygens mission

    CERN Document Server

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

  17. Cassini data assessment report

    International Nuclear Information System (INIS)

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

  18. Stratiform and Convective Precipitation Observed by Multiple Radars during the DYNAMO/AMIE Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Min; Kollias, Pavlos; Feng, Zhe; Zhang, Chidong; Long, Charles N.; Kalesse, Heike; Chandra, Arunchandra; Kumar, Vickal; Protat, Alain

    2014-11-01

    The motivation for this research is to develop a precipitation classification and rain rate estimation method using cloud radar-only measurements for Atmospheric Radiation Measurement (ARM) long-term cloud observation analysis, which are crucial and unique for studying cloud lifecycle and precipitation features under different weather and climate regimes. Based on simultaneous and collocated observations of the Ka-band ARM zenith radar (KAZR), two precipitation radars (NCAR S-PolKa and Texas A&M University SMART-R), and surface precipitation during the DYNAMO/AMIE field campaign, a new cloud radar-only based precipitation classification and rain rate estimation method has been developed and evaluated. The resulting precipitation classification is equivalent to those collocated SMART-R and S-PolKa observations. Both cloud and precipitation radars detected about 5% precipitation occurrence during this period. The convective (stratiform) precipitation fraction is about 18% (82%). The 2-day collocated disdrometer observations show an increased number concentration of large raindrops in convective rain compared to dominant concentration of small raindrops in stratiform rain. The composite distributions of KAZR reflectivity and Doppler velocity also show two distinct structures for convective and stratiform rain. These indicate that the method produces physically consistent results for two types of rain. The cloud radar-only rainfall estimation is developed based on the gradient of accumulative radar reflectivity below 1 km, near-surface Ze, and collocated surface rainfall (R) measurement. The parameterization is compared with the Z-R exponential relation. The relative difference between estimated and surface measured rainfall rate shows that the two-parameter relation can improve rainfall estimation.

  19. Improving quantitative precipitation nowcasting with a local ensemble transform Kalman filter radar data assimilation system: observing system simulation experiments

    Directory of Open Access Journals (Sweden)

    Chih-Chien Tsai

    2014-03-01

    Full Text Available This study develops a Doppler radar data assimilation system, which couples the local ensemble transform Kalman filter with the Weather Research and Forecasting model. The benefits of this system to quantitative precipitation nowcasting (QPN are evaluated with observing system simulation experiments on Typhoon Morakot (2009, which brought record-breaking rainfall and extensive damage to central and southern Taiwan. The results indicate that the assimilation of radial velocity and reflectivity observations improves the three-dimensional winds and rain-mixing ratio most significantly because of the direct relations in the observation operator. The patterns of spiral rainbands become more consistent between different ensemble members after radar data assimilation. The rainfall intensity and distribution during the 6-hour deterministic nowcast are also improved, especially for the first 3 hours. The nowcasts with and without radar data assimilation have similar evolution trends driven by synoptic-scale conditions. Furthermore, we carry out a series of sensitivity experiments to develop proper assimilation strategies, in which a mixed localisation method is proposed for the first time and found to give further QPN improvement in this typhoon case.

  20. Proposed experiment to detect air showers with the Jicamarca radar system

    International Nuclear Information System (INIS)

    When an extremely high energy particle interacts in the atmosphere, the collision induces a multiplicative cascade of charged particles, which grows exponentially until the energy per secondary degrades enough to dissipate in ionization of the surrounding air. During this process the compact cloud of energetic secondary particles travels 10-20 km through the atmosphere, leaving a column of ionization behind it. This ionized column quickly recombines, but for a period of order 0.1 ms it is highly reflective at frequencies below 100 MHz. This ionization trail, which is comparable in ionization density to that of a micro-meteor, should be clearly detectable using standard radar methods. We propose radar measurements using the facilities operated by Cornell University and the Instituto Geofisico del Peru (IGP) at the Jicamarca Radio Observatory near Lima, Peru. This facility's primary instrument is 49.92 MHz incoherent scatter radar, transmitting up to 1.5 MW of pulse power

  1. Dielectric Constant of Titan's South Polar Region from Cassini Radio Science Bistatic Scattering Observations

    Science.gov (United States)

    Marouf, E.; Rappaport, N.; French, R.; Simpson, R.; Kliore, A.; McGhee, C.; Schinder, P.; Anabtawi, A.

    2008-12-01

    Four out of six Radio Science bistatic scattering (bistatic-radar) observations of Titan's surface completed during the Cassini nominal mission yielded detectable quasi-specular 3.6 cm-λ (X-band) surface echoes, making Titan the most distant solar system object for which bistatic echoes have been successfully detected. Right circularly polarized sinusoidal signal was transmitted by Cassini and both the right and left circularly polarized (RCP and LCP) surface reflected components were observed at the 70-m stations of NASA Deep Space Network. Cassini was maneuvered continuously to track the region of Titan's surface where mirror-like (quasi-specular) reflected signals may be observed. The experiments were designed for incidence angles θ close to the Brewster, or polarization, angle of likely surface compositions. Careful measurement of the system noise temperature allowed determination of the absolute power in each polarized echo component and hence their ratio. The polarization ratio, the known observation geometry, and Fresnel reflection theory were then used to determine the dielectric constant ɛ. Three near-equatorial (~ 5 to 15° S) observations on flyby T14 inbound and outbound and on flyby T34 inbound yielded weak but clearly detectable echoes. The echoes were intermittent along the ground track, indicating mostly rough terrain occasionally interrupted by patches of relatively flat areas. For the two observations on T14, polarization ratio measurements for two localized but widely separated surface regions (~ 15° S, ~ 14 and 140° W) conducted at angles θ ~ 56° and 64°, close to the Brewster angle for ices, imply ɛ ~ 1.6 for both regions, suggesting liquid hydrocarbons although alternative interpretations are possible (Marouf et al., 2006 Fall AGU, P11A- 07). In sharp contrast, a single high latitude (~81-86° S, ~ 45-155° W) observation on T27 inbound yielded much stronger surface echoes that lasted for almost the full duration of the experiment

  2. The browse file of NASA/JPL quick-look radar images from the Loch Linnhe 1989 experiment

    Science.gov (United States)

    Brown, Walter E., Jr. (Editor)

    1989-01-01

    The Jet Propulsion Laboratory (JPL) Aircraft Synthetic Aperture Radar (AIRSAR) was deployed to Scotland to obtain radar imagery of ship wakes generated in Loch Linnhe. These observations were part of a joint US and UK experiment to study the internal waves generated by ships under partially controlled conditions. The AIRSAR was mounted on the NASA-Ames DC-8 aircraft. The data acquisition sequence consisted of 8 flights, each about 6 hours in duration, wherein 24 observations of the instrumented site were made on each flight. This Browse File provides the experimenters with a reference of the real time imagery (approximately 100 images) obtained on the 38-deg track. These radar images are copies of those obtained at the time of observation and show the general geometry of the ship wake features. To speed up processing during this flight, the images were all processed around zero Doppler, and thus azimuth ambiguities often occur when the drift angel (yaw) exceeded a few degrees. However, even with the various shortcomings, it is believed that the experimenter will find the Browse File useful in establishing a basis for further investigations.

  3. CASSIUS: The Cassini Uplink Scheduler

    Science.gov (United States)

    Bellinger, Earl

    2012-01-01

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

  4. Saturn satellites as seen by Cassini Mission

    OpenAIRE

    Coradini, A; Capaccioni, F.; Cerroni, P.; Filacchione, G.; Magni, G; Orosei, R.; F. Tosi; Turrini, D

    2009-01-01

    In this paper we will summarize some of the most important results of the Cassini mission concerning the satellites of Saturn. Given the long duration of the mission, the complexity of the payload onboard the Cassini Orbiter and the amount of data gathered on the satellites of Saturn, it would be impossible to describe all the new discoveries made, therefore we will describe only some selected, paramount examples showing how Cassini's data confirmed and extended ground-based observations. In ...

  5. Basics and first experiments demonstrating isolation improvements in the agile polarimetric FM-CW radar – PARSAX

    OpenAIRE

    Krasnov, O.A.; Babur, G.P.; Wang, Z.; Ligthart, L.P.; Van der Zwan, F.

    2010-01-01

    The article describes the IRCTR PARSAX radar system, the S-band high-resolution Doppler polarimetric frequency modulated continuous wave (FM-CW) radar with dual-orthogonal sounding signals, which has the possibility to measure all elements of the radar target polarization scattering matrix simultaneously, in one sweep. The performance of such radar depends of the level of sounding signals orthogonality. In the main operational mode, the radar will be used for atmospheric remote sensing and po...

  6. Cassini at Saturn: The Final Two Years

    Science.gov (United States)

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

    2015-10-01

    After 11 years in orbit, the Cassini-Huygens Mission to Saturn, a collaboration of NASA, ESA, and ASI, continues to wow the imagination and reveal unprecedented findings. Every year Cassini produces answers to questions raised by the Voyager flybys, while at the same time posing new questions that can only be answered with a long duration mission using a flagship-class spacecraft. Here we sample a few of Cassini's discoveries from the past year and give an overview of Cassini's final two years.

  7. The Determination Of Titan's Rotational State From Cassini SAR Images

    Science.gov (United States)

    Persi Del Marmo, P.; Iess, L.; Picardi, G.; Seu, R.; Bertotti, B.

    2007-12-01

    SAR images acquired by the spacecraft Cassini in overlapping strips have been used to determine the vectorial angular velocity of Titan. The method entails the tracking of surface landmarks at different times (and mean anomalies). Cassini radar observations have provided so far 14 high resolution image pairs of the same portion of Titan surface, spanning a period from 2004 to 2007. Each image is referenced both in an inertial frame and in the IAU, Titan-centric, body-fixed reference frame. This referencing is quite precise, as the position of Cassini relative to Titan is known with an accuracy smaller than 100 m during each flyby. The IAU body-fixed frame assumes a spin axis different from the actual one. Therefore, in this putative frame a landmark appears at different geographic coordinates in the two observations. By correlating the two images of the same surface region, one gets a two-dimensional vector, which retains information about the true spin axis. This vector provides the magnitude and direction of the displacement to be applied to a reference point of each image in order to produce maximum correlation. The correlation results therefore in a new Titan-centric, inertial referencing of the images, R(t1) and R(t2). The spin axis s is then obtained by requiring that [R(t2) - R(t1)] s = 0 for each overlapping image pairs. Due to experimental errors (dominated by image correlation errors and inaccuracies in the spacecraft orbit relative to Titan) the left hand sides cannot be simultaneously zeroed and the spin axis must be determined by means of a least square procedure. The magnitude of the angular velocity is then derived from the angle between the vectors R(t1) and R(t2) and the known time difference between the two observations. Our analysis indicates that the Titan pole coordinates are consistent with the occupancy of the fourth Cassini state. The uncertainties are obtained assuming a realistic error of 250 m in the reconstruction of the inertially

  8. DSS 14 antenna calibrations for GSSR/VLA Saturn radar experiments

    Science.gov (United States)

    Guiar, C. N.; Riggs, R. L.; Stevens, R.; Wert, M.

    1988-01-01

    The DSS 14 pointing and gain were calibrated to support X-band bistatic radar observations of Saturn's rings. The observations used the Goldstone Solar System Radar and the National Radio Astronomy Observatory's Very Large Array (VLA) in Socorro, New Mexico. The pointing calibrations were based on conscan offset data collected during Voyager 1 and 2 support passes. The conscan data show angle-of-arrival sensing with no bias and 0.3 mdeg 1-sigma error. Using the calibrations, demonstrated blind pointing performance on Saturn was less than 3 mdeg 1-sigma error. Meteorological observations at the site were used to reduce elevation errors caused by atmospheric refraction. The techniques used corrected about one-third of the error-poorer than expected performance.

  9. Dynamic Experiment Design Regularization Approach to Adaptive Imaging with Array Radar/SAR Sensor Systems

    OpenAIRE

    Stewart Santos; José Tuxpan; Yuriy Shkvarko

    2011-01-01

    We consider a problem of high-resolution array radar/SAR imaging formalized in terms of a nonlinear ill-posed inverse problem of nonparametric estimation of the power spatial spectrum pattern (SSP) of the random wavefield scattered from a remotely sensed scene observed through a kernel signal formation operator and contaminated with random Gaussian noise. First, the Sobolev-type solution space is constructed to specify the class of consistent kernel SSP estimators with the reproducing kernel ...

  10. Radar orthogonality and radar length in Finsler and metric spacetime geometry

    OpenAIRE

    Pfeifer, Christian

    2014-01-01

    The radar experiment connects the geometry of spacetime with an observers measurement of spatial length. We investigate the radar experiment on Finsler spacetimes which leads to a general definition of radar orthogonality and radar length. The directions radar orthogonal to an observer form the spatial equal time surface an observer experiences and the radar length is the physical length the observer associates to spatial objects. We demonstrate these concepts on a forth order polynomial Fins...

  11. Application of Radar Reflectivity Factor in Initializing Cloud-Resolving Mesoscale Model. Part Ⅱ: Numerical Simulation Experiments

    Institute of Scientific and Technical Information of China (English)

    LIU Hongya; XU Haiming; XUE Jishan; HU Zhijin; SHEN Tongli

    2008-01-01

    Microphysics elements and vertical velocity retrieved were incorporated using the nudging method into the initial data assimilation of GRAPES (Global/Regional Assimilation and Prediction System) model.Simulation experiments indicated that nudging technique was effective in forcing the model forecast gradually consistent to the observations, yielding the thermodynamically and dynamically balanced analysis field. As viewed from the simulation results, water vapor is vital to precipitation, and it is a governing factor for the amount and duration of precipitation. The initial cloud water, rain water, and vertical velocity determine the strength distribution of convection and precipitation at the beginning time of forecast; the horizontal wind field steers the motion of the mesoscale weather system embedded in and impacts the position of precipitation zone to a large extent. The simulation experiments show that the influence of the initial retrieval data on prediction weakens with the increase of forecast time, and within the first hour of forecast, the retrieval data have an important impact on the evolution of the weather system, but its influence becomes trivial after the first three hours. Changing the nudging coefficient and the integral time-spacing of numerical model will bring some influences to the results. Herein only one radar reflectivity was used, the radar observations did not cover the whole model domain, and some empirical parameters were used in the retrieval method, therefore some differences still lie between simulation and observation to a certain extent, and further studies on several aspects are expected.

  12. The proximity of Mercury's spin to Cassini state 1 from adiabatic invariance

    Science.gov (United States)

    Peale, S. J.

    2006-04-01

    In determining Mercury's core structure from its rotational properties, the value of the normalized moment of inertia, C/MR, from the location of Cassini 1 is crucial. If Mercury's spin axis occupies Cassini state 1, its position defines the location of the state, where the axis is fixed in the frame precessing with the orbit. Although tidal and core-mantle dissipation drive the spin to the Cassini state with a time scale O(10) years, the spin might still be displaced from the Cassini state if the variations in the orbital elements induced by planetary perturbations, which change the position of the Cassini state, cause the spin to lag behind as it attempts to follow the state. After being brought to the state by dissipative processes, the spin axis is expected to follow the Cassini state for orbit variations with time scales long compared to the 1000 year precession period of the spin about the Cassini state because the solid angle swept out by the spin axis as it precesses is an adiabatic invariant. Short period variations in the orbital elements of small amplitude should cause displacements that are commensurate with the amplitudes of the short period terms. The exception would be if there are forcing terms in the perturbations that are nearly resonant with the 1000 year precession period. The precision of the radar and eventual spacecraft measurements of the position of Mercury's spin axis warrants a check on the likely proximity of the spin axis to the Cassini state. How confident should we be that the spin axis position defines the Cassini state sufficiently well for a precise determination of C/MR? By following simultaneously the spin position and the Cassini state position during long time scale orbital variations over past 3 million years [Quinn, T.R., Tremaine, S., Duncan, M., 1991. Astron. J. 101, 2287-2305] and short time scale variations for 20,000 years [JPL Ephemeris DE 408; Standish, E.M., private communication, 2005], we show that the spin axis

  13. Basics and first experiments demonstrating isolation improvements in the agile polarimetric FM-CW radar – PARSAX

    NARCIS (Netherlands)

    Krasnov, O.A.; Babur, G.P.; Wang, Z.; Ligthart, L.P.; Van der Zwan, F.

    2010-01-01

    The article describes the IRCTR PARSAX radar system, the S-band high-resolution Doppler polarimetric frequency modulated continuous wave (FM-CW) radar with dual-orthogonal sounding signals, which has the possibility to measure all elements of the radar target polarization scattering matrix simultane

  14. Cassini magnetometer measurements in the Jovian environment

    Science.gov (United States)

    Dougherty, M. K.

    2001-05-01

    M. K. Dougherty, and the Cassini magnetometer team The recent Cassini flyby of Jupiter had the spacecraft flying along the dusk flank of the magnetosphere, a region which has only been visited very briefly before during the Ulysses outbound pass. The unique Cassini flyby resulted in the spacecraft making numerous entries into the magnetosheath region as well as into the magnetosphere itself. Initial results from the magnetometer instrument will be described including information concerning the solar wind IMF, the large amount of mirror mode activity measured within the magnetosheath and incursions into the magnetosphere proper.

  15. The relationship between the microwave radar cross section and both wind speed and stress: Model function studies using Frontal Air-Sea Interaction Experiment data

    Science.gov (United States)

    Weissman, David E.; Davidson, Kenneth L.; Brown, Robert A.; Friehe, Carl A.; Li, Fuk

    1994-01-01

    The Frontal Air-Sea Interaction Experiment (FASINEX) provided a unique data set with coincident airborne scatterometer measurements of the ocean surface radar cross section (RCS)(at Ku band) and near-surface wind and wind stress. These data have been analyzed to study new model functions which relate wind speed and surface friction velocity (square root of the kinematic wind stress) to the radar cross section and to better understand the processes in the boundary layer that have a strong influence on the radar backscatter. Studies of data from FASINEX indicate that the RCS has a different relation to the friction velocity than to the wind speed. The difference between the RCS models using these two variables depends on the polarization and the incidence angle. The radar data have been acquired from the Jet Propulsion Laboratory airborne scatterometer. These data span 10 different flight days. Stress measurements were inferred from shipboard instruments and from aircraft flying at low altitudes, closely following the scatterometer. Wide ranges of radar incidence angles and environmental conditions needed to fully develop algorithms are available from this experiment.

  16. Performance evaluation of lunar penetrating radar onboard the rover of CE-3 probe based on results from ground experiments

    Science.gov (United States)

    Zhang, Hong-Bo; Zheng, Lei; Su, Yan; Fang, Guang-You; Zhou, Bin; Feng, Jian-Qing; Xing, Shu-Guo; Dai, Shun; Li, Jun-Duo; Ji, Yi-Cai; Gao, Yun-Ze; Xiao, Yuan; Li, Chun-Lai

    2014-12-01

    Lunar Penetrating Radar (LPR) onboard the rover that is part of the Chang'e-3 (CE-3) mission was firstly utilized to obtain in situ measurements about geological structure on the lunar surface and the thickness of the lunar regolith, which are key elements for studying the evolutional history of lunar crust. Because penetration depth and resolution of LPR are related to the scientific objectives of this mission, a series of ground-based experiments using LPR was carried out, and results of the experimental data were obtained in a glacial area located in the northwest region of China. The results show that the penetration depth of the first channel antenna used for LPR is over 79 m with a resolution of 2.8 m, and that for the second channel antenna is over 50.8 m with a resolution of 17.1 cm.

  17. Performance evaluation of lunar penetrating radar onboard the rover of CE-3 probe based on results from ground experiments

    International Nuclear Information System (INIS)

    Lunar Penetrating Radar (LPR) onboard the rover that is part of the Chang'e-3 (CE-3) mission was firstly utilized to obtain in situ measurements about geological structure on the lunar surface and the thickness of the lunar regolith, which are key elements for studying the evolutional history of lunar crust. Because penetration depth and resolution of LPR are related to the scientific objectives of this mission, a series of ground-based experiments using LPR was carried out, and results of the experimental data were obtained in a glacial area located in the northwest region of China. The results show that the penetration depth of the first channel antenna used for LPR is over 79 m with a resolution of 2.8 m, and that for the second channel antenna is over 50.8 m with a resolution of 17.1 cm

  18. Constructing a Merged Cloud-Precipitation Radar Dataset for Tropical Convective Clouds during the DYNAMO/AMIE Experiment at Addu Atoll

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Zhe; McFarlane, Sally A.; Schumacher, Courtney; Ellis, Scott; Comstock, Jennifer M.; Bharadwaj, Nitin

    2014-05-16

    To improve understanding of the convective processes key to the Madden-Julian-Oscillation (MJO) initiation, the Dynamics of the MJO (DYNAMO) and Atmospheric Radiation Measurement MJO Investigation Experiment (AMIE) collected four months of observations from three radars, the S-band Polarization Radar (S-Pol), the C-band Shared Mobile Atmospheric Research & Teaching Radar (SMART-R), and Ka-band Zenith Radar (KAZR) on Addu Atoll in the tropical Indian Ocean. This study compares the measurements from the S-Pol and SMART-R to those from the more sensitive KAZR in order to characterize the hydrometeor detection capabilities of the two scanning precipitation radars. Frequency comparisons for precipitating convective clouds and non-precipitating high clouds agree much better than non-precipitating low clouds for both scanning radars due to issues in ground clutter. On average, SMART-R underestimates convective and high cloud tops by 0.3 to 1.1 km, while S-Pol underestimates cloud tops by less than 0.4 km for these cloud types. S-Pol shows excellent dynamic range in detecting various types of clouds and therefore its data are well suited for characterizing the evolution of the 3D cloud structures, complementing the profiling KAZR measurements. For detecting non-precipitating low clouds and thin cirrus clouds, KAZR remains the most reliable instrument. However, KAZR is attenuated in heavy precipitation and underestimates cloud top height due to rainfall attenuation 4.3% of the time during DYNAMO/AMIE. An empirical method to correct the KAZR cloud top heights is described, and a merged radar dataset is produced to provide improved cloud boundary estimates, microphysics and radiative heating retrievals.

  19. Quantum radar

    CERN Document Server

    Lanzagorta, Marco

    2011-01-01

    This book offers a concise review of quantum radar theory. Our approach is pedagogical, making emphasis on the physics behind the operation of a hypothetical quantum radar. We concentrate our discussion on the two major models proposed to date: interferometric quantum radar and quantum illumination. In addition, this book offers some new results, including an analytical study of quantum interferometry in the X-band radar region with a variety of atmospheric conditions, a derivation of a quantum radar equation, and a discussion of quantum radar jamming.This book assumes the reader is familiar w

  20. Exploring the surface liquid and lake regions of Titan with laboratory experimentation and Cassini spacecraft data

    Science.gov (United States)

    Wasiak, Felix C.

    The surface liquids and lake regions of Titan are studied utilizing three unique techniques, the results of which are reported in this dissertation. The development of a facility to simulate the surface conditions of Titan, and to conduct experiments on samples within that facility, brings an understanding of Titan's surface not possible through observation and modeling alone. The properties of this facility are presented, including conceptual methodology, design, implementation, performance, and experimental results. The facility, the main component of which is a simulation chamber, allows for Titan temperatures of 90 - 94 K and a 1.5 bar N2 atmosphere. The sample cryogenic liquids or ice undergoing experimentation are condensed within the chamber itself. During experiments, evaporation rates are determined by directly measuring mass, while vapor concentrations are determined using a gas chromatograph fitted with a flame ionization detector. The infrared (IR) spectra of liquid and ice constituents are analyzed with a Fourier transform infrared spectroscopy spectrometer (FTIR) via a fiber optic probe, and all pertinent data is logged in a computer. With the Cassini spacecraft currently orbiting Saturn and conducting periodic close flybys of Titan, a unique opportunity exists to search for change in lake size and shorelines in the northern lake region due to the temporally spaced overlapping data coverage. The results of a Geographic Information System (GIS) approach to monitoring Titan's northern lakes for change found no discernible change in northern lake size or shorelines over a 32 month period. GIS analysis of an estuary of Kraken Mare, for synthetic aperture radar (SAR) swaths taken 47 days apart, indicate a transient feature, with implications for short-term dynamic processes. A geological characterization of Ligeia Mare, the second largest sea on Titan, was performed utilizing Cassini SAR swaths. SAR swaths were mosaicked, and the mosaic interpreted so as

  1. High resolution general purpose D-layer experiment for EISCAT incoherent scatter radars using selected set of random codes

    Directory of Open Access Journals (Sweden)

    T. Turunen

    Full Text Available The ionospheric D-layer is a narrow bandwidth radar target often with a very small scattering cross section. The target autocorrelation function can be obtained by transmitting a series of relatively short coded pulses and computing the correlation between data obtained from different pulses. The spatial resolution should be as high as possible and the spatial side lobes of the codes used should be as small as possible. However, due to the short pulse repetition period (in the order of milliseconds at any instant, the radar receives detectable scattered signals not only from the pulse illuminating the D-region but also from 3–5 ambiguous-range pulses, which makes it difficult to produce a reliable estimate near zero lag of the autocorrelation function. A new experimental solution to this measurement problem, using a selected set of 40-bit random codes with 4 µs elements giving 600 m spatial resolution is presented. The zero lag is approximated by dividing the pulse into two 20-bit codes and computing the correlation between those two pulses. The lowest altitudes of the E-layer are measured by dividing the pulse into 5 pieces of 8 bits, which allows for computation of 4 lags. In addition, coherent integration of data from four pulses is used for obtaining separately the autocorrelation function estimate for the lowest altitudes and in cases when the target contains structures with a long coherence time. Design details and responses of the experiment are given, and analysed test data are shown.

    Key words. Radio science (signal processing; Ionosphere (plasma temperature and density; instruments and techniques

  2. Radar Chart

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Radar Chart collection is an archived product of summarized radar data. The geographic coverage is the 48 contiguous states of the United States. These hourly...

  3. Determination of radar MTF

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, D. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    The ultimate goal of the Current Meter Array (CMA) is to be able to compare the current patterns detected with the array with radar images of the water surface. The internal wave current patterns modulate the waves on the water surface giving a detectable modulation of the radar cross-section (RCS). The function relating the RCS modulations to the current patterns is the Modulation Transfer Function (MTF). By comparing radar images directly with co-located CMA measurements the MTF can be determined. In this talk radar images and CMA measurements from a recent experiment at Loch Linnhe, Scotland, will be used to make the first direct determination of MTF for an X and S band radar at low grazing angles. The technical problems associated with comparing radar images to CMA data will be explained and the solution method discussed. The results suggest the both current and strain rate contribute equally to the radar modulation for X band. For S band, the strain rate contributes more than the current. The magnitude of the MTF and the RCS modulations are consistent with previous estimates when the wind is blowing perpendicular to the radar look direction.

  4. Multifrequency radar observations of bare surface soil moisture content: A laboratory experiment

    NARCIS (Netherlands)

    Mancini, M.; Hoeben, R.; Troch, P.A.

    1999-01-01

    This paper reports on a laboratory experiment that investigates the use of active microwave observations to estimate volumetric soil moisture content. The experiment, held in 1995, was set up at the European Microwave Signature Laboratory, Joint Research Centre of the European Communities, Ispra (It

  5. Hemispherical Resonator Gyro: an IRU for Cassini

    Science.gov (United States)

    Litty, Edward C.; Gresham, Lennor L.; Toole, Patrick A.; Beisecker, Debra A.

    1996-10-01

    The JPL Inertial Reference Unit (IRU) is the single most sophisticated assembly on the Cassini spacecraft. At the core of the IRU is the state-of-the-art, Litton Hemispherical Resonator Gyro (HRG). Launched in October 1997, Cassini's trajectory utilizes gravity assist maneuvers around Venus (two), Earth, and Jupiter over a seven year period, arriving at Saturn in June 2004. Its tour of the Saturnian system will last an additional four years. Although the Stellar Reference Unit (SRU) provides the ultimate reference for the spacecraft Attitude and Articulation Control System (AACS) and can be used to control the spacecraft under benign conditions, the Cassini IRU is essential during maneuvers and fault recovery operations, and for precision attitude stabilization during science data acquisition. Therefore, IRU reliability over the long Cassini mission is a critical concern. Following an extensive evaluation of possible alternatives, the Hemispherical Resonator Gyro (HRG) based IRU developed by Litton Guidance and Control Systems, was chosen for the Cassini mission. The HRG is an attitude rate sensor that has no physical wear-out mechanisms. Based on a principle first described by G. H. Bryan (1890) in his paper, 'On Beats in the Vibrations of a Revolving Cylinder or Bell', the HRG is created by vibrating a quartz resonator. This paper discusses the theory and modifications required to the design of the standard Space Inertial Reference Unit to adapt it to meet the requirements of the Cassini mission and the AACS interface. The Cassini mission is the first use of an IRU for a deep space planetary mission that does not use a spun-mass sensor.

  6. Radar Fundamentals, Presentation

    OpenAIRE

    Jenn, David

    2008-01-01

    Topics include: introduction, radar functions, antennas basics, radar range equation, system parameters, electromagnetic waves, scattering mechanisms, radar cross section and stealth, and sample radar systems.

  7. Cassini's Grand Finale: The Final Orbits

    Science.gov (United States)

    Spilker, Linda; Edgington, Scott

    2016-04-01

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

  8. A scaled down laboratory experiment of cross-borehole pulse radar signatures for detection of a terminated tunnel

    Science.gov (United States)

    Cho, Jae-Hyoung; Jung, Ji-Hyun; Kim, Se-Yun; Yook, Jong-Gwan

    2016-09-01

    In the cross-borehole pulse radar signatures measured near the front end of a terminated tunnel, the time-of-arrival (TOA) with fully penetrated tunnel is significantly shortened due to the relatively fast pulse propagation in an empty tunnel compared with the TOA obtained without a tunnel. To analyze the TOA variation with the protrusion length of the terminated tunnel from the line-of-sight between two antennas or boreholes, additional borehole pairs are required around the terminated tunnel in spite of their high construction costs. As an alternative, a laboratory scaled down experiment, which has a high ability to simulate different underground configurations, is designed for investigation into the TOA effects of tunnel termination. A round ceramic rod with a careful selection of its dielectric constant is immersed in pure water in a water tank and used to simulate the tunnel in the experiment. Coaxial fed dipole antennas with balanced wire and ferrite cores are used not only to suppress borehole-guided waves but also to generate a symmetric radiation pattern. The accuracy of the laboratory scaled down experiment is verified by the symmetricity of the measured diffraction pattern of the fully penetrated ceramic rod. Then, the TOA variation is measured for the protrusion length of the ceramic rod relative to the line-of-sight between two antennas from  +80 mm to  ‑80 mm with an equal step of 5 mm. Based on the scaled down experimental measurements of the TOA, it is found that a tunnel 1.2 m away from the measuring cross-borehole section closely approaches the scaled up variation curve under the same conditions of the protrusion length.

  9. Radar equations for modern radar

    CERN Document Server

    Barton, David K

    2012-01-01

    Based on the classic Radar Range-Performance Analysis from 1980, this practical volume extends that work to ensure applicability of radar equations to the design and analysis of modern radars. This unique book helps you identify what information on the radar and its environment is needed to predict detection range. Moreover, it provides equations and data to improve the accuracy of range calculations. You find detailed information on propagation effects, methods of range calculation in environments that include clutter, jamming and thermal noise, as well as loss factors that reduce radar perfo

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

    International Nuclear Information System (INIS)

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

  11. Layered Subsurface Structure at the Chang'e-3 Landing Site Derived from Imaging Data: Awaiting Ground Truth from Chang'e-3 Radar Experiments

    Science.gov (United States)

    Qiao, L.; Xiao, Z.; Xiao, L.; Zhao, J.

    2014-12-01

    Quantifying the subsurface stratigraphic and tectonic features of the Moon, with a depth from a few to thousands of meters, can provide significant information for solving scientific mysteries concerning regional and global evolution history. In December 2013, the Chinese Chang'e-3 (CE-3) spacecraft, carrying the Yutu (Jade Rabbit) rover, successfully landed on the northern Mare Imbrium, the Moon. The surface in-situ radar experiments by CE-3 mission provide an unprecedented opportunity to study the shallow subsurface geology of the Moon. While the processing and interpretation of radar observations usually depend on certain geophysical models and should consider regional geological settings. In this work, we quantified the subsurface structure at the CE-3 landing site using imaging data and illustrated a multi-layer subsurface structure model including three layers of regolith, two layers of basalt deposits and one layer of ejecta. Our result can provide essential references for CE-3 radar data processing and interpretation. The CE-3 radar observations can in turn validate previous technique for quantifying subsurface geology using imaging data, thus further deepening our understanding of lunar geoscience and exploration.

  12. Design and development of the Cassini main engine assembly Gimbal mechanism

    Science.gov (United States)

    Rudolph, Dale

    1996-01-01

    Cassini is an international cooperative effort between NASA, which is producing the orbiter spacecraft, the European Space Agency, which is providing the Huygens Probe, and the Italian Space Agency, which is responsible for the spacecraft radio antenna and portions of three scientific experiments. In the U.S., the mission is managed by NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. Lockheed-Martin successfully bid on the contract to build the PMS (Propulsion Module Subsystem) for this project. The Cassini spacecraft will be launched on an expedition to Saturn in October, 1997. Its mission is to enter orbit around Saturn in July, 2004, and to explore its moons, rings, and magnetic environment for four years. Cassini will carry the Huygens probe, an instrument package equipped with a parachute, which is designed to study the atmosphere and surface of Saturn's largest moon, Titan.

  13. Cassini observations of Saturn's southern polar cusp

    CERN Document Server

    Arridge, C S; Achilleos, N; Bogdanova, Y V; Bunce, E J; Cowley, S W H; Fazakerley, A N; Khurana, K K; Lamy, L; Leisner, J S; Roussos, E; Russell, C T; Zarka, P; Coates, A J; Dougherty, M K; Jones, G H; Krimigis, S M; Krupp, N

    2016-01-01

    The magnetospheric cusps are important sites of the coupling of a magnetosphere with the solar wind. The combination of both ground- and space-based observations at Earth have enabled considerable progress to be made in understanding the terrestrial cusp and its role in the coupling of the magnetosphere to the solar wind via the polar magnetosphere. Voyager 2 fully explored Neptune's cusp in 1989 but highly inclined orbits of the Cassini spacecraft at Saturn present the most recent opportunity to repeatedly studying the polar magnetosphere of a rapidly rotating planet. In this paper we discuss observations made by Cassini during two passes through Saturn's southern polar magnetosphere. Our main findings are that i) Cassini directly encounters the southern polar cusp with evidence for the entry of magnetosheath plasma into the cusp via magnetopause reconnection, ii) magnetopause reconnection and entry of plasma into the cusp can occur over a range of solar wind conditions, and iii) double cusp morphologies are...

  14. Navigational Use of Cassini Delta V Telemetry

    Science.gov (United States)

    Roth, Duane C.; Antreasian, Peter G.; Ardalan, Shadan M.; Criddle, Kevin E.; Goodson, Troy; Ionasescu, Rodica; Jones, Jeremy B.; Parcher, Daniel W.; Pelletier, Frederic J.; Thompson, Paul F.; Vaughan, Andrew T.

    2008-01-01

    Telemetry data are used to improve navigation of the Saturn orbiting Cassini spacecraft. Thrust induced delta V's are computed on-board the spacecraft, recorded in telemetry, and downlinked to Earth. This paper discusses how and why the Cassini Navigation team utilizes spacecraft delta V telemetry. Operational changes making this information attractive to the Navigation Team will be briefly discussed, as will spacecraft hardware and software algorithms responsible for the on-board computation. An analysis of past delta V telemetry, providing calibrations and accuracies that can be applied to the estimation of future delta V activity, is described.

  15. Cassini states for black hole binaries

    OpenAIRE

    Correia, Alexandre C. M.

    2015-01-01

    Cassini states correspond to the equilibria of the spin axis of a body when its orbit is perturbed. They were initially described for planetary satellites, but the spin axes of black hole binaries also present this kind of equilibria. In previous works, Cassini states were reported as spin-orbit resonances, but actually the spin of black hole binaries is in circulation and there is no resonant motion. Here we provide a general description of the spin dynamics of black hole binary systems base...

  16. Radar imaging

    OpenAIRE

    Borden, Brett; Cheney, Margaret

    2013-01-01

    The article of record as published may be found at http://dx.doi.org/1088/0266-5611/29/5/050301 Because of their ability to operate without regard to day, night or weather conditions, radar systems are ubiquitous in remote sensing operations and are used in a wide variety of commercial and military applications. High resolution radar imaging, however, is a remote sensing subcategory that requires raw radar data to be collected over an artificially extended aperture that is much...

  17. Monitoring Ground Subsidence in Hong Kong via Spaceborne Radar: Experiments and Validation

    Directory of Open Access Journals (Sweden)

    Yuxiao Qin

    2015-08-01

    Full Text Available The persistent scatterers interferometry (PSI technique is gradually becoming known for its capability of providing up to millimeter accuracy of measurement on ground displacement. Nevertheless, there is still quite a good amount of doubt regarding its correctness or accuracy. In this paper, we carried out an experiment corroborating the capability of the PSI technique with the help of a traditional survey method in the urban area of Hong Kong, China. Seventy three TerraSAR-X (TSX and TanDEM-X (TDX images spanning over four years are used for the data process. There are three aims of this study. The first is to generate a displacement map of urban Hong Kong and to check for spots with possible ground movements. This information will be provided to the local surveyors so that they can check these specific locations. The second is to validate if the accuracy of the PSI technique can indeed reach the millimeter level in this real application scenario. For validating the accuracy of PSI, four corner reflectors (CR were installed at a construction site on reclaimed land in Hong Kong. They were manually moved up or down by a few to tens of millimeters, and the value derived from the PSI analysis was compared to the true value. The experiment, carried out in unideal conditions, nevertheless proved undoubtedly that millimeter accuracy can be achieved by the PSI technique. The last is to evaluate the advantages and limitations of the PSI technique. Overall, the PSI technique can be extremely useful if used in collaboration with other techniques, so that the advantages can be highlighted and the drawbacks avoided.

  18. Cassini UVIS Saturn Auroral Images from the 2013 HST/Cassini Campaign

    OpenAIRE

    Pryor, Wayne; Jouchoux, Alain; Esposito, Larry; Crary, Franck; Radioti, Aikaterini; Grodent, Denis; Gustin, Jacques; Gérard, Jean-Claude; Kurth, William; Mitchell, Donald; Nichols, Jonathan; Badman, Sarah

    2013-01-01

    In 2013 coordinated observations of Saturn by the Cassini spacecraft and Hubble Space Telescope (HST) were obtained. During these observations the Cassini spacecraft provided a high-latitude view of Saturn's auroras. Intense auroras were observed by the Ultraviolet Imaging Spectrograph (UVIS) from close range (about 5 Saturn radii away). A 6-frame UVIS movie has been constructed from some of the observations from May 20- 21, 2013 showing the evolution of two bright auroral features. We report...

