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Donald Anderson - One of the best experts on this subject based on the ideXlab platform.
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The Galileo Solid-State Imaging experiment
Space Science Reviews, 1992Co-Authors: Michael J. S. Belton, Kenneth P. Klaasen, Maurice C. Clary, James L. Anderson, Clifford D. Anger, Michael H. Carr, Clark R. Chapman, Merton E. Davies, Ronald Greeley, Donald AndersonAbstract:The Solid State Imaging (SSI) experiment on the Galileo Orbiter spacecraft utilizes a high-resolution (1500 mm focal length) television camera with an 800 × 800 pixel virtual-phase, charge-coupled detector. It is designed to return images of Jupiter and its satellites that are characterized by a combination of sensitivity levels, spatial resolution, geometric fiedelity, and spectral range unmatched by imaging data obtained previously. The spectral range extends from approximately 375 to 1100 nm and only in the near ultra-violet region (∼ 350 nm) is the spectral coverage reduced from previous missions. The camera is approximately 100 times more sensitive than those used in the Voyager mission, and, because of the nature of the satellite encounters, will produce images with approximately 100 times the ground resolution (i.e., ∼ 50 m lp^-1) on the Galilean satellites. We describe aspects of the detector including its sensitivity to energetic particle radiation and how the requirements for a large full-well capacity and long-term stability in operating voltages led to the choice of the virtual phase chip. The F /8.5 camera system can reach point sources of V (mag) ∼ 11 with S/N ∼ 10 and extended sources with surface brightness as low as 20 kR in its highest gain state and longest exposure mode. We describe the performance of the system as determined by ground calibration and the improvements that have been made to the telescope (same basic catadioptric design that was used in Mariner 10 and the Voyager high-resolution cameras) to reduce the scattered light reaching the detector. The images are linearly digitized 8-bits deep and, after flat-fielding, are cosmetically clean. Information ‘preserving’ and ‘non-preserving’ on-board data compression capabilities are outlined. A special “summation” mode, designed for use deep in the Jovian radiation belts, near Io, is also described. The detector is ‘preflashed’ before each exposure to ensure the photometric linearity. The dynamic range is spread over 3 gain states and an exposure range from 4.17 ms to 51.2 s. A low-level of radial, third-order, geometric distortion has been measured in the raw images that is entirely due to the optical design. The distortion is of the pincushion type and amounts to about 1.2 pixels in the corners of the images. It is expected to be very stable. We discuss the measurement objectives of the SSI experiment in the Jupiter system and emphasize their relationships to those of other experiments in the Galileo Project. We outline objectives for Jupiter atmospheric science, noting the relationship of SSI data to that to be returned by experiments on the atmospheric entry Probe. We also outline SSI objectives for satellite surfaces, ring structure, and ‘darkside’ (e.g., aurorae, lightning, etc.) experiments. Proposed cruise measurement objectives that relate to encounters at Venus, Moon, Earth, Gaspra, and, possibly, Ida are also briefly outlined. The article concludes with a description of a ‘fully distributed’ data analysis system (HIIPS) that SSI team members intend to use at their home institutions. We also list the nature of systematic data products that will become available to the scientific community. Finally, we append a short ‘historical’ note outlining the responsibilities and roles of institutions and individuals that have been involved in the 14 year development of the SSI experiment so far.
Nasa - One of the best experts on this subject based on the ideXlab platform.