  19. Managing Cassini Safe Mode Attitude at Saturn

    Science.gov (United States)

    Burk, Thomas A.

    2010-01-01

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

  20. Modernization of the Cassini Ground System

    Science.gov (United States)

    Razo, Gus; Fujii, Tammy J.

    2014-01-01

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

  1. Variations of topside ionospheric scale heights over Millstone Hill during the 30-day incoherent scatter radar experiment

    Directory of Open Access Journals (Sweden)

    L. Liu

    2007-10-01

    Full Text Available A 30-day incoherent scatter radar (ISR experiment was conducted at Millstone Hill (288.5° E, 42.6° N from 4 October to 4 November 2002. The altitude profiles of electron density Ne, ion and electron temperature (Ti and Te, and line-of-sight velocity during this experiment were processed to deduce the topside plasma scale height Hp, vertical scale height VSH, Chapman scale height Hm, ion velocity, and the relative altitude gradient of plasma temperature (dTp/dh/Tp, as well as the F2 layer electron density (NmF2 and height (hmF2. These data are analyzed to explore the variations of the ionosphere over Millstone Hill under geomagnetically quiet and disturbed conditions. Results show that ionospheric parameters generally follow their median behavior under geomagnetically quiet conditions, while the main feature of the scale heights, as well as other parameters, deviated significantly from their median behaviors under disturbed conditions. The enhanced variability of ionospheric scale heights during the storm-times suggests that the geomagnetic activity has a major impact on the behavior of ionospheric scale heights, as well as the shape of the topside electron density profiles. Over Millstone Hill, the diurnal behaviors of the median VSH and Hm are very similar to each other and are not so tightly correlated with that of the plasma scale height Hp or the plasma temperature. The present study confirms the sensitivity of the ionospheric scale heights over Millstone Hill to thermal structure and dynamics. The values of VSH/Hp tend to decrease as (dTp/dh/Tp becomes larger or the dynamic processes become enhanced.

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

    Science.gov (United States)

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

    2011-01-01

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

  3. Determining Titan surface topography from Cassini SAR data

    Science.gov (United States)

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

    2009-01-01

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

  4. Cassini-VIMS at Jupiter: Solar occultation measurements using Io

    Science.gov (United States)

    Formisano, V.; D'Aversa, E.; Bellucci, G.; Baines, K.H.; Bibring, J.-P.; Brown, R.H.; Buratti, B.J.; Capaccioni, F.; Cerroni, P.; Clark, R.N.; Coradini, A.; Cruikshank, D.P.; Drossart, P.; Jaumann, R.; Langevin, Y.; Matson, D.L.; McCord, T.B.; Mennella, V.; Nelson, R.M.; Nicholson, P.D.; Sicardy, B.; Sotin, C.; Chamberlain, M.C.; Hansen, G.; Hibbits, K.; Showalter, M.; Filacchione, G.

    2003-01-01

    We report unusual and somewhat unexpected observations of the jovian satellite Io, showing strong methane absorption bands. These observations were made by the Cassini VIMS experiment during the Jupiter flyby of December/January 2000/2001. The explanation is straightforward: Entering or exiting from Jupiter's shadow during an eclipse, Io is illuminated by solar light which has transited the atmosphere of Jupiter. This light, therefore becomes imprinted with the spectral signature of Jupiter's upper atmosphere, which includes strong atmospheric methane absorption bands. Intercepting solar light refracted by the jovian atmosphere, Io essentially becomes a "miffor" for solar occultation events of Jupiter. The thickness of the layer where refracted solar light is observed is so large (more than 3000 km at Io's orbit), that we can foresee a nearly continuous multi-year period of similar events at Saturn, utilizing the large and bright ring system. During Cassini's 4-year nominal mission, this probing tecnique should reveal information of Saturn's atmosphere over a large range of southern latitudes and times. ?? 2003 Elsevier Inc. All rights reserved.

  5. Saturn's ULF wave foreshock boundary: Cassini observations

    CERN Document Server

    Andres, Nahuel; Bertucci, Cesar; Mazelle, Christian; Dougherty, Michele K

    2012-01-01

    Even though the solar wind is highly supersonic, intense ultra-low frequency (ULF) wave activity has been detected in regions just upstream of the bow shocks of magnetized planets. This feature was first observed ahead of the Earth's bow shock, and the corresponding region was called the ULF wave foreshock, which is embedded within the planet's foreshock. The properties as well as the spatial distribution of ULF waves within the Earth's foreshock have been extensively studied over the last three decades and have been explained as a result of plasma instabilities triggered by solar wind ions backstreaming from the bow shock. Since July 2004, the Cassini spacecraft has characterized the Saturnian plasma environment including its upstream region. Since Cassini's Saturn orbit insertion (SOI) in June 2004 through August 2005, we conducted a detailed survey and analysis of observations made by the Vector Helium Magnetometer (VHM). The purpose of the present study is to characterize the properties of waves observed ...

  6. Cassini Imaging Science: Initial Results on Phoebe and Iapetus

    OpenAIRE

    Porco, C. C.; Dyudina, U.; Ingersoll, A. P.

    2005-01-01

    The Cassini Imaging Science Subsystem acquired high-resolution imaging data on the outer Saturnian moon, Phoebe, during Cassini's close flyby on 11 June 2004 and on Iapetus during a flyby on 31 December 2004. Phoebe has a heavily cratered and ancient surface, shows evidence of ice near the surface, has distinct layering of different materials, and has a mean density that is indicative of an ice-rock mixture. Iapetus's dark leading side (Cassini Regio) is ancient, heavily cratered terrain bise...

  7. Cassini UVIS observations of Titan nightglow spectra

    OpenAIRE

    Ajello, Joseph M.; West, Robert A.; Gustin, Jacques; Larsen, Kristopher; Stewart, A. Ian F.; Esposito, Larry W.; Mcclintock, William E.; Holsclaw, Gregory M.; Bradley, E. Todd

    2012-01-01

    In this paper we present the first nightside EUV and FUV airglow limb spectra of Titan showing molecular emissions. The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed photon emissions of Titan's day and night limb-airglow and disk-airglow on multiple occasions, including during an eclipse observation. The 71 airglow observations analyzed in this paper show EUV (600-1150 Å) and FUV (1150-1900 Å) atomic multiplet lines and band emissions arising from either photoelectron induced fluor...

  8. Cassini observations of Saturn's southern polar cusp

    OpenAIRE

    Arridge, Christopher Stephen; Jasinski, J. M.; Achilleos, Nicholas; Bogdanova, Y. V.; E. J. Bunce; Cowley, S. W. H; A. N. Fazakerley; Khurana, K K; Lamy, Laurent; J. S. Leisner; Roussos, E; Russell, C. T.; Zarka, P.; Coates, A. J.; Dougherty, M. K.

    2016-01-01

    The magnetospheric cusps are important sites of the coupling of a magnetosphere with the solar wind. The combination of both ground- and space-based observations at Earth have enabled considerable progress to be made in understanding the terrestrial cusp and its role in the coupling of the magnetosphere to the solar wind via the polar magnetosphere. Voyager 2 fully explored Neptune’s cusp in 1989 but highly inclined orbits of the Cassini spacecraft at Saturn present the most recent opportunit...

  9. Cassini states for black hole binaries

    Science.gov (United States)

    Correia, Alexandre C. M.

    2016-03-01

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

  10. Cassini observations of Saturn's southern polar cusp

    Science.gov (United States)

    Arridge, C. S.; Jasinski, J. M.; Achilleos, N.; Bogdanova, Y. V.; Bunce, E. J.; Cowley, S. W. H.; Fazakerley, A. N.; Khurana, K. K.; Lamy, L.; Leisner, J. S.; Roussos, E.; Russell, C. T.; Zarka, P.; Coates, A. J.; Dougherty, M. K.; Jones, G. H.; Krimigis, S. M.; Krupp, N.

    2016-04-01

    The magnetospheric cusps are important sites of the coupling of a magnetosphere with the solar wind. The combination of both ground- and space-based observations at Earth has enabled considerable progress to be made in understanding the terrestrial cusp and its role in the coupling of the magnetosphere to the solar wind via the polar magnetosphere. Voyager 2 fully explored Neptune's cusp in 1989, but highly inclined orbits of the Cassini spacecraft at Saturn present the most recent opportunity to repeatedly study the polar magnetosphere of a rapidly rotating planet. In this paper we discuss observations made by Cassini during two passes through Saturn's southern polar magnetosphere. Our main findings are that (i) Cassini directly encounters the southern polar cusp with evidence for the entry of magnetosheath plasma into the cusp via magnetopause reconnection, (ii) magnetopause reconnection and entry of plasma into the cusp can occur over a range of solar wind conditions, and (iii) double cusp morphologies are consistent with the position of the cusp oscillating in phase with Saturn's global magnetospheric periodicities.

  11. Cassini states for black-hole binaries

    CERN Document Server

    Correia, Alexandre C M

    2016-01-01

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

  12. Cassini Scientist for a Day: an international contest in Greece

    Science.gov (United States)

    Solomonidou, Anezina; Moussas, Xenophon; Xystouris, Georgios; Coustenis, Athena; Lebreton, Jean-Pierre; Katsavrias, Christos; Bampasidis, Georgios; Kyriakopoulos, Konstantinos; Kouloumvakos, Athanasios; Patsou, Ioanna

    2013-04-01

    The Cassini Outreach Team of NASA's Jet Propulsion Laboratory is being organizing a brilliant school contest in Astronomy focusing in the Saturnian system. This essay contest provides school students all around the worlds with the opportunity to get involved in astronomy and astrophysics and planetary sciences in particular. From 2010 the 'Cassini Scientist for a Day' contest has being one of the most successful as well as important outreach activities of ESA and NASA in Greece with hundreds of participants all over Greece. The number of participants is growing rapidly every year. This type of school competition in Greece is particularly important since Astronomy and Astrophysics and Space Sciences, although very popular, are not included in the school curricula and thus students rarely have the opportunity to experience and participate actively in these subjects. For the years 2010 and 2011, the Space Physics Group of the Astronomy, Astrophysics and Mechanics section of the University of Athens in association with external colleagues has been selected as the co-ordinator of NASA for the competition in Greece. Under the guidance of Cassini Outreach team, the members of the Space Physics Group have informed, explained and spread the rules of the competition at primary, secondary and high schools all over Greece. In general, the students have the option to choose Cassini monitoring between three targets of the Saturnian system, which the participants show that will bring the best scientific result. Their arguments should be summarized in an essay of 500 words more or less. They also have the option to do team work through groups of maximum three students. The participation in the contest for 2010 was unexpectedly high and thoroughly satisfied. The winners awarded through a ceremony which was held in the largest amphitheater at the central building of the University of Athens, that was fully packed. The following year 2011 the participation increased up to 300% while

  13. Mercury radar speckle dynamics

    Science.gov (United States)

    Holin, Igor V.

    2010-06-01

    Current data reveal that Mercury is a dynamic system with a core which has not yet solidified completely and is at least partially decoupled from the mantle. Radar speckle displacement experiments have demonstrated that the accuracy in spin-dynamics determination for Earth-like planets can approach 10 -5. The extended analysis of space-time correlation properties of radar echoes shows that the behavior of speckles does not prevent estimation of Mercury's instantaneous spin-vector components to accuracy of a few parts in 10 7. This limit can be reached with more powerful radar facilities and leads to constraining the interior in more detail from effects of spin dynamics, e.g., from observation of the core-mantle interplay through high precision monitoring of the 88-day spin-variation of Mercury's crust.

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

    Science.gov (United States)

    Equils, Douglas J.

    2008-01-01

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

  15. Weather Radar Stations

    Data.gov (United States)

    Department of Homeland Security — These data represent Next-Generation Radar (NEXRAD) and Terminal Doppler Weather Radar (TDWR) weather radar stations within the US. The NEXRAD radar stations are...

  16. The architecture of the Cassini division

    Science.gov (United States)

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

    2010-01-01

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

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

    Science.gov (United States)

    Murdin, P.

    2000-11-01

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

  18. Hydrogeophysical characterization of transport processes in fractured rock by combining push-pull and single-hole ground penetrating radar experiments

    Science.gov (United States)

    Shakas, Alexis; Linde, Niklas; Baron, Ludovic; Bochet, Olivier; Bour, Olivier; Le Borgne, Tanguy

    2016-02-01

    The in situ characterization of transport processes in fractured media is particularly challenging due to the considerable spatial uncertainty on tracer pathways and dominant controlling processes, such as dispersion, channeling, trapping, matrix diffusion, ambient and density driven flows. We attempted to reduce this uncertainty by coupling push-pull tracer experiments with single-hole ground penetrating radar (GPR) time-lapse imaging. The experiments involved different injection fractures, chaser volumes and resting times, and were performed at the fractured rock research site of Ploemeur in France (H+ network, hplus.ore.fr/en). For the GPR acquisitions, we used both fixed and moving antenna setups in a borehole that was isolated with a flexible liner. During the fixed-antenna experiment, time-varying GPR reflections allowed us to track the spatial and temporal dynamics of the tracer during the push-pull experiment. During the moving antenna experiments, we clearly imaged the dominant fractures in which tracer transport took place, fractures in which the tracer was trapped for longer time periods, and the spatial extent of the tracer distribution (up to 8 m) at different times. This demonstrated the existence of strongly channelized flow in the first few meters and radial flow at greater distances. By varying the resting time of a given experiment, we identified regions affected by density-driven and ambient flow. These experiments open up new perspectives for coupled hydrogeophysical inversion aimed at understanding transport phenomena in fractured rock formations.

  19. Update on VLBA Astrometry of Cassini

    Science.gov (United States)

    Jones, Dayton L.; Folkner, William M.; Jacobson, Robert A.; Jacobs, Christopher S.; Romney, Jon; Dhawan, Vivek; Fomalont, Edward B.

    2015-01-01

    The NRAO Very Long Baseline Array (VLBA) has been used to measure positions of the Cassini spacecraft 2-3 times per year during the decade since it arrived at Saturn. Combining these measurements with fits for Cassini's orbit about Saturn from Doppler tracking by the NASA Deep Space Network provides accurate positions for the Saturn system barycenter in the inertial International Celestial Reference Frame (ICRF) at each observing epoch. These positions in turn help to improve our knowledge of Saturn's orbit and thus the planetary ephemeris on which future interplanetary spacecraft navigation, pulsar timing, and studies of solar system dynamics depend. This observational program will continue to the end of Cassini's mission in 2017, thereby covering as large a fraction of Saturn's orbital period as possible. A multi-year period of accurate astrometry also increases the range of times over which ephemeris improvements can be extrapolated. Our current residuals with respect to JPL's DE430 ephemeris are approximately 0.2 mas in right ascension and 0.3 mas in declination. The primary error sources are residual troposphere delay calibration errors and uncertainties in the ICRF positions of some of our phase reference sources. The reference source position uncertainties are being reduced by continuing VLBI observations. Similar VLBI techniques will be applied to the Juno spacecraft when it begins orbiting Jupiter in 2016, thereby improving the orbit for this planet as well. This work has been carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Support from the NASA Planetary Astronomy Program is gratefully acknowledged. The VLBA is a facility of the National Radio Astronomy Observatory, which is operated by Associated Universities, Inc, under a cooperative agreement with the National Science Foundation.

  20. A Traveling Exhibit of Cassini Image Science

    Science.gov (United States)

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

    2007-10-01

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

  1. Die Cassini-Karte (1750-1815)

    OpenAIRE

    Helfer, Malte

    2009-01-01

    Die Cassini-Karte deckt als historische topographische Karte aus dem späten 18. bzw. frühen 19. Jahrhundert den französischen Teil der Großregion SaarLorLux ab. Gemeinsam mit der Tranchot-Müffling-Karte für den deutschen Bereich sowie der Ferraris-Karte für den wallonischen Teil sowie das Großherzogtum Luxemburg kann so die Situation fast der gesamten Großregion SaarLorLux vor den umwälzenden Veränderungen durch die industrielle Revolution dargestellt werden. 1

  2. Simulation of Radar-Backscattering from Phobos - A Contribution to the Experiment MARSIS aboard MarsExpress

    Science.gov (United States)

    Plettemeier, D.; Hahnel, R.; Hegler, S.; Safaeinili, A.; Orosei, R.; Cicchetti, A.; Plaut, J.; Picardi, G.

    2009-04-01

    MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) on board MarsExpress is the first and so far the only space borne radar that observed the Martian moon Phobos. Radar echoes were measured for different flyby trajectories. The primary aim of the low frequency sounding of Phobos is to prove the feasibility of deep sounding, into the crust of Phobos. In this poster we present a numerical method that allows a very precise computation of radar echoes backscattered from the surface of large objects. The software is based on a combination of physical optics calculation of surface scattering of the radar target, and Method of Moments to calculate the radiation pattern of the whole space borne radar system. The calculation of the frequency dependent radiation pattern takes into account all relevant gain variations and coupling effects aboard the space craft. Based on very precise digital elevation models of Phobos, patch models in the resolution of lambda/10 were generated. Simulation techniques will be explained and a comparison of simulations and measurements will be shown. SURFACE BACKSCATTERING SIMULATOR FOR LARGE OBJECTS The computation of surface scattering of the electromagnetic wave incident on Phobos is based on the Physical Optics method. The scattered field can be expressed by the induced equivalent surface currents on the target. The Algorithm: The simulation program itself is split into three phases. In the first phase, an illumination test checks whether a patch will be visible from the position of the space craft. If this is not the case, the patch will be excluded from the simulation. The second phase serves as a preparation stage for the third phase. Amongst other tasks, the dyadic products for the Js and Ms surface currents are calculated. This is a time-memory trade-off: the simulation will need additional 144 bytes of RAM for every patch that passes phase one. However, the calculation of the dyads is expensive, so that considerable

  3. Simulation of Radar-Backscattering from Phobos - A Contribution to the Experiment MARSIS aboard MarsExpress

    Science.gov (United States)

    Plettemeier, D.; Hahnel, R.; Hegler, S.; Safaeinili, A.; Orosei, R.; Cicchetti, A.; Plaut, J.; Picardi, G.

    2009-04-01

    MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) on board MarsExpress is the first and so far the only space borne radar that observed the Martian moon Phobos. Radar echoes were measured for different flyby trajectories. The primary aim of the low frequency sounding of Phobos is to prove the feasibility of deep sounding, into the crust of Phobos. In this poster we present a numerical method that allows a very precise computation of radar echoes backscattered from the surface of large objects. The software is based on a combination of physical optics calculation of surface scattering of the radar target, and Method of Moments to calculate the radiation pattern of the whole space borne radar system. The calculation of the frequency dependent radiation pattern takes into account all relevant gain variations and coupling effects aboard the space craft. Based on very precise digital elevation models of Phobos, patch models in the resolution of lambda/10 were generated. Simulation techniques will be explained and a comparison of simulations and measurements will be shown. SURFACE BACKSCATTERING SIMULATOR FOR LARGE OBJECTS The computation of surface scattering of the electromagnetic wave incident on Phobos is based on the Physical Optics method. The scattered field can be expressed by the induced equivalent surface currents on the target. The Algorithm: The simulation program itself is split into three phases. In the first phase, an illumination test checks whether a patch will be visible from the position of the space craft. If this is not the case, the patch will be excluded from the simulation. The second phase serves as a preparation stage for the third phase. Amongst other tasks, the dyadic products for the Js and Ms surface currents are calculated. This is a time-memory trade-off: the simulation will need additional 144 bytes of RAM for every patch that passes phase one. However, the calculation of the dyads is expensive, so that considerable

  4. A data assimilation experiment of RASTA airborne cloud radar data during HyMeX IOP16

    Science.gov (United States)

    Saussereau, Gaël; Caumont, Olivier; Delanoë, Julien

    2015-04-01

    The main goal of HyMeX first special observing period (SOP1), which took place from 5 September to 5 November 2012, was to document the heavy precipitation events and flash floods that regularly affect the north-western Mediterranean coastal areas. In the two-month campaign, around twenty rainfall events were documented in France, Italy, and Spain. Among the instrumental platforms that were deployed during SOP1, the Falcon 20 of the Safire unit (http://www.safire.fr/) made numerous flights in storm systems so as to document their thermodynamic, microphysical, and dynamical properties. In particular, the RASTA cloud radar (http://rali.projet.latmos.ipsl.fr/) was aboard this aircraft. This radar measures vertical profiles of reflectivity and Doppler velocity above and below the aircraft. This unique instrument thus allows us to document the microphysical properties and the speed of wind and hydrometeors in the clouds, quasi-continuously in time and at a 60-m vertical resolution. For this field campaign, a special version of the numerical weather prediction (NWP) Arome system was developed to cover the whole north-western Mediterranean basin. This version, called Arome-WMed, ran in real time during the SOP in order to, notably, schedule the airborne operations, especially in storm systems. Like the operational version, Arome-WMed delivers forecasts at a horizontal resolution of 2.5 km with a one-moment microphysical scheme that predicts the evolution of six water species: water vapour, cloud liquid water, rainwater, pristine ice, snow, and graupel. Its three-dimensional variational (3DVar) data assimilation (DA) system ingests every three hours (at 00 UTC, 03 UTC, etc.) numerous observations (radiosoundings, ground automatic weather stations, radar, satellite, GPS, etc.). In order to provide improved initial conditions to Arome-WMed, especially for heavy precipitation events, RASTA data were assimilated in Arome-WMed 3DVar DA system for IOP16 (26 October 2012), to

  5. Software Radar Technology

    OpenAIRE

    Tang Jun; Wu Hong; Wei Kun-peng

    2015-01-01

    In this paper, the definition and the key features of Software Radar, which is a new concept, are proposed and discussed. We consider the development of modern radar system technology to be divided into three stages: Digital Radar, Software radar and Intelligent Radar, and the second stage is just commencing now. A Software Radar system should be a combination of various modern digital modular components conformed to certain software and hardware standards. Moreover, a software radar system w...

  6. Enhancing Cassini Operations & Science Planning Tools

    Science.gov (United States)

    Castello, Jonathan

    2012-01-01

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

  7. Cassini-Huygens results on Titan's surface

    Institute of Scientific and Technical Information of China (English)

    Athena Coustenis; Mathieu Hirtzig

    2009-01-01

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

  8. Cassini-Huygens results on Titan's surface

    International Nuclear Information System (INIS)

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

  9. Limitations of Radar Coordinates

    OpenAIRE

    Bini, Donato; Lusanna, Luca; Mashhoon, Bahram

    2004-01-01

    The construction of a radar coordinate system about the world line of an observer is discussed. Radar coordinates for a hyperbolic observer as well as a uniformly rotating observer are described in detail. The utility of the notion of radar distance and the admissibility of radar coordinates are investigated. Our results provide a critical assessment of the physical significance of radar coordinates.

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

    Science.gov (United States)

    1997-01-01

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

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

    OpenAIRE

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

    2009-01-01

    This study reports direct detection by the Cassini plasma spectrometer of freshly-produced water-group ions (O+, OH+, H2O+, H3O+) and heavier water dimer ions (HxO(2))(+) very close to Enceladus where the plasma begins to emerge from the plume. The data were obtained during two close ( 52 and 25 km) flybys of Enceladus in 2008 and are similar to ion data in cometary comas. The ions are observed in detectors looking in the Cassini ram direction exhibiting energies consistent with the Cassini s...

  12. The proximity of Mercury's spin to Cassini state 1

    OpenAIRE

    Peale, S. J.

    2005-01-01

    In determining Mercury's core structure from its rotational properties, the value of the normalized moment of inertia, $C/MR^2$, from the location of Cassini 1 is crucial. If Mercury's spin axis occupies Cassini state 1, its position defines the location of the state. The spin might be displaced from the Cassini state if the spin is unable to follow the changes in the state position induced by the variations in the orbital parameters and the geometry of the solar system. The spin axis is expe...

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

    Science.gov (United States)

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

    2011-01-01

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

  14. RADAR PPI Scope Overlay

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — RADAR PPI Scope Overlays are used to position a RADAR image over a station at the correct resolution. The archive maintains several different RADAR resolution...

  15. Advances in bistatic radar

    CERN Document Server

    Willis, Nick

    2007-01-01

    Advances in Bistatic Radar updates and extends bistatic and multistatic radar developments since publication of Willis' Bistatic Radar in 1991. New and recently declassified military applications are documented. Civil applications are detailed including commercial and scientific systems. Leading radar engineers provide expertise to each of these applications. Advances in Bistatic Radar consists of two major sections: Bistatic/Multistatic Radar Systems and Bistatic Clutter and Signal Processing. Starting with a history update, the first section documents the early and now declassified military

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

    Science.gov (United States)

    Lee, Allan Y.; Wang, Eric K.

    2013-01-01

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

  17. Cassini Observes the Active South Pole of Enceladus

    Science.gov (United States)

    Porco, C. C.; Helfenstein P.; Thomas, P. C.; Ingersoll, A. P.; Wisdom, J.; West, R.; Neukum, G.; Denk, T.; Wagner, R.; Roatsch, T.; Kieffer, S.; Turtle, E.; McEwen, A.; Johnson, T. V.; Rathbun, J.; Veverka, J.; Wilson, D.; Perry, J.; Spitale, J.; Brahic, A.; Burns, J. A.; DelGenio, A. D.; Dones, L.; Murray, C. D.; Squyres, S.

    2007-01-01

    Cassini has identified a geologically active province a the south pole of Saturn's moon Enceladus. The shape of Enceladus suggests a possible intense heating epoch in the past by capture into a 1:4 secondary spin/orbit resonance.

  18. Kosmischer Staubsammler - Weltraumsonde Cassini meldet Erfolge nach Heidelberg

    OpenAIRE

    Trieloff, Mario; Srama, Ralf

    2016-01-01

    Die europäisch-amerikanische Raummission Cassini-Huygens startete im Oktober 1997. Ein Ziel, die Erforschung des Gasplaneten Saturn und seiner Monde. Mit an Bord sind zwölf wissenschaftliche Instrumente. Darunter der Cosmic Dust Analyser, kurz CDA. Ein Staubdetektor, an dessen Konstruktion auch das Max-Planck-Institut für Kernphysik Heidelberg, sowie die Universität Heidelberg beteiligt waren. Bis heute sendet Cassini Daten zur Erde - und die liefern der Wissenschaft neue Erkenntnisse zur Zus...

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

    OpenAIRE

    Nixon, Conor A.; Achterberg, Richard K.; Romani, Paul. N.; Allen, Mark; Zhang, Xi; Teanby, Nicholas A.; Irwin, Patrick G. J.; Flasar, F. Michael

    2010-01-01

    The flybys of Jupiter by the Voyager spacecraft in 1979, and over two decades later by Cassini in 2000, have provided us with unique datasets from two different epochs, allowing the investigation of seasonal change in the atmosphere. In this paper we model zonal averages of thermal infrared spectra from the two instruments, Voyager 1 IRIS and Cassini CIRS, to retrieve the vertical and meridional profiles of temperature, and the abundances of the two minor hydrocarbons, acetylene (C_2H_2) and ...

  20. Radar scattering of linear dunes and mega-yardangs: Application to Titan

    Science.gov (United States)

    Paillou, Philippe; Seignovert, Benoît; Radebaugh, Jani; Wall, Stephen

    2016-05-01

    The Ku-band (13.8 GHz - 2.2 cm) RADAR instrument onboard the Cassini-Huygens spacecraft has revealed the richness of the surface of Titan, as numerous seas, lakes, rivers, cryo-volcanic flows and vast dune fields have been discovered. Linear dunes are a major geomorphological feature present on Titan, covering up to 17% of its surface, mainly in equatorial regions. However, the resolution of the RADAR instrument is not good enough to allow a detailed study of the morphology of these features. In addition, other linear wind-related landforms, such as mega-yardangs (linear wind-abraded ridges formed in cohesive rocks), are likely to present a comparable radar signature that could be confused with the one of dunes. We conducted a comparative study of the radar radiometry of both linear dunes and mega-yardangs, based on representative terrestrial analogues: the linear dunes located in the Great Sand Sea in western Egypt and in the Namib Desert in Namibia, and the mega-yardangs observed in the Lut Desert in eastern Iran and in the Borkou Desert in northern Chad. We analysed the radar scattering of both terrestrial linear dunes and mega-yardangs, using high-resolution radar images acquired by the X-band (9.6 GHz - 3.1 cm) sensor of the TerraSAR-X satellite. Variations seen in the radar response of dunes are the result of a contrast between the dune and interdune scattering, while for mega-yardangs these variations are the result of a contrast between ridges and erosion valleys. We tested a simple surface scattering model, with parameters derived from the local topography and surface roughness estimates, to accurately reproduce the radar signal variations for both landforms. It appears that we can discriminate between two types of dunes - bare interdunes as in Egypt and sand-covered interdunes as in Namibia, and between two types of mega-yardangs - young yardangs as in Iran and older ones as in Chad. We applied our understanding of the radar scattering to the analysis of

  1. Hydrologic applications of weather radar

    Science.gov (United States)

    Seo, Dong-Jun; Habib, Emad; Andrieu, Hervé; Morin, Efrat

    2015-12-01

    By providing high-resolution quantitative precipitation information (QPI), weather radars have revolutionized hydrology in the last two decades. With the aid of GIS technology, radar-based quantitative precipitation estimates (QPE) have enabled routine high-resolution hydrologic modeling in many parts of the world. Given the ever-increasing need for higher-resolution hydrologic and water resources information for a wide range of applications, one may expect that the use of weather radar will only grow. Despite the tremendous progress, a number of significant scientific, technological and engineering challenges remain to realize its potential. New challenges are also emerging as new areas of applications are discovered, explored and pursued. The purpose of this special issue is to provide the readership with some of the latest advances, lessons learned, experiences gained, and science issues and challenges related to hydrologic applications of weather radar. The special issue features 20 contributions on various topics which reflect the increasing diversity as well as the areas of focus in radar hydrology today. The contributions may be grouped as follows: Radar QPE (Kwon et al.; Hall et al.; Chen and Chandrasekar; Seo and Krajewski; Sandford).

  2. Radar-to-Radar Interference Suppression for Distributed Radar Sensor Networks

    OpenAIRE

    Wen-Qin Wang; Huaizong Shao

    2014-01-01

    Radar sensor networks, including bi- and multi-static radars, provide several operational advantages, like reduced vulnerability, good system flexibility and an increased radar cross-section. However, radar-to-radar interference suppression is a major problem in distributed radar sensor networks. In this paper, we present a cross-matched filtering-based radar-to-radar interference suppression algorithm. This algorithm first uses an iterative filtering algorithm to suppress the radar-to-radar ...

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

    Science.gov (United States)

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

    2016-05-01

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

  4. Radar and Lidar Radar DEM

    Science.gov (United States)

    Liskovich, Diana; Simard, Marc

    2011-01-01

    Using radar and lidar data, the aim is to improve 3D rendering of terrain, including digital elevation models (DEM) and estimates of vegetation height and biomass in a variety of forest types and terrains. The 3D mapping of vegetation structure and the analysis are useful to determine the role of forest in climate change (carbon cycle), in providing habitat and as a provider of socio-economic services. This in turn will lead to potential for development of more effective land-use management. The first part of the project was to characterize the Shuttle Radar Topography Mission DEM error with respect to ICESat/GLAS point estimates of elevation. We investigated potential trends with latitude, canopy height, signal to noise ratio (SNR), number of LiDAR waveform peaks, and maximum peak width. Scatter plots were produced for each variable and were fitted with 1st and 2nd degree polynomials. Higher order trends were visually inspected through filtering with a mean and median filter. We also assessed trends in the DEM error variance. Finally, a map showing how DEM error was geographically distributed globally was created.

  5. Cassini/MIMI Science Today and Tomorrow

    Science.gov (United States)

    Mitchell, D. G.

    2014-12-01

    Between Saturn Orbit Insertion in July 2004 and the present, the Magnetospheric IMaging Instrument (MIMI) on the Cassini spacecraft has measured electrons and ions (energies ~5 keV to over 10 MeV and energetic neutrals (energies ~5 - 200 keV) throughout Saturn's magnetosphere including Saturn's bow shock and magnetopause, plasma sheet, magnetotail, and cis-moon spaces. MIMI observations have included auroral acceleration, magnetotail reconnection, global and local-scale injection events, identifications of charged particle species,, dual and multiple periodicities associated with planetary rotation, and the seasonal variations of many of these phenomena. Most recent MIMI investigations have shown (1) short-period charged-particle oscillations (~1 hour) at high latitude are associated with similar magnetic field, radio, and aurora variations (2) quasi-periodic relativistic electron injection in Saturn's outer magnetosphere, (3) modeling of radiation belt particles to explain their distribution and energy spectrum, and to anticipate the population inside the D-ring, (4) continuing the imaging of energetic neutral atoms (ENAs) from the heliosheath and beyond, (5) characterizing the interaction of Titan with the un-shocked solar wind, (6) deep tail observations supporting the "bowl model" of plasma sheet curvature, (7) asymmetries in the charged particles that are associated with a still-unexplained noon-midnight electric field, (8) local time variations in the energetic particle periodicities, (9) and signatures of satellite-magnetosphere interactions and their implications for both the body and the whole system. During the final sets of orbits of the Cassini Mission at Saturn (dubbed the Grand Finale, which includes the F-ring—periapsis outside the F-ring—and the Proximal Orbits—periapsis between the innermost D-ring and the atmosphere), MIMI will make the first-ever measurements of the innermost radiation belts of Saturn, detailed ENA imaging of charged

  6. Ten Years of ENA Imaging from Cassini

    Science.gov (United States)

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

    2014-05-01

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

  7. Use of various types of radars in studying birds researches

    Directory of Open Access Journals (Sweden)

    A. V. Matsyura

    2005-04-01

    Full Text Available In article the review of radars which are used for ornithological researches is resulted. In work advantages and lacks of the basic types of radars for the account of birds are submitted. On the basis of world experience the expediency of use of radar technical equipment for research of migrations of birds is confirmed.

  8. Radar imaging and holography

    CERN Document Server

    Pasmurov, A

    2005-01-01

    Increasing information content is an important scientific problem in modern observation systems development. Radar, or microwave, imaging can be used for this purpose. This book provides an overview of the field and explains why a unified approach based on wave field processing techniques, including holographic and tomographic approaches, is necessary in high resolution radar design. The authors discuss new areas in imaging radar theory, holographic radar, the questions of estimation and improving radar image quality, and various practical applications.

  9. The Cassini project: Lessons learned through operations

    International Nuclear Information System (INIS)

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

  10. The Cassini project: Lessons learned through operations

    Science.gov (United States)

    McCormick, Egan D.

    1998-01-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

  12. Cassini-Huygens Science Highlights: Surprises in the Saturn System

    Science.gov (United States)

    Spilker, Linda; Altobelli, Nicolas; Edgington, Scott

    2014-05-01

    The Cassini-Huygens mission has greatly enhanced our understanding of the Saturn system. Fundamental discoveries have altered our views of Saturn, its retinue of icy moons including Titan, the dynamic rings, and the system's complex magnetosphere. Launched in 1997, the Cassini-Huygens spacecraft spent seven years traveling to Saturn, arriving in July 2004, roughly two years after the northern winter solstice. Cassini has orbited Saturn for 9.5 years, delivering the Huygens probe to its Titan landing in 2005, crossing northern equinox in August 2009, and completing its Prime and Equinox Missions. It is now three years into its 7-year Solstice mission, returning science in a previously unobserved seasonal phase between equinox and solstice. As it watches the approach of northern summer, long-dark regions throughout the system become sunlit, allowing Cassini's science instruments to probe as-yet unsolved mysteries. Key Cassini-Huygens discoveries include icy jets of material streaming from tiny Enceladus' south pole, lakes of liquid hydrocarbons and methane rain on giant Titan, three-dimensional structures in Saturn's rings, and curtain-like aurorae flickering over Saturn's poles. The Huygens probe sent back amazing images of Titan's surface, and made detailed measurements of the atmospheric composition, structure and winds. Key Cassini-Huygens science highlights will be presented. The Solstice Mission continues to provide new science. First, the Cassini spacecraft observes seasonally and temporally dependent processes on Saturn, Titan, Enceladus and other icy satellites, and within the rings and magnetosphere. Second, it addresses new questions that have arisen during the mission thus far, for example providing qualitatively new measurements of Enceladus and Titan that could not be accommodated in the earlier mission phases. Third, it will conduct a close-in mission at Saturn yielding fundamental knowledge about the interior of Saturn. This grand finale of the

  13. RTG performance on Galileo and Ulysses and Cassini test results

    International Nuclear Information System (INIS)

    Power output from telemetry for the two Galileo RTGs are shown from the 1989 launch to the recent Jupiter encounter. Comparisons of predicted, measured and required performance are shown. Similar comparisons are made for the RTG on the Ulysses spacecraft which completed its planned mission in 1995. Also presented are test results from small scale thermoelectric modules and full scale converters performed for the Cassini program. The Cassini mission to Saturn is scheduled for an October 1997 launch. Small scale module test results on thermoelectric couples from the qualification and flight production runs are shown. These tests have exceeded 19,000 hours are continuing to provide increased confidence in the predicted long term performance of the Cassini RTGs. Test results are presented for full scale units both ETGs (E-6, E-7) and RTGs (F-2, F-5) along with mission power predictions. F-5, fueled in 1985, served as a spare for the Galileo and Ulysses missions and plays the same role in the Cassini program. It has successfully completed all acceptance testing. The ten years storage between thermal vacuum tests is the longest ever experienced by an RTG. The data from this test are unique in providing the effects of long term low temperature storage on power output. All ETG and RTG test results to date indicate that the power requirements of the Cassini spacecraft will be met. BOM and EOM power margins of at least five percent are predicted. copyright 1997 American Institute of Physics

  14. RTG performance on Galileo and Ulysses and Cassini test results

    International Nuclear Information System (INIS)

    Power output from telemetry for the two Galileo RTGs are shown from the 1989 launch to the recent Jupiter encounter. Comparisons of predicted, measured and required performance are shown. Similar comparisons are made for the RTG on the Ulysses spacecraft which completed its planned mission in 1995. Also presented are test results from small scale thermoelectric modules and full scale converters performed for the Cassini program. The Cassini mission to Saturn is scheduled for an October 1997 launch. Small scale module test results on thermoelectric couples from the qualification and flight production runs are shown. These tests have exceeded 19,000 hours are continuing to provide increased confidence in the predicted long term performance of the Cassini RTGs. Test results are presented for full scale units both ETGs (E-6, E-7) and RTGs (F-2, F-5) along with mission power predictions. F-5, fueled in 1985, served as a spare for the Galileo and Ulysses missions and plays the same role in the Cassini program. It has successfully completed all acceptance testing. The ten years storage between thermal vacuum tests is the longest ever experienced by an RTG. The data from this test are unique in providing the effects of long term low temperature storage on power output. All ETG and RTG test results to date indicate that the power requirements of the Cassini spacecraft will be met. BOM and EOM power margins of at least five percent are predicted

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

    Science.gov (United States)

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

    1993-01-01

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

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

    Science.gov (United States)

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

    1993-01-01

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

  17. Radar hydrometeorology using a vertically pointing radar

    OpenAIRE

    Cluckie, I. D.; R. J. Griffith; Lane, A; Tilford, K. A.

    2002-01-01

    International audience A Vertically Pointing Radar (VPR) has been commissioned and deployed at a number of sites in southern England, to investigate numerically spatial and temporal variations in the vertical reflectivity profile (Zvp); particularly those associated with the intersection by the radar beam of a melting layer ? the bright band. Comparisons with data from other instrumentation, notably with the S-band research radar at Chilbolton, but also with disdrometer data and rainfall m...

  18. Radar hydrometeorology using a vertically pointing radar

    OpenAIRE

    Cluckie, I. D.; R. J. Griffith; Lane, A; Tilford, K. A.

    2000-01-01

    A Vertically Pointing Radar (VPR) has been commissioned and deployed at a number of sites in southern England, to investigate numerically spatial and temporal variations in the vertical reflectivity profile (Zvp); particularly those associated with the intersection by the radar beam of a melting layer – the bright band. Comparisons with data from other instrumentation, notably with the S-band research radar at Chilbolton, but also with disdrometer data and rainfall measurements from a number ...

  19. Adaptive radar resource management

    CERN Document Server

    Moo, Peter

    2015-01-01

    Radar Resource Management (RRM) is vital for optimizing the performance of modern phased array radars, which are the primary sensor for aircraft, ships, and land platforms. Adaptive Radar Resource Management gives an introduction to radar resource management (RRM), presenting a clear overview of different approaches and techniques, making it very suitable for radar practitioners and researchers in industry and universities. Coverage includes: RRM's role in optimizing the performance of modern phased array radars The advantages of adaptivity in implementing RRMThe role that modelling and

  20. Radar and ARPA manual

    CERN Document Server

    Bole, A G

    2013-01-01

    Radar and ARPA Manual focuses on the theoretical and practical aspects of electronic navigation. The manual first discusses basic radar principles, including principles of range and bearing measurements and picture orientation and presentation. The text then looks at the operational principles of radar systems. Function of units; aerial, receiver, and display principles; transmitter principles; and sitting of units on board ships are discussed. The book also describes target detection, Automatic Radar Plotting Aids (ARPA), and operational controls of radar systems, and then discusses radar plo

  1. Automation of Cassini Support Imaging Uplink Command Development

    Science.gov (United States)

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

    2010-01-01

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

  2. Spaceborne radar studies of Venus

    International Nuclear Information System (INIS)

    Data obtained from the Pioneer Venus radar mapper experiment are discussed. The mission was primarily developed to study the atmosphere of Venus. A highly eccentric orbit (eccentricity of 0.84, period of 24 h) was selected. The instrumentation has two operating modes: altimetry and imaging. Three parameters were measured for every radar spot size: altitude, surface roughness and radar reflectivity at a normal incidence. The measurements have been extended to a topographic map. The results suggest that the Beta region consists of two large shields and that the equatorial region is dominated by Aphrodite Terra. It also appears that the surface of Venus is very smooth and that it lacks great basins and the global plate tectonics present on earth

  3. Lunar Radar Cross Section at Low Frequency

    Science.gov (United States)

    Rodriguez, P.; Kennedy, E. J.; Kossey, P.; McCarrick, M.; Kaiser, M. L.; Bougeret, J.-L.; Tokarev, Y. V.

    2002-01-01

    Recent bistatic measurements of the lunar radar cross-section have extended the spectrum to long radio wavelength. We have utilized the HF Active Auroral Research Program (HAARP) radar facility near Gakona, Alaska to transmit high power pulses at 8.075 MHz to the Moon; the echo pulses were received onboard the NASA/WIND spacecraft by the WAVES HF receiver. This lunar radar experiment follows our previous use of earth-based HF radar with satellites to conduct space experiments. The spacecraft was approaching the Moon for a scheduled orbit perturbation when our experiment of 13 September 2001 was conducted. During the two-hour experiment, the radial distance of the satellite from the Moon varied from 28 to 24 Rm, where Rm is in lunar radii.

  4. Cassini UVIS observations of Titan nightglow spectra

    Science.gov (United States)

    Ajello, Joseph M.; West, Robert A.; Gustin, Jacques; Larsen, Kristopher; Stewart, A. Ian F.; Esposito, Larry W.; McClintock, William E.; Holsclaw, Gregory M.; Bradley, E. Todd

    2012-12-01

    In this paper we present the first nightside EUV and FUV airglow limb spectra of Titan showing molecular emissions. The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed photon emissions of Titan's day and night limb-airglow and disk-airglow on multiple occasions, including during an eclipse observation. The 71 airglow observations analyzed in this paper show EUV (600-1150 Å) and FUV (1150-1900 Å) atomic multiplet lines and band emissions arising from either photoelectron induced fluorescence and solar photo-fragmentation of molecular nitrogen (N2) or excitation by magnetosphere plasma. The altitude of the peak UV emissions on the limb during daylight occurred inside the thermosphere at the altitude of the topside ionosphere (near 1000 km altitude). However, at night on the limb, a subset of emission features, much weaker in intensity, arise in the atmosphere with two different geometries. First, there is a twilight photoelectron-excited glow that persists with solar depression angle up to 25-30 degrees past the terminator, until the solar XUV shadow height passes the altitude of the topside ionosphere (1000-1200 km). The UV twilight glow spectrum is similar to the dayglow but weaker in intensity. Second, beyond 120° solar zenith angle, when the upper atmosphere of Titan is in total XUV darkness, there is indication of weak and sporadic nightside UV airglow emissions excited by magnetosphere plasma collisions with ambient thermosphere gas, with similar N2 excited features as above in the daylight or twilight glow over an extended altitude range.

  5. Updating the Reference Trajectory for the Cassini Solstice Mission

    Science.gov (United States)

    Valerino, Powtawche N.

    2014-01-01

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

  6. Validation of GPM Ka-Radar Algorithm Using a Ground-based Ka-Radar System

    Science.gov (United States)

    Nakamura, Kenji; Kaneko, Yuki; Nakagawa, Katsuhiro; Furukawa, Kinji; Suzuki, Kenji

    2016-04-01

    GPM led by the Japan Aerospace Exploration Agency (JAXA) and the National Aeronautics and Space Administration of US (NASA) aims to observe global precipitation. The core satellite is equipped with a microwave radiometer (GMI) and a dual-frequency radar (DPR) which is the first spaceborne Ku/Ka-band dual-wavelength radar dedicated for precipitation measurement. In the DPR algorithm, measured radar reflectivity is converted to effective radar reflectivity by estimating the rain attenuation. Here, the scattering/attenuation characteristics of Ka-band radiowaves are crucial, particularly for wet snow. A melting layer observation using a dual Ka-band radar system developed by JAXA was conducted along the slope of Mt. Zao in Yamagata Prefecture, Japan. The dual Ka-band radar system consists of two nearly identical Ka-band FM-CW radars, and the precipitation systems between two radars were observed in opposite directions. From this experiment, equivalent radar reflectivity (Ze) and specific attenuation (k) were obtained. The experiments were conducted for two winter seasons. During the data analyses, it was found that k estimate easily fluctuates because the estimate is based on double difference calculation. With much temporal and spatial averaging, k-Ze relationship was obtained for melting layers. One of the results is that the height of the peak of k seems slightly higher than that of Ze. The results are compared with in-situ precipitation particle measurements.

  7. Fractal characteristics for binary noise radar waveform

    Science.gov (United States)

    Li, Bing C.

    2016-05-01

    Noise radars have many advantages over conventional radars and receive great attentions recently. The performance of a noise radar is determined by its waveforms. Investigating characteristics of noise radar waveforms has significant value for evaluating noise radar performance. In this paper, we use binomial distribution theory to analyze general characteristics of binary phase coded (BPC) noise waveforms. Focusing on aperiodic autocorrelation function, we demonstrate that the probability distributions of sidelobes for a BPC noise waveform depend on the distances of these sidelobes to the mainlobe. The closer a sidelobe to the mainlobe, the higher the probability for this sidelobe to be a maximum sidelobe. We also develop Monte Carlo framework to explore the characteristics that are difficult to investigate analytically. Through Monte Carlo experiments, we reveal the Fractal relationship between the code length and the maximum sidelobe value for BPC waveforms, and propose using fractal dimension to measure noise waveform performance.

  8. Weather Radar Impact Zones

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These data represent an inventory of the national impacts of wind turbine interference with NEXRAD radar stations. This inventory was developed by the NOAA Radar...

  9. Network radar countermeasure systems integrating radar and radar countermeasures

    CERN Document Server

    Jiang, Qiuxi

    2016-01-01

    This is the very first book to present the network radar countermeasure system. It explains in detail the systematic concept of combining radar and radar countermeasures from the perspective of the information acquisition of target location, the optimization of the reconnaissance and detection, the integrated attack of the signals and facilities, and technological and legal developments concerning the networked system. It achieves the integration of the initiative and passivity, detection and jamming. The book explains how the system locates targets, completes target identification, tracks targets and compiles the data.

  10. Digital LPI Radar Detector

    OpenAIRE

    Ong, Peng Ghee; Teng, Haw Kiad

    2001-01-01

    Approved for public release; distribution is unlimited The function of a Low Probability ofIntercept (LPI) radar is to prevent its interception by an Electronic Support (ES) receiver. This objective is generally achieved through the use of a radar waveform that is mismatched to those waveforms for which an ES receiver is tuned. This allows the radar to achieve a processing gain, with respect to the ES receiver, that is equal to the time-bandwidth product ofthe radar waveform. This...

  11. Secondary Surveillance Radar Antenna

    OpenAIRE

    Schejbal, Vladimír; Bezoušek, Pavel; Pidanič, Jan; Chyba, Milan

    2013-01-01

    This paper deals with a secondary surveillance radar (SSR) array antenna, which is intended for a system combining the secondary surveillance radar antenna and the primary surveillance radar antenna. It describes the patch array elements and the synthesis for the secondary surveillance radar array, considering both elevation and azimuth patterns for sum, difference, and sidelobe-suppression beams, and suspended stripline couplers. The utilization of multilayer techniques allows the connection...

  12. Software Radar Technology

    Directory of Open Access Journals (Sweden)

    Tang Jun

    2015-08-01

    Full Text Available In this paper, the definition and the key features of Software Radar, which is a new concept, are proposed and discussed. We consider the development of modern radar system technology to be divided into three stages: Digital Radar, Software radar and Intelligent Radar, and the second stage is just commencing now. A Software Radar system should be a combination of various modern digital modular components conformed to certain software and hardware standards. Moreover, a software radar system with an open system architecture supporting to decouple application software and low level hardware would be easy to adopt "user requirements-oriented" developing methodology instead of traditional "specific function-oriented" developing methodology. Compared with traditional Digital Radar, Software Radar system can be easily reconfigured and scaled up or down to adapt to the changes of requirements and technologies. A demonstration Software Radar signal processing system, RadarLab 2.0, which has been developed by Tsinghua University, is introduced in this paper and the suggestions for the future development of Software Radar in China are also given in the conclusion.

  13. Radar: Human Safety Net

    Science.gov (United States)

    Ritz, John M.

    2016-01-01

    Radar is a technology that can be used to detect distant objects not visible to the human eye. A predecessor of radar, called the telemobiloscope, was first used to detect ships in the fog in 1904 off the German coast. Many scientists have worked on the development and refinement of radar (Hertz with electromagnetic waves; Popov with determining…

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

    Science.gov (United States)

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

    2014-01-01

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

  15. Observational Constraints on Planet Nine: Cassini Range Observations

    CERN Document Server

    Holman, Matthew J

    2016-01-01

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

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

    NARCIS (Netherlands)

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

    2010-01-01

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

  17. Cassini High Rate Detector V16.0

    Science.gov (United States)

    Economou, T.; DiDonna, P.

    2016-05-01

    The High Rate Detector (HRD) from the University of Chicago is an independent part of the CDA instrument on the Cassini Orbiter that measures the dust flux and particle mass distribution of dust particles hitting the HRD detectors. This data set includes all data from the HRD through December 31, 2015. Please refer to Srama et al. (2004) for a detailed HRD description.

  18. Pulse Doppler radar

    CERN Document Server

    Alabaster, Clive

    2012-01-01

    This book is a practitioner's guide to all aspects of pulse Doppler radar. It concentrates on airborne military radar systems since they are the most used, most complex, and most interesting of the pulse Doppler radars; however, ground-based and non-military systems are also included. It covers the fundamental science, signal processing, hardware issues, systems design and case studies of typical systems. It will be a useful resource for engineers of all types (hardware, software and systems), academics, post-graduate students, scientists in radar and radar electronic warfare sectors and milit

  19. Radar and optical leonids

    Directory of Open Access Journals (Sweden)

    N. Brosch

    2004-01-01

    Full Text Available We present joint optical-radar observations of meteors collected near the peak of the Leonid activity in 2002. We show four examples of joint detections with a large, phased array L-band radar and with intensified video cameras. The general characteristic of the radar-detected optical meteors is that they show the radar detection below the termination of the optical meteor. Therefore, at least some radar events associated with meteor activity are neither head echoes nor trail echoes, but probably indicate the formation of 'charged clouds' after the visual meteor is extinguished.

  20. Understanding radar systems

    CERN Document Server

    Kingsley, Simon

    1999-01-01

    What is radar? What systems are currently in use? How do they work? This book provides engineers and scientists with answers to these critical questions, focusing on actual radar systems in use today. It is a perfect resource for those just entering the field, or as a quick refresher for experienced practitioners. The book leads readers through the specialized language and calculations that comprise the complex world of radar engineering as seen in dozens of state-of-the-art radar systems. An easy to read, wide ranging guide to the world of modern radar systems.

  1. Cassini Science Highlights: Surprises in the Saturn System

    Science.gov (United States)

    Spilker, Linda J.

    2012-10-01

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

  2. Neutrino Radar

    CERN Document Server

    Panigrahi, P K

    2002-01-01

    We point out that with improving our present knowledge of experimental neutrino physics it will be possible to locate nuclear powered vehicles like submarines, aircraft carriers and UFOs and detect nuclear testing. Since neutrinos cannot be shielded, it will not be possible to escape these detection. In these detectors it will also be possible to perform neutrino oscillation experiments during any nuclear testing.

  3. Liquid Beam Ion Desorption Mass Spectrometry for Evaluating CASSINI Data

    Science.gov (United States)

    Stolz, Ferdinand; Reviol, Rene; Srama, Ralf; Trieloff, Mario; Postberg, Frank; Abel, Bernd

    2013-04-01

    Saturn's moon Enceladus emits plumes of ice particles from an area near its south pole which are detected and chemically analyzed by the Cosmic Dust Analyzer (CDA) on board the CASSINI spacecraft. Studying these ice particles provides unique insights into Enceladus geological properties. Technically the CDA is a time-of-flight mass spectrometer which delivers mass spectra of the particles and their fragments. Since interpretation of the available CDA data is particularly challenging we employ a laboratory experiment to imitate experimental conditions in space. Key part of our experimental setup is a micron-sized water beam in high vacuum. This beam is rapidly heated up by an infrared laser pulse, which is tuned to excite the OH-stretch vibration of water molecules. This causes the water beam to dissipate into small droplets, some of which carry a net charge even though the laser energy is well below the molecular ionisation energy. The charged droplets are then analyzed in a time-of-flight mass spectrometer. With this experimental setup we successfully simulated the space born ice particles measured at Enceladus. By varying the laser intensity in our experiments, we can vary the amount of energy deposited in the liquid beam, and thus model different particle velocities. Also, variation of solute concentration in the water beam provides valuable information about ice particle composition. Some examples for anorganic solutes studied so far are sodium chloride, ammonia and hydrogen sulfite. A special feature of our experimental technique is that desorption of particles from the liquid beam is particularly soft. This is explained by the fact that all laser energy is absorbed by the water molecules. In this way molecular bonds of solutes stay intact and molecular solutes are transferred into the droplet phase without getting destroyed. This is particularly interesting in the context of analyzing organic compounds - some of which have been detected at Enceladus. Using

  4. FMWC Radar for Breath Detection

    DEFF Research Database (Denmark)

    Suhr, Lau Frejstrup; Tafur Monroy, Idelfonso; Vegas Olmos, Juan José

    We report on the experimental demonstration of an FMCW radar operating in the 25.7 - 26.6 GHz range with a repetition rate of 500 sweeps per second. The radar is able to track the breathing rate of an adult human from a distance of 1 meter. The experiments have utilized a 50 second recording window...... to accurately track the breathing rate. The radar utilizes a saw tooth modulation format and a low latency receiver. A breath tracking radar is useful both in medical scenarios, diagnosing disorders such as sleep apnea, and for home use where the user can monitor its health. Breathing is a central part of every...... sensing as other systems rely on either measuring the airflow at the mouth and nose through a mask or with a stretchable wire around the chest. In this paper a wireless system that is able to measure the breath rate of a human from a distance is presented. The system is based on a commercially available...

  5. Coherence theory applied to space radio astronomy: Cassini/RPWS, a practical implementation.

    Science.gov (United States)

    Lecacheux, A.

    2009-04-01

    Solar and planetary, space radio astronomy has taken advantage of several technical and methodological improvements, from the first age - when simple wire antennas and analogue filters were used (RAE, IMP, Voyager) -, later - when spacecraft spin (ISEE, Ulysses) could be exploited for source direction retrieval, and up to now - with the current use of on board digital correlators analyzing multiple wire antennas (Cassini, Stereo). Indeed, correlation analysis from multiple sensors allows, in principle, the full second order statistics of the analyzed signal to be retrieved, thus providing, with respect to simple antenna system, some extra information on the received radio waves (mainly the spatial brightness distribution and intrinsic polarisation of the observed radio source). In the real case of experiments aboard interplanetary spacecraft, one has to take into account a number of undesirable instrumental effects, for instance the perturbation of the antenna response by the spacecraft conductive body or the limitation of the signal to noise ratio by the available telemetry rate. In this talk, taking as a working example the Cassini/RPWS data, we develop a consistent statistical model of such a correlator, which allows actual measurements to be easily characterized and reliably inverted. Some results from observations of Jovian and Saturnian radiating sources are provided as illustrative examples.

  6. Near-infrared spectra of liquid/solid acetylene under Titan relevant conditions and implications for Cassini/VIMS detections

    Science.gov (United States)

    Singh, S.; Cornet, T.; Chevrier, V. F.; Combe, J.-Ph.; McCord, T. B.; Roe, L. A.; Le Mouélic, S.; Le Menn, E.; Wasiak, F. C.

    2016-05-01

    Acetylene is thought to be abundant on Titan according to most photochemical models. While detected in the atmosphere, its likely presence at the surface still lacks physical evidence. It is thought that solid acetylene could be a major component of Titan's lakes shorelines and dry lakebed, detected as the 5 μm-bright deposits with the Cassini/VIMS instrument. Acetylene could also be present under its liquid form as dissolved solids in Titan's methane-ethane lakes, as emphasized by thermodynamics studies. This paper is devoted to the near-infrared spectroscopy study of acetylene under solid and liquid phases between 1 and 2.2 μm, synthesized in a Titan simulation chamber that is able to reproduce extreme temperature conditions. From experiments, we observed a ∼10% albedo increase between liquid acetylene at 193-188 K and solid acetylene at 93 K. Using the NIR spectroscopy technique we successfully calculated the reflectivity ratio of solid/liquid acetylene as 1.13. The second difference we observed between liquid and solid acetylene is a shift in the major absorption band detected at 1.54 μm, the shift of ∼0.01 μm occurring toward higher wavelength. In order to assess the detectability of acetylene on Titan using the Cassini/VIMS instrument, we adapted our spectra to the VIMS spectral resolution. The spectral band at 1.55 μm and a negative slope at 2.0 μm falls in the Cassini/VIMS atmospheric windows over several VIMS infrared spectels, thus Cassini/VIMS should be able to detect acetylene.

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

    Science.gov (United States)

    West, R. A.

    2014-12-01

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

  8. Laser radar in robotics

    Energy Technology Data Exchange (ETDEWEB)

    Carmer, D.C.; Peterson, L.M. [Environmental Research Inst. of Michigan, Ann Arbor, MI (United States)

    1996-02-01

    In this paper the authors describe the basic operating principles of laser radar sensors and the typical algorithms used to process laser radar imagery for robotic applications. The authors review 12 laser radar sensors to illustrate the variety of systems that have been applied to robotic applications wherein information extracted from the laser radar data is used to automatically control a mechanism or process. Next, they describe selected robotic applications in seven areas: autonomous vehicle navigation, walking machine foot placement, automated service vehicles, manufacturing and inspection, automotive, military, and agriculture. They conclude with a discussion of the status of laser radar technology and suggest trends seen in the application of laser radar sensors to robotics. Many new applications are expected as the maturity level progresses and system costs are reduced.

  9. Netted LPI radars

    OpenAIRE

    Menychtas, Charalampos.

    2011-01-01

    Approved for public release; distribution is unlimited. A significant number of Low Probability of Intercept (LPI) radars are used in various military applications, from guided weapons (such anti-ship missile), to large platforms (aircrafts, ships), to large systems (Integrated Air Defense Systems - IADS). The purpose of this thesis is to evaluate the performance of netted LPI radar systems. To do so, it commences with establishing the theoretical background for the LPI radar techniques an...

  10. Phased-array radar design application of radar fundamentals

    CERN Document Server

    Jeffrey, Thomas

    2009-01-01

    Phased-Array Radar Design is a text-reference designed for electrical engineering graduate students in colleges and universities as well as for corporate in-house training programs for radar design engineers, especially systems engineers and analysts who would like to gain hands-on, practical knowledge and skills in radar design fundamentals, advanced radar concepts, trade-offs for radar design and radar performance analysis.

  11. Integration of Spacecraft Telemetry into Navigation Operations for the Cassini-Huygens Mission

    Science.gov (United States)

    Ardalan, S.M.; Antreasian, P.G.; Criddle, K.E.; Ionasescu, R.; Jacobson, R.A.; Jones, J.B.; MacKenzie, R.A.; Parcher, D.W.; Pelletier, F.J.; Roth, D.C.; Thompson, P.F.; Vaughan, A.T.

    2008-01-01

    The Cassini orbiter is the largest and most complex interplanetary spacecraft ever built. Since attaining orbit around Saturn in the summer of 2004, Cassini, along with its Huygens probe, have been continually improving our understanding Saturn, its satellites, its enigmatic rings system, and of the solar system. One of the hallmarks of the Cassini- Huygens Project is the close working relationship between the many teams required to operate such a sophisticated spacecraft. Their ingenuity has enabled them to find new and different ways to improve their processes during Cassini's prime 4-year orbital tour. This paper will discuss the relationship between Cassini's Navigation and Spacecraft Teams and the work required to properly configure Cassini's telemetry system for Navigation. A detailed explanation of how the Navigation Team utilizes spacecraft telemetry and analysis demonstrating the benefits will also be provided. Finally, telemetry requirements for Navigation for future missions will be addressed.

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

    Science.gov (United States)

    Pelletier, Frederic J.; Antreasian, Peter; Ardalan, Shadan; Buffington, Brent; Criddle, Kevin; Ionasescu, Rodica; Jacobson, Robert; Jones, Jeremy; Nandi, Sumita; Nolet, Simon; Parcher, Daniel; Roth, Duane; Smith, Jonathon; Thompson, Paul

    2012-01-01

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

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

    Science.gov (United States)

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

    2012-01-01

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

  14. Airport Surveillance Radar : Model 11

    Data.gov (United States)

    Department of Transportation — The Airport Surveillance Radar Model 11 (ASR-11) is a short-range digital, integrated primary and secondary surveillance radar (SSR) radar system with a 60 nautical...

  15. Enhanced Geometric Metadata for Cassini Optical Remote Sensing Instruments

    Science.gov (United States)

    Gordon, Mitchell K.; Showalter, M. R.; Wells, B.; Ballard, L.; Heather, N.

    2012-10-01

    In the past few years, the PDS Rings Node developed the Outer Planets Unified Search (OPUS), along with preview images or footprint diagrams for all OPUS supported data, and enhanced geometric metadata for Cassini ISS Saturn system data. Typically, geometric metadata for outer planets remote sensing observations is available only for the center of the instrument field of view. In our first effort at generating enhanced metadata, we calculated values for a fine grid of points over the entire field of view of Cassini ISS images using the most current SPICE kernel files. That project produce enhanced metadata specific to the rings; consequently the metadata was tied to the ring plane of Saturn. The combination of OPUS and the data base of enhanced geometric metadata provided a powerful, well received tool, and resulted in additional funding to extend metadata generation. We are developing a set of tools to produce geometric metadata for Cassini ISS, VIMS, UVIS, and CIRS Saturn data. This metadata will not be restricted to ring plane calculations and will support searches based on latitude and longitude for the planet and satellites as well as parameters such as viewing and illumination geometry. We also identify all known bodies and rings in the field of view, so target based search results will be comprehensive rather providing a subset based on the designated primary target. This autumn we have begun the incremental inclusion of the new metadata in the OPUS data base. In a subsequent phase we intend to expand our web services to include on-the-fly production of user selected geometric backplanes for each product returned by OPUS. http://pds-rings.seti.org/search/ Acknowledgments: This development has been supported by the Planetary Data System, by JPL through a special grant from the Cassini Project, and by research grants from STScI and NASA.

  16. Transport coefficients for shape degrees in terms of Cassini ovaloids

    OpenAIRE

    Ivanyuk, F. A.; Hofmann, H.; Pashkevich, V. V.; Yamaji, S.

    1997-01-01

    Previous computations of the potential landscape with the shapes parameterized in terms of Cassini ovaloids are extended to collective dynamics at finite excitations. Taking fission as the most demanding example of large scale collective motion, transport coefficients are evaluated along a fission path. We concentrate on those for average motion, namely stiffness C, friction \\gamma and inertia M. Their expressions are formulated within a locally harmonic approximation and the help of linear r...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1991-01-01

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

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

    OpenAIRE

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

    2010-01-01

    Work on the Global Compositae Checklist has highlighted uncertainties and errors in the nomenclatural parameters of many genera and subgenera described by Henri Cassini. Problems concern rank (subgenus vs. genus); type designation; correct place of valid publication; alternative names; and other miscellaneous issues. An annotated list with correct nomenclatural information for 391 generic names or designations is provided, including types (newly designated here for 17 names) and one new combi...

  19. Master Control Design of Polar Detection Ice Radar

    International Nuclear Information System (INIS)

    This paper focuses on the design of the master control software dedicated for the application of high-resolution polar detection ice radar. The central part of proposed software is FPGA, which plays roles of collecting radar echo data, playback of chirp signal, data transmission to upper computer, coherent integral accumulation of digitized data and system control of the whole radar system. The performances of proposed system is demonstrated through real-field experiments

  20. Five years of Cassini CIRS Thermal Observations of Saturn's Rings

    Science.gov (United States)

    Spilker, Linda J.; Altobelli, N.; Flandes, J. A.; Morishima, R.; Leyrat, C.; Pilorz, S.; Ferrari, C.; Edgington, S.; Brooks, S.

    2009-09-01

    An extensive set of thermal measurements of Saturn's main rings (A, B, C and Cassini division) has been returned by the Cassini Composite Infrared spectrometer over the past five years. Data on the lit and unlit rings have been acquired over a variety of solar phase angles, spacecraft elevations and local hour angles. The solar elevation angle has varied from 24 degrees at the start of the mission through zero at equinox. Phase angle and solar elevation angle are two of the strongest determinants of ring temperature; the lit face of the main rings cooled by over 30 K with approaching equinox. Thermal phase curves of the main rings exhibit a nonlinear variation in temperature with phase angle, with pronounced surges at phase angles less than 50 degrees. The larger optical depth regions, such as regions in the A and B rings, also show slight changes in this surge with changing solar elevation. This effect may be related to interparticle shadowing within the rings. The temperature of the main rings decreases as the solar elevation angle declines. The temperature in the optically thin C ring and Cassini division decreases by only a few degrees over a broad range of solar elevation, decreasing more rapidly at smaller solar elevation. Detailed thermal modeling is under way to fit these data. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2009 California Institute of Technology. Government sponsorship acknowledged.

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

    Science.gov (United States)

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

    2010-01-01

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

  2. Cassini at Saturn Proximal Orbits - Attitude Control Challenges

    Science.gov (United States)

    Burk, Thomas A.

    2013-01-01

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

  3. Concept overview for TITAN probes following CASSINI-HUYGENS

    Science.gov (United States)

    Lebleu, Denis

    2008-09-01

    The NASA/ESA/ASI CASSINI-HUYGENS mission has renewed our view of the Saturnian system and its potential promises to allow us to enhance in our understanding of the evolution of the Solar System and eventual life beyond Earth. TITAN was revealed by HUYGENS, designed by Thales Alenia Space France, and the CASSINI numerous flybys, and the end of the nominal Cassini mission in mid 2008 will leave us with a long list of outstanding questions. Both in the USA and Europe, scientists and agencies have initiated work to define a future mission to Titan and the Saturnian System, via the NASA OPAG and ESA Cosmic Vision programmes. This paper proposes an overview of potential Titan probe concepts enabling to reach the objectives identified by the scientific community. In addition to a large mobility vehicle, a montgolfière or balloon, lighter vehicles addressing specific science features are identified complementary to the primary mission: · High latitude coverage · High altitude measurements · Trade-off between a low number of probes with more science versus a larger number of probes.

  4. Java Radar Analysis Tool

    Science.gov (United States)

    Zaczek, Mariusz P.

    2005-01-01

    Java Radar Analysis Tool (JRAT) is a computer program for analyzing two-dimensional (2D) scatter plots derived from radar returns showing pieces of the disintegrating Space Shuttle Columbia. JRAT can also be applied to similar plots representing radar returns showing aviation accidents, and to scatter plots in general. The 2D scatter plots include overhead map views and side altitude views. The superposition of points in these views makes searching difficult. JRAT enables three-dimensional (3D) viewing: by use of a mouse and keyboard, the user can rotate to any desired viewing angle. The 3D view can include overlaid trajectories and search footprints to enhance situational awareness in searching for pieces. JRAT also enables playback: time-tagged radar-return data can be displayed in time order and an animated 3D model can be moved through the scene to show the locations of the Columbia (or other vehicle) at the times of the corresponding radar events. The combination of overlays and playback enables the user to correlate a radar return with a position of the vehicle to determine whether the return is valid. JRAT can optionally filter single radar returns, enabling the user to selectively hide or highlight a desired radar return.

  5. Decoders for MST radars

    Science.gov (United States)

    Woodman, R. F.

    1983-01-01

    Decoding techniques and equipment used by MST radars are described and some recommendations for new systems are presented. Decoding can be done either by software in special-purpose (array processors, etc.) or general-purpose computers or in specially designed digital decoders. Both software and hardware decoders are discussed and the special case of decoding for bistatic radars is examined.

  6. Intelligent radar data processing

    Science.gov (United States)

    Holzbaur, Ulrich D.

    The application of artificial intelligence principles to the processing of radar signals is considered theoretically. The main capabilities required are learning and adaptation in a changing environment, processing and modeling information (especially dynamics and uncertainty), and decision-making based on all available information (taking its reliability into account). For the application to combat-aircraft radar systems, the tasks include the combination of data from different types of sensors, reacting to electronic counter-countermeasures, evaluation of how much data should be acquired (energy and radiation management), control of the radar, tracking, and identification. Also discussed are related uses such as monitoring the avionics systems, supporting pilot decisions with respect to the radar system, and general applications in radar-system R&D.

  7. Micropower impulse radar imaging

    Energy Technology Data Exchange (ETDEWEB)

    Hall, M.S.

    1995-11-01

    From designs developed at the Lawrence Livermore National Laboratory (LLNL) in radar and imaging technologies, there exists the potential for a variety of applications in both public and private sectors. Presently tests are being conducted for the detection of buried mines and the analysis of civil structures. These new systems use a patented ultra-wide band (impulse) radar technology known as Micropower Impulse Radar (GPR) imaging systems. LLNL has also developed signal processing software capable of producing 2-D and 3-D images of objects embedded in materials such as soil, wood and concrete. My assignment while at LLNL has focused on the testing of different radar configurations and applications, as well as assisting in the creation of computer algorithms which enable the radar to scan target areas of different geometeries.

  8. Spaceborne weather radar

    Science.gov (United States)

    Meneghini, Robert; Kozu, Toshiaki

    1990-01-01

    The present work on the development status of spaceborne weather radar systems and services discusses radar instrument complementarities, the current forms of equations for the characterization of such aspects of weather radar performance as surface and mirror-image returns, polarimetry, and Doppler considerations, and such essential factors in spaceborne weather radar design as frequency selection, scanning modes, and the application of SAR to rain detection. Attention is then given to radar signal absorption by the various atmospheric gases, rain drop size distribution and wind velocity determinations, and the characteristics of clouds, as well as the range of available estimation methods for backscattering, single- and dual-wavelength attenuation, and polarimetric and climatological characteristics.

  9. Principles of modern radar radar applications

    CERN Document Server

    Scheer, James A

    2013-01-01

    Principles of Modern Radar: Radar Applications is the third of the three-volume seriesof what was originally designed to be accomplished in one volume. As the final volumeof the set, it finishes the original vision of a complete yet bounded reference for radartechnology. This volume describes fifteen different system applications or class ofapplications in more detail than can be found in Volumes I or II.As different as the applications described, there is a difference in how these topicsare treated by the authors. Whereas in Volumes I and II there is strict adherence tochapter format and leve

  10. A Study of MMW Collision Avoidance Radar System for Trains

    Directory of Open Access Journals (Sweden)

    Liu Hai-bo

    2013-06-01

    Full Text Available Collision avoidance radar for trains is pregnant for safety transportation. In order to realize low cost and high performance of azimuth accuracy, we have developed MMW (Milli-Meter Wave radar, which employs switched phased array and frequency stepped technology. This paper analyses the radiation patterns of transmitting/receiving antennas and compensation method for amplitude/phase errors of synthetic wideband frequency stepped signal. To confirm the operation of the radar, low cost millimeter-wave collision avoidance radar was fabricated. Lots of experiments confirmed a high azimuth and range resolution.

  11. Detecting and classifying low probability of intercept radar

    CERN Document Server

    Pace, Phillip E

    2003-01-01

    The drive is on to devise LPI radar systems that evade hostile detection as well as develop non-cooperative intercept devices that outsmart enemy LPI radar. Based on the author's own design experience, this comprehensive, hands-on book gives you the latest design and development techniques to innovate new LPI radar systems and discover new ways to intercept enemy LPI radar. and help you visually identify waveform parameters. Filled with more than 500 equations that provide rigorous mathematical detail, this book can be used by both entry-level and seasoned engineers. Besides thoroughly treatin

  12. Radar Location Equipment Development Program: Phase I

    International Nuclear Information System (INIS)

    The work described in this report represents the first phase of a planned three-phase project designed to develop a radar system for monitoring waste canisters stored in a thick layer of bedded salt at the Waste Isolation Pilot Plant near Carlsbad, New Mexico. The canisters will be contained in holes drilled into the floor of the underground waste storage facility. It is hoped that these measurements can be made to accuracies of +-5 cm and +-20, respectively. The initial phase of this project was primarily a feasibility study. Its principal objective was to evaluate the potential effectiveness of the radar method in the planned canister monitoring application. Its scope included an investigation of the characteristics of radar signals backscattered from waste canisters, a test of preliminary data analysis methods, an assessment of the effects of salt and bentonite (a proposed backfill material) on the propagation of the radar signals, and a review of current ground-penetrating radar technology. A laboratory experiment was performed in which radar signals were backscattered from simulated waste canisters. The radar data were recorded by a digital data acquisition system and were subsequently analyzed by three different computer-based methods to extract estimates of canister location and tilt. Each of these methods yielded results that were accurate within a few centimeters in canister location and within 10 in canister tilt. Measurements were also made to determine the signal propagation velocities in salt and bentonite (actually a bentonite/sand mixture) and to estimate the signal attenuation rate in the bentonite. Finally, a product survey and a literature search were made to identify available ground-penetrating radar systems and alternative antenna designs that may be particularly suitable for this unique application. 10 refs., 21 figs., 4 tabs

  13. Pulse Radar Technique for Reflectometry on Thermonuclear Plasmas

    NARCIS (Netherlands)

    Hugenholtz, C. A. J.; Heijnen, S. H.

    1991-01-01

    new method to measure density profiles of thermonuclear plasmas with fast pulse radar is proposed. A number of important benefits of pulse radar above the generally used swept frequency reflectometry are given. A test bench experiment at 34 GHz, using pulses with 1.5-ns rise and fall times, showed t

  14. Ground-penetrating radar methods

    Science.gov (United States)

    Ground-penetrating radar geophysical methods are finding greater and greater use in agriculture. With the ground-penetrating radar (GPR) method, an electromagnetic radio energy (radar) pulse is directed into the subsurface, followed by measurement of the elapsed time taken by the radar signal as it ...

  15. Radar and electronic navigation

    CERN Document Server

    Sonnenberg, G J

    2013-01-01

    Radar and Electronic Navigation, Sixth Edition discusses radar in marine navigation, underwater navigational aids, direction finding, the Decca navigator system, and the Omega system. The book also describes the Loran system for position fixing, the navy navigation satellite system, and the global positioning system (GPS). It reviews the principles, operation, presentations, specifications, and uses of radar. It also describes GPS, a real time position-fixing system in three dimensions (longitude, latitude, altitude), plus velocity information with Universal Time Coordinated (UTC). It is accur

  16. Polarimetric Doppler Weather Radar

    Science.gov (United States)

    Bringi, V. N.; Chandrasekar, V.

    2001-10-01

    This work provides a detailed introduction to the principles of Doppler and polarimetric radar, focusing in particular on their use in the analysis of weather systems. The authors first discuss underlying topics such as electromagnetic scattering, polarization, and wave propagation. They then detail the engineering aspects of pulsed Doppler polarimetric radar, before examining key applications in meteorology and remote sensing. The book is aimed at graduate students of electrical engineering and atmospheric science as well as practitioners involved in the applications of polarimetric radar.