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Galileo Earth/Moon News Conference
2017Co-Authors: NasaAbstract:This NASA Kennedy Space Center (KSC) video release (Part 1 of 2) begins with a presentation given by William J. O'Neil (Galileo Project Manager) describing the status and position of the Galileo spacecraft 7 days prior to the Galileo Earth-2 flyby. Slides are presented including diagrams of the Galileo spacecraft trajectory, trajectory correction maneuvers, and the Venus and asteroid flybys. Torrence Johnson (Galileo Project Scientist) follows Mr. O'Neil with an explanation of the Earth/Moon science activities that will be undertaken during the second Galileo/Earth encounter. These activities include remote sensing, magnetospheric and plasma measurements, and images taken directly from Galileo of the Earth and Moon. Dr. Joseph Veverka (Galileo Imaging Team, Cornell University) then gives a brief presentation of the data collected by the first Galileo/Gaspra asteroid flyby. Images sampled from the 57 photographs taken of Gaspra are presented along with discussions of Gaspra's morphology, shape and size, and surface features. These presentations are followed by a question and answer period given for the benefit of scientific journalists whose subjects include overall Galileo spacecraft health, verification of the Gaspra images timeframe, and the condition of certain scientific spacecraft instruments. Part 2 of this video can be retrieved by using Report No. NONP-NASA-VT-2000001078.
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Galileo Press Conference from JPL
2017Co-Authors: NasaAbstract:This two-tape Jet Propulsion Laboratory (JPL) video production presents a Dec. 8, 1992 press conference held at JPL to discuss the final Galileo spacecraft encounter with Earth before beginning its journey to Jupiter. The main theme of the conference was centered on the significance of the 2nd and final Earth/Moon flyby as being the spacecraft's last planetary encounter in the solar system before reaching Jupiter, as well as final flight preparations prior to its final journey. Each person of the five member panel was introduced by Robert MacMillan (JPL Public Information Mgr.) before giving brief presentations including slides and viewgraphs covering their area of expertise regarding Galileo's current status and future plans. After the presentations, the media was given an opportunity to ask questions of the panel regarding the mission. Mr. Wesley Huntress (Dir. of Solar System Exploration (NASA)), William J. ONeill (Galileo Project Manager), Neal E. Ausman, Jr. (Galileo Mission Director), Dr. Torrence V. Johnson (Galileo Project Scientist) and Dr. Ronald Greeley (Member, Imaging Team, Colorado St. Univ.) made up the panel and discussed topics including: Galileo's interplanetary trajectory; Project status and performance review; instrument calibration activities; mission timelines; lunar observation and imaging; and general lunar science. Also included in the last three minutes of the video are simulations and images of the 2nd Galileo/Moon encounter.
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Galileo Mission Science Briefing
2017Co-Authors: NasaAbstract:The first of two tapes of the Galileo Mission Science press briefing is presented. The panel is moderated by George Diller from the Kennedy Space Center (KSC) Public Affairs Office. The participants are John Conway, the director of Payload and operations at Kennedy; Donald E. Williams, Commander of STS-43, the shuttle mission which will launch the Galileo mission; John Casani, the Deputy Assistant Director of Flight Projects at the Jet Propulsion Lab (JPL); Dick Spehalski, Galileo Project Manager at JPL; and Terrence Johnson, Galileo Project Scientist at JPL. The briefing begins with an announcement of the arrival of the Galileo Orbiter at KSC. The required steps prior to the launch are discussed. The mission trajectory and gravity assists from planetary and solar flybys are reviewed. Detailed designs of the orbiter are shown. The distance that Galileo will travel from the sun precludes the use of solar energy for heat. Therefore Radioisotope heater units are used to keep the equipment at operational temperature. A video of the arrival of the spacecraft at KSC and final tests and preparations is shown. Some of the many science goals of the mission are reviewed. Another video showing an overview of the Galileo mission is presented. During the question and answer period, the issue of the use of plutonium on the mission is broached, which engenders a review of the testing methods used to ensure the safety of the capsules containing the hazardous substance. This video has actual shots of the orbiter, as it is undergoing the final preparations and tests for the mission.
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Galileo Science Writers' Briefing
2017Co-Authors: NasaAbstract:This NASA Kennedy video production presents Part 1 of a press conference held at JPL on August 8, 1989. The briefing in its entirety covers the Galileo Project's mission design from launch to completion in 1997 and is moderated by JPL Public Information Mgr. Robert Macmillan. Part 1 of the 3 part video series includes presentations by Richard J. Spehalski (Galileo Project Manager) and Clayne M. Yeates (Acting Science Mission Design Manager). Mr. Spehalski's presentation includes