  17. EISCAT Svalbard radar

    Science.gov (United States)

    Lehtinen, Markku; Kangas, Jorma

    1992-02-01

    The main fields of interest of the Finnish scientists in EISCAT research are listed. Finnish interests in the Polar Cap Radar (PMR) and areas where the Finnish contribution could be important are addressed: radar techniques; sporadic E layers in the polar cap; atmospheric models; auroral studies in the polar cap; nonthermal plasmas in the F region; coordinated measurements with the Cluster satellites; studies of the ionospheric traveling; convection vortices; polar cap absorption; studies of lower atmosphere; educational program. A report on the design specification of an ionospheric and atmospheric radar facility based on the archipelago of Svalbard (Norway) is summarized.

  18. A Revised Sensitivity Model for Cassini INMS: Results at Titan

    Science.gov (United States)

    Teolis, B. D.; Niemann, H. B.; Waite, J. H.; Gell, D. A.; Perryman, R. S.; Kasprzak, W. T.; Mandt, K. E.; Yelle, R. V.; Lee, A. Y.; Pelletier, F. J.; Miller, G. P.; Young, D. T.; Bell, J. M.; Magee, B. A.; Patrick, E. L.; Grimes, J.; Fletcher, G. G.; Vuitton, V.

    2015-07-01

    Cassini Ion Neutral Mass Spectrometer (INMS) measurements from roughly a hundred Titan encounters over the Cassini mission yield neutral and ion densities systematically lower, by factors approximately 2 to 3, than estimates from several other spacecraft systems, including the Attitude and Articulation Control System, and Navigation system. In this paper we present a new INMS instrument sensitivity model, obtained by re-analyzing (1) the capture and transmission of neutral gas through the instrument, and (2) the detector gain reduction during pre-launch testing. By correcting for an under-estimation of gas leakage out of the instrument into space by the original calibration model, and adjusting for the gain change, the new model brings INMS densities into much closer agreement with the other Cassini systems. Accordingly, the INMS ion densities are revised upward by a constant detector sensitivity correction factor of 1.55±21 %, while the neutral sensitivities have a complex instrument pointing direction dependence, due (mostly) to the effect of the INMS vent and antechamber-to-closed source tube. In the special case of on-ram pointing the neutral densities are revised upward by a constant factor of 2.2±23 %. The corrected neutral and ion sensitivities given here are applicable to all previously published INMS results at Titan, Enceladus and elsewhere in the Saturn system. The new model gives reliable densities at high ram angles, in some cases above 90 degrees, thereby expanding the list of Titan flybys from which INMS densities may be extracted. We apply the model to obtain accurate densities from several off-ram Titan flybys which gave unusual neutral density vs. altitude profiles, or unreasonably high densities, with the original calibration.

  19. The Saturnian satellite Rhea as seen by Cassini VIMS

    Science.gov (United States)

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

    2012-01-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

  1. Detection of Weather Radar Clutter

    OpenAIRE

    Bøvith, Thomas; Nielsen, Allan Aasbjerg; Hansen, Lars Kai

    2008-01-01

    Weather radars provide valuable information on precipitation in the atmosphere but due to the way radars work, not only precipitation is observed by the weather radar. Weather radar clutter, echoes from non-precipitating targets, occur frequently in the data, resulting in lowered data quality. Especially in the application of weather radar data in quantitative precipitation estimation and forecasting a high data quality is important. Clutter detection is one of the key components in achieving...

  2. Deconvolution of variability and uncertainty in the Cassini safety analysis

    International Nuclear Information System (INIS)

    The standard method for propagation of uncertainty in a risk analysis requires rerunning the risk calculation numerous times with model parameters chosen from their uncertainty distributions. This was not practical for the Cassini nuclear safety analysis, due to the computationally intense nature of the risk calculation. A less computationally intense procedure was developed which requires only two calculations for each accident case. The first of these is the standard 'best-estimate' calculation. In the second calculation, variables and parameters change simultaneously. The mathematical technique of deconvolution is then used to separate out an uncertainty multiplier distribution, which can be used to calculate distribution functions at various levels of confidence

  3. Flight Path Control Design for the Cassini Solstice Mission

    Science.gov (United States)

    Ballard, Christopher G.; Ionasescu, Rodica

    2011-01-01

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

  4. Optical navigation planning process for the Cassini Solstice Mission

    Science.gov (United States)

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

    2011-01-01

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

  5. Doppler radar sensing of fish physiological motion

    Science.gov (United States)

    Hafner, Noah

    The monitoring vital of signs for fish is critical for advancing the study of trophic and energetic strategies, distributions and behavior, environmental impact, and aquaculture approaches. Presented here is a new approach for monitoring fish metabolic state without the trauma and stress associated with capture, surgical ECG, or other implanted sensing systems. Original research contributions include analysis for radar operation under water, development of radar systems for aquatic operation, and application of these systems to non invasively sense the heart and gill motion of fish. Tilapia and Sturgeon were studied to test the efficacy across varied fish body shapes and sizes, ranging from 0.1 to 1.3m in snout to tail length. Monitoring experiments were conducted with eleven tilapia and three sturgeons to assess activity level participated in these experiments, the results from which include activity level monitoring (tilapia: still or fidgeting 94% of time observed), ventilation rate (tilapia: 42 bpm, sturgeon: 145 bpm), and heart rate (tilapia: 41 bpm, sturgeon: 35 bpm). Bland-Altman analysis of radar and ECG measured heart rate indicate agreement between the two measurement techniques and the suitability of radar as an alternative to ECG. The initial steps for developing a system for practical application is also presented including designs for radar system miniaturization and discussion on further characterization steps with less constrained environments.

  6. Mimo radar waveform design for spectrum sharing with cellular systems a Matlab based approach

    CERN Document Server

    Khawar, Awais; Clancy, T Charles

    2016-01-01

    This book discusses spectrum sharing between cellular systems and radars. The book addresses a novel way to design radar waveforms that can enable spectrum sharing between radars and communication systems, without causing interference to communication systems, and at the same time achieving radar objectives of target detection, estimation, and tracking. The book includes a MATLAB-based approach, which provides reader with a way to learn, experiment, compare, and build on top of existing algorithms.

  7. Estimating the vertical structure of intense Mediterranean precipitation using two X-band weather radar systems

    OpenAIRE

    Berne, A.D.; Delrieu, G.; Andrieu, H.

    2005-01-01

    The present study aims at a preliminary approach of multiradar compositing applied to the estimation of the vertical structure of precipitation¿an important issue for radar rainfall measurement and prediction. During the HYDROMET Integrated Radar Experiment (HIRE¿98), the vertical profile of reflectivity was measured, on the one hand, with an X-band vertically pointing radar system, and, on the other hand, with an X-band RHI scanning protocol radar. The analysis of the raw data highlights the...

  8. Wind Profiling Radar

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Clutter present in radar return signals as used for wind profiling is substantially removed by carrying out a Daubechies wavelet transformation on a time series of...

  9. Comparative analysis of Cassini's titan flybys T25-T33 according to the measurements of Cassini-MIMI and CAPS

    International Nuclear Information System (INIS)

    Complete text of publication follows. In this study we focused on 9 targeted Titan flybys of Cassini between DOY 053-180 in 2007 (T25-T33). We analyzed the measurements of the Cassini MIMI-LEMMS and CAPS-IMS instruments, and also used the data of the onboard Magnetometer. During these flybys Titan was located at approximately the same position (at ∼13.5 SLT) along its orbit, the unique T32 - when the moon was found in Saturn's magnetosheath - was observed in this period as well. Since the relative positions of the dominant ionization sources (solar EUV, charge exchange, magnetospheric electron impacts) were similar during these flybys, it is reasonable to compare the measurements and get a more detailed picture of Titan's global plasma environment. The flybys were carried out during the high inclination phase of the Cassini Tour. Our analysis was focused on the differential intensities of energetic electrons and ions, and we also used the low energy ion measurements of CAPS-IMS. Another question that we investigated was concentrated on T32, during which the magnetosphere was significantly more compressed compared to the other flybys of this group. Therefore we analysed the possibility of a solar event reaching Saturn at this time. In April and May 2007 there were several active regions on the Sun, so we used plasma parameters measured by the Venus Express spacecraft (which was approximately along the Sun-Saturn line) to estimate whether the energetic particles of a CME erupted towards Saturn could have been responsible for the compression detected during T32.

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

    CERN Document Server

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

    2010-01-01

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

  11. VLBA Astrometric Observations of the Cassini Spacecraft at Saturn

    CERN Document Server

    Jones, D L; Dhawan, V; Romney, J; Folkner, W M; Lanyi, G; Border, J; Jacobson, R

    2010-01-01

    The planetary ephemeris is an essential tool for interplanetary spacecraft navigation, studies of solar system dynamics (including, for example, barycenter corrections for pulsar timing ephemeredes), the prediction of occultations, and tests of general relativity. We are carrying out a series of astrometric VLBI observations of the Cassini spacecraft currently in orbit around Saturn, using the Very Long Baseline Array (VLBA). These observations provide positions for the center of mass of Saturn in the International Celestial Reference Frame (ICRF) with accuracies ~0.3 milli-arcsecond (1.5 nrad), or about 2 km at the average distance of Saturn. This paper reports results from eight observing epochs between 2006 October and 2009 April. These data are combined with two VLBA observations by other investigators in 2004 and a Cassini-based gravitational deflection measurement by Fomalont et al. in 2009 to constrain a new ephemeris (DE 422). The DE 422 post-fit residuals for Saturn with respect to the VLBA data are ...

  12. Interior Models for Saturn's Moon Titan Consistent with Cassini Observations

    Science.gov (United States)

    Castillo-Rogez, Julie

    2013-10-01

    We demonstrate that a model of Titan's interior with a core dominated by hydrated silicates can explain three major geophysical constraints available for this body: the mean moment of inertia (revised values currently in the literature or being published), tidal Love number k2, both of which were inferred from Cassini radio science observations, as well as indirect estimate of the dissipation factor inferred from Titan's orbital properties. Other models in which ice has remained partially mixed with silicates as a consequence of limited early heating fail to explain the dissipation factor. A core hydrated in silicate is difficult to maintain over the long term and may be in the process of dehydrating, which may involve significant transfer of water enriched in salts from the core to the ocean and destabilize the high-pressure ice layer. We will present possible observations that could help test this model with future observations to be obtained by the Cassini Orbiter. Acknowledgements: This work has been carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. Government sponsorship acknowledged.

  13. Estimation of Enceladus Plume Density Using Cassini Flight Data

    Science.gov (United States)

    Wang, Eric K.; Lee, Allan Y.

    2011-01-01

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

  14. Cassini/CIRS Observations of Saturn's "Storm Alley"

    Science.gov (United States)

    Hesman, Brigette E.

    2010-01-01

    In the Voyager era storms on Saturn were observed predominantly in the northern hemisphere, however, in recent years storm activity has been confined to a narrow range of latitudes referred to as "storm alley" (approx.40degS planetographic latitude). Throughout Cassini's prime mission storms have been detected by two independent instruments: ISS through dayside images and RPWS using radio emissions from Saturn Electrostatic Discharges (SED's) (Dyudina et al. 2007). Analysis of these storms indicates that the cloud tops are in the 200 - 500rnbar altitude range. During Saturn's Equinox, in August 2009, lSS imaged lightning on the night side in storm alley when ring-shine was at a minimum (Dyudina et al. 2010). This study indicates that lightning may have originated as deep as the water cloud. Decently, Cassini/CIRS was targeted at storm alley while a storm, originally detected by amateurs, was ongoing (March 2010). Phosphine can be used as a tracer of vertical transport because it is a disequilibrium species that falls off with altitude in the upper troposphere. CIRS can measure temperature and phosphine abundance independently in the altitude range where these cloud tops occur. Early analysis of these data shows stronger phosphine absorption at storm longitudes. This is an indication that powerful updrafts were dredging material upward into the upper troposphere. The results of the analysis of the March 2010 CIRS observations of storm alley will be presented.

  15. Cassini Thruster Calibration Algorithm Using Reaction Wheel Biasing Data

    Science.gov (United States)

    Rizvi, Farheen

    2012-01-01

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

  16. Jovian atmospheric dynamics: an update after Galileo and Cassini

    International Nuclear Information System (INIS)

    The Galileo and Cassini spacecrafts have greatly enhanced the observational record of Jupiter's tropospheric dynamics, particularly through returning high spatial resolution, multi-spectral and global imaging data with episodic coverage over periods of months to years. These data, along with those from Earth-based telescopes, have revealed the stability of Jupiter's zonal jets, captured the evolution of vortices and equatorial waves, and mapped the distributions of lightning and moist convection. Because no observations of Jupiter's interior exist, a forward modelling approach has been used to relate observations at cloud level to models of shallow or deep jet structure, shallow or deep jet forcing and energy transfer between turbulence, vortices and jets. A range of observed phenomena can be reproduced in shallow models, though the Galileo probe winds and jet stability arguments hint at the presence of deep jets. Many deep models, however, fail to reproduce Jupiter-like non-zonal features (e.g. vortices). Jupiter's dynamics likely include both deep and shallow processes, requiring an integrated approach to future modelling-an important goal for the post-Galileo and Cassini era

  17. Titan Surface Temperatures as Measured by Cassini CIRS

    Science.gov (United States)

    Jennings, Donald E.; Flasar, F.M.; Kunde, V.G.; Nixon, C.A.; Romani, P.N.; Samuelson, R.E.; Coustenis, A.; Courtin, R.

    2009-01-01

    Thermal radiation from the surface of Titan reaches space through a spectral window of low opacity at 19-microns wavelength. This radiance gives a measure of the brightness temperature of the surface. Composite Infrared Spectrometer' (CIRS) observations from Cassini during its first four years at Saturn have permitted latitude mapping of zonally averaged surface temperatures. The measurements are corrected for atmospheric opacity using the dependence of radiance on emission angle. With the more complete latitude coverage and much larger dataset of CIRS we have improved upon the original results from Voyager IRIS. CIRS measures the equatorial surface brightness temperature to be 93.7+/-0.6 K, the same as the temperature measured at the Huygens landing site. The surface brightness temperature decreases by 2 K toward the south pole and by 3 K toward the north pole. The drop in surface temperature between equator and north pole implies a 50% decrease in methane saturation vapor pressure and relative humidity; this may help explain the large northern lakes. The H2 mole fraction is derived as a by-product of our analysis and agrees with previous results. Evidence of seasonal variation in surface and atmospheric temperatures is emerging from CIRS measurements over the Cassini mission.

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

    Science.gov (United States)

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

    2008-01-01

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

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

    Science.gov (United States)

    Sarani, Siamak

    2010-01-01

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

  20. A barrier radar concept

    Science.gov (United States)

    Marshall, J.; Ball, C.; Weissman, I.

    A description is given of a low power, light-weight radar that can be quickly set up and operated on batteries for extended periods of time to detect airborne intruders. With low equipment and operating costs, it becomes practical to employ a multiplicity of such radars to provide an unbroken intrusion fence over the desired perimeter. Each radar establishes a single transmitted fan beam extending vertically from horizon to horizon. The beam is generated by a two-face array antenna built in an A-frame configuration and is shaped, through phasing of the array elements, to concentrate the transmitter power in a manner consistent with the expected operating altitude ceiling of the targets of interest. The angular width of this beam in the dimension transverse to the fan depends on the radar transmission frequency and the antenna aperture dimension, but is typically wide enough so that a target at the maximum altitude or range will require tens of seconds to pass through the beam. A large number of independent samples of radar data will thus be available to provide many opportunities for target detection.

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

    Science.gov (United States)

    Meakin, Peter C.

    2008-01-01

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

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

    Science.gov (United States)

    1997-01-01

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

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

    Science.gov (United States)

    1997-01-01

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

  4. An overview of the risk uncertainty assessment process for the Cassini space mission

    International Nuclear Information System (INIS)

    The Cassini spacecraft is a deep space probe whose mission is to explore the planet Saturn and its moons. Since the spacecraft's electrical requirements will be supplied by radioisotope thermoelectric generators (RTGs), the spacecraft designers and mission planners must assure that potential accidents involving the spacecraft do not pose significant human risk. The Cassini risk analysis team is seeking to perform a quantitative uncertainty analysis as a part of the overall mission risk assessment program. This paper describes the uncertainty analysis methodology to be used for the Cassini mission and compares it to the methods that were originally developed for evaluation of commercial nuclear power reactors

  5. Tidal Control of Jet Eruptions Observed by Cassini ISS

    Science.gov (United States)

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

    2012-01-01

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

  6. Airport Surveillance Radar : Model 7

    Data.gov (United States)

    Department of Transportation — The Airport Surveillance Radar Model 7 (ASR-7) is a short-range (60 nautical miles (nmi)) analog radar system used to detect and report the presence and location of...

  7. Airport Surveillance Radar : Model 8

    Data.gov (United States)

    Department of Transportation — The Airport Surveillance Radar Model 8 (ASR-8) is a short-range (60 nautical mile (nmi)), analog radar system used to detect and report the presence and location of...

  8. Synthetic Aperture Radar - Hardware Development

    OpenAIRE

    Rosner, V.; Seller, R.; L. Dudas; Kazi, K.; Miko, G.

    2009-01-01

    Experimental real and synthetic aperture radar are developed from the base-band digital unit to the analogue RF parts, based on solid state units, using pulse compression for radar imaging. Proper QPSK code is found for matched filter.

  9. The MST Radar Technique

    Science.gov (United States)

    Balsley, B. B.

    1985-01-01

    The past ten year have witnessed the development of a new radar technique to examine the structure and dynamics of the atmosphere between roughly 1 to 100 km on a continuous basis. The technique is known as the MST (for Mesosphere-Stratosphere-Troposphere) technique and is usable in all weather conditions, being unaffected by precipitation or cloud cover. MST radars make use of scattering from small scale structure in the atmospheric refractive index, with scales of the order of one-half the radar wavelength. Pertinent scale sizes for middle atmospheric studies typically range between a fraction of a meter and a few meters. The structure itself arises primarily from atmospheric turbulence. The technique is briefly described along with the meteorological parameters it measures.

  10. Radar for tracer particles

    CERN Document Server

    Ott, Felix; Huang, Kai

    2016-01-01

    We introduce a radar system capable of tracking a $5$mm spherical target continuously in three dimensions. The $10$GHz (X-band) radar system has a transmission power of $1$W and operates in the near field of the horn antennae. By comparing the phase shift of the electromagnetic wave traveling through the free space with an IQ-Mixer, we obtain the relative movement of the target with respect to the antennae. From the azimuth and inclination angles of the receiving antennae obtained in the calibration, we reconstruct the target trajectory in a three-dimensional Cartesian system. Finally, we test the tracking algorithm with target moving in circular as well as in pendulum motions, and discuss the capability of the radar system.

  11. Pricing of radar data

    OpenAIRE

    Linder, Martin; Nylin, Tobias

    2013-01-01

    In this thesis we examine the issue regarding pricing of radar data and surveillance to the operators of air navigation service (ANS) at the aerodromes in Sweden. The question of who should be responsible for providing radar data to the operators is being managed that results in if it should be LFV, as it is today, the government or another authority. This is being examined since LFV in 2010 lost its monopoly position in the terminal area in Sweden. LFV still has monopoly on the en route part...

  12. Ground penetrating radar

    CERN Document Server

    Daniels, David J

    2004-01-01

    Ground-penetrating radar has come to public attention in recent criminal investigations, but has actually been a developing and maturing remote sensing field for some time. In the light of recent expansion of the technique to a wide range of applications, the need for an up-to-date reference has become pressing. This fully revised and expanded edition of the best-selling Surface-Penetrating Radar (IEE, 1996) presents, for the non-specialist user or engineer, all the key elements of this technique, which span several disciplines including electromagnetics, geophysics and signal processing. The

  13. Radar for tracer particles

    OpenAIRE

    Ott, Felix; Herminghaus, Stephan; Huang, Kai

    2016-01-01

    We introduce a radar system capable of tracking a $5$mm spherical target continuously in three dimensions. The $10$GHz (X-band) radar system has a transmission power of $1$W and operates in the near field of the horn antennae. By comparing the phase shift of the electromagnetic wave traveling through the free space with an IQ-Mixer, we obtain the relative movement of the target with respect to the antennae. From the azimuth and inclination angles of the receiving antennae obtained in the cali...

  14. Noncircular features in Saturn's rings III: The Cassini Division

    Science.gov (United States)

    French, Richard G.; Nicholson, Philip D.; McGhee-French, Colleen A.; Lonergan, Katherine; Sepersky, Talia; Hedman, Mathew M.; Marouf, Essam A.; Colwell, Joshua E.

    2016-08-01

    We have conducted a comprehensive survey of 22 sharp-edged ringlets and gaps in the Cassini Division of Saturn's rings, making use of nearly 200 high-SNR stellar and radio occultation chords obtained by the Cassini VIMS, UVIS, and RSS instruments between 2005 and 2013. We measure eccentricities from as small as ae = 80 m to nearly 30 km, free normal modes with amplitudes from ∼ 0.1 to 4.1 km, and detectable inclinations as small as asini = 0.2 km. Throughout the entire region, the Mimas 2.1 ILR (inner Lindblad resonance) produces systematic forced m = 2 distortions that quantitatively match the expected amplitudes, phases, and pattern speed. The narrow Russell, Jeffreys, Kuiper, Bessel, and Barnard gaps are simplest, and do not contain dense ringlets. Their outer edges are generally quite sharp and four of them are circular to within ∼0.25 km, whereas most of the inner gap edges have significant eccentricities. Three gaps are more complex, containing one or more isolated ringlets. First among these is the 361 km-wide Huygens gap, containing two ringlets. The wider Huygens ringlet has nearly identical eccentricities on the two edges, in addition to OLR-type (outer Lindblad resonance) normal modes on the inner edge and ILR-type modes on the outer edge. A secondary m = 1 (eccentric) mode is present on the outer edge of the ringlet, with a pattern speed similar to that of the B ring's outer edge. Variations in the ringlet's width are complex, but are statistically consistent with the expected magnitudes resulting from the random superposition of the multiple normal modes on the two edges. Also present in the Huygens gap is the very narrow so-called Strange ringlet, with a substantial eccentricity and inclination, as well as both ILR- and OLR-type normal modes. The 100 km-wide Herschel gap's inner edge is highly eccentric, with at least seven ILR-type normal modes. The outer gap edge is also eccentric, and hosts four OLR-type normal modes, and a secondary m = 1 mode

  15. Titan's atmospheric composition: from Voyager to Cassini and beyond

    Science.gov (United States)

    Coustenis, A.

    2007-12-01

    Titan's atmosphere was revealed by the Voyager missions in the 80s. The trace composition was in particular inferred from infrared spectra by the V1/IRIS Spectrometer. ISO gave us an opportunity to further explore this exciting milieu in 1997 (Coustenis et al., 1998; 2003) and brought the discovery of new molecules : H2O and C6H6. Our understanding of Titan's atmospheric chemical composition has recently been enhanced by the data returned by the Cassini instruments. Spectra recorded by the Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft have been processed from the Titan flybys spanning three years now since SOI (Flasar et al., 2005; Teanby et al., 2006, Vinatier et al., 2006; Nixon et al., 2006; Coustenis et al., 2007). The spectra characterize various regions on Titan from 85°S to 80°N with a variety of emission angles. We have studied the emission observed in the CIRS detector arrays (covering the 10-1500 cm-1 spectral range with apodized resolutions of 2.54 or 0.53 cm-1). We have used temperature profiles retrieved from the inversion of the emission observed in the methane band at 1304 cm-1 and a line-by-line radiative transfer code to infer the abundances of the trace constituents and some of their isotopes in Titan's stratosphere (Coustenis et al., 2007a). The composite spectra show several signatures of previously identified molecules: hydrocarbons, nitriles, H2O and CO2. Besides these well-known trace species, a firm detection of benzene (C6H6) is provided by CIRS at 674 cm-1 and allows for the study of its latitudinal variations. No longitudinal variations were found for any of the gases. Information is retrieved on the meridional variations of the trace constituents and tied to predictions by dynamical-photochemical models (Hourdin et al., 2004; Lavvas et al., 2007). Molecules showing a significant enhancement at northern latitudes are the nitriles (HC3N, HCN) and the complex hydrocarbons (C4H2, C3H4). The D/H ratio on Titan was

  16. Incorporating CCSDS telemetry standards and philosophy on Cassini

    Science.gov (United States)

    Day, John C.; Elson, Anne B.

    1995-01-01

    The Cassini project at the Jet Propulsion Laboratory (JPL) is implementing a spacecraft telemetry system based on the Consultative Committee for Space Data Systems (CCSDS) packet telemetry standards. Resolving the CCSDS concepts with a Ground Data System designed to handle time-division-multiplexed telemetry and also handling constraints unique to a deep-space planetary spacecraft (such as fixed downlink opportunities, small downlink rates and requirements for on-board data storage) have resulted in spacecraft and ground system design challenges. Solving these design challenges involved adapting and extending the CCSDS telemetry standards as well as changes to the spacecraft and ground system designs. The resulting spacecraft/ground system design is an example of how new ideas and philosophies can be incorporated into existing systems and design approaches without requiring significant rework. In addition, it shows that the CCSDS telemetry standards can be successfully applied to deep-space planetary spacecraft.

  17. CASSINI UVIS STELLAR OCCULTATION OBSERVATIONS OF SATURN's RINGS

    International Nuclear Information System (INIS)

    The Cassini spacecraft's Ultraviolet Imaging Spectrograph (UVIS) includes a high-speed photometer (HSP) that has observed more than 100 stellar occultations by Saturn's rings. Here, we document a standardized technique applied to the UVIS-HSP ring occultation datasets delivered to the Planetary Data System as higher level data products. These observations provide measurements of ring structure that approaches the scale of the largest common ring particles (∼5 m). The combination of multiple occultations at different viewing geometries enables reconstruction of the three-dimensional structure of the rings. This inversion of the occultation data depends on accurate calibration of the data so that occultations of different stars taken at different times and under different viewing conditions can be combined to retrieve ring structure. We provide examples of the structure of the rings as seen from several occultations at different incidence angles to the rings, illustrating changes in the apparent structure with viewing geometry.

  18. Deconvolution of variability and uncertainty in the Cassini safety analysis

    International Nuclear Information System (INIS)

    The standard method for propagation of uncertainty in a risk analysis requires rerunning the risk calculation numerous times with model parameters chosen from their uncertainty distributions. This was not practical for the Cassini nuclear safety analysis, due to the computationally intense nature of the risk calculation. A less computationally intense procedure was developed which requires only two calculations for each accident case. The first of these is the standard open-quotes best-estimateclose quotes calculation. In the second calculation, variables and parameters change simultaneously. The mathematical technique of deconvolution is then used to separate out an uncertainty multiplier distribution, which can be used to calculate distribution functions at various levels of confidence. copyright 1998 American Institute of Physics

  19. Easier access to Cassini/MIMI public data

    Science.gov (United States)

    Kusterer, M. B.; Christon, S. P.; Mitchell, D. G.; DiFabio, R. D.; Hamilton, D. C.; Krimigis, S. M.; Manweiler, J. W.; Paranicas, C.; Vandegriff, J. D.

    2012-12-01

    We present calibrated, higher order data products, a data user guide, and public analysis software for the Magnetosphere Imaging Instrument (MIMI) on Cassini. These new products simplify the process of using and analyzing MIMI data. While raw MIMI data and basic calibration information has been available in the PDS, the new user guide describes the most up to date steps needed to convert the data into science units. The guide offers detailed procedures for reading and calibrating data from all three MIMI sensors: LEMMS, CHEMS, and INCA. Furthermore, we are now providing public access to software implementing the details in the user guide. We now make available pre-calibrated data products, including CHEMS 20 day energy-time spectrograms (for multiple species), and LEMMS energy-time spectrograms. Averaged LEMMS data is also available. For INCA, we include high spatial resolution ENA image skymaps and high time-of-flight resolution ion angle distribution images. Finally, we also have created ENA movies.

  20. Cassini Main Engine Assembly Cover Flight Management and Performance

    Science.gov (United States)

    Somawardhana, Ruwan P.; Millard, Jerry M.

    2010-01-01

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

  1. Radar techniques using array antennas

    CERN Document Server

    Wirth, Wulf-Dieter

    2001-01-01

    This book gives an introduction to the possibilities of radar technology based on active array antennas, giving examples of modern practical systems. There are many valuable lessons presented for designers of future high standard multifunction radar systems for military and civil applications. The book will appeal to graduate level engineers, researchers, and managers in the field of radar, aviation and space technology.

  2. Human walking estimation with radar

    NARCIS (Netherlands)

    Dorp, Ph. van; Groen, F.C.A.

    2003-01-01

    Radar can be used to observe humans that are obscured by objects such as walls. These humans cannot be visually observed. The radar measurements are used to animate an obscured human in virtual reality. This requires detailed information about the motion. The radar measurements give detailed informa

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

    Science.gov (United States)

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

    2010-05-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

  5. OCCULTATION OBSERVATIONS OF SATURN'S B RING AND CASSINI DIVISION

    International Nuclear Information System (INIS)

    The outer edge of Saturn's B ring is strongly affected by the nearby 2:1 inner Lindblad resonance of Mimas and is distorted approximately into a centered elliptical shape, which at the time of the Voyager 1 and 2 encounters was oriented with its periapse toward Mimas. Subsequent observations have shown that the actual situation is considerably more complex. We present a complete set of historical occultation measurements of the B-ring edge, including the 1980 Voyager 1 and 1981 Voyager 2 radio and stellar occultations, the 1989 occultation of 28 Sgr, two independently analyzed occultations observed with the Hubble Space Telescope in 1991 and 1995, and a series of ring profiles from 12 diametric (ansa-to-ansa) occultations observed in 2005, using the Cassini Radio Science Subsystem (RSS). After making an approximate correction for systematic errors in the reconstructed spacecraft trajectories, we obtain orbit fits to features in the rings with rms residuals well under 1 km, in most cases. Fits to the B-ring edge in the RSS data reveal a systematic variation in the maximum optical depth at the very edge of the ring as a function of its orbital radius. We compare the B-ring measurements to an m = 2 distortion aligned with Mimas, and show that there have been substantial phase shifts over the past 25 years. Finally, we present freely precessing equatorial elliptical models for 16 features in the Cassini Division. The inner edges of the gaps are generally eccentric, whereas the outer edges are nearly circular, with ae < 0.5 km.

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

    International Nuclear Information System (INIS)

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

  7. Cassini Radio and Plasma Wave Observations at Saturn

    Science.gov (United States)

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

    2005-01-01

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

  8. The Structure of Titan's Atmosphere from Cassini Radio Occultations

    Science.gov (United States)

    Schinder, Paul J.; Flasar, F. Michael; Marouf, Essam A.; French, Richard G.; McGhee, Colleen A.; Kliore, Arvydas J.; Rappaport, Nicole J.; Barbinis, Elias; Fleischman, Don; Anabtawi, Aseel

    2011-01-01

    We present results from the two radio occultations of the Cassini spacecraft by Titan in 2006, which probed mid-southern latitudes. Three of the ingress and egress soundings occurred within a narrow latitude range, 31.34 deg S near the surface, and the fourth at 52.8 deg S. Temperature - altitude profiles for all four occultation soundings are presented, and compared with the results of the Voyager 1 radio occultation (Lindal et al., 1983), the HASI instrument on the Huygens descent probe (Fulchignoni et al., 2005), and Cassini CIRS results (Flasar et al., 2005; Achterberg et al., 2008b). Sources of error in the retrieved temperature - altitude profiles are also discussed, and a major contribution is from spacecraft velocity errors in the reconstructed ephemeris. These can be reduced by using CIRS data at 300 km to make along-track adjustments of the spacecraft timing. The occultation soundings indicate that the temperatures just above the surface at 31-34 deg S are about 93 K, while that at 53 deg S is about 1 K colder. At the tropopause, the temperatures at the lower latitudes are all about 70 K, while the 53 deg S profile is again 1 K colder. The temperature lapse rate in the lowest 2 km for the two ingress (dawn) profiles at 31 and 33 deg S lie along a dry adiabat except within approximately 200m of the surface, where a small stable inversion occurs. This could be explained by turbulent mixing with low viscosity near the surface. The egress profile near 34 deg S shows a more complex structure in the lowest 2 km, while the egress profile at 53 deg S is more stable.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-09-01

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

  10. Progress reports for period November 1--30, 1994 -- Joint UK/US Radar Program

    Energy Technology Data Exchange (ETDEWEB)

    Twogood, R.E.; Brase, J.M.; Mantrom, D.D.; Chambers, D.H.; Robey, H.F.

    1994-12-19

    This report gives the principle investigator, objectives, recent accomplishments, milestones for reporting period, expected milestones for ensuing period, other issues and planned expenditures for the following programs: airborne RAR/SAR; radar data processor; ground-based SAR signal processing workstation; static airborne radar; multi-aperture space-time array radar; radar field experiments; data analysis and detection theory; management; E-2C radar data analysis;modeling and analysis; current meter array; UCSB wave tank; stratified flow facility; and IR sensor system. Budget status is also given.

  11. Cassini/VIMS Spectra and Time-Evolution of Precipitation-Associated Surface Brightenings on Titan

    OpenAIRE

    Barnes, J.W.; Buratti, B.J.; Turtle, E. P.; Bow, J.; Dalba, P. A.; Perry, J.; Rodriguez, S; Lé Mouélic, S.; Baines, K. H.; Sotin, C.; Lorenz, R. D.; Malaska, M.J.; McCord, T.B.; Brown, R.H.; Clark, R.N.

    2012-01-01

    Large areas of Titan’s surface brightened at all wavelengths as seen from Cassini/VIMS for several months. The brightenings occurred after a large storm and rainfall event, and may relate to volatile refreezing due to evaporative cooling.

  12. Fiboquadratic Sequences and Extensions of the Cassini Identity Raised From the Study of Rithmomachia

    OpenAIRE

    Guardia, Tomás; Jiménez, Douglas

    2015-01-01

    In this paper, we introduce fiboquadratic sequences as an extension to infinity of the board of Rithmomachia and we prove that this extension gives raise to fiboquadratic sequences which we define here. Also, fiboquadratic sequences provide extensions of Cassini's Identity.

  13. Bistatic Forward Scattering Radar Detection and Imaging

    Directory of Open Access Journals (Sweden)

    Hu Cheng

    2016-06-01

    Full Text Available Forward Scattering Radar (FSR is a special type of bistatic radar that can implement image detection, imaging, and identification using the forward scattering signals provided by the moving targets that cross the baseline between the transmitter and receiver. Because the forward scattering effect has a vital significance in increasing the targets’ Radar Cross Section (RCS, FSR is quite advantageous for use in counter stealth detection. This paper first introduces the front line technology used in forward scattering RCS, FSR detection, and Shadow Inverse Synthetic Aperture Radar (SISAR imaging and key problems such as the statistical characteristics of forward scattering clutter, accurate parameter estimation, and multitarget discrimination are then analyzed. Subsequently, the current research progress in FSR detection and SISAR imaging are described in detail, including the theories and experiments. In addition, with reference to the BeiDou navigation satellite, the results of forward scattering experiments in civil aircraft detection are shown. Finally, this paper considers future developments in FSR target detection and imaging and presents a new, promising technique for stealth target detection.

  14. Cassini nightside observations of the oscillatory motion of Saturn's northern auroral oval

    OpenAIRE

    Bunce, E. J.; Grodent, D. C.; Jinks, S.L.; Andrews, D. J.; Badman, S. V.; Coates, A. J.; Cowley, S. W. H.; Dougherty, M. K.; W. S. Kurth; Mitchell, D.G.; G. Provan

    2014-01-01

    In recent years we have benefitted greatly from the first in-orbit multi-wavelength images of Saturn's polar atmosphere from the Cassini spacecraft. Specifically, images obtained from the Cassini UltraViolet Imaging Spectrograph (UVIS) provide an excellent view of the planet's auroral emissions, which in turn give an account of the large-scale magnetosphere-ionosphere coupling and dynamics within the system. However, obtaining near-simultaneous views of the auroral regions with in situ measur...

  15. Cassini States with Dissipation: Why Obliquity Tides Cannot Inflate Hot Jupiters

    OpenAIRE

    Fabrycky, Daniel C.; Johnson, Eric T.; Goodman, Jeremy

    2007-01-01

    Some short-period exoplanets (hot Jupiters) are observed by their transits to have anomalously large radii. It has been suggested that these planets are in a resonance involving persistent misalignment and synchronous precession of their spin and orbital angular momenta, a Cassini state, and that the attendant tidal heating inflates the planet. We argue against this. Using explicit tidal integrations, we show that although an oblique Cassini state can dissipate many times the rotational energ...

  16. Cassini ISS Astrometry by the Astronomy Unit at Queen Mary, University of London - An Overview

    OpenAIRE

    Cooper, Nicholas J; Murray, Carl D.; Evans, Michael W.; Beurle, Kevin; Williams, Gareth

    2012-01-01

    Program available at: http://www.imcce.fr/hosted_sites/naroo/program.html International audience The Cassini group within the Astronomy Unit at Queen Mary, University of London (QMUL) has been using the Imaging Science Subsystem (ISS) of the Cassini Spacecraft to make astrometric observations of the inner satellites and F ring of Saturn since 2004. Further observations are planned until the end of the mission in 2017. Here we summarize this work and describe how the astrometric data is ...

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

    OpenAIRE

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

    2014-01-01

    We report on the first analysis of magnetospheric cusp observations at Saturn by multiple in situ instruments onboard the Cassini spacecraft. Using this we infer the process of reconnection was occurring at Saturn's magnetopause. This agrees with remote observations that showed the associated auroral signatures of reconnection. Cassini crossed the northern cusp around noon local time along a poleward trajectory. The spacecraft observed ion energy-latitude dispersionsa characteristic signature...

  18. Rain radar instrument definition

    Science.gov (United States)

    Vincent, Nicolas; Chenebault, J.; Suinot, Noel; Mancini, Paolo L.

    1996-12-01

    As a result of a pre-phase a study, founded by ESA, this paper presents the definition of a spaceborne Rain Radar, candidate instrument for earth explorer precipitation mission. Based upon the description of user requirements for such a dedicated mission, a mission analysis defines the most suitable space segment. At system level, a parametric analysis compares pros and cons of instrument concepts associated with rain rate retrieval algorithms in order to select the most performing one. Several trade-off analysis at subsystem level leads then to the definition of the proposed design. In particular, as pulse compression is implemented in order to increase the radar sensitivity, the selected method to achieve a pulse response with a side-lobe level below--60 dB is presented. Antenna is another critical rain radar subsystem and several designs are com pared: direct radiating array, single or dual reflector illuminated by single or dual feed arrays. At least, feasibility of centralized amplification using TWTA is compared with criticality of Tx/Rx modules for distributed amplification. Mass and power budgets of the designed instrument are summarized as well as standard deviations and bias of simulated rain rate retrieval profiles. The feasibility of a compliant rain radar instrument is therefore demonstrated.

  19. Synthetic Aperture Radar Interferometry

    Science.gov (United States)

    Rosen, P. A.; Hensley, S.; Joughin, I. R.; Li, F.; Madsen, S. N.; Rodriguez, E.; Goldstein, R. M.

    1998-01-01

    Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristics of the surface. This paper reviews the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.

  20. Radar scattering of linear dunes and mega-yardangs: Application to Titan

    CERN Document Server

    Paillou, Philippe; Radebaugh, Jani; Wall, Stephen

    2015-01-01

    The Ku-band (13.8 GHz - 2.2 cm) RADAR instrument onboard the Cassini-Huygens spacecraft has revealed the richness of the surface of Titan, as numerous seas, lakes, rivers, cryo-volcanic flows and vast dune fields have been discovered. Linear dunes are a major geomorphological feature present on Titan, covering up to 17% of its surface, mainly in equatorial regions. However, the resolution of the RADAR instrument is not good enough to allow a detailed study of the morphology of these features. In addition, other linear wind-related landforms, such as mega-yardangs (linear wind-abraded ridges formed in cohesive rocks), are likely to present a comparable radar signature that could be confused with the one of dunes. We conducted a comparative study of the radar radiometry of both linear dunes and mega-yardangs, based on representative terrestrial analogues: the linear dunes located in the Great Sand Sea in western Egypt and in the Namib Desert in Namibia, and the mega-yardangs observed in the Lut Desert in easter...

  1. Airborne Radar Observations of Severe Hailstorms: Implications for Future Spaceborne Radar

    Science.gov (United States)

    Heymsfield, Gerald M.; Tian, Lin; Li, Lihua; McLinden, Matthew; Cervantes, Jaime I.

    2013-01-01

    A new dual-frequency (Ku and Ka band) nadir-pointing Doppler radar on the high-altitude NASA ER-2 aircraft, called the High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP), has collected data over severe thunderstorms in Oklahoma and Kansas during the Midlatitude Continental Convective Clouds Experiment (MC3E). The overarching motivation for this study is to understand the behavior of the dualwavelength airborne radar measurements in a global variety of thunderstorms and how these may relate to future spaceborne-radar measurements. HIWRAP is operated at frequencies that are similar to those of the precipitation radar on the Tropical Rainfall Measuring Mission (Ku band) and the upcoming Global Precipitation Measurement mission satellite's dual-frequency (Ku and Ka bands) precipitation radar. The aircraft measurements of strong hailstorms have been combined with ground-based polarimetric measurements to obtain a better understanding of the response of the Ku- and Ka-band radar to the vertical distribution of the hydrometeors, including hail. Data from two flight lines on 24 May 2011 are presented. Doppler velocities were approx. 39m/s2at 10.7-km altitude from the first flight line early on 24 May, and the lower value of approx. 25m/s on a second flight line later in the day. Vertical motions estimated using a fall speed estimate for large graupel and hail suggested that the first storm had an updraft that possibly exceeded 60m/s for the more intense part of the storm. This large updraft speed along with reports of 5-cm hail at the surface, reflectivities reaching 70 dBZ at S band in the storm cores, and hail signals from polarimetric data provide a highly challenging situation for spaceborne-radar measurements in intense convective systems. The Ku- and Ka-band reflectivities rarely exceed approx. 47 and approx. 37 dBZ, respectively, in these storms.

  2. Radar facies of unconsolidated sediments in The Netherlands : A radar stratigraphy interpretation method for hydrogeology

    NARCIS (Netherlands)

    Overmeeren, R.A. van

    1998-01-01

    Since 1990, The Netherlands Institute of Applied Geoscience TNO has been carrying out ground penetrating radar (GPR) measurements to assess the potential for imaging and characterising different hydrogeological targets in more than 30 pilot areas in The Netherlands. The experience gained by processi

  3. The use of radar for bathymetry assessment

    OpenAIRE

    Aardoom, J.H.; Greidanus, H.S.F.

    1998-01-01

    The bottom topography in shallow seas can be observed by air- and spaceborne imaging radar. Bathymetric information derived from radar data is limited in accuracy, but radar has a good spatial coverage. The accuracy can be increased by assimilating the radar imagery into existing or insitu gathered bathymetric data. The paper reviews the concepts of bathymetry assessment by radar, the radar imaging mechanism, and the possibilities and limitations of the use of radar data in rapid assessment.

  4. Influence of the vertical profile of reflectivity on radar-estimated rain rates at short time steps

    NARCIS (Netherlands)

    Berne, A.D.; Delrieu, G.; Andrieu, H.; Creutin, J.D.

    2004-01-01

    The present study aims to demonstrate the major influence of the vertical heterogeneity of rainfall on radar rain gauge assessment. For this purpose, an experimental setup was deployed during the HYDROMET Integrated Radar Experiment (HIRE-98) based on a conventional S-band weather radar operating at

  5. The global plasma environment of Titan as observed by Cassini Plasma Spectrometer during the first two close encounters with Titan

    OpenAIRE

    Szego, K; Bebesi, Z.; Erdos, G.; L. Foldy; Crary, F.; McComas, D. J.; Young, D. T.; Bolton, S.; Coates, A. J.; A. M. Rymer; Hartle, R. E.; Sittler, E. C.; Reisenfeld, D.; Bethelier, J. J.; Johnson, R. E.

    2005-01-01

    The Cassini spacecraft flew by Titan on October 26, 2004 and December 13, 2004. In both cases it entered the ionosphere of Titan, allowing exploration of its plasma environment. Using observations from the Cassini Plasma Spectrometer (CAPS) and the Cassini magnetometer along the inbound legs of both flybys, we examine Titan's global plasma environment. On both occasions CAPS detected plasma populations distinct from those of the Kronian magnetosphere at about 1 - 1.5 Saturn radii from the moo...

  6. Coalescing binaries and Doppler experiments

    OpenAIRE

    Vecchio, A.; Bertotti, B.; Iess, L.

    1997-01-01

    We discuss the sensitivity of the CASSINI experiments to gravitational waves emitted by the in-spiral of compact binaries. We show that the maximum distance reachable by the instrument is $\\sim 100$ Mpc. In particular, CASSINI can detect massive black hole binaries with chirp mass $\\simgt 10^6 \\Ms$ in the Virgo Cluster with signal-to-noise ratio between 5 and 30 and possible compact objects of mass $\\simgt 30 \\Ms$ orbiting the massive black hole that our Galactic Centre is likely to harbour.

  7. A Study on the Determination of Concrete Thickness and Effective Measurement Area using Radar

    Energy Technology Data Exchange (ETDEWEB)

    Rhim, Hong Chul; Lee, Ji Hoon; Son, Byung Oh [Yonsei University, Seoul (Korea, Republic of)

    2000-08-15

    Radar is becoming a popular tool for condition assessment of concrete structures. The advancement of radar method to concrete structures requires a systematic approach, which incorporates the fundamentals of radar theory and the characteristics of concrete as a material with electromagnetic properties. The research work presented in this paper deals with the establishment of effective measurement area for radar measurements, the determination of concrete thickness using radar, and the calculation of the dielectric constant of concrete from radar measurements. As results, formulas have been suggested to determine optimum measurement area for concrete, using radar and concrete thickness has been successfully identified for specimens used in this work. In the experiments, five concrete specimens which have the dimensions of 900mm (length) x 600mm (width) with thickness variation from 50mm to 250mm are used

  8. Intercontinental Bistatic Radar Test Observation of Asteroid 1998 WT24

    Science.gov (United States)

    Righini, S.; Poppi, S.; Montebugnoli, S.; DiMartino, M.; Saba, L.; Delbo, M.; Ostro, S.; Monari, J.; Poloni, M.; Orlati, A.

    2002-01-01

    We describe the first intercontinental planetary radar test performed in Italy observing the near Earth asteroid (NEA) 33342 (1998 WT24) in December 2001 by means of the bistatic configurations Goldstone (California, USA)-Medicina (Italy) and Evpatoria (Ukraine)-Medicina. The experiment goal was to characterize the system for realtime radar follow-up observations of NEAs and artificial orbiting debris, in the framework of a feasibility study which aims at using the Sardinia Radio Telescope, at present under construction, also as a planetary radar facility. We report the preliminary results of the radar observations carried out by the IRA-CNR (Instituto di Radioastronomia - Consiglio Nazionale delle Ricerche) and the OATo (Osservatorio Astronomico di Torino) groups, aimed at exploring the scientific potentials of a new space radar program, using the existing facilities in Italy. The planetary radar technique is uniquely capable of investigating geometry and surface properties of various solar system objects, demonstrating advantages over the optical methods in its high spatial resolution and ability to obtain three-dimensional images. A single radar detection allows to obtain extremely accurate orbital elements, improving the instantaneous positional uncertainties by orders of magnitude with respect to an optically determined orbit. Radar is a powerful means to spatially resolve NEAs by measuring the distribution of the echo power in time delay (range) and Doppler frequency (line-of-sight velocity) with extreme precision in each coordinate, as it provides detailed information about the target physical properties like size, shape, rotation, near-surface bulk density and roughness and internal density distribution. The Medicina 32m antenna had been successfully used for the first time as the receiving part of a bistatic configuration during a test experiment (September 2001) held to check the capabilities of the entire data acquisition system. This test was possible

  9. Underwater probing with laser radar

    Science.gov (United States)

    Carswell, A. I.; Sizgoric, S.

    1975-01-01

    Recent advances in laser and electro optics technology have greatly enhanced the feasibility of active optical probing techniques aimed at the remote sensing of water parameters. This paper describes a LIDAR (laser radar) that has been designed and constructed for underwater probing. The influence of the optical properties of water on the general design parameters of a LIDAR system is considered. Discussion of the specific details in the choice of the constructed LIDAR is given. This system utilizes a cavity dumped argon ion laser transmitter capable of 50 watt peak powers, 10 nanosecond pulses and megahertz pulse repetition rates at 10 different wavelengths in the blue green region of the spectrum. The performance of the system, in proving various types of water, is demonstrated by summarizing the results of initial laboratory and field experiments.

  10. Detecting weather radar clutter using satellite-based nowcasting products

    OpenAIRE

    Jensen, Thomas B. S.; Gill, Rashpal S.; Overgaard, Søren; Hansen, Lars Kai; Nielsen, Allan Aasbjerg

    2006-01-01

    This contribution presents the initial results from experiments with detection of weather radar clutter by information fusion with satellite based nowcasting products. Previous studies using information fusion of weather radar data and first generation Meteosat imagery have shown promising results for the detecting and removal of clutter. Naturally, the improved spatio-temporal resolution of the Meteosat Second Generation sensors, coupled with its increased number of spectral bands, is expect...

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

    Science.gov (United States)

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

    1990-01-01

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

  12. The interior structure of Enceladus from Cassini gravity measurements

    Science.gov (United States)

    Iess, Luciano

    2015-04-01

    The Cassini spacecraft flew by the small Saturnian moon Enceladus in three close flybys (April 28, 2010, November 30, 2010 and May 2, 2012, to carry out measurements of the satellite's gravity field [1]. One of the main motivations was the search for a hemispherical asymmetry in the gravity field, the gravitational counterpart of the striking North-South asymmetry shown by optical imaging and other Cassini instruments in the geological features of the moon. The estimation of Enceladus' gravity field by Cassini was especially complex because of the small surface gravity (0.11 m/s2), the short duration of the gravitational interaction (only a few minutes) and the small, nearly impulsive, neutral particles drag occurring when the spacecraft crossed the south polar plume during the first and the third flyby. Including the non-gravitational acceleration due to the plume in the dynamical model was crucial to obtain a reliable solution for the gravity field. In order to maximize the sensitivity to the hemispherical asymmetry, controlled by the spherical harmonic coefficient J3, the closest approaches occurred at the low altitudes (respectively 100, 48 and 70 km), and at high latitudes in both hemispheres (89°S, 62°N, and 72°S). Enceladus' gravity field is dominated by large quadrupole terms not far from those expected for a body in a relaxed shape. Although the deviations from the hydrostaticity are weak (J2/C22=3.55±0.05), the straightforward application of the Radau-Darwin approximation yields a value of the moment of inertia factor (MOIF=C/MR2) that is incompatible (0.34) with the differentiated interior structure suggested by cryovolcanism and the large heat flow. The other remarkable feature of the gravity field is the small but still statistically significant value of J3 (106 x J3 = -115.3±22.9). A differentiated interior structure (corresponding to a smaller MOIF) may be reconciled with the gravity measurement by assuming that the rocky core has retained some

  13. Surface Contour Radar (SCR) contributions to FASINEX

    Science.gov (United States)

    Walsh, E. J.

    1988-01-01

    The SCR was asked to participate in the Frontal Air-Sea Interaction Experiment (FASINEX) to provide directional wave spectra. The NASA P-3 carrying the SCR, the Radar Ocean Wave Spectrometer, and the Airborne Oceanographic Lidar was one of five aircrafts and two ocean research ships participating in this coordinated study of the air sea interaction in the vicinity of a sea surface temperature front near 28 deg N, 70 deg W. Analysis of data from the February 1986 experiment is still ongoing, but results already submitted for publication strengthen the hypothesis that off-nadir radar backscatter is closely correlated to wind stress. The SCR provided valuable information on the directional wave spectrum and its spatial variation.

  14. Mapping Variations in Ring Shadow Cooling with Cassini CIRS

    Science.gov (United States)

    Brooks, S. M.; Spilker, L. J.; Morishima, R.; Pilorz, S.

    2011-12-01

    We use data from Cassini's Composite Infrared Spectrometer to characterize ring shadow cooling and to document radial variations in ring thermal inertia. CIRS records infrared radiation between 7 and 1000 microns. Far infrared radiation (16.7 - 1000 microns) is recorded at focal plane 1 (FP1). Thermal emission from Saturn's rings peaks at FP1 wavelengths. As shown in Spilker et al. (2005, 2006), ring thermal emission is well characterized as blackbody emission multiplied by a scalar factor related to the emissivity of the rings. Ring temperatures are generally warmer and the rings show significantly more thermal contrast at larger solar elevations. The thermal budget of the rings is dominated by incident solar radiation. When ring particles enter Saturn's shadow this source of energy is abruptly cut off with a consequential decrease in ring temperature. In order to quantify this cooling, FP1 scanned the main rings repeatedly with a constant offset from the ingress shadow boundary. From such shadow observations we create cooling curves at specific locations. By resampling the FP1 scans onto a consistent radial grid, we can document the cooling of the ensemble of ring particles as they enter Saturn's shadow. Observations of the lit side of the rings reveal that shadow cooling is most significant in the C ring and Cassini Division. More modest cooling occurs in the B and A rings. More importantly, we can show that cooling rates vary with location within each ring. These cooling rates reflect local reactions to the short-term change in thermal forcing as the ring particles enter Saturn's shadow. Observations of the unlit side of the rings tell a different tale. The optically thin rings show some shadow cooling, but this cooling is not as pronounced as on the lit side. No evidence for shadow cooling exists for the unlit A and B rings. Temperature variations on the unlit sides of these optically thick rings appear to reflect thermal forcings that vary with Saturn season

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

    Science.gov (United States)

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

    2016-01-01

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

  16. Juno and Cassini Proximal: Giant Steps Towards Understanding Giant Planets

    Science.gov (United States)

    Stevenson, D. J.

    2014-12-01

    In 2016-17, Juno and Cassini Proximal will provide comparable large advances in our understanding of the interiors of Jupiter and Saturn. Both will provide high accuracy gravity and magnetic field data, while Juno will in addition determine the water abundance deep in the Jovian atmosphere, essential for understanding of giant planet formation and the density of the outer envelope (needed to construct interior models). Although Jupiter and Saturn are both gas giants, they differ in important ways (magnetic field, strength of zonal flows, enrichment in heavy elements, and probably the distribution of helium within). The opportunity to contrast and compare will be invaluable. Juno and Cassini are expected to determine the gravity field to about a part in 109 though with different spatial coverage and with less accurate determination near the poles. The determination of Jupiter's likely central concentration of heavy elements is particularly challenging because it is only a few percent at most of the total mass and yet important for understanding Jupiter's formation, which in turn likely determined the architecture of our solar system. This determination will be done from gravity, water determination and magnetic field and also aided by advances in our understanding of material properties. The corresponding determination for Saturn may prove easier (because the heavy element enrichment is a larger fraction of the mass) though complicated by lack of knowledge of water abundance and the need to identify a more precise value for the deep rotation of the planet (difficult for Saturn because of the lack of a measurable magnetic dipole tilt thus far). For both planets, the higher harmonics of gravity will likely be controlled by differential rotation (the zonal flows) and this will tell us their depth, an issue of major interest in the dynamics of these bodies. The magnetic field structure for Jupiter will be determined to higher accuracy than the Earth's core field (since

  17. Diurnal Variations of Titan's Surface Temperatures From Cassini -CIRS Observations

    Science.gov (United States)

    Cottini, Valeria; Nixon, Conor; Jennings, Don; Anderson, Carrie; Samuelson, Robert; Irwin, Patrick; Flasar, F. Michael

    The Cassini Composite Infrared Spectrometer (CIRS) observations of Saturn's largest moon, Titan, are providing us with the ability to detect the surface temperature of the planet by studying its outgoing radiance through a spectral window in the thermal infrared at 19 m (530 cm-1) characterized by low opacity. Since the first acquisitions of CIRS Titan data the in-strument has gathered a large amount of spectra covering a wide range of latitudes, longitudes and local times. We retrieve the surface temperature and the atmospheric temperature pro-file by modeling proper zonally averaged spectra of nadir observations with radiative transfer computations. Our forward model uses the correlated-k approximation for spectral opacity to calculate the emitted radiance, including contributions from collision induced pairs of CH4, N2 and H2, haze, and gaseous emission lines (Irwin et al. 2008). The retrieval method uses a non-linear least-squares optimal estimation technique to iteratively adjust the model parameters to achieve a spectral fit (Rodgers 2000). We show an accurate selection of the wide amount of data available in terms of footprint diameter on the planet and observational conditions, together with the retrieved results. Our results represent formal retrievals of surface brightness temperatures from the Cassini CIRS dataset using a full radiative transfer treatment, and we compare to the earlier findings of Jennings et al. (2009). The application of our methodology over wide areas has increased the planet coverage and accuracy of our knowledge of Titan's surface brightness temperature. In particular we had the chance to look for diurnal variations in surface temperature around the equator: a trend with slowly increasing temperature toward the late afternoon reveals that diurnal temperature changes are present on Titan surface. References: Irwin, P.G.J., et al.: "The NEMESIS planetary atmosphere radiative transfer and retrieval tool" (2008). JQSRT, Vol. 109, pp

  18. Mapping submarine sand waves with multiband imaging radar - 2. Experimental results and model comparison

    NARCIS (Netherlands)

    Vogelzang, J.; Wensink, G.J.; Calkoen, C.J.; Kooij, M.W.A. van der

    1997-01-01

    On August 16, 1989, and on July 12, 1991, experiments were performed to study the mapping of submarine sand waves with the airborne imaging radar, a polarimetric (and, in 1991, interferometric) airborne P, L, and C band synthetic aperture radar system. The experiments took place in an area 30 km off

  19. A New Look at Titan's Zonal Winds from Cassini Radio Occultations

    Science.gov (United States)

    Flasar, F. M.; Schinder, P. J.

    2012-01-01

    We use the existing thirteen Cassini radio'occultation soundings to construct a meridional cross section of geopotential height vs. pressure and latitude. The assumption of balanced flow permits the construction of a similar cross section of zonal winds, from near the surface to the 0.1'mbar level. In the lower troposphere, the winds are approx.10 m/s, except within 20deg of the equator, where they are much smaller. The winds increase higher up in the troposphere to nearly 40 m/s in the tropopause region, but then decay rapidly in the lower stratosphere to near'zero values at 20 mbar (approx.80 km), reminiscent of the Huygens Doppler Wind Experiment result. This null zone extends over most latitudes, except for limited bands at mid'latitudes. Higher up in the stratosphere, the winds become larger. They are highest in the northern (winter) hemisphere. We compare the occultation results with the DWE and CIRS retrievals and discuss the similarities and differences among the data sets.

  20. Software Radar signal processing

    OpenAIRE

    T. Grydeland; Lind, F. D.; Erickson, P J; J. M. Holt

    2005-01-01

    Software infrastructure is a growing part of modern radio science systems. As part of developing a generic infrastructure for implementing Software Radar systems, we have developed a set of reusable signal processing components. These components are generic software-based implementations for use on general purpose computing systems. The components allow for the implementation of signal processing chains for radio frequency signal reception, correlation-based data processing, and cross-correla...

  1. Detection of Weather Radar Clutter

    DEFF Research Database (Denmark)

    Bøvith, Thomas

    2008-01-01

    Weather radars provide valuable information on precipitation in the atmosphere but due to the way radars work, not only precipitation is observed by the weather radar. Weather radar clutter, echoes from non-precipitating targets, occur frequently in the data, resulting in lowered data quality....... Especially in the application of weather radar data in quantitative precipitation estimation and forecasting a high data quality is important. Clutter detection is one of the key components in achieving this goal. This thesis presents three methods for detection of clutter. The methods use supervised...... and precipitating and non-precipitating clouds. Another method uses the difference in the motion field of clutter and precipitation measured between two radar images. Furthermore, the direction of the wind field extracted from a weather model is used. The third method uses information about the refractive index...

  2. Investigating the Composition of Saturn's Rings Using Cassini CIRS Data

    Science.gov (United States)

    Nugent, C. R.; Spilker, L. J.; Edgington, S. G.; Russell, C. T.; Pilorz, S. H.; Altobelli, N.; Gudipati, M.

    2007-12-01

    Although it has long been known that Saturn's rings are primarily composed of water ice, the identities of the trace constituents-- which provide subtle color to the rings and could shed light on their origin and formation-- remain poorly understood. These trace constituents may affect the thermal infrared part of the rings' spectral signature. Previous observations have not observed any such effects. However, they have been hindered by one or more major problems: 1) the inability to observe the entire wavelength interval through the earth's atmosphere, 2) low spectral resolution, and 3) limited range of geometries. Data obtained with Cassini's Composite Infrared Spectrometer (CIRS) instrument circumvents these difficulties. We report results from a preliminary investigation of ring composition using CIRS data over the wavelength range of 10 to 600 cm-1. The rings spectra observed by CIRS are a complicated combination of thermal emissions, the effects of scattering from ring particles (broad size distribution) and noise. Before the signal can be examined for the faint absorption features from contaminants, the contributions of scattering and thermal emission must be accounted for and removed using Mie scattering and standard radiation transfer techniques. We present the initial results of this investigation. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, and was sponsored by the Space Grant program.

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

    CERN Document Server

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

    2016-01-01

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

  4. Cassini/Huygens your messages en route for Titan

    Science.gov (United States)

    1997-02-01

    This unprecedented operation will soon be coming to an end. The Internet site will not be accepting messages after 1 March 1997, although it will remain active to incorporate regularly updated information on the Cassini/Huygens mission at least until the launch in October 1997. ESA has decided to open the site to audio messages as well until 1 March 1997. Files, which must be no larger than 250 KB, should sent to the electronic letterbox sound@huygens.com in WAV or AIFF format. We shall be concluding this exceptional operation by producing a CD-ROM containing written and audio messages within the limits of the space available. We therefore propose that all media announce the forthcoming end of the operation and stress the additional possibility of sending in audio as well as written messages that will leave for Titan in October 1997. Radio or television stations wishing to offer listeners or viewers the opportunity to transmit their messages over the air can forward them to us on audio or video (Betacam) cassettes. N.B. No more than three twenty-second messages per station. For further information, please contact : ESA Public Relations Division Tel: +33.1.53.69.71.55 Fax : +33.1.53.69.76.90

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

    CERN Document Server

    Spitale, Joseph N

    2015-01-01

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

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

    CERN Document Server

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

    2015-01-01

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

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

    CERN Document Server

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

    2015-01-01

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

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

    CERN Document Server

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

    2015-01-01

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

  9. SOLAR OCCULTATION BY TITAN MEASURED BY CASSINI/UVIS

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-04-01

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

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

    CERN Document Server

    Soria, Roberto; Ohtsuka, Yasuyo

    2013-01-01

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

  11. Coherent dust cloud observed by three Cassini instruments

    CERN Document Server

    Khalisi, Emil

    2015-01-01

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

  12. CASSINI VIMS OBSERVATIONS SHOW ETHANE IS PRESENT IN TITAN'S RAINFALL

    International Nuclear Information System (INIS)

    Observations obtained over two years by the Cassini Imaging Science Subsystem suggest that rain showers fall on the surface. Using measurements obtained by the Visual Infrared Mapping Spectrometer, we identify the main component of the rain to be ethane, with methane as an additional component. We observe five or six probable rainfall events, at least one of which follows a brief equatorial cloud appearance, suggesting that frequent rainstorms occur on Titan. The rainfall evaporates, sublimates, or infiltrates on timescales of months, and in some cases it is associated with fluvial features but not with their creation or alteration. Thus, Titan exhibits frequent 'gentle rainfall' instead of, or in addition to, more catastrophic events that cut rivers and lay down large fluvial deposits. Freezing rain may also be present, and the standing liquid may exist as puddles interspersed with patches of frost. The extensive dune deposits found in the equatorial regions of Titan imply multi-season arid conditions there, which are consistent with small, but possibly frequent, amounts of rain, in analogy to terrestrial deserts.

  13. Radar techniques using array antennas

    CERN Document Server

    Wirth, Wulf-Dieter

    2013-01-01

    Radar Techniques Using Array Antennas is a thorough introduction to the possibilities of radar technology based on electronic steerable and active array antennas. Topics covered include array signal processing, array calibration, adaptive digital beamforming, adaptive monopulse, superresolution, pulse compression, sequential detection, target detection with long pulse series, space-time adaptive processing (STAP), moving target detection using synthetic aperture radar (SAR), target imaging, energy management and system parameter relations. The discussed methods are confirmed by simulation stud

  14. Multiparameter radar study of rainfall: Potential application to area-time integral studies

    Science.gov (United States)

    Raghavan, R.; Chandrasekar, V.

    1994-01-01

    Multiparameter radars measure one or more additional parameters in addition to the coventional reflectivity factor. The combination of radar observations from a multiparameter radar is used to study the time evolution of rainstorms. A technique is presented to self-consistently compare the area-time integral (ATI) and rainfall volume estimates from convective storms, using two different measurements from a multiparameter radar. Rainfall volumes for the lifetime of individual storms are computed using the reflectivity at S band (10-cm wavelength) as well as one-way specific attenuation at X band (3-cm wavelength). Area-time integrals are computed by summing all areas in each radar snapshot having reflectivities (S band) in excess of a preselected threshold. The multiparameter radar data used in this study were acquired by the National Center for Atmospheric Research (NCAR) CP-2 radar during the Cooperative Huntsville Meteorological Experiment (COHMEX) and the Convection and Precipitation/Electrification Experiment (CaPE), respectively. ATI studies were accomplished in this work using multiparameter radar data acquired during the lifetime of six convective events that occurred in the COHMEX radar coverage area. A case study from the COMHEX field campaign (20 July 1986) was selected to depict the various stages in the evolution of a storm over which the ATI and rainfall volume computations were performed using multiparameter radar data. Another case study from the CaPE field campaign (12 August 1991) was used to demonstrate the evolution of a convective cell based on differential reflectivity observations.

  15. Reconfigurable L-Band Radar

    Science.gov (United States)

    Rincon, Rafael F.

    2008-01-01

    The reconfigurable L-Band radar is an ongoing development at NASA/GSFC that exploits the capability inherently in phased array radar systems with a state-of-the-art data acquisition and real-time processor in order to enable multi-mode measurement techniques in a single radar architecture. The development leverages on the L-Band Imaging Scatterometer, a radar system designed for the development and testing of new radar techniques; and the custom-built DBSAR processor, a highly reconfigurable, high speed data acquisition and processing system. The radar modes currently implemented include scatterometer, synthetic aperture radar, and altimetry; and plans to add new modes such as radiometry and bi-static GNSS signals are being formulated. This development is aimed at enhancing the radar remote sensing capabilities for airborne and spaceborne applications in support of Earth Science and planetary exploration This paper describes the design of the radar and processor systems, explains the operational modes, and discusses preliminary measurements and future plans.

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

    Science.gov (United States)

    Burk, Thomas; Bates, David

    2008-01-01

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

  17. Unique scene description from radar and infrared images

    Science.gov (United States)

    Blanquart, Jacques G.; Orgiazzi, Philippe; Grenier, Gilles; Cothenet, A.

    1990-10-01

    Two different visual descriptions provided by two image sensors (radar and infrared camera) contain information of the same scene. We want to associate them, using different methods of fusion, in order to improve our knowledge of the scene. Two approaches are described in this paper: navigation and recognition. In the first approach, the radar is the predominant sensor and we use cartographic information of the area to guide the fusion process. In the second approach, we find regions of interest in the radar image that are used to extract features in the infrared image. To experiment our algorithm, we are using a PtSi infrared camera (3-5jtm) with a 512*5 12 matrix and a millimeterwave radar, that are looking at the same area from an airplane, to detect objects like buildings, roads, fields ... . It is the basis of further developments within an expert system including more complex notions of image processing objects.

  18. Correlation recognition for range image of laser radar

    Institute of Scientific and Technical Information of China (English)

    Jianfeng Sun; Qi Li; Wei Lu; Qi Wang

    2007-01-01

    The target recognition of laser radar becomes hot research in recent years, because laser radar can produce high space resolution and collect rich target information, such as range image, intensity image and Doppler image. In the vertical detection of laser radar, the problem of in-plane target rotation invariance is firstly solved. In the paper, a new support vector machine (SVM) correlation filter is presented, which simultaneously has the attractive attributes of SVM and common correlation filter. Exploiting the idea of margin of separation maximization, the design criterion is produced. The filter is synthetic by the multiple training images which are generated by rotating one image. The real range images of laser radar are used to finish the correlation experiments. The results show that the filter is not sensitive to the noise, the correlation peak is changed slightly for the different testing images, and the precision of location is high.This design way can be used in other recognition fields.

  19. Detecting weather radar clutter using satellite-based nowcasting products

    DEFF Research Database (Denmark)

    Jensen, Thomas B.S.; Gill, Rashpal S.; Overgaard, Søren;

    2006-01-01

    This contribution presents the initial results from experiments with detection of weather radar clutter by information fusion with satellite based nowcasting products. Previous studies using information fusion of weather radar data and first generation Meteosat imagery have shown promising results...... for the detecting and removal of clutter. Naturally, the improved spatio-temporal resolution of the Meteosat Second Generation sensors, coupled with its increased number of spectral bands, is expected to yield even better detection accuracies. Weather radar data from three C-band Doppler weather radars...... Application Facility' of EUMETSAT and is based on multispectral images from the SEVIRI sensor of the Meteosat-8 platform. Of special interest is the 'Precipitating Clouds' product, which uses the spectral information coupled with surface temperatures from Numerical Weather Predictions to assign probabilities...

  20. Weather radars – the new eyes for offshore wind farms?

    DEFF Research Database (Denmark)

    Trombe, Pierre-Julien; Pinson, Pierre; Vincent, Claire Louise;

    2014-01-01

    Offshore wind fluctuations are such that dedicated prediction and control systems are needed for optimizing the management of wind farms in real-time. In this paper, we present a pioneer experimentRadar@Sea – in which weather radars are used for monitoring the weather at the Horns Rev offshore...... inputs to prediction systems for anticipating changes in the wind fluctuation dynamics, generating improved wind power forecasts and developing specific control strategies. However, integrating weather radar observations into automated decision support systems is not a plug-and-play task...... observed at Horns Rev and (iv) we discuss the future perspectives for weather radars in wind energy. Copyright © 2013 John Wiley & Sons, Ltd....

  1. Removing interfering clutter associated with radar pulses that an airborne radar receives from a radar transponder

    Science.gov (United States)

    Ormesher, Richard C.; Axline, Robert M.

    2008-12-02

    Interfering clutter in radar pulses received by an airborne radar system from a radar transponder can be suppressed by developing a representation of the incoming echo-voltage time-series that permits the clutter associated with predetermined parts of the time-series to be estimated. These estimates can be used to estimate and suppress the clutter associated with other parts of the time-series.

  2. Radar imaging mechanism of marine sand waves at very low grazing angle illumination

    OpenAIRE

    Hennings, Ingo; Herbers, Dagmar

    2005-01-01

    The investigations carried out between 2002-2004 during several field experiments within the Op-erational radar and optical mapping in monitoring hydrodynamic, morphodynamic and environ-mental parameters for coastal management project (OROMA) aimed to improve the effectiveness of new monitoring technologies such as shipborne imaging radars in coastal waters. The coastal monitoring radar of the GKSS Research Centre, Geesthacht, Germany, is based on a Kelvin Hughes RSR 1000 X-band (9.42 GHz) VV...

  3. Statistical and neural classifiers in estimating rain rate from weather radar measurements

    OpenAIRE

    C. I. Christodoulou; S. C. Michaelides

    2007-01-01

    International audience Weather radars are used to measure the electromagnetic radiation backscattered by cloud raindrops. Clouds that backscatter more electromagnetic radiation consist of larger droplets of rain and therefore they produce more rain. The idea is to estimate rain rate by using weather radar as an alternative to rain-gauges measuring rainfall on the ground. In an experiment during two days in June and August 1997 over the Italian-Swiss Alps, data from weather radar and surrou...

  4. Comparison of radar data versus rainfall data

    OpenAIRE

    Espinosa, B.; T.V. Hromadka II; Perez, R.

    2015-01-01

    Doppler radar data are increasingly used in rainfall-runoff synthesis studies, perhaps due to radar data availability, among other factors. However, the veracity of the radar data are often a topic of concern. In this paper, three Doppler radar outcomes developed by the United States National Weather Service at three radar sites are examined and compared to actual rain gage data for two separate severe storm events in order to assess accuracy in the published radar estimates of rainfall. Beca...

  5. PDS and NASA Tournament Laboratory Project to Engage Citizen Scientists and to Provide New Access to Cassini Data

    Science.gov (United States)

    Odess, Jennifer; Gordon, Mitch; Showalter, Mark; LaMora, Andy; Del Villar, Ambi; Raugh, Anne; Erickson, Kristen; Galica, Carol; Grayzeck, Ed; Morgan, Thomas; Knopf, Bill

    2014-11-01

    Jennifer Odess (1), Mitch Gordon (2), Mark Showalter (2), Andy LaMora (1), Ambi Del Villar (1), Anne Raugh (3), Kristen Erickson (4), Carol Galica (4), Ed Grayzeck (5), T. Morgan (5), and Bill Knopf (4)1. Appirio Top Coder, Inc2. SETI Institute3. University of Maryland4. NASA Headquarters5. Goddard Space Flight CenterThe Planetary Data System (PDS), working with the NASA Tournament Lab (NTL) and TopCoder® , is using challenge-based competition to generate new applications that increase both access to planetary data and discoverability—allowing users to “mine” data, and thus, to make new discoveries from data already “on the ground”. The first challenge-based completion was an optimized database and API for comet data at the PDS Small Bodies Node (SBN) in 2012. Since start-up, the installation at SBN has been tweaked to provide access to the comet data holdings of the SBN, and has introduced new users and new developers to PDS data. A follow-on contest using Cassini images from the PDS Rings Discipline Node, was designed to challenge the competitors to create new, more transparent, agile tools for public access to NASA’s planetary data, where “public” includes citizen scientists and educators. The experience gained with the API at SBN was applied to establishing a second installation at the PDS Planetary Rings Node (Rings), to serve as the basis to develop similar access tools at Rings to make the growing archive of Cassini images available through the API. The Cassini-Rings project had as its goal to develop a crowd-sourcing project with eventual application across the PDS holdings. From the contest results, a preliminary algorithm can detect known satellites hidden in Saturn’s rings which should prove valuable to programmers. The contest approach is also of potential use to educators for exercises studying the solar system. The progress to date and results of this citizen-scientist project will be discussed.

  6. Broadview Radar Altimetry Toolbox

    Science.gov (United States)

    Mondéjar, Albert; Benveniste, Jérôme; Naeije, Marc; Escolà, Roger; Moyano, Gorka; Roca, Mònica; Terra-Homem, Miguel; Friaças, Ana; Martinho, Fernando; Schrama, Ernst; Ambrózio, Américo; Restano, Marco

    2016-07-01

    The universal altimetry toolbox, BRAT (Broadview Radar Altimetry Toolbox) which can read all previous and current altimetry missions' data, incorporates now the capability to read the upcoming Sentinel-3 L1 and L2 products. ESA endeavoured to develop and supply this capability to support the users of the future Sentinel-3 SAR Altimetry Mission. BRAT is a collection of tools and tutorial documents designed to facilitate the processing of radar altimetry data. This project started in 2005 from the joint efforts of ESA (European Space Agency) and CNES (Centre National d'Études Spatiales), and it is freely available at http://earth.esa.int/brat. The tools enable users to interact with the most common altimetry data formats. The BratGUI is the front-end for the powerful command line tools that are part of the BRAT suite. BRAT can also be used in conjunction with MATLAB/IDL (via reading routines) or in C/C++/Fortran via a programming API, allowing the user to obtain desired data, bypassing the data-formatting hassle. BRAT can be used simply to visualise data quickly, or to translate the data into other formats such as NetCDF, ASCII text files, KML (Google Earth) and raster images (JPEG, PNG, etc.). Several kinds of computations can be done within BRAT involving combinations of data fields that the user can save for posterior reuse or using the already embedded formulas that include the standard oceanographic altimetry formulas. The Radar Altimeter Tutorial, that contains a strong introduction to altimetry, shows its applications in different fields such as Oceanography, Cryosphere, Geodesy, Hydrology among others. Included are also "use cases", with step-by-step examples, on how to use the toolbox in the different contexts. The Sentinel-3 SAR Altimetry Toolbox shall benefit from the current BRAT version. While developing the toolbox we will revamp of the Graphical User Interface and provide, among other enhancements, support for reading the upcoming S3 datasets and

  7. Radar foundations for imaging and advanced concepts

    CERN Document Server

    Sullivan, Roger

    2004-01-01

    Through courses internally taught at IDA, Dr. Roger Sullivan has devised a book that brings readers fully up to speed on the most essential quantitave aspects of general radar in order to introduce study of the most exciting and relevant applications to radar imaging and advanced concepts: Synthetic Aperture Radar (4 chapters), Space-time Adaptive Processing, moving target indication (MTI), bistatic radar, low probability of intercept (LPI) radar, weather radar, and ground-penetrating radar. Whether you're a radar novice or experienced professional, this is an essential refer

  8. Parametric estimation of ultra wideband radar targets

    Institute of Scientific and Technical Information of China (English)

    Fan Ping; Jing Zhanrong

    2009-01-01

    Based on the analysis of impulse response properties, a scattering model of ultra wideband (UWB) radar targets is developed to estimate the target parameters exactly. With this model, two algorithms of multiple signal classification (MUSIC), and matrix pencil (MP), are introduced to calculate the scattering center parame-ters of targets and their performances are compared. The simulation experiments show that there are no differ-ences in the estimation precision of MUSIC and MP methods when the signal-to-noise ratio (SNR) is larger than 13 dB. However, the MP method has a better performance than that of MUSIC method when the SNR is smaller than 13 dB. Besides, the time consuming of MP method is leas than that of MUSIC method. Therefore, the MP algorithm is preferred for the parametric estimation of UWB radar targets.

  9. Crosshole investigations - results from borehole radar investigations

    International Nuclear Information System (INIS)

    A new borehole radar system has been designed, built and tested. The system consists of borehole transmitter and receiver probes, a signal control unit for communication with the borehole probes, and a computer unit for storage and display of data. The system can be used both in singlehole and crosshole modes and probing ranges of 115 m and 300 m, respectively, have been obtained at Stripa. The borehole radar is a short pulse system which uses center frequencies in the range 20 to 60 MHz. Single hole reflection measurements have been used to identify fracture zones and to determine their position and orientation. The travel time and amplitude of the first arrival measured in a crosshole experiment can be used as input data in a tomographic analysis. (orig./DG)

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

    Science.gov (United States)

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

    2008-01-01

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

  11. Cassini is placed in a protective garmet in preparation for its move to Pad 40, CCAS

    Science.gov (United States)

    1997-01-01

    Workers in the Payload Hazardous Servicing Facility (PHSF) place a protective covering over the Cassini spacecraft in preparation for its move to Launch Complex 40, Cape Canaveral Air Station (CCAS). Cassini is an international mission conducted by the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA), and the Italian Space Agency (ASI). The two-story-tall spacecraft, scheduled for launch on Oct. 6, is destined to arrive at Saturn in July 2004, where it will study the planet, its rings, moons and magnetic environment in detail over a four-year period. The Cassini mission is managed for NASA's Office of Space Science by the Jet Propulsion Laboratory, a division of the California Institute of Technology.

  12. Cassini is lifted for placement on a transporter which will move it to Pad 40, CCAS

    Science.gov (United States)

    1997-01-01

    In the Payload Hazardous Servicing Facility (PHSF), the Cassini spacecraft is being lifted for placement on a transporter which will move it to Launch Complex 40, Cape Canaveral Air Station (CCAS). Cassini is an international mission conducted by the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA), and the Italian Space Agency (ASI). The two-story-tall spacecraft, scheduled for launch on Oct. 6, is destined to arrive at Saturn in July 2004, where it will study the planet, its rings, moons and magnetic environment in detail over a four-year period. The Cassini mission is managed for NASA's Office of Space Science by the Jet Propulsion Laboratory, a division of the California Institute of Technology.

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

    Science.gov (United States)

    Wagner, Sean; Buffington, Brent

    2014-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Tokar, Robert L [Los Alamos National Laboratory; Thomsen, Michelle F [Los Alamos National Laboratory; Wilson, Robert J [Los Alamos National Laboratory; Johnson, R E [UNIV OF VIRGINIA; Young, D T [SWRI; Crary, F J [SWRI; Coates, A J [MSSL; Jones, G H [MSSL; Paty, C S [GIT

    2009-01-01

    This study reports direct detection by the Cassini plasma spectrometer of freshly-produced water-group ions (O{sup +}, OH{sup +}, H{sub 2}O{sup +}, H{sub 3}O{sup +}) and heavier water dimer ions (H{sub x}O{sub 2}{sup +}) very close to Enceladus and where the plasma begins to emerge from the Enceladus plume The data wcre obtained during two close (52 and 25 km) flybys of Enceladus in 2008, and are similar to ion data in cometary comas. The ions are observed in detectors looking in the Cassini ram direction at energies consistent with the Cassini speed, indicating a nearly stagnant plasma flow in the plume. North of Enceladus the plasma slowing commences about 4 to 6 Enceladus radii away, while south of Enccladus signatures ofthe interaction are detected as far as 22 Enceladus radii away.

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

    Energy Technology Data Exchange (ETDEWEB)

    Schock, Alfred; Noravian, Heros; Sankarankandath

    1990-11-30

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

  16. Mapping Ring Particle Cooling across Saturn's Rings with Cassini CIRS

    Science.gov (United States)

    Brooks, Shawn M.; Spilker, L. J.; Edgington, S. G.; Pilorz, S. H.; Deau, E.

    2010-10-01

    Previous studies have shown that the rings' thermal inertia, a measure of their response to changes in the thermal environment, varies from ring to ring. Thermal inertia can provide insight into the physical structure of Saturn's ring particles and their regoliths. Low thermal inertia and quick temperature responses are suggestive of ring particles that have more porous or fluffy regoliths or that are riddled with cracks. Solid, coherent particles can be expected to have higher thermal inertias (Ferrari et al. 2005). Cassini's Composite Infrared Spectrometer has recorded millions of spectra of Saturn's rings since its arrival at Saturn in 2004 (personal communication, M. Segura). CIRS records far infrared radiation between 10 and 600 cm-1 (16.7 and 1000 µm) at focal plane 1 (FP1), which has a field of view of 3.9 mrad. Thermal emission from Saturn's rings peaks in this wavelength range. FP1 spectra can be used to infer ring temperatures. By tracking how ring temperatures vary, we can determine the thermal inertia of the rings. In this work we focus on CIRS observations of the shadowed portion of Saturn's rings. The thermal budget of the rings is dominated by the solar radiation absorbed by its constituent particles. When ring particles enter Saturn's shadow this source of energy is abruptly cut off. As a result, ring particles cool as they traverse Saturn's shadow. From these shadow observations we can create cooling curves at specific locations across the rings. We will show that the rings' cooling curves and thus their thermal inertia vary not only from ring to ring, but by location within the individual rings. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2010 California Institute of Technology. Government sponsorship acknowledged.

  17. Cassini Imaging Science Subsystem observations of Titan's south polar cloud

    Science.gov (United States)

    West, R. A.; Del Genio, A. D.; Barbara, J. M.; Toledo, D.; Lavvas, P.; Rannou, P.; Turtle, E. P.; Perry, J.

    2016-05-01

    In May of 2012 images of Titan obtained by the Cassini Imaging Science Subsystem (ISS) showed a newly-formed cloud patch near the southern pole. The cloud has unusual morphology and texture suggesting that it is formed by condensation at an altitude much higher than expected for any of the known organics in Titan's atmosphere. We measured the altitude to be 300 ± 10 km from images when the feature was on the limb. Limb images suggest that the initial stages of the formation began in late 2011. It was just visible in images obtained in 2014 but is not expected to be visible in the future due to enveloping darkness as the season progresses. The feature has a slightly different color than the surrounding haze. Its optical thickness is near 2 at 889 nm wavelength and the particle imaginary refractive index must be less than 5 × 10-4 at that wavelength. Wind vectors derived from a time series show that it is rotating about a center offset by 4.5° from Titan's solid-body spin axis, consistent with that found from the temperature field by Achterberg et al. (Achterberg, R.K., Conrath, B.J., Gierasch, P.J., Flasar, F.M., Nixon, C.A. [2008a]. Icarus 197, 549-555) and subsequent measurements. The feature rotates at an angular velocity near the rate expected for transport of angular momentum from the low latitudes to the pole. The clumpy texture of the feature resembles that of terrestrial cloud fields undergoing open cell convection, an unusual configuration initiated by downwelling.

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

    Science.gov (United States)

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

    2013-01-01

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

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

    Science.gov (United States)

    Barstow, J. K.; Irwin, P. G. J.; Fletcher, L. N.; Giles, R. S.; Merlet, C.

    2016-06-01

    In its decade of operation the Cassini mission has allowed us to look deep into Saturn's atmosphere and investigate the processes occurring below its enshrouding haze. We use Visual and Infrared Mapping Spectrometer (VIMS) 4.6-5.2 μm data from early in the mission to investigate the location and properties of Saturn's cloud structure between 0.6 and 5 bar. We average nightside spectra from 2006 over latitude circles and model the spectral limb darkening using the NEMESIS radiative transfer and retrieval tool. We present our best-fit deep cloud model for latitudes -40∘ < λ <50∘ , along with retrieved abundances for NH3, PH3 and AsH3. We find an increase in NH3 abundance at the equator, a cloud base at ˜2.3 bar and no evidence for cloud particles with strong absorption features in the 4.6-5.2 μm wavelength range, all of which are consistent with previous work. Non-scattering cloud models assuming a composition of either NH3 or NH4SH, with a scattering haze overlying, fit limb darkening curves and spectra at all latitudes well; the retrieved optical depth for the tropospheric haze is decreased in the northern (winter) hemisphere, implying that the haze has a photochemical origin. Our ability to test this hypothesis by examining spectra at different seasons is restricted by the varying geometry of VIMS observations over the life of the mission, and the appearance of the Saturn storm towards the end of 2010.

  20. Investigating Titan's Atmospheric Chemistry at Low Temperature in Support of the NASA Cassini Mission

    Science.gov (United States)

    Sciamma-O'Brien, Ella; Salama, Farid

    2013-01-01

    Titan's atmosphere, composed mainly of N2 and CH4, is the siege of a complex chemistry induced by solar UV radiation and electron bombardment from Saturn's magnetosphere. This organic chemistry occurs at temperatures lower than 200 K and leads to the production of heavy molecules and subsequently solid aerosols that form the orange haze surrounding Titan. The Titan Haze Simulation (THS) experiment has been developed on the COSMIC simulation chamber at NASA Ames in order to study the different steps of Titan's atmospheric chemistry at low temperature and to provide laboratory data in support for Cassini data analysis. The chemistry is simulated by plasma in the stream of a supersonic expansion. With this unique design, the gas mixture is adiabatically cooled to Titan-like temperature (approx. 150 K) before inducing the chemistry by plasma discharge. Different gas mixtures containing N2, CH4, and the first products of the N2,-CH4 chemistry (C2H2, C2H4, C6H6...) but also heavier molecules such as PAHs or nitrogen containing PAHs can be injected. Both the gas phase and solid phase products resulting from the plasma-induced chemistry can be monitored and analyzed. Here we present the results of recent gas phase and solid phase studies that highlight the chemical growth evolution when injecting heavier hydrocarbon trace elements in the initial N2-CH4 mixture. Due to the short residence time of the gas in the plasma discharge, only the first steps of the chemistry have time to occur in a N2-CH4 discharge. However by adding acetylene and benzene to the initial N2-CH4 mixture, we can study the intermediate steps of Titan's atmospheric chemistry as well as specific chemical pathways. These results show the uniqueness of the THS experiment to help understand the first and intermediate steps of Titan fs atmospheric chemistry as well as specific chemical pathways leading to Titan fs haze formation.

  1. Synthetic Aperture Radar - Hardware Development

    Directory of Open Access Journals (Sweden)

    V. Rosner

    2009-06-01

    Full Text Available Experimental real and synthetic aperture radar are developed from the base-band digital unit to the analogue RF parts, based on solid state units, using pulse compression for radar imaging. Proper QPSK code is found for matched filter.

  2. Terahertz radar cross section measurements

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Heiselberg, Henning; Jepsen, Peter Uhd

    2010-01-01

    We perform angle- and frequency-resolved radar cross section (RCS) measurements on objects at terahertz frequencies. Our RCS measurements are performed on a scale model aircraft of size 5-10 cm in polar and azimuthal configurations, and correspond closely to RCS measurements with conventional radar...

  3. Performance indicators modern surveillance radar

    NARCIS (Netherlands)

    Nooij, P.N.C.; Theil, A.

    2014-01-01

    Blake chart computations are widely employed to rank detection coverage capabilities of competitive search radar systems. Developed for comparable 2D radar systems with a mechanically rotating reflector antenna, it was not necessary to regard update rate and plot quality in Blake's chart. To charact

  4. Equatorial MST radars: Further consideration

    Science.gov (United States)

    Lagos, P.

    1983-01-01

    The results presented give additional support to the need of equatorial MST radars in order to obtain more information on the nature of equatorial waves in the MST region. Radar deduced winds such as obtained at Jicamarca for periods of months indicate that with these data the full range of equatorial waves, with time scales of seconds to years, can be studied.

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

    Science.gov (United States)

    Lunine, Jonathan I.

    2015-04-01

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

  6. 100 years of radar

    CERN Document Server

    Galati, Gaspare

    2016-01-01

    This book offers fascinating insights into the key technical and scientific developments in the history of radar, from the first patent, taken out by Hülsmeyer in 1904, through to the present day. Landmark events are highlighted and fascinating insights provided into the exceptional people who made possible the progress in the field, including the scientists and technologists who worked independently and under strict secrecy in various countries across the world in the 1930s and the big businessmen who played an important role after World War II. The book encourages multiple levels of reading. The author is a leading radar researcher who is ideally placed to offer a technical/scientific perspective as well as a historical one. He has taken care to structure and write the book in such a way as to appeal to both non-specialists and experts. The book is not sponsored by any company or body, either formally or informally, and is therefore entirely unbiased. The text is enriched by approximately three hundred ima...

  7. Atmospheric radar sounding

    Science.gov (United States)

    Crane, R. K.

    1972-01-01

    Monostatic and bistatic radar techniques for the measurement of the structure of volume targets in the troposphere and lower stratosphere are reviewed. The targets considered are thin turbulent layers in the lower stratosphere and rain in the troposphere. The measurements of scattering from thin turbulent layers show that layers are generally detected at or near the tropopause, and in 31 out of 34 sets of measurements, layers were detected above the tropopause in the lower 10 km of the stratosphere. The threshold for turbulent layer detection corresponds to an equivalent thickness product of ten to the minus 13th power times the cube root of m at a range of 100 km and for layers with less than 1000 m thickness. The measurement of scattering by rain shows that in the New England area both convective and widespread rain consists of a number of small cells. On average, the cells appear to have a half-intensity width of 3 to 4 km as measured with a radar system with a 1.8 km resolution cell size for cells at 100 km range.

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

    Science.gov (United States)

    Manor-Chapman, Emily

    2013-01-01

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

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

    Science.gov (United States)

    Brown, Jay

    2008-01-01

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

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

    CERN Document Server

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

    2014-01-01

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

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

    Science.gov (United States)

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

    2011-01-01

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

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

    Science.gov (United States)

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

    2009-01-01

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

  13. THE FORMATION SURFACE OF THE ELECTRIC DISCHARGE OF THE SPARK PLUG "CASSINI"

    OpenAIRE

    Мельник, Вікторія Миколаївна; Карачун, Володимир Володимирович

    2015-01-01

    The paper examines the possibility of increasing the surface of the electric discharge in the ignition devices of the working mixture of internal combustion engines. It is shown that the change of shape of the lower end of the Central electrode of the spark plug with a flat conductive "CASSINI ovals allows you to create the enhanced surface electric discharge in the form of a column volt with the cross-section in the shape of ovals of CASSINI", which creates the opportunity to increase spark ...

  14. Spectral properties of the Saturnian satellite Tethys as derived from Cassini-VIMS data

    OpenAIRE

    Stephan, K.; Jaumann, Ralf; Wagner, Roland; Clark, R.N.; Cruikshank, D. P.; Dalle Ore, C.; Brown, R.H.; Giese, B; Roatsch, T.; Matson, D.L.; Baines, K. H.; Filacchione, G.; Capaccioni, F.; Buratti, B.J.; Nicholson, P. D.

    2012-01-01

    Since 2004 the Cassini spacecraft performed numerous targeted and non-targeted flybys at the major Saturnian satellites. During these flybys the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft [1] detects the spectral properties of the satellites’ surfaces in the wavelength range from 0.35 to 5.1 μm with a spectral resolution that allows the mapping of the distribution of major surface compounds like H2O ice as well as discov-ery/identification of minor and/or t...

  15. Cassini Imaging Science: Initial Results on Saturn's Rings and Small Satellites

    OpenAIRE

    Porco, C. C.; Dyudina, U.; Ingersoll, A. P.

    2005-01-01

    Images acquired of Saturn's rings and small moons by the Cassini Imaging Science Subsystem (ISS) during the first 9 months of Cassini operations at Saturn have produced many new findings. These include new saturnian moons; refined orbits of new and previously known moons; narrow diffuse rings in the F-ring region and embedded in gaps within the main rings; exceptionally fine-scale ring structure in moderate– to high–optical depth regions; new estimates for the masses of ring-region moons, as ...

  16. THE TEST OF APPLYING RADAR TREC WIND IN THREE-DIMENSIONAL VARIATIONAL ASSIMILATION

    Institute of Scientific and Technical Information of China (English)

    WAN Qi-lin; XUE Ji-shan; CHEN Zhi-tong; LIU Chun-xia

    2006-01-01

    The application of radar-derived TREC wind to 3DVAR assimilation system of GRAPeS-3DVar developed by Chinese Academy of Meteorological Sciences is introduced. The resulting fundamental feature is estimated when radar TREC wind is assimilated into GRAPeS-3DVar system. It was found that radar TREC wind has better potential of the application in GRAPeS-3DVar system and can effectively improve the analyzed results. Moreover a numerical experiment is performed in which tropical cyclones make landfall and transform;it also showed that the predicted effect can be improved when the radar TREC wind is added into GRAPeS-3DVar system.

  17. Research on Atmospheric Disturbance Correction method of ground-based radar interferometry

    International Nuclear Information System (INIS)

    The high-frequency signal is often used as the communication signal of Ground-based radar, which is susceptible to atmospheric effects. An atmospheric disturbance correction of radar signal is required to obtain the monitoring accuracy of better than millimeter in precision deformation monitoring using ground-based radar interferometry. In this paper, we analyzed the experimental-data change of ground-based radar in the atmospheric disturbance statistically and proposed a correction method based on the discrete stable point in the global environment. The following experiment proved that this method can optimize the measurement results for the scene of small-scale

  18. Planetary Geology with Imaging Radar: Insights from Earth-based Lunar Studies, 2001–2015

    Science.gov (United States)

    Campbell, Bruce A.

    2016-06-01

    Radar exploration of the Solar System changed dramatically during and beyond the period of the Magellan mission to Venus. These changes included an expansion of the community familiar with microwave data, and the forging of a strong connection with polarimetric scattering models developed through terrestrial field measurements and airborne radar studies. During the period, advances in computing power and imaging techniques also allowed Earth-based radar experiments to acquire data at the highest spatial resolutions permitted by their transmitter systems. This paper traces these developments through a case study of lunar observations over the past 15 years, and their implications for ongoing and future Solar System radar studies.

  19. Radar polarimetry applied to the classification of underground targets

    Science.gov (United States)

    Moriyama, Toshifumi; Nakamura, Masafumi; Yamaguchi, Yoshio; Yamada, Hiroyoshi; Boerner, Wolfgang-Martin

    1997-12-01

    This paper discusses the classification of target buried in the underground by the radar polarimetry. The subsurface radar is used in the detection of objects buried beneath the ground surface, such as archeological exploration, pipes, gas cables and cavities. However, in addition to target echo, the subsurface radar receives various echoes including clutter, because the underground is inhomogeneous medium. Therefore, the subsurface radar needs the ability to distinguish these echoes. In order to enhance the ability, we first applied the polarization anisotropy coefficient to classify the echo into isotropic target (plate, sphere) and anisotropic target (wire, pipe). It is easy to find the man- made target buried in the underground by polarization anisotropy coefficient. Second, we used a three-component decomposition technique for a scattering matrix. Third, we tried to classify targets using polarimetric signature approach. Moreover, the characteristic polarization state gives the oriented angle of anisotropic target. Therefore, these values contribute the classification of the target. The field experiments using an FM-CW radar system were carried out to show the usefulness of the radar polarimetry. In this paper, several detection and classification results are displayed. It is shown that these techniques improve the detection capability of buried target.

  20. Processing of 3D Weather Radar Data with Application for Assimilation in the NWP Model

    Directory of Open Access Journals (Sweden)

    Ośródka Katarzyna

    2014-09-01

    Full Text Available The paper is focused on the processing of 3D weather radar data to minimize the impact of a number of errors from different sources, both meteorological and non-meteorological. The data is also quantitatively characterized in terms of its quality. A set of dedicated algorithms based on analysis of the reflectivity field pattern is described. All the developed algorithms were tested on data from the Polish radar network POLRAD. Quality control plays a key role in avoiding the introduction of incorrect information into applications using radar data. One of the quality control methods is radar data assimilation in numerical weather prediction models to estimate initial conditions of the atmosphere. The study shows an experiment with quality controlled radar data assimilation in the COAMPS model using the ensemble Kalman filter technique. The analysis proved the potential of radar data for such applications; however, further investigations will be indispensable.

  1. On the use of radar-based quantitative precipitation estimates for precipitation frequency analysis

    Science.gov (United States)

    Eldardiry, Hisham; Habib, Emad; Zhang, Yu

    2015-12-01

    The high spatio-temporal resolutions of radar-based multi-sensor Quantitative Precipitation Estimates (QPEs) makes them a potential complement to the gauge records for engineering design purposes, such as precipitation frequency analysis. The current study investigates three fundamental issues that arise when radar-based QPE products are used in frequency analysis: (a) Effect of sample size due to the typically short records of radar products; (b) Effect of uncertainties present in radar-rainfall estimation algorithms; and (c) Effect of the frequency estimation approach adopted. The study uses a 13-year dataset of hourly, 4 × 4 km2 radar-based over a domain that covers Louisiana, USA. Data-based investigations, as well as synthetic simulations, are performed to quantify the uncertainties associated with the radar-based derived frequencies, and to gain insight into the relative contributions of short record lengths and those from conditional biases in the radar product. Three regional estimation procedures were tested and the results indicate the sensitivity of the radar frequency estimates to the selection of the estimation approach and the impact on the uncertainties of the derived extreme quantiles. The simulation experiments revealed that the relatively short radar records explained the majority of the uncertainty associated with the radar-based quantiles; however, they did not account for any tangible contribution to the systematic underestimation observed between radar- and gauge-based frequency estimates. This underestimation was mostly attributable to the conditional bias inherent in the radar product. Addressing such key outstanding problems in radar-rainfall products is necessary before they can be fully and reliably used for frequency analysis applications.

  2. Further developments of EISCAT as an MST radar

    Science.gov (United States)

    Rottger, J.

    1984-01-01

    The principal capabilities of EISCAT as an MST radar were described. Since the VHF transmitter of the EISCAT system is not yet delivered, only the UHF system could be used for radar experiments. Considerable developments in the year 1983 have now strongly improved the reliability of the operations. Most of the experiments were and will be done to investigate the high latitude ionosphere and thermosphere, but some time was also devoted to observations of the lower and middle atmosphere, particularly during the MAP/WINE compaign.

  3. Estimating the vertical structure of intense Mediterranean precipitation using two X-band weather radar systems

    NARCIS (Netherlands)

    Berne, A.D.; Delrieu, G.; Andrieu, H.

    2005-01-01

    The present study aims at a preliminary approach of multiradar compositing applied to the estimation of the vertical structure of precipitation¿an important issue for radar rainfall measurement and prediction. During the HYDROMET Integrated Radar Experiment (HIRE¿98), the vertical profile of reflect

  4. Space Radar Image of North Sea, Germany

    Science.gov (United States)

    1994-01-01

    This is an X-band image of an oil slick experiment conducted in the North Sea, Germany. The image is centered at 54.58 degrees north latitude and 7.48 degrees east longitude. This image was acquired by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle Endeavour on October 6, 1994, during the second flight of the spaceborne radar. The experiment was designed to differentiate between petroleum oil spills and natural slicks floating on the sea surface. Two types of petroleum oil and six types of oils resembling natural sea surface slicks were poured on the sea surface from ships and a helicopter just before the space shuttle flew over the region. At the bottom of the image is the Sylt peninsula, a famous holiday resort. Twenty-six gallons (100 liters) of diesel oil was dissipated due to wave action before the shuttle reached the site. The oil spill seen at the uppermost part of the image is about 105 gallons (400 liters) of heavy heating oil and the largest spill is about 58 gallons (220 liters) of oleyl alcohol, resembling a 'natural oil' like the remaining five spills used to imitate natural slicks that have occurred offshore from various states. The volume of these other oils spilled on the ocean surface during the five experimental spills varied from 16 gallons to 21 gallons (60 liters to 80 liters). The distance between neighboring spills was about half a mile (800 meters) at the most. The largest slick later thinned out to monomolecular sheets of about 10 microns, which is the dimension of a molecule. Oceanographers found that SIR-C/X-SAR was able to clearly distinguish the oil slicks from algae products dumped nearby. Preliminary indications are that various types of slicks may be distinguished, especially when other radar wavelengths are included in the analysis. Radar imaging of the world's oceans on a continuing basis may allow oceanographers in the future to detect and clean up oil spills much more

  5. Clear-air radar observations of the atmospheric boundary layer

    Science.gov (United States)

    Ince, Turker

    2001-10-01

    This dissertation presents the design and operation of a high-resolution frequency-modulated continuous-wave (FM- CW) radar system to study the structure and dynamics of clear-air turbulence in the atmospheric boundary layer (ABL). This sensitive radar can image the vertical structure of the ABL with both high spatial and temporal resolutions, and provide both qualitative information about the morphology of clear-air structures and quantitative information on the intensity of fluctuations in refractive-index of air. The principles of operation and the hardware and data acquisition characteristics of the radar are described in the dissertation. In October 1999, the radar participated in the Cooperative Atmosphere-Surface Exchange Study (CASES'99) Experiment to characterize the temporal structure and evolution of the boundary-layer features in both convective and stable conditions. The observed structures include clear-air convection, boundary layer evolution, gravity waves, Kelvin-Helmholtz instabilities, stably stratified layers, and clear-air turbulence. Many of the S-band radar images also show high- reflectivity returns from Rayleigh scatterers such as insects. An adaptive median filtering technique based on local statistics has, therefore, been developed to discriminate between Bragg and Rayleigh scattering in clear-air radar observations. The filter is tested on radar observations of clear air convection with comparison to two commonly used image processing techniques. The dissertation also examines the statistical mean of the radar-measured C2n for clear-air convection, and compares it with the theoretical predictions. The study also shows that the inversion height, local thickness of the inversion layer, and the height of the elevated atmospheric layers can be estimated from the radar reflectivity measurements. In addition, comparisons to the radiosonde-based height estimates are made. To examine the temporal and spatial structure of C2n , the dissertation

  6. Radar sensing of polar regions

    International Nuclear Information System (INIS)

    In order to monitor ecological conditions, study the processes of energy and mass transfer, and predict climate in polar regions it is necessary to introduce modern means of remote sensing. This paper considers potential applications and presents results of remote sensing of the ocean surface, ice, and soil-vegetation ground cover in polar regions obtained by satellite and aircraft side-looking radar. Unlike optical systems, surface studies using radar systems are not limited by illumination, or restricted by clouds and fog. Interpretation of radar data was based on comparisons between the coefficients of inverse diffusion and direct measurements made at test sites. The structure of ocean waves is reflected in radar images, revealing processes such as surface currents, internal waves, eddies, and frontal zones. Control data have shown economic disasters such as oil spills and drifting pollutants from coastal cities into the sea. Prospects are presented for using radar sensing for resolving a number of scientific and practical problems for the study of ice in the Arctic Basin. Radar methods also permit the characterization of soil-vegetation ground cover. In regions intensively used for agriculture, geochemical processes taking place under the earth and on its surface affect the soil structure and dielectric permeability at the surface level, and are evident in radar images. Results are presented of studies aimed at tracking the processes of spring thaw, areas subject to thermal erosion, floods, and vegetation condition

  7. Radar, Insect Population Ecology, and Pest Management

    Science.gov (United States)

    Vaughn, C. R. (Editor); Wolf, W. (Editor); Klassen, W. (Editor)

    1979-01-01

    Discussions included: (1) the potential role of radar in insect ecology studies and pest management; (2) the potential role of radar in correlating atmospheric phenomena with insect movement; (3) the present and future radar systems; (4) program objectives required to adapt radar to insect ecology studies and pest management; and (5) the specific action items to achieve the objectives.

  8. Cloud structure of Jupiter’s troposphere from Cassini VIMS

    Science.gov (United States)

    Giles, Rohini S.; Fletcher, Leigh N.; Irwin, Patrick G.

    2014-11-01

    Cassini VIMS 4.5-5.1μm thermal emission spectra were used to study the composition and cloud structure of Jupiter’s middle troposphere during the 2000/2001 flyby. The radiance observed varies considerably across the planet (a factor of 50 between the warm North Equatorial Belt and the cool Equatorial Zone) but the spectral shape remains constant, suggesting the presence of a spectrally flat, spatially inhomogeneous cloud deck. Spectra were analysed using the NEMESIS radiative transfer code and retrieval algorithm. Both night- and day-side nadir spectra could be well reproduced using a model with a single, compact, grey cloud deck. For hotter spectra, this grey cloud could be located as deep as 3.0 bar, but the cooler spectra required the cloud deck to be at pressures of 1.2 bar or less. At these pressures, the clouds are expected to be NH4SH or NH3, but the single-scattering albedos of pure ices of NH3 or NH4SH produce spectral features that are incompatible with the VIMS data. These spectral signatures may be masked by complex rimming/coating processes, and/or by the presence of multiple cloud decks. Retrievals show that the cloud optical thickness varies significantly with latitude and longitude. The North Equatorial Belt contains discrete cloud-free “hot-spots” whose radiance is twice as bright as the coolest parts of the belt. The turbulent region in the wake of the Great Red Spot (GRS) has the thickest clouds of the South Equatorial Belt; these begin to thin out on the opposite hemisphere, 180° away from the GRS. The relatively low spectral resolution and model degeneracies mean that no variability could be detected (or ruled out) in the gaseous species (NH3, PH3 and other disequilibrium species). A limb darkening analysis was carried out using the nightside observations. Extreme inhomogeneity within latitude circles meant that simultaneous retrievals at different emission angles were not possible. However, forward modelling was used to show that

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

    Science.gov (United States)

    DelGenio, Anthony D.; Barbara, John M.

    2013-01-01

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

  10. Under the Radar

    CERN Document Server

    Goss, WM

    2010-01-01

    This is the biography of Ruby Payne-Scott (1912 to 1981). As the first female radio astronomer (and one of the first people in the world to consider radio astronomy), she made classic contributions to solar radio physics. She also played a major role in the design of the Australian government's Council for Scientific and Industrial Research radars, which were in turn of vital importance in the Southwest Pacific Theatre in World War II and were used by Australian, US and New Zealand personnel. From a sociological perspective, her career also offers many examples of the perils of being a female academic in the first half of the 20th century. Written in an engaging style and complemented by many historical photographs this book gives a fascinating insight into the beginning of radio astronomy and the role of a pioneering woman in astronomy.

  11. Material integrity verification radar

    International Nuclear Information System (INIS)

    The International Atomic Energy Agency (IAEA) has the need for verification of 'as-built' spent fuel-dry storage containers and other concrete structures. The IAEA has tasked the Special Technologies Laboratory (STL) to fabricate, test, and deploy a stepped-frequency Material Integrity Verification Radar (MIVR) system to nondestructively verify the internal construction of these containers. The MIVR system is based on previously deployed high-frequency, ground penetrating radar (GPR) systems that have been developed by STL for the U.S. Department of Energy (DOE). Whereas GPR technology utilizes microwave radio frequency energy to create subsurface images, MTVR is a variation for which the medium is concrete instead of soil. The purpose is to nondestructively verify the placement of concrete-reinforcing materials, pipes, inner liners, and other attributes of the internal construction. The MIVR system underwent an initial field test on CANDU reactor spent fuel storage canisters at Atomic Energy of Canada Limited (AECL), Chalk River Laboratories, Ontario, Canada, in October 1995. A second field test at the Embalse Nuclear Power Plant in Embalse, Argentina, was completed in May 1996. The DOE GPR also was demonstrated at the site. Data collection and analysis were performed for the Argentine National Board of Nuclear Regulation (ENREN). IAEA and the Brazilian-Argentine Agency for the Control and Accounting of Nuclear Material (ABACC) personnel were present as observers during the test. Reinforcing materials were evident in the color, two-dimensional images produced by the MIVR system. A continuous pattern of reinforcing bars was evident and accurate estimates on the spacing, depth, and size were made. The potential uses for safeguard applications were jointly discussed. The MIVR system, as successfully demonstrated in the two field tests, can be used as a design verification tool for IAEA safeguards. A deployment of MIVR for Design Information Questionnaire (DIQ

  12. Signal processing in noise waveform radar

    CERN Document Server

    Kulpa, Krzysztof

    2013-01-01

    This book is devoted to the emerging technology of noise waveform radar and its signal processing aspects. It is a new kind of radar, which use noise-like waveform to illuminate the target. The book includes an introduction to basic radar theory, starting from classical pulse radar, signal compression, and wave radar. The book then discusses the properties, difficulties and potential of noise radar systems, primarily for low-power and short-range civil applications. The contribution of modern signal processing techniques to making noise radar practical are emphasized, and application examples

  13. Air and spaceborne radar systems an introduction

    CERN Document Server

    Lacomme, Philippe; Hardange, Jean-Philippe; Normant, Eric

    2001-01-01

    A practical tool on radar systems that will be of major help to technicians, student engineers and engineers working in industry and in radar research and development. The many users of radar as well as systems engineers and designers will also find it highly useful. Also of interest to pilots and flight engineers and military command personnel and military contractors. """"This introduction to the field of radar is intended for actual users of radar. It focuses on the history, main principles, functions, modes, properties and specific nature of modern airborne radar. The book examines radar's

  14. Introduction to radar target recognition

    CERN Document Server

    Tait, P

    2006-01-01

    This new text provides an overview of the radar target recognition process and covers the key techniques being developed for operational systems. It is based on the fundamental scientific principles of high resolution radar, and explains how the techniques can be used in real systems, taking into account the characteristics of practical radar system designs and component limitations. It also addresses operational aspects, such as how high resolution modes would fit in with other functions such as detection and tracking. Mathematics is kept to a minimum and the complex techniques and issues are

  15. Gyroklystron-Powered WARLOC Radar

    Science.gov (United States)

    Danly, B. G.; Cheung, W. J.; Gregers-Hansen, V.; Linde, G.; Ngo, M.

    2003-12-01

    A high-power, coherent, W-band (94 GHz) millimeter-wave radar has been developed at the Naval Research Laboratory. This radar, named WARLOC, employs a 100 kW peak power, 10 kW average power gyro-klystron as the final power amplifier, an overmoded transmission line system, and a quasi-optical duplexer, together with a high gain antenna, four-channel receiver, and state-of-the-art signal processing. The gyro-amplifiers and the implementation in the WARLOC radar will be described.

  16. 77 HHz radar for automobile

    Directory of Open Access Journals (Sweden)

    O. M. Lyashuk

    2012-02-01

    Full Text Available Modern requirements to safety and comfort of drivers and passengers of a car cause continuous development of corresponding technical facilities. Technologies that provide implementation of these requirements are on the first place for the developers of cars. One of the most important requirement is an analysis of road situation, where various sensors are used. One of them is radar. Principle of action, basic parameters and application of radar RS-200 is considered in this article. Radar is used in modern cars of brand Mersedes Benz and works on frequency 77 HHz. It uses the LFM (linear frequency modulation with the programmatic setting of resolution for distance.

  17. Flight evaluation of a radar cursor technique

    Science.gov (United States)

    Perez, J.

    1980-03-01

    Preliminary results are presented of a flight test evaluation of a radar cursor technique to be used as an aid in acquiring and tracking the desired ground track during airborne radar approaches. The test was performed using a Sikorsky CH-53A helicopter. The airborne radar system used was a BENDIX RDR-1400A modified to electronically produce a radar cursor display of course error. Airborne radar approaches were made to an offshore and an airport test environment. The specific purpose of the test was to evaluate the practical utility of the radar cursor as an aid to performing airborne radar approaches. The preliminary conclusion of this test is that the use of the radar cursor improved course acquisition and ground tracking significantly with pilotage errors and total system cross-track errors reduced by one-half or better. The radar cursor technique shows potential in reducing airspace requirements for airborne radar approaches.

  18. Radar HRRP Modeling using Dynamic System for Radar Target Recognition

    OpenAIRE

    A. Ajorloo; M. Hadavi; Bastani, M. H.; Nayebi, M. M.

    2014-01-01

    High resolution range profile (HRRP) is being known as one of the most powerful tools for radar target recognition. The main problem with range profile for radar target recognition is its sensitivity to aspect angle. To overcome this problem, consecutive samples of HRRP were assumed to be identically independently distributed (IID) in small frames of aspect angles in most of the related works. Here, considering the physical circumstances of maneuver of an aerial target, we have proposed dynam...

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

    Science.gov (United States)

    Goo, Sherwin

    2014-01-01

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

  20. First imaging results from the Iapetus B/C flyby of the Cassini spacecraft

    OpenAIRE

    Denk, T.; Neukum, G.; Roatsch, T.; McEwen, A. S.; Turtle, E. P.; Thomas, P. C.; Helfenstein, P.; Wagner, R. J.; Porco, C. C.; Perry, J. E.; Giese, B; Johnson, T V; Veverka, J

    2005-01-01

    Cassini had a relatively close flyby at Iapetus on New Year's Eve 2005. The 288 ISS images set various constraints on the origin theories of the dark/bright dichotomy, as revealed multiple surface structures at up to 740 m/pxl size.

  1. Exploring Methods to Rule out Surface Compositional Types on Titan Using Cassini VIMS T20 Data

    OpenAIRE

    Buratti, B.J.; Pitman, K. M.; Brown, R.H.; Barnes, J.W.; Baines, K.; Clark, R.; Jaumann, R.; Nicholson, P.; Sotin, C.

    2007-01-01

    During the Oct. 25, 2006, Cassini T20 Titan flyby, VIMS observed Bohai Sinus, a dune-free area exhibiting apparent color differences between materials. Our goal is to develop methods to exclude possible non-H2O endmember candidates for this region.

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

    Science.gov (United States)

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

    2002-01-01

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

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

    Science.gov (United States)

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

    1997-01-01

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

  4. Radar spectrum opportunities for cognitive communications transmission

    OpenAIRE

    Wang, L.; McGeehan, JP; Williams, C; Doufexi, A

    2008-01-01

    In relation to opportunistic access to radar spectrum, the impact of the radar on a communication system is investigated in this paper. This paper illustrates that by exploring the spatial and temporal opportunities in the radar spectrum and therefore improving the tolerance level to radar interference, a substantial increase on the throughput of a communication system is possible. Results are presented regarding the impact of swept radars on a WiMAX system. The results show the impact of SIR...

  5. C波段调频连续波天气雷达探测系统及观测试验%The C-band FMCW pointing weather radar system and its observa-tion experiment

    Institute of Scientific and Technical Information of China (English)

    阮征; 金龙; 葛润生; 李丰; 吴俊

    2015-01-01

    The C-band Frequency Modulation Continuous Wave (C-FMCW)vertically pointing radar was developed with a new-ly signal processing technology.The C-FMCW radar uses the two-dimensional FFT signal processing technology,with the lowest detectable echo power of -170 dBm,and the quantitative calibration is difficult for weak signal.For a standard signal source analog echo point frequency,its frequency signal is able to be broadened to the signal with the same scanning range as the radar system,to get the calibration curve with the minimum input power up to -169.77 dBm,in which the calibration curve inflection point is able to confirm that the radar noise power is about -168 dBm.The spectral density of reflectivity can be computed from the spectrum of quantitative calibration.The data observed from the C-FMCW radar are compared with the SA scanning radar on Dingyuan,Anhui Province from June of 2013.The comparison analysis uses the data from the 48 km and 83 km CINRAD/SA Bengbu and Hefei radar,respectively,for the August 24 precipitation event.This event includes the two stages with convective cloud and stratiform cloud respectively.The reflectivity vertical distributions in the stratiform cloud for the C-FMCW radar and CINRAD/SA weather radar are basically in agreement,showing that the calculation of the C-FMCW radar system is reasonable.The average difference between the C-FMCW radar and SA radar in Bengbu in terms of the root mean square difference is 1.75 dB,and that between it and the Hefei SA radar is 2.02 dB.A preliminary analysis using the products and the spectral density of reflectivity,shows that the C-FMCW radar has a good prospect in the identification for the different particle phase thickness in precipitation cloud body,the study of echoes in the boundary layer of the clear atmosphere. And,it can also help to recognize the strong variations of vertical motion in the severe rain clouds.%对降水云更高时、空分辨率观测资料的需求推动了天气

  6. Temperate Ice Depth-Sounding Radar

    Science.gov (United States)

    Jara-Olivares, V. A.; Player, K.; Rodriguez-Morales, F.; Gogineni, P.

    2008-12-01

    Glaciers in several parts of the world are reported to be retreating and thinning rapidly over the last decade. Radar instruments can be used to provide a wealth of information regarding the internal and basal conditions of large and small ice masses. These instruments typically operate in the VHF and UHF regions of the electromagnetic spectrum. For temperate-ice sounding, however, the high water content produces scattering and attenuation in propagating radar waves at VHF and UHF frequencies, which significantly reduce the penetration depths. Radars operating in the HF band are better suited for systematic surveys of the thickness and sub-glacial topography of temperate-ice regions. We are developing a dual-frequency Temperate-Ice-Depth Sounding Radar (TIDSoR) that can penetrate through water pockets, thus providing more accurate measurements of temperate ice properties such as thickness and basal conditions. The radar is a light-weight, low power consumption portable system for surface-based observations in mountainous terrain or aerial surveys. TIDSoR operates at two different center frequencies: 7.7 MHz and 14 MHz, with a maximum output peak power of 20 W. The transmit waveform is a digitally generated linear frequency-modulated chirp with 1 MHz bandwidth. The radar can be installed on aircrafts such as the CReSIS UAV [1], DCH-6 (Twin Otter), or P-3 Orion for aerial surveys, where it could be supported by the airplane power system. For surface based experiments, TIDSoR can operate in a backpack configuration powered by a compact battery system. The system can also be installed on a sled towed by a motorized vehicle, in which case the power supply can be replaced by a diesel generator. The radar consists of three functional blocks: the digital section, the radio-frequency (RF) section, and the antenna, and is designed to weigh less than 2 kg, excluding the power supply. The digital section generates the transmit waveforms as well as timing and control signals

  7. Compressive Sensing for MIMO Radar

    CERN Document Server

    Yu, Yao; Poor, H Vincent

    2009-01-01

    Multiple-input multiple-output (MIMO) radar systems have been shown to achieve superior resolution as compared to traditional radar systems with the same number of transmit and receive antennas. This paper considers a distributed MIMO radar scenario, in which each transmit element is a node in a wireless network, and investigates the use of compressive sampling for direction-of-arrival (DOA) estimation. According to the theory of compressive sampling, a signal that is sparse in some domain can be recovered based on far fewer samples than required by the Nyquist sampling theorem. The DOA of targets form a sparse vector in the angle space, and therefore, compressive sampling can be applied for DOA estimation. The proposed approach achieves the superior resolution of MIMO radar with far fewer samples than other approaches. This is particularly useful in a distributed scenario, in which the results at each receive node need to be transmitted to a fusion center for further processing.

  8. Continuing Improvement in the Planetary Ephemeris with VLBA Observations of Cassini

    Science.gov (United States)

    Jones, Dayton L.; Folkner, William M.; Jacobson, Robert A.; Jacobs, Christopher S.; Romney, Jonathan D.; Dhawan, Vivek; Fomalont, Edward B.

    2016-06-01

    During the past decade a continuing series of measurements of the barycentric position of the Saturn system in the inertial International Celestial Reference Frame (ICRF) has led to a significant improvement in our knowledge of Saturn's orbit. This in turn has improved the current accuracy and time range of the solar system ephemeris produced and maintained by the Jet Propulsion Laboratory. Our observing technique involves high-precision astrometry of the radio signal from Cassini with the NRAO Very Long Baseline Array, combined with solutions for the orbital motion of Cassini about the Saturn barycenter from Doppler tracking by the Deep Space Network. Our VLBA astrometry is done in a phase-referencing mode, providing nrad-level relative positions between Cassini and angularly nearby extragalactic radio sources. The positions of those reference radio sources are tied to the ICRF through dedicated VLBI observations by several groups around the world. We will present recent results from our astrometric observations of Cassini through early 2016. This program will continue until the end of the Cassini mission in 2017, although future improvement in Saturn's orbit will be more incremental because we have already covered more that a quarter of Saturn's orbital period. The Juno mission to Jupiter, which will orbit Jupiter for about 1.5 years starting in July 2016, will provide an excellent opportunity for us to apply the same VLBA astrometry technique to improve the orbit of Jupiter by a factor of several. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work made use of the Swinburne University of Technology software correlator, developed as part of the Australian Major National Research Facilities Program and operated under license. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract

  9. Surprises in the Saturn System: 10 Years of Cassini Discoveries and More Excitement to Come

    Science.gov (United States)

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

    2014-12-01

    Cassini's findings have revolutionized our understanding of Saturn, its complex rings, the amazing assortment of moons and the planet's dynamic magnetic environment. The robotic spacecraft arrived in 2004 after a 7-year flight from Earth, dropped a parachuted probe named Huygens to study the atmosphere and surface of Saturn's big moon Titan, and commenced making astonishing discoveries that continue today. Icy jets shoot from the tiny moon Enceladus; Titan's hydrocarbon lakes and seas are dominated by liquid ethane and methane, and complex pre-biotic chemicals form in the atmosphere and rain to the surface; 3-dimensional structures rise above Saturn's rings, and a giant Saturn storm circled the entire planet. Cassini's findings at Saturn have also fundamentally altered many of our concepts of how planets form around stars. The Solstice Mission continues to provide fundamental new science as Cassini observes seasonal and temporal changes, and addresses new questions that have arisen during the mission thus far. The mission's grand finale occurs in 2017, with 22 inclined orbits between the innermost D ring and the upper portions of Saturn's atmosphere, enabling unique gravity and magnetic field measurements of the planet, unprecedented determination of the ring mass, some of the highest resolution measurements of the rings and Saturn, and in situ observations in a completely new region around the planet. Highlights from 10 years of Cassini's ambitious inquiry at Saturn will be presented along with the remarkable science that will be collected in the next three years. Cassini-Huygens is a cooperative undertaking by NASA, the European Space Agency (ESA), and the Italian space agency (Agenzia Spaziale Italiana, ASI). This work was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2014 California Institute of Technology. Government sponsorship is acknowledged.

  10. Bistatic and Multistatic Radar Systems

    OpenAIRE

    Bezousek, P.; V. Schejbal

    2008-01-01

    Radar systems, based on bistatic radar concept attracted a substantial attention in the recent years. Passive coherent location systems using \\"transmitters of opportunity\\" like radio or TV broadcasters, GSM base stations, satellite communication and GNSS signals proved their potential in detection and tracking moving targets over a significant area. In this paper the multistatic location system with non-cooperative transmitters is described and various aspects of signal processing and signa...

  11. Bistatic and Multistatic Radar Systems

    OpenAIRE

    V. Schejbal; Bezousek, P.

    2008-01-01

    Radar systems, based on bistatic radar concept attracted a substantial attention in the recent years. Passive coherent location systems using "transmitters of opportunity" like radio or TV broadcasters, GSM base stations, satellite communication and GNSS signals proved their potential in detection and tracking moving targets over a significant area. In this paper the multistatic location system with non-cooperative transmitters is described and various aspects of signal processing and signal ...

  12. The NASA Polarimetric Radar (NPOL)

    Science.gov (United States)

    Petersen, Walter A.; Wolff, David B.

    2013-01-01

    Characteristics of the NASA NPOL S-band dual-polarimetric radar are presented including its operating characteristics, field configuration, scanning capabilities and calibration approaches. Examples of precipitation science data collections conducted using various scan types, and associated products, are presented for different convective system types and previous field campaign deployments. Finally, the NASA NPOL radar location is depicted in its home base configuration within the greater Wallops Flight Facility precipitation research array supporting NASA Global Precipitation Measurement Mission ground validation.

  13. Algebraic and Adaptive MIMO Radar

    OpenAIRE

    Morency, Matthew

    2015-01-01

    Breaking causality is the main distinction of the multiple-input multiple-output (MIMO) paradigm as used for active sensing/radar. This is because the transmitting side can be optimized in many ways to manipulate the capabilities of the system. Adaptive beamforming is a fundamental problem in array-processing, communications, and radar among other fields which has once again garnered significant research interest in recent years within the MIMO paradigm. In this work, transmit adaptive beamfo...

  14. Wind Turbine Radar Cross Section

    OpenAIRE

    David Jenn; Cuong Ton

    2012-01-01

    The radar cross section (RCS) of a wind turbine is a figure of merit for assessing its effect on the performance of electronic systems. In this paper, the fundamental equations for estimating the wind turbine clutter signal in radar and communication systems are presented. Methods of RCS prediction are summarized, citing their advantages and disadvantages. Bistatic and monostatic RCS patterns for two wind turbine configurations, a horizontal axis three-blade design and a vertical axi...

  15. Bistatic and Multistatic Radar Systems

    Directory of Open Access Journals (Sweden)

    V. Schejbal

    2008-09-01

    Full Text Available Radar systems, based on bistatic radar concept attracted a substantial attention in the recent years. Passive coherent location systems using "transmitters of opportunity" like radio or TV broadcasters, GSM base stations, satellite communication and GNSS signals proved their potential in detection and tracking moving targets over a significant area. In this paper the multistatic location system with non-cooperative transmitters is described and various aspects of signal processing and signal parameters are discussed.

  16. Cancellation of singularities for synthetic aperture radar

    Science.gov (United States)

    Caday, Peter

    2015-01-01

    In a basic model for synthetic aperture radar (SAR) imaging, one wishes to recover a function or distribution f from line integrals over circles whose centers lie on a given curve γ. In this paper, we consider the problem of recovering the singularities (wavefront set) of f given its SAR data, and specifically whether it is possible to choose a singular f whose singularities are hidden from γ, meaning that its SAR data is smooth. We show that f 's singularities can be hidden to leading order if a certain discrete reflection map is the identity, and give examples where this is the case. Finally, numerical experiments illustrate the hiding of singularities.

  17. Cancellation of singularities for synthetic aperture radar

    International Nuclear Information System (INIS)

    In a basic model for synthetic aperture radar (SAR) imaging, one wishes to recover a function or distribution f from line integrals over circles whose centers lie on a given curve γ. In this paper, we consider the problem of recovering the singularities (wavefront set) of f given its SAR data, and specifically whether it is possible to choose a singular f whose singularities are hidden from γ, meaning that its SAR data is smooth. We show that f 's singularities can be hidden to leading order if a certain discrete reflection map is the identity, and give examples where this is the case. Finally, numerical experiments illustrate the hiding of singularities. (paper)

  18. Stereo CUTLASS - A new capability for the SuperDARN HF radars

    Directory of Open Access Journals (Sweden)

    M. Lester

    2004-01-01

    Full Text Available The Super Dual Auroral Radar Network (SuperDARN, which consists of networks of HF radars surrounding the northern and southern poles, has proven to be an extremely successful experimental technique in a wide range of scientific areas. The basic design of the radars, which contributes to SuperDARN, has remained virtually unchanged since the first radar was built in the early 1980s. This paper presents the first results of a significant new development of the basic system. Termed "Stereo", this development involves the addition of a duplicate receive channel and makes use of the spare duty cycle available in the current transmitters. The Stereo system has been implemented on the two radars that form the Co-operative UK Twin Located Auroral Sounding System (CUTLASS, which are the easternmost pair of radars in the Northern Hemisphere SuperDARN chain. Instead of the standard 7 pulse sequence normally employed by the radars, two such pulse sequences are interleaved and transmitted at different frequencies separated by more than 15kHz. This development allows for the radar to run two entirely different experimental modes simultaneously. Here we describe the basic Stereo system and some of the early results. We also identify potential new experiments which could be run with Stereo to complement the existing standard SuperDARN radar.

    Key words. Ionosphere (ionosphere-magnetosphere interactions; ionospheric irregularities; instruments and techniques

  19. Coded continuous wave meteor radar

    Science.gov (United States)

    Vierinen, Juha; Chau, Jorge L.; Pfeffer, Nico; Clahsen, Matthias; Stober, Gunter

    2016-03-01

    The concept of a coded continuous wave specular meteor radar (SMR) is described. The radar uses a continuously transmitted pseudorandom phase-modulated waveform, which has several advantages compared to conventional pulsed SMRs. The coding avoids range and Doppler aliasing, which are in some cases problematic with pulsed radars. Continuous transmissions maximize pulse compression gain, allowing operation at lower peak power than a pulsed system. With continuous coding, the temporal and spectral resolution are not dependent on the transmit waveform and they can be fairly flexibly changed after performing a measurement. The low signal-to-noise ratio before pulse compression, combined with independent pseudorandom transmit waveforms, allows multiple geographically separated transmitters to be used in the same frequency band simultaneously without significantly interfering with each other. Because the same frequency band can be used by multiple transmitters, the same interferometric receiver antennas can be used to receive multiple transmitters at the same time. The principles of the signal processing are discussed, in addition to discussion of several practical ways to increase computation speed, and how to optimally detect meteor echoes. Measurements from a campaign performed with a coded continuous wave SMR are shown and compared with two standard pulsed SMR measurements. The type of meteor radar described in this paper would be suited for use in a large-scale multi-static network of meteor radar transmitters and receivers. Such a system would be useful for increasing the number of meteor detections to obtain improved meteor radar data products.

  20. Propagation of radar rainfall uncertainty in urban flood simulations

    Science.gov (United States)

    Liguori, Sara; Rico-Ramirez, Miguel

    2013-04-01

    hydrodynamic sewer network model implemented in the Infoworks software was used to model the rainfall-runoff process in the urban area. The software calculates the flow through the sewer conduits of the urban model using rainfall as the primary input. The sewer network is covered by 25 radar pixels with a spatial resolution of 1 km2. The majority of the sewer system is combined, carrying both urban rainfall runoff as well as domestic and trade waste water [11]. The urban model was configured to receive the probabilistic radar rainfall fields. The results showed that the radar rainfall ensembles provide additional information about the uncertainty in the radar rainfall measurements that can be propagated in urban flood modelling. The peaks of the measured flow hydrographs are often bounded within the uncertainty area produced by using the radar rainfall ensembles. This is in fact one of the benefits of using radar rainfall ensembles in urban flood modelling. More work needs to be done in improving the urban models, but this is out of the scope of this research. The rainfall uncertainty cannot explain the whole uncertainty shown in the flow simulations, and additional sources of uncertainty will come from the structure of the urban models as well as the large number of parameters required by these models. Acknowledgements The authors would like to acknowledge the BADC, the UK Met Office and the UK Environment Agency for providing the various data sets. We also thank Yorkshire Water Services Ltd for providing the urban model. The authors acknowledge the support from the Engineering and Physical Sciences Research Council (EPSRC) via grant EP/I012222/1. References [1] Browning KA, 1978. Meteorological applications of radar. Reports on Progress in Physics 41 761 Doi: 10.1088/0034-4885/41/5/003 [2] Rico-Ramirez MA, Cluckie ID, Shepherd G, Pallot A, 2007. A high-resolution radar experiment on the island of Jersey. Meteorological Applications 14: 117-129. [3] Villarini G, Krajewski WF

  1. Cassini revisited by the Cassini-Huygens probe: dynamical and photometric study of the rings with the ISS images

    International Nuclear Information System (INIS)

    In the Solar system, the planetary rings represent a fantastic opportunity of studying a majority of phenomena taking place in the thin discs. One can find discs at all redshifts and on all scales of the Universe. Planetary discs are very different: among the Jovian rings, one finds a halo of fine and diffuse dust; the rings of Uranus are very compact, like radially confined strings and the system of rings of Neptune consists of azimuthally stable arcs. However our interest goes on Saturn which has the most complex and widest system of rings known to date: 484 000 km and a vertical extension which increases with the distance to Saturn (typically less than 1 km to 10 000 km). The interest of such a matter organization around Saturn plus its many moons (more than one forty including 8 of a size of several hundreds kilometers) gave birth to the exploration mission CASSINI, supposed to allow the development and the refinement of models set up at the flybies of the two interplanetary probes VOYAGER. The CASSINI Mission began its nominal tour on January, 15 2005 after the orbital insertion the 1 July 2004 and the dropping of HUYGENS probe on january, 14 2005 on Titan's surface. The purpose of this thesis consists to revisit two subjects unsolved of long date in the photometric and dynamic behaviours of the Saturn's rings. In a first part, we try to solve the problem of accretion of matter within the Roche limit by studying the F ring. This ring, since its discovery in 1979 by Pioneer 11, is involved in a most various dynamic theories to explain its complex multi-radial structure and its variable azimuthal structure. We showed that the multi-radial structure of this ring can be understood by the existence of a spiral which is rolled up around a central area, bright, eccentric and inclined: the core. The lifespan of this spiral is not the same one as the core, suggesting that the processes which create the spiral are periodic. Moreover, we showed that the structure of the

  2. Radar Ground Echo Characteristics Measurement Method and Experiment in Vertical Incidence Region%垂直入射大地回波特性测量方法与实验

    Institute of Scientific and Technical Information of China (English)

    徐福元; 张海; 陈祝明; 段锐; 成彬彬

    2011-01-01

    To characterize the radar ground echo in vertical incidence region, S band and 8 mm band linear frequency modulation continuous wave ( LFMCW) radar scatterometer are carried out to measure radar ground echo for farmland and sand. A return database in vertical incidence region of two terrain in the S band and 8 mm band is obtained. The calculation method of ground reflection coefficient and scattering coefficient is given, by which the ground reflection and scattering coefficients are obtained with the measured return data of two terrain in the S band and 8 mm band. The experimental results provide the design consideration for the radar altimeter and microwave remote sensing system.%针对垂直入射区雷达大地回波的特性,利用S波段和8 mm波段线性调频连续波雷达散射计,开展了农田和沙地2种地形的回波测量实验,获取了2种地形在S波段和8mm波段的垂直入射区回波数据,给出了地面反射系数和散射系数的计算方法,并利用该方法由测量回波数据得出了2种地形在S波段和8 mm波段的反射和散射系数.该结果为雷达高度表和微波遥感等系统提供了设计依据.

  3. Coherent Doppler Laser Radar: Technology Development and Applications

    Science.gov (United States)

    Kavaya, Michael J.; Arnold, James E. (Technical Monitor)

    2000-01-01

    NASA's Marshall Space Flight Center has been investigating, developing, and applying coherent Doppler laser radar technology for over 30 years. These efforts have included the first wind measurement in 1967, the first airborne flights in 1972, the first airborne wind field mapping in 1981, and the first measurement of hurricane eyewall winds in 1998. A parallel effort at MSFC since 1982 has been the study, modeling and technology development for a space-based global wind measurement system. These endeavors to date have resulted in compact, robust, eyesafe lidars at 2 micron wavelength based on solid-state laser technology; in a factor of 6 volume reduction in near diffraction limited, space-qualifiable telescopes; in sophisticated airborne scanners with full platform motion subtraction; in local oscillator lasers capable of rapid tuning of 25 GHz for removal of relative laser radar to target velocities over a 25 km/s range; in performance prediction theory and simulations that have been validated experimentally; and in extensive field campaign experience. We have also begun efforts to dramatically improve the fundamental photon efficiency of the laser radar, to demonstrate advanced lower mass laser radar telescopes and scanners; to develop laser and laser radar system alignment maintenance technologies; and to greatly improve the electrical efficiency, cooling technique, and robustness of the pulsed laser. This coherent Doppler laser radar technology is suitable for high resolution, high accuracy wind mapping; for aerosol and cloud measurement; for Differential Absorption Lidar (DIAL) measurements of atmospheric and trace gases; for hard target range and velocity measurement; and for hard target vibration spectra measurement. It is also suitable for a number of aircraft operations applications such as clear air turbulence (CAT) detection; dangerous wind shear (microburst) detection; airspeed, angle of attack, and sideslip measurement; and fuel savings through

  4. Radar target detection simulation

    Directory of Open Access Journals (Sweden)

    Tarig Ibrahim Osman

    2014-12-01

    Full Text Available Standard radar detection process requires that the sensor output is compared to a predetermined threshold. The threshold is selected based on a-priori knowledge available and/or certain assumptions. However, any knowledge and/or assumptions become in adequate due to the presence of multiple targets with varying signal return and usually non stationary background. Thus, any predetermined threshold may result in either increased false alarm rate or increased track loss. Even approaches where the threshold is adaptively varied will not perform well in situations when the signal return from the target of interest is too low compared to the average level of the background .Track-before-detect techniques eliminate the need for a detection threshold and provide detecting and tracking targets with lower signal-to-noise ratios than standard methods. However, although trackbefore-detect techniques eliminate the need for detection threshold at sensor's signal processing stage, they often use tuning thresholds at the output of the filtering stage .This paper presents a computerized simulation model for target detection process. Moreover, the proposed model method is based on the target motion models, the output of the detection process can easily be employed for maneuvering target tracking.

  5. MST radar data management

    Science.gov (United States)

    Nastrom, G. D.

    1984-01-01

    One atmospheric variable which can be deduced from stratosphere-troposphere (ST) radar data other than wind speed and direction is C sub n sup 2, related to the eddy dissipation rate. The computation of C sub n sup 2 makes use of the transmitted power (average, or peak plus duty cycle), the range of the echoes, and the returned power. The returned power can be calibrated only if a noise source of known strength is imposed; e.g., in the absence of absolute calibration, one can compare the diurnal noise signal with the galactic sky temperature. Thus to compute C sub n sup 2 one needs the transmitter power, the returned signal as a function of height, and the returned noise at an altitude so high that it is not contaminated by any signal. Now C sub n sup 2 relates with the amount of energy within the inertial subrange, and for many research studies it may be desirable to relate this with background flow as well as shears or irregularities on the size of the sample volume. The latter are quantified by the spectral width.

  6. Bistatic radar using a spaceborne illuminator

    Science.gov (United States)

    Whitewood, Aric Pierre

    A bistatic radar has a physically separated transmitter and receiver. This research pro gramme investigates a bistatic radar system which uses a spaceborne synthetic aperture radar transmitter on board the European Space Agency's Envisat satellite and a station ary, ground based receiver. The advantages of this variant of the bistatic configuration includes the passive and therefore covert nature of the receiver, its relatively low cost, in addition to the possibility of using a non-cooperative transmitter. The theory behind bistatic SAR systems is covered, including the specific case investi gated. The design, construction and testing of the bistatic receiver, which uses two separate channels, for the direct signal from the satellite (for synchronisation purposes) and the re flected signals from the imaged scene is also described. A SAR processing scheme using an adapted chirp scaling algorithm is presented and demonstrated through simulations to produce focused images for the scenario. The results of several bistatic imaging experiments are analysed through comparisons with theoretical impulse responses, and comparisons with satellite photographs, the corresponding monostatic image produced by Envisat, and the bistatic ambiguity function. It is demonstrated that focused images may be produced with such a system, although the performance achievable is dependent upon the imaging geometry. Different look direc tions of the receiver produce widely differing resolution values. The optimum choice of look direction must be weighed against possible direct signal interference in the reflected signal channel. Other effects, such as azimuth ambiguities caused by the sampling of the mov ing transmitter beam by the pulse repetition frequency may also have an effect, depending upon the combined transmit/receive beam pattern. Aspects of the system that could be investigated in the future are identified, for example the addition of an extra channel to the receiver in order to

  7. Design, Performance and Optimization for Multimodal Radar Operation

    Directory of Open Access Journals (Sweden)

    Surendra S. Bhat

    2012-09-01

    Full Text Available This paper describes the underlying methodology behind an adaptive multimodal radar sensor that is capable of progressively optimizing its range resolution depending upon the target scattering features. It consists of a test-bed that enables the generation of linear frequency modulated waveforms of various bandwidths. This paper discusses a theoretical approach to optimizing the bandwidth used by the multimodal radar. It also discusses the various experimental results obtained from measurement. The resolution predicted from theory agrees quite well with that obtained from experiments for different target arrangements.

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

    Science.gov (United States)

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

    2011-10-01

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

  9. Solid-State Cloud Radar System (CRS) Upgrade and Deployment

    Science.gov (United States)

    McLinden, Matt; Heymsfield, Gerald; Li, Lihua; Racette, Paul; Coon, Michael; Venkatesh, Vijay

    2015-01-01

    The recent decade has brought rapid development in solid-state power amplifier (SSPA) technology. This has enabled the use of solid-state precipitation radar in place of high-power and high-voltage systems such as those that use Klystron or Magnetron transmitters. The NASA Goddard Space Flight Center has recently completed a comprehensive redesign of the 94 gigahertz Cloud Radar System (CRS) to incorporate a solid-state transmitter. It is the first cloud radar to achieve sensitivity comparable to that of a high-voltage transmitter using solid-state. The NASA Goddard Space Flight Center's Cloud Radar System (CRS) is a 94 gigahertz Doppler radar that flies on the NASA ER-2 high-altitude aircraft. The upgraded CRS system utilizes a state-of-the-art solid-state 94 gigahertz power amplifier with a peak transmit power of 30 watts. The modernized CRS system is detailed here with data results from its deployment during the 2014 Integrated Precipitation and Hydrology Experiment (IPHEX).

  10. Managing Risk for Cassini During Mission Operations and Data Analysis (MOandDA)

    Science.gov (United States)

    Witkowski, Mona M.

    2002-01-01

    A Risk Management Process has been tailored for Cassini that not only satisfies the requirements of NASA and JPL, but also allows the Program to proactively identify and assess risks that threaten mission objectives. Cassini Risk Management is a team effort that involves both management and engineering staff. The process is managed and facilitated by the Mission Assurance Manager (MAM), but requires regular interactions with Program Staff and team members to instill the risk management philosophy into the day to day mission operations. While Risk Management is well defined for projects in the development phase, it is a relatively new concept for Mission Operations. The Cassini team has embraced this process and has begun using it in an effective, proactive manner, to ensure mission success. It is hoped that the Cassini Risk Management Process will form the basis by which risk management is conducted during MO&DA on future projects. proactive in identifying, assessing and mitigating risks before they become problems. Cost ehtiveness is achieved by: Comprehensively identifying risks Rapidly assessing which risks require the expenditure of pruject cewums Taking early actions to mitigate these risks Iterating the process frequently, to be responsive to the dynamic internal and external environments The Cassini Program has successfully implemented a Risk Management Process for mission operations, The initial SRL has been developed and input into he online tool. The Risk Management webbased system has been rolled out for use by the flight team and risk owners we working proactive in identifying, assessing and mitigating risks before they become problems. Cost ehtiveness is achieved by: Comprehensively identifying risks Rapidly assessing which risks require the expenditure of pruject cewums Taking early actions to mitigate these risks Iterating the process frequently, to be responsive to the dynamic internal and external environments The Cassini Program has successfully

  11. Wave Normal and Poynting Vector Calculations using the Cassini Radio and Plasma Wave Instrument

    Science.gov (United States)

    Hospodarsky, G. B.; Averkamp, T. F.; Kurth, W. S.; Gurnett, D. A.; Dougherty, M.; Inan, Umran; Wood, Troy

    2001-01-01

    Wave normal and Poynting vector measurements from the Cassini radio and plasma wave instrument (RPWS) are used to examine the propagation characteristics of various plasma waves during the Earth flyby on August 18, 1999. Using the five-channel waveform receiver (WFR), the wave normal vector is determined using the Means method for a lightning-induced whistler, equatorial chorus, and a series of low-frequency emissions observed while Cassini was in the magnetosheath. The Poynting vector for these emissions is also calculated from the five components measured by the WFR. The propagation characteristics of the lightning-induced whistler were found to be consistent with the whistler wave mode of propagation, with propagation antiparallel to the magnetic field (southward) at Cassini. The sferic associated with this whistler was observed by both Cassini and the Stanford VLF group at the Palmer Station in Antarctica. Analysis of the arrival direction of the sferic at the Palmer Station suggests that the lightning stroke is in the same sector as Cassini. Chorus was observed very close (within a few degrees) to the magnetic equator during the flyby. The chorus was found to propagate primarily away from the magnetic equator and was observed to change direction as Cassini crossed the magnetic equator. This suggests that the source region of the chorus is very near the magnetic equator. The low-frequency emission in the magnetosheath has many of the characteristics of lion roars. The average value of the angle between the wave normal vector and the local magnetic field was found to be 16 degrees, and the emissions ranged in frequency from 0. 19 to 0.75 f(sub ce), where f(sub ce) is the electron cyclotron frequency. The wave normal vectors of these waves were primarily in one direction for each individual burst (either parallel or antiparallel to the local field) but varied in direction throughout the magnetosheath. This suggests that the sources of the emissions are far from

  12. Radar imaging mechanism of marine sand waves at very low grazing angle illumination caused by unique hydrodynamic interactions

    OpenAIRE

    Hennings, Ingo; Herbers, D.

    2006-01-01

    The investigations carried out between 2002 and 2004 during six field experiments within the Operational Radar and Optical Mapping in monitoring hydrodynamic, morphodynamic and environmental parameters for coastal management (OROMA) project aimed to improve the effectiveness of new remote sensing monitoring technologies such as shipborne imaging radars in coastal waters. The coastal monitoring radar of the GKSS Research Center, Geesthacht, Germany, is based on a Kelvin Hughes RSR 1000 X band ...

  13. Coded continuous wave meteor radar

    Directory of Open Access Journals (Sweden)

    J. Vierinen

    2015-07-01

    Full Text Available The concept of coded continuous wave meteor radar is introduced. The radar uses a continuously transmitted pseudo-random waveform, which has several advantages: coding avoids range aliased echoes, which are often seen with commonly used pulsed specular meteor radars (SMRs; continuous transmissions maximize pulse compression gain, allowing operation with significantly lower peak transmit power; the temporal resolution can be changed after performing a measurement, as it does not depend on pulse spacing; and the low signal to noise ratio allows multiple geographically separated transmitters to be used in the same frequency band without significantly interfering with each other. The latter allows the same receiver antennas to be used to receive multiple transmitters. The principles of the signal processing are discussed, in addition to discussion of several practical ways to increase computation speed, and how to optimally detect meteor echoes. Measurements from a campaign performed with a coded continuous wave SMR are shown and compared with two standard pulsed SMR measurements. The type of meteor radar described in this paper would be suited for use in a large scale multi-static network of meteor radar transmitters and receivers. This would, for example, provide higher spatio-temporal resolution for mesospheric wind field measurements.

  14. Coded continuous wave meteor radar

    Science.gov (United States)

    Vierinen, J.; Chau, J. L.; Pfeffer, N.; Clahsen, M.; Stober, G.

    2015-07-01

    The concept of coded continuous wave meteor radar is introduced. The radar uses a continuously transmitted pseudo-random waveform, which has several advantages: coding avoids range aliased echoes, which are often seen with commonly used pulsed specular meteor radars (SMRs); continuous transmissions maximize pulse compression gain, allowing operation with significantly lower peak transmit power; the temporal resolution can be changed after performing a measurement, as it does not depend on pulse spacing; and the low signal to noise ratio allows multiple geographically separated transmitters to be used in the same frequency band without significantly interfering with each other. The latter allows the same receiver antennas to be used to receive multiple transmitters. The principles of the signal processing are discussed, in addition to discussion of several practical ways to increase computation speed, and how to optimally detect meteor echoes. Measurements from a campaign performed with a coded continuous wave SMR are shown and compared with two standard pulsed SMR measurements. The type of meteor radar described in this paper would be suited for use in a large scale multi-static network of meteor radar transmitters and receivers. This would, for example, provide higher spatio-temporal resolution for mesospheric wind field measurements.

  15. Radar rainfall image repair techniques

    Directory of Open Access Journals (Sweden)

    Stephen M. Wesson

    2004-01-01

    Full Text Available There are various quality problems associated with radar rainfall data viewed in images that include ground clutter, beam blocking and anomalous propagation, to name a few. To obtain the best rainfall estimate possible, techniques for removing ground clutter (non-meteorological echoes that influence radar data quality on 2-D radar rainfall image data sets are presented here. These techniques concentrate on repairing the images in both a computationally fast and accurate manner, and are nearest neighbour techniques of two sub-types: Individual Target and Border Tracing. The contaminated data is estimated through Kriging, considered the optimal technique for the spatial interpolation of Gaussian data, where the 'screening effect' that occurs with the Kriging weighting distribution around target points is exploited to ensure computational efficiency. Matrix rank reduction techniques in combination with Singular Value Decomposition (SVD are also suggested for finding an efficient solution to the Kriging Equations which can cope with near singular systems. Rainfall estimation at ground level from radar rainfall volume scan data is of interest and importance in earth bound applications such as hydrology and agriculture. As an extension of the above, Ordinary Kriging is applied to three-dimensional radar rainfall data to estimate rainfall rate at ground level. Keywords: ground clutter, data infilling, Ordinary Kriging, nearest neighbours, Singular Value Decomposition, border tracing, computation time, ground level rainfall estimation

  16. The PROUST radar: First results

    Science.gov (United States)

    Bertin, F.; Cremieu, A.; Glass, M.; Massebeuf, M.; Ney, R.; Petitdidier, M.

    1987-01-01

    The stratosphere-troposphere radar PROUST (prototype de radar pour l'observation en UHF de la stratosphère et troposphère) is located at Saint Santin, France (44°39'N; 2°12'E), a place devoted to the French ionospheric incoherent scatter facility whose frequency is 935 MHz. The use of this equipment as stratosphere-troposphere radar has required important modifications of the transmitting and receiving systems, which have been planned in several steps. In a first one, the radar works in a bistatic mode with a 600-m height resolution, allowing measurements in the altitude range 3-10 km. The first results presented here have been obtained with this configuration during two campaigns. In the first one, observations can be interpreted in terms of lee waves; in the second, an intense turbulence activity associated with a high-altitude temperature inversion is observed. In this last case, the oscillations observed in the vertical wind are consistent with trapped gravity waves generated by a decaying turbulence in a stratified medium. In a second step, now operating, a 30-m height resolution has been implemented and will allow a better understanding of these phenomena. In its final version, the PROUST radar will operate in a monostatic mode that will permit to extend the observations up to 15 km.

  17. Microphysical Retrieval from Doppler Radar Reflectivity Using Variational Data Assimilation

    Institute of Scientific and Technical Information of China (English)

    LI Yongping; ZHU Guofu; XUE Jishan

    2006-01-01

    One of the microphysical variables, the rainwater mixing ratio qr, is retrieved from the observed reflectivity of Doppler radar by a 3D variational data assimilation system. The qr as an analysis variable is obtained by minimizing a cost function defined as the difference between observed radar reflectivity and its retrieval from qr, plus the difference between qr and its background field from a mesoscale model's prediction. Covariance matrix of the background field's error is determined by the so-called NMC method. A method called the second-order auto-regression (SOAR) is used to calculate the coefficients of regressive filtering to fit in with small spatial scale such as cumulus in the process of spatial transformation. An ideal experiment demonstrates the correctness of this system and a sensitivity experiment proves that the random error of observed reflectivity has effect on the analyzed results. At last an experiment with observed data from the Doppler radar at Ma'anshan City in Anhui Province on 19 June 2002 was performed. The retrieved analysis variable qr in this test shows structures in detail, which coincide with the distribution of the echo picture observed by the radar.

  18. Simulation model study of limitation on the locating distance of a ground penetrating radar; Chichu tansa radar no tansa kyori genkai ni kansuru simulation model no kochiku

    Energy Technology Data Exchange (ETDEWEB)

    Nakauchi, T.; Tsunasaki, M.; Kishi, M.; Hayakawa, H. [Osaka Gas Co. Ltd., Osaka (Japan)

    1996-10-01

    Various simulations were carried out under various laying conditions to obtain the limitation of locating distance for ground penetrating radar. Recently, ground penetrating radar has been remarked as location technology of obstacles such as the existing buried objects. To enhance the theoretical model (radar equation) of a maximum locating distance, the following factors were examined experimentally using pulse ground penetrating radar: ground surface conditions such as asphalt pavement, diameter of buried pipes, material of buried pipes, effect of soil, antenna gain. The experiment results well agreed with actual field experiment ones. By adopting the antenna gain and effect of the ground surface, the more practical simulation using underground models became possible. The maximum locating distance was more improved by large antenna than small one in actual field. It is assumed that large antenna components contributed to improvement of gain and reduction of attenuation during passing through soil. 5 refs., 12 figs.

  19. Two-dimensional and full polarimetric imaging by a synthetic aperture FM-CW radar

    Science.gov (United States)

    Yamaguchi, Yoshio; Nishikawa, Toru; Sengoku, Masakazu; Boerner, Wolfgang-Martin

    1995-03-01

    This paper applies the principle of radar polarimetry to a synthetic aperture frequency-modulated continuous wave (FM-CW) radar and presents results based on two-dimensional (2-D) full polarimetric imaging. It is shown that the polarimetric target reflection coefficients obtained by the synthetic aperture FM-CW radar are elements of a Sinclair scattering matrix, although the coefficients are derived from a wide band signal. Using the scattering matrix optimization procedure, a 2-D polarimetric imaging experiment (including Co-Pol maximum, minimum, span, and phase imaging) of an orthogonally placed linear target set was successfully carried out in the laboratory. This result demonstrates the validity of X-band (8.2-9.2 GHz) FM-CW radar polarimetry, and it presents a demonstration of a full polarimetric 2-D FM-CW imaging radar system.

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

    Science.gov (United States)

    Bates, David M.

    2010-01-01

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

  1. Radio and Plasma Wave Observations at Saturn from Cassini's Approach and First Orbit

    Science.gov (United States)

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

    2005-01-01

    We report data from the Cassini radio and plasma wave instrument during the approach and first orbit at Saturn. During the approach, radio emissions from Saturn showed that the radio rotation period is now 10 hours 45 minutes 45 k 36 seconds, about 6 minutes longer than measured by Voyager in 1980 to 1981. In addition, many intense impulsive radio signals were detected from Saturn lightning during the approach and first orbit. Some of these have been linked to storm systems observed by the Cassini imaging instrument. Within the magnetosphere, whistler-mode auroral hiss emissions were observed near the rings, suggesting that a strong electrodynamic interaction is occurring in or near the rings.

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

    Science.gov (United States)

    Burk, Thomas A.

    2011-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-06-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

  5. Global-scale surface spectral variations on Titan seen from Cassini/VIMS

    Science.gov (United States)

    Barnes, J.W.; Brown, R.H.; Soderblom, L.; Buratti, B.J.; Sotin, C.; Rodriguez, S.; Le, Mouelic S.; Baines, K.H.; Clark, R.; Nicholson, P.

    2007-01-01

    We present global-scale maps of Titan from the Visual and Infrared Mapping Spectrometer (VIMS) instrument on Cassini. We map at 64 near-infrared wavelengths simultaneously, covering the atmospheric windows at 0.94, 1.08, 1.28, 1.6, 2.0, 2.8, and 5 ??m with a typical resolution of 50 km/pixel or a typical total integration time of 1 s. Our maps have five to ten times the resolution of ground-based maps, better spectral resolution across most windows, coverage in multiple atmospheric windows, and represent the first spatially resolved maps of Titan at 5 ??m. The VIMS maps provide context and surface spectral information in support of other Cassini instruments. We note a strong latitudinal dependence in the spectral character of Titan's surface, and partition the surface into 9 spectral units that we describe in terms of spectral and spatial characteristics. ?? 2006 Elsevier Inc. All rights reserved.

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

    Science.gov (United States)

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

    2009-01-01

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

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

    Science.gov (United States)

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

    2013-01-01

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

  8. Cloud Features and Zonal Wind Measurements of Saturn's Atmosphere as Observed by Cassini/VIMS

    CERN Document Server

    Choi, David S; Brown, Robert H; 10.1029/2008JE003254

    2013-01-01

    We present an analysis of data about Saturn's atmosphere from Cassini's Visual and Infrared Mapping Spectrometer (VIMS), focusing on the meteorology of the features seen in the 5-micron spectral window. We present VIMS mosaics and discuss the morphology and general characteristics of the features backlit by Saturn's thermal emission. We have also constructed a zonal wind profile from VIMS feature tracking observation sequences using an automated cloud feature tracker. Comparison with previously constructed profiles from Voyager and Cassini imaging data reveals broad similarities, suggesting minimal vertical shear of the zonal wind. However, areas of apparent wind shear are present in the VIMS zonal wind profile at jet stream cores. In particular, our analysis shows that the equatorial jet reaches speeds exceeding 450 m/s, similar to speeds obtained during the Voyager era. This suggests that recent inferences of relatively slower jet speeds of ~275-375 m/s are confined to the upper troposphere and that the dee...

  9. Obstacle penetrating dynamic radar imaging system

    Science.gov (United States)

    Romero, Carlos E.; Zumstein, James E.; Chang, John T.; Leach, Jr.. Richard R.

    2006-12-12

    An obstacle penetrating dynamic radar imaging system for the detection, tracking, and imaging of an individual, animal, or object comprising a multiplicity of low power ultra wideband radar units that produce a set of return radar signals from the individual, animal, or object, and a processing system for said set of return radar signals for detection, tracking, and imaging of the individual, animal, or object. The system provides a radar video system for detecting and tracking an individual, animal, or object by producing a set of return radar signals from the individual, animal, or object with a multiplicity of low power ultra wideband radar units, and processing said set of return radar signals for detecting and tracking of the individual, animal, or object.

  10. Design of multi-frequency CW radars

    CERN Document Server

    Jankiraman, Mohinder

    2007-01-01

    This book deals with the basic theory for design and analysis of Low Probability of Intercept (LPI) radar systems. The design of one such multi-frequency high resolution LPI radar, PANDORA, is covered.

  11. NOAA NEXt-Generation RADar (NEXRAD) Products

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset consists of Level III weather radar products collected from Next-Generation Radar (NEXRAD) stations located in the contiguous United States, Alaska,...

  12. MST radar data-base management

    Science.gov (United States)

    Wickwar, V. B.

    1983-01-01

    Data management for Mesospheric-Stratospheric-Tropospheric, (MST) radars is addressed. An incoherent-scatter radar data base is discussed in terms of purpose, centralization, scope, and nature of the data base management system.

  13. Meteor detection on ST (MST) radars

    Science.gov (United States)

    Avery, S. K.

    1987-01-01

    The ability to detect radar echoes from backscatter due to turbulent irregularities of the radio refractive index in the clear atmosphere has lead to an increasing number of established mesosphere - stratosphere - troposphere (MST or ST) radars. Humidity and temperature variations are responsible for the echo in the troposphere and stratosphere and turbulence acting on electron density gradients provides the echo in the mesosphere. The MST radar and its smaller version, the ST radar, are pulsed Doppler radars operating in the VHF - UHF frequency range. These echoes can be used to determine upper atmosphere winds at little extra cost to the ST radar configuration. In addition, the meteor echoes can supplement mesospheric data from an MST radar. The detection techniques required on the ST radar for delineating meteor echo returns are described.

  14. Progress in existing and planned MST radars

    Science.gov (United States)

    Vanzandt, T. E.

    1986-01-01

    Radar systems are described which use two different wind measuring techniques: the partial-reflection drift technique and the mesosphere-stratosphere-troposphere (MST) or Doppler beam-swing radar technique. The advantages and disadvantages of each technique are discussed.

  15. Extended Target Recognition in Cognitive Radar Networks

    Directory of Open Access Journals (Sweden)

    Xiqin Wang

    2010-11-01

    Full Text Available We address the problem of adaptive waveform design for extended target recognition in cognitive radar networks. A closed-loop active target recognition radar system is extended to the case of a centralized cognitive radar network, in which a generalized likelihood ratio (GLR based sequential hypothesis testing (SHT framework is employed. Using Doppler velocities measured by multiple radars, the target aspect angle for each radar is calculated. The joint probability of each target hypothesis is then updated using observations from different radar line of sights (LOS. Based on these probabilities, a minimum correlation algorithm is proposed to adaptively design the transmit waveform for each radar in an amplitude fluctuation situation. Simulation results demonstrate performance improvements due to the cognitive radar network and adaptive waveform design. Our minimum correlation algorithm outperforms the eigen-waveform solution and other non-cognitive waveform design approaches.

  16. Radar Observation of Insects - Mosquitoes

    Science.gov (United States)

    Frost, E.; Downing, J.

    1979-01-01

    Tests were conducted at several sites over the coastal lowlands of New Jersey and over a region of high plains and low mountains in Oklahoma. In one area, a salt marsh in New Jersey, extensive ground tests were combined with laboratory data on expected insect backscatter to arrive at an extremely convincing model of the insect origin of most Dot Angels. A great deal of insight was studied from radar on the buildup and dispersal of insect swarms, since radar can follow where other means of trapping and observation cannot. Data on large-scale behavior as a function of wind and topography are presented. Displayed techniques which show individual or small swarm motion within some larger cloud or mass, or which can show the overall motion over great distances were developed. The influence of wind and terrain on insect motion and dispersal is determined from radar data.

  17. GMTI radar minimum detectable velocity.

    Energy Technology Data Exchange (ETDEWEB)

    Richards, John Alfred

    2011-04-01

    Minimum detectable velocity (MDV) is a fundamental consideration for the design, implementation, and exploitation of ground moving-target indication (GMTI) radar imaging modes. All single-phase-center air-to-ground radars are characterized by an MDV, or a minimum radial velocity below which motion of a discrete nonstationary target is indistinguishable from the relative motion between the platform and the ground. Targets with radial velocities less than MDV are typically overwhelmed by endoclutter ground returns, and are thus not generally detectable. Targets with radial velocities greater than MDV typically produce distinct returns falling outside of the endoclutter ground returns, and are thus generally discernible using straightforward detection algorithms. This document provides a straightforward derivation of MDV for an air-to-ground single-phase-center GMTI radar operating in an arbitrary geometry.

  18. Airborne Differential Doppler Weather Radar

    Science.gov (United States)

    Meneghini, R.; Bidwell, S.; Liao, L.; Rincon, R.; Heymsfield, G.; Hildebrand, Peter H. (Technical Monitor)

    2001-01-01

    The Precipitation Radar aboard the Tropical Rain Measuring Mission (TRMM) Satellite has shown the potential for spaceborne sensing of snow and rain by means of an incoherent pulsed radar operating at 13.8 GHz. The primary advantage of radar relative to passive instruments arises from the fact that the radar can image the 3-dimensional structure of storms. As a consequence, the radar data can be used to determine the vertical rain structure, rain type (convective/stratiform) effective storm height, and location of the melting layer. The radar, moreover, can be used to detect snow and improve the estimation of rain rate over land. To move toward spaceborne weather radars that can be deployed routinely as part of an instrument set consisting of passive and active sensors will require the development of less expensive, lighter-weight radars that consume less power. At the same time, the addition of a second frequency and an upgrade to Doppler capability are features that are needed to retrieve information on the characteristics of the drop size distribution, vertical air motion and storm dynamics. One approach to the problem is to use a single broad-band transmitter-receiver and antenna where two narrow-band frequencies are spaced apart by 5% to 10% of the center frequency. Use of Ka-band frequencies (26.5 GHz - 40 GHz) affords two advantages: adequate spatial resolution can be attained with a relatively small antenna and the differential reflectivity and mean Doppler signals are directly related to the median mass diameter of the snow and raindrop size distributions. The differential mean Doppler signal has the additional property that this quantity depends only on that part of the radial speed of the hydrometeors that is drop-size dependent. In principle, the mean and differential mean Doppler from a near-nadir viewing radar can be used to retrieve vertical air motion as well as the total mean radial velocity. In the paper, we present theoretical calculations for the

  19. Scanning ARM Cloud Radar Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Widener, K; Bharadwaj, N; Johnson, K

    2012-06-18

    The scanning ARM cloud radar (SACR) is a polarimetric Doppler radar consisting of three different radar designs based on operating frequency. These are designated as follows: (1) X-band SACR (X-SACR); (2) Ka-band SACR (Ka-SACR); and (3) W-band SACR (W-SACR). There are two SACRs on a single pedestal at each site where SACRs are deployed. The selection of the operating frequencies at each deployed site is predominantly determined by atmospheric attenuation at the site. Because RF attenuation increases with atmospheric water vapor content, ARM's Tropical Western Pacific (TWP) sites use the X-/Ka-band frequency pair. The Southern Great Plains (SGP) and North Slope of Alaska (NSA) sites field the Ka-/W-band frequency pair. One ARM Mobile Facility (AMF1) has a Ka/W-SACR and the other (AMF2) has a X/Ka-SACR.

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

    CERN Document Server

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

    2013-01-01

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

  1. I termini di Cassini e Laplace della rifrazione atmosferica misurati alla Meridiana Clementina

    Science.gov (United States)

    Sigismondi, Costantino

    2016-05-01

    The measures of the atmospheric refraction terms of Cassini and Laplace are made at the Clementine Meridian Line of S. Maria degli Angeli in Rome by comparing the observed positions of the center of the Sun with the ones calculated without atmosphere. Three linear systems with the data of 21 Dec 2015; 18 Jan and 6 Feb 2016 give the refraction terms of tan(z) and tan3(z).

  2. Statistics of Langmuir wave amplitudes observed inside Saturn's foreshock by the Cassini spacecraft

    Czech Academy of Sciences Publication Activity Database

    Píša, David; Hospodarsky, G. B.; Kurth, W. S.; Santolík, Ondřej; Souček, Jan; Gurnett, D. A.; Masters, A.; Hill, M. E.

    2015-01-01

    Roč. 120, č. 4 (2015), s. 2531-2542. ISSN 2169-9380 R&D Projects: GA ČR GAP205/10/2279; GA ČR(CZ) GAP209/12/2394 Institutional support: RVO:68378289 Keywords : Langmuir waves * foreshock * Saturn * Cassini Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.440, year: 2013 http://onlinelibrary.wiley.com/doi/10.1002/2014JA020560/abstract

  3. Fmcw Mmw Radar For Automotive Longitudinal Control

    OpenAIRE

    David, William

    1997-01-01

    This report presents information on millimeter wave (MMW) radar for automotive longitudinal control. It addresses the fundamental capabilities and limitations of millimeter waves for ranging and contrasts their operation with that of conventional microwave radar. The report analyzes pulsed and FMCW radar configurations, and provides detailed treatment of FMCW radar operating at MMW frequency, its advantages and disadvantages as they relate to range and velocity measurements.

  4. High-precision positioning of radar scatterers

    OpenAIRE

    Dheenathayalan, P.; Small, D; Schubert, A.; Hanssen, R.F.

    2016-01-01

    Remote sensing radar satellites cover wide areas and provide spatially dense measurements, with millions of scatterers. Knowledge of the precise position of each radar scatterer is essential to identify the corresponding object and interpret the estimated deformation. The absolute position accuracy of synthetic aperture radar (SAR) scatterers in a 2D radar coordinate system, after compensating for atmosphere and tidal effects, is in the order of centimeters for TerraSAR-X (TSX) spotlight imag...

  5. Goldstone solar system radar signal processing

    Science.gov (United States)

    Jurgens, R. F.; Satorius, E.; Sanchez, O.

    1992-01-01

    A performance analysis of the planetary radar data acquisition system is presented. These results extend previous computer simulation analysis and are facilitated by the development of a simple analytical model that predicts radar system performance over a wide range of operational parameters. The results of this study are useful to both the radar systems designer and the science investigator in establishing operational radar data acquisition parameters which result in the best systems performance for a given set of input conditions.

  6. Radar operation in a hostile electromagnetic environment

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2014-03-01

    Radar ISR does not always involve cooperative or even friendly targets. An adversary has numerous techniques available to him to counter the effectiveness of a radar ISR sensor. These generally fall under the banner of jamming, spoofing, or otherwise interfering with the EM signals required by the radar sensor. Consequently mitigation techniques are prudent to retain efficacy of the radar sensor. We discuss in general terms a number of mitigation techniques.

  7. Properties of the MIMO radar ambiguity function

    OpenAIRE

    Chen, Chun-Yang; Vaidyanathan, P.P.

    2008-01-01

    MIMO (multiple-input multiple-output) radar is an emerging technology which has drawn considerable attention. Unlike the traditional SIMO (single-input multiple-output) radar, which transmits scaled versions of a single waveform in the antenna elements, the MIMO radar transmits independent waveforms in each of the antenna elements. It has been shown that MIMO radar systems have many advantages such as high spatial resolution, improved parameter identifiability, and enhanced flexibility for tr...

  8. An MSK Waveform for Radar Applications

    Science.gov (United States)

    Quirk, Kevin J.; Srinivasan, Meera

    2009-01-01

    We introduce a minimum shift keying (MSK) waveform developed for use in radar applications. This waveform is characterized in terms of its spectrum, autocorrelation, and ambiguity function, and is compared with the conventionally used bi-phase coded (BPC) radar signal. It is shown that the MSK waveform has several advantages when compared with the BPC waveform, and is a better candidate for deep-space radar imaging systems such as NASA's Goldstone Solar System Radar.

  9. Digital Radar For Efficient Surveillance

    Directory of Open Access Journals (Sweden)

    Vamsikrishna Chitithoti

    2012-10-01

    Full Text Available The aim of the work is to provide a high efficient surveillance for very costly material like jewelry, gold ornaments and diamonds. In this work an ultra-sonic sensor is collaboratedwith the digital radar, this sensor senses the range which belongs to it and the digital radar detects the obstacle which falls in that range and sounds alarm as soon as the alarm switched on the driver connected to firing gun will become on and the firing starts on that obstacle or person who come unauthorized . In this way our work can barge the costly equipment effectively.

  10. Digital Radar For Efficient Surveillance

    OpenAIRE

    Vamsikrishna Chitithoti; K Bala Krishna

    2012-01-01

    The aim of the work is to provide a high efficient surveillance for very costly material like jewelry, gold ornaments and diamonds. In this work an ultra-sonic sensor is collaboratedwith the digital radar, this sensor senses the range which belongs to it and the digital radar detects the obstacle which falls in that range and sounds alarm as soon as the alarm switched on the driver connected to firing gun will become on and the firing starts on that obstacle or person who come unauthorized . ...

  11. Wind Turbine Radar Cross Section

    Directory of Open Access Journals (Sweden)

    David Jenn

    2012-01-01

    Full Text Available The radar cross section (RCS of a wind turbine is a figure of merit for assessing its effect on the performance of electronic systems. In this paper, the fundamental equations for estimating the wind turbine clutter signal in radar and communication systems are presented. Methods of RCS prediction are summarized, citing their advantages and disadvantages. Bistatic and monostatic RCS patterns for two wind turbine configurations, a horizontal axis three-blade design and a vertical axis helical design, are shown. The unique electromagnetic scattering features, the effect of materials, and methods of mitigating wind turbine clutter are also discussed.

  12. Portable receiver for radar detection

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, Christopher D.; Kotter, Dale K.

    2008-10-14

    Various embodiments are described relating to a portable antenna-equipped device for multi-band radar detection. The detection device includes a plurality of antennas on a flexible substrate, a detection-and-control circuit, an indicator and a power source. The antenna may include one or more planar lithographic antennas that may be fabricated on a thin-film substrate. Each antenna may be tuned to a different selection frequency or band. The antennas may include a bolometer for radar detection. Each antenna may include a frequency selective surface for tuning to the selection frequency.

  13. Compressive sensing for urban radar

    CERN Document Server

    Amin, Moeness

    2014-01-01

    With the emergence of compressive sensing and sparse signal reconstruction, approaches to urban radar have shifted toward relaxed constraints on signal sampling schemes in time and space, and to effectively address logistic difficulties in data acquisition. Traditionally, these challenges have hindered high resolution imaging by restricting both bandwidth and aperture, and by imposing uniformity and bounds on sampling rates.Compressive Sensing for Urban Radar is the first book to focus on a hybrid of two key areas: compressive sensing and urban sensing. It explains how reliable imaging, tracki

  14. Highly integrated low power radars

    CERN Document Server

    Saponara, Sergio; Ragonese, Egidio

    2014-01-01

    In recent years, advances in radio detection and ranging technology, sustained by new achievements in the fields of signal processing and electronic components, have permitted the adoption of radars in many civil and defense applications.This resource discusses how highly integrated radar has been adopted by several new markets such as contactless vital sign monitoring (heart rate, breath rate) or harbour traffic control, as well as several applications for vehicle driver assistance. You are provided with scenarios, applications, and requirements, while focusing on the trade-offs between flexi

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

    Science.gov (United States)

    Krening, Samantha C.

    2013-01-01

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

  16. Cassini UVIS Observations of the Io Plasma Torus. 4; Modeling Temporal and Azimuthal Variability

    Science.gov (United States)

    Steffl, A. J.; Delamere, P. A.; Bagenal, F.

    2008-01-01

    In this fourth paper in a series, we present a model of the remarkable temporal and azimuthal variability of the Io plasma torus observed during the Cassini encounter with Jupiter. Over a period of three months, the Cassini Ultraviolet Imaging Spectrograph (UVIS) observed a dramatic variaton in the average torus composition. Superimposed on this long-term variation, is a 10.07-hour periodicity caused by azimuthal variation in plasma composition subcorotating relative to System III longitude. Quite surprisingly, the amplitude of the azimuthal variation appears to be modulated at the beat frequency between the System III period and the observed 10.07-hour period. Previously, we have successfully modeled the months-long compositional change by supposing a factor of three increase in the amount of material supplied to Io's extended neutral clouds. Here, we extend our torus chemistry model to include an azimuthal dimension. We postulate the existence of two azimuthal variations in the number of superthermal electrons in the torus: a primary variation that subcorotates with a period of 10.07 hours and a secondary variation that remains fixed in System III longitude. Using these two hot electron variations, our model can reproduce the observed temporal and azimuthal variations observed by Cassini UVIS.

  17. Groundbased Observations of Io [OI]6300 A Emission During the Galileo 124, 125, and Cassini Encounters

    Science.gov (United States)

    Oliversen, R. J.; Morgenthaler, J. P.; Scherb, F.; Woodward, R. C.; Smyth, W. H.; Lupie, O. L.

    2003-01-01

    For the past 12 years, we have conducted a synoptic study of [OI] 6300 A emission from Io using the high-resolution (R 120,000) stellar spectrograph at the National Solar Observatory McMath-Pierce telescope. We showed in a recent paper that this emission allows us to use Io as a localized probe of the three-dimensional plasma torus structure. We report on selected recent spectroscopic observations of Io [OI] 6300 A emission obtained during the Galileo I24 (1999-Oct-11) and I25 (1999-Nov-26) encounters with Io and the Cassini Jupiter encounter (closest approach 2000-Dec-30). The exposure time for each spectrum was 15 minutes, with a 5.2 x 5.2 aperture centered on Io. We obtained over 100 spectra for the I24 encounter during 1999 October 9-13, over 100 spectra for the I25 encounter during 1999 November 24-30, and for the Cassini Jupiter flyby almost 600 spectra from 2000 December to 2001 January 21. We use our database of observations to track long- and short-term variations in torus structure. We compare our results to Galileo, Cassini, HST, and other groundbased contemporaneous observations to gain insight into torus variability and structure.

  18. The new approach of polarimetric attenuation correction for improving radar quantitative precipitation estimation(QPE)

    Science.gov (United States)

    Gu, Ji-Young; Suk, Mi-Kyung; Nam, Kyung-Yeub; Ko, Jeong-Seok; Ryzhkov, Alexander

    2016-04-01

    To obtain high-quality radar quantitative precipitation estimation data, reliable radar calibration and efficient attenuation correction are very important. Because microwave radiation at shorter wavelength experiences strong attenuation in precipitation, accounting for this attenuation is the essential work at shorter wavelength radar. In this study, the performance of different attenuation/differential attenuation correction schemes at C band is tested for two strong rain events which occurred in central Oklahoma. And also, a new attenuation correction scheme (combination of self-consistency and hot-spot concept methodology) that separates relative contributions of strong convective cells and the rest of the storm to the path-integrated total and differential attenuation is among the algorithms explored. A quantitative use of weather radar measurement such as rainfall estimation relies on the reliable attenuation correction. We examined the impact of attenuation correction on estimates of rainfall in heavy rain events by using cross-checking with S-band radar measurements which are much less affected by attenuation and compared the storm rain totals obtained from the corrected Z and KDP and rain gages in these cases. This new approach can be utilized at shorter wavelength radars efficiently. Therefore, it is very useful to Weather Radar Center of Korea Meteorological Administration preparing X-band research dual Pol radar network.

  19. Resolving SSM/I-Ship Radar Rainfall Discrepancies from AIP-3

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The third algorithm intercomparison project (AIP-3) involved rain estimates from more than 50satellite rainfall algorithms and ground radar measurements within the Intensive Flux Array (IFA) over the equatorial western Pacific warm pool region during the Tropical Ocean Global Atmosphere coupled Ocean-Atmosphere Response Experiment (TOGA COARE). Early results indicated that there was a systematic bias between rainrates from satellite passive microwave and ground radar measurements. The mean rainrate from radar measurements is about 50% underestimated compared to that from passive microwave-based retrieval algorithms. This paper is designed to analyze rain patterns from the Florida State University rain retrieval algorithm and radar measurements to understand physically the rain discrepancies. Results show that there is a clear range-dependent bias associated with the radar measurements.However, this range-dependent systematical bias is almost eliminated with the corrected radar rainrates.Results suggest that the effects from radar attenuation correction, calibration and beam filling are the major sources of rain discrepancies. This study demonstrates that rain retrievals based on satellite measurements from passive microwave radiometers such as the Special Sensor of Microwave Imager (SSM/I)are reliable, while rain estimates from ground radar measurements are correctable.

  20. 46 CFR 130.310 - Radar.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Radar. 130.310 Section 130.310 Shipping COAST GUARD... EQUIPMENT AND SYSTEMS Navigational Equipment § 130.310 Radar. Each vessel of 100 or more gross tons must be fitted with a general marine radar in the pilothouse....

  1. Microwave Doppler radar in unobtrusive health monitoring

    International Nuclear Information System (INIS)

    This article frames the use of microwave Doppler radar in the context of ubiquitous, non-obstructive health monitoring. The use of a 24GHz CW (continuous wave) Doppler radar based on a commercial off-the-shelf transceiver for remote sensing of heart rate and respiration rate based on the acquisition and processing of the signals delivered by the radar is briefly presented

  2. 46 CFR 167.40-40 - Radar.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Radar. 167.40-40 Section 167.40-40 Shipping COAST GUARD... Requirements § 167.40-40 Radar. All mechanically propelled vessels of 1,600 gross tons and over in ocean or coastwise service must be fitted with a marine radar system for surface navigation. Facilities for...

  3. Fundamental aspects of netted radar performance

    OpenAIRE

    Teng, Y

    2010-01-01

    Netted radar employs several spatially distributed transmitters and receivers for information retrieval. This system topology offers many advantages over traditional monostatic and bistatic systems which use a single transmitter and a single receiver. For example, it provides better utilization of reflected energy, more flexible system arrangement and enhanced information retrieval capability. Therefore, the netted radar system is of emerging interests among radar researchers. ...

  4. 46 CFR 108.717 - Radar.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Radar. 108.717 Section 108.717 Shipping COAST GUARD... Miscellaneous Equipment § 108.717 Radar. Each self-propelled unit of 1,600 gross tons and over in ocean or coastwise service must have— (a) A marine radar system for surface navigation; and (b) Facilities on...

  5. Efficient Ways to Learn Weather Radar Polarimetry

    Science.gov (United States)

    Cao, Qing; Yeary, M. B.; Zhang, Guifu

    2012-01-01

    The U.S. weather radar network is currently being upgraded with dual-polarization capability. Weather radar polarimetry is an interdisciplinary area of engineering and meteorology. This paper presents efficient ways to learn weather radar polarimetry through several basic and practical topics. These topics include: 1) hydrometeor scattering model…

  6. Slotted waveguide antennas for practical radar systems

    OpenAIRE

    Sekretarov, S. S.; Vavriv, D. M.

    2009-01-01

    This article summarizes recent results on the development, fabrication, and application of slotted waveguide antenna systems for practical radar systems, including Ka-band helicopter collision avoidance and weather radar, Ku-band surveillance and tracking radar, and X-band airborne SAR system. The corresponding design solutions, antenna characteristics, and test results are presented and discussed.

  7. Jet stream related observations by MST radars

    Science.gov (United States)

    Gage, K. S.

    1983-01-01

    An overview of the jet stream and its observation by MST radar is presented. The climatology and synoptic and mesoscale structure of jet streams is briefly reviewed. MST radar observations of jet stream winds, and associated waves and turbulence are then considered. The possibility of using a network of ST radars to track jet stream winds in near real time is explored.

  8. Principles of modern radar advanced techniques

    CERN Document Server

    Melvin, William

    2012-01-01

    Principles of Modern Radar: Advanced Techniques is a professional reference for practicing engineers that provides a stepping stone to advanced practice with in-depth discussions of the most commonly used advanced techniques for radar design. It will also serve advanced radar academic and training courses with a complete set of problems for students as well as solutions for instructors.

  9. Fully polarimetric analysis of weather radar signatures

    OpenAIRE

    Galletti, Michele; Bebbington, David; Chandra, Madhukar; Börner, Thomas

    2008-01-01

    In this work the concept of depolarization response, namely the degree of polarization as a function of transmit polarization state, is investigated. Application examples are shown in the field of radar meteorology, namely for hydrometeor identification with fully polarimetric weather radar signatures. Data are from POLDIRAD, DLR research weather radar.

  10. Nonlinearity correction and dispersion analysis in FMCW laser radar

    Science.gov (United States)

    Zhao, Hao; Liu, Bingguo; Liu, Guodong; Chen, Fengdong; Zhuang, Zhitao; Yu, Yahui; Gan, Yu

    2014-12-01

    Frequency Modulated Continuous Wave laser radar is one of the most important ways to measure the large-size targets , combining the advantages of laser with conventional FMCW radar. Dispersion compensation and non-linear calibration are two key aspects in FMCW laser radar measurement. The paper studies the method of frequency-sampling to correct the Nonlinearity and analyzes the importance of dispersion compensation. We set up experimental verification platform, choose 1550nm band continuously tunable external cavity infrared laser as the light source, use all-fiber optical device structures, choose balanced detectors as photoelectric conversion, and finally acquire data with high speed PCI-E data acquisition card, write a measurement software with Labview. We measured the gage block 1 meter away. The experiment results show that the frequency sampling method correct the Nonlinearity well and there is a significant impact on the accuracy because of the fiber dispersion, dispersion must be compensated to obtain high accuracy. The experiment lays the foundation for further research on FMCW Laser radar.

  11. Space Radar Image of Oberpfaffenhofen, Germany

    Science.gov (United States)

    1999-01-01

    This is a false-color, three-frequency image of the Oberpfaffenhofen supersite, southwest of Munich in southern Germany, which shows the differences in what the three radar bands can see on the ground. The image covers a 27- by 36-kilometer (17- by 22-mile) area. The center of the site is 48.09 degrees north and 11.29 degrees east. The image was acquired by the Spaceborne Imaging Radar C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) onboard space shuttle Endeavour on April 13, 1994, just after a heavy storm which covered the all area with 20 centimeters (8 inches) of snow. The dark area in the center of the image is Lake Ammersee. The two smaller lakes above the Ammersee are the Worthsee and the Pilsensee. On the right of the image is the tip of the Starnbergersee. The outskirt of the city of Munich can be seen at the top of the image. The Oberpfaffenhofen supersite is the major test site for X-SAR calibration and scientific experiments such as ecology, hydrology and geology. This color composite image is a three-frequency overlay. L-band total power was assigned red, the C-band total power is shown in green and the X-band VV polarization appears blue. The colors on the image stress the differences between the L-band, C-band and X-band images. If the three frequencies were seeing the same thing, the image will appear in black and white. For example, the blue areas corresponds to area for which the X-band backscatter is relatively higher than the backscatter at L-and C-band; this behavior is characteristic of clear cuts or shorter vegetation. Similarly, the forested areas have a reddish tint. Finally, the green areas seen at the southern tip of both the Ammersee and the Pilsensee lakes indicate a marshy area. Spaceborne Imaging Radar-C and X-Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR

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

    Directory of Open Access Journals (Sweden)

    Arutyunyan Anna

    2012-08-01

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

  13. SMAP Radar Processing and Calibration

    Science.gov (United States)

    West, R.; Jaruwatanadilok, S.; Kwoun, O.; Chaubell, M.

    2013-01-01

    The Soil Moisture Active Passive (SMAP) mission is part of the NASA space-based Earth observation program, and consists of an L-band radar and radiometer scheduled for launch into sun synchronous orbit in late 2014. A joint effort of the Jet Propulsion Laboratory (JPL) and the Goddard Space Flight Center (GSFC), the SMAP mission draws heavily on the design and risk reduction heritage of the Hydrosphere State (Hydros) mission [1], [2]. The SMAP science and applications objectives are to: 1) understand processes that link the terrestrial water, energy and carbon cycles, 2) estimate global water and energy fluxes at the land surface, 3) quantify net carbon flux in boreal landscapes, 4) enhance weather and climate forecast skill, and 5) develop improved flood prediction and drought monitoring capability. To meet these science objectives, SMAP ground processing will combine the attributes of the radar and radiometer observations (in terms of their spatial resolution and sensitivity to soil moisture, surface roughness, and vegetation) to estimate soil moisture with 4% volumetric accuracy at a resolution of 10 km, and freeze-thaw state at a resolution of 1-3 km. Model sensitivities translate the soil moisture accuracy to a radar backscatter accuracy of 1 dB (1 sigma) at 3 km resolution and a brightness temperature accuracy of 1.3 K at 40 km resolution. This paper will describe the level 1 radar processing and calibration challenges and the choices made so far for the algorithms and software implementation.

  14. Radar monitoring of oil pollution

    Science.gov (United States)

    Guinard, N. W.

    1970-01-01

    Radar is currently used for detecting and monitoring oil slicks on the sea surface. The four-frequency radar system is used to acquire synthetic aperature imagery of the sea surface on which the oil slicks appear as a nonreflecting area on the surface surrounded by the usual sea return. The value of this technique was demonstrated, when the four-frequency radar system was used to image the oil spill of tanker which has wrecked. Imagery was acquired on both linear polarization (horizontal, vertical) for frequencies of 428, 1228, and 8910 megahertz. Vertical returns strongly indicated the presence of oil while horizontal returns failed to detect the slicks. Such a result is characteristic of the return from the sea and cannot presently be interpreted as characteristics of oil spills. Because an airborne imaging radar is capable of providing a wide-swath coverage under almost all weather conditions, it offers promise in the development of a pollution-monitoring system that can provide a coastal watch for oil slicks.

  15. Synthetic aperture radar capabilities in development

    Energy Technology Data Exchange (ETDEWEB)

    Miller, M. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    The Imaging and Detection Program (IDP) within the Laser Program is currently developing an X-band Synthetic Aperture Radar (SAR) to support the Joint US/UK Radar Ocean Imaging Program. The radar system will be mounted in the program`s Airborne Experimental Test-Bed (AETB), where the initial mission is to image ocean surfaces and better understand the physics of low grazing angle backscatter. The Synthetic Aperture Radar presentation will discuss its overall functionality and a brief discussion on the AETB`s capabilities. Vital subsystems including radar, computer, navigation, antenna stabilization, and SAR focusing algorithms will be examined in more detail.

  16. Research relative to weather radar measurement techniques

    Science.gov (United States)

    Smith, Paul L.

    1992-01-01

    Research relative to weather radar measurement techniques, which involves some investigations related to measurement techniques applicable to meteorological radar systems in Thailand, is reported. A major part of the activity was devoted to instruction and discussion with Thai radar engineers, technicians, and meteorologists concerning the basic principles of radar meteorology and applications to specific problems, including measurement of rainfall and detection of wind shear/microburst hazards. Weather radar calibration techniques were also considered during this project. Most of the activity took place during two visits to Thailand, in December 1990 and February 1992.

  17. Mars Radar Opens a Planet's Third Dimension

    Science.gov (United States)

    2008-01-01

    Radar sounder instruments orbiting Mars have looked beneath the Martian surface and opened up the third dimension for planetary exploration. The technique's success is prompting scientists to think of all the other places in the Solar System where they would like to use radar sounders. The first radar sounder at Mars was the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on the European Space Agency's Mars Express Orbiter. It has been joined by the complementary Shallow Subsurface Radar (SHARAD), operating at a different wavelength aboard NASA's Mars Reconnaissance Orbiter. The data in this animation are from SHARAD.

  18. Radar Image of Galapagos Island

    Science.gov (United States)

    1994-01-01

    This is an image showing part of Isla Isabella in the western Galapagos Islands. It was taken by the L-band radar in HH polarization from the Spaceborne Imaging Radar C/X-Band Synthetic Aperture Radar on the 40th orbit of the space shuttle Endeavour. The image is centered at about 0.5 degree south latitude and 91 degrees west longitude and covers an area of 75 by 60 kilometers (47 by 37 miles). The radar incidence angle at the center of the image is about 20 degrees.The western Galapagos Islands, which lie about 1,200 kilometers (750 miles) west of Ecuador in the eastern Pacific, have six active volcanoes similar to the volcanoes found in Hawaii. Since the time of Charles Darwin's visit to the area in 1835, there have been over 60 recorded eruptions of these volcanoes. This SIR-C/X-SAR image of Alcedo and Sierra Negra volcanoes shows the rougher lava flows as bright features, while ash deposits and smooth pahoehoe lava flows appear dark. A small portion of Isla Fernandina is visible in the extreme upper left corner of the image.The Galapagos Islands are one of the SIR-C/X-SAR supersites and data of this area will be taken several times during the flight to allow scientists to conduct topographic change studies and to search for different lava flow types, ash deposits and fault lines.Spaceborne Imaging Radar-C and X-Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by

  19. Enhanced Weather Radar (EWxR) System

    Science.gov (United States)

    Kronfeld, Kevin M. (Technical Monitor)

    2003-01-01

    An airborne weather radar system, the Enhanced Weather Radar (EWxR), with enhanced on-board weather radar data processing was developed and tested. The system features additional weather data that is uplinked from ground-based sources, specialized data processing, and limited automatic radar control to search for hazardous weather. National Weather Service (NWS) ground-based Next Generation Radar (NEXRAD) information is used by the EWxR system to augment the on-board weather radar information. The system will simultaneously display NEXRAD and on-board weather radar information in a split-view format. The on-board weather radar includes an automated or hands-free storm-finding feature that optimizes the radar returns by automatically adjusting the tilt and range settings for the current altitude above the terrain and searches for storm cells near the atmospheric 0-degree isotherm. A rule-based decision aid was developed to automatically characterize cells as hazardous, possibly-hazardous, or non-hazardous based upon attributes of that cell. Cell attributes are determined based on data from the on-board radar and from ground-based radars. A flight path impact prediction algorithm was developed to help pilots to avoid hazardous weather along their flight plan and their mission. During development the system was tested on the NASA B757 aircraft and final tests were conducted on the Rockwell Collins Sabreliner.

  20. All-optical bandwidth-tailorable radar

    CERN Document Server

    Zou, Weiwen; Long, Xin; Zhang, Siteng; Cui, Yuanjun; Chen, Jianping

    2015-01-01

    Radar has been widely used in military, security, and rescue. Metamaterial cloak is employed in stealth targets to evade radar detection. Hence modern radar should be reconfigurable at multi-bands for detecting stealth targets, which might be realized based on microwave photonics. Here, we demonstrate an all-optical bandwidth-tailorable radar architecture. It is a coherent system utilizing one mode-locked laser for both signal generation and reception. Heterodyning of two individually filtered optical pulses that are pre-chirped via wavelength-to-time mapping generates wideband linearly-chirped radar signal. The working bands can be flexibly tailored with desired bandwidth at user-preferred carrier frequency. After modulated onto the pre-chirped optical pulse, radar echoes are time-stretched and frequency-compressed by several times. The digitization becomes much easier without loss of detection ability. We believe that the demonstration can innovate the radar's architecture with ultra-high range resolution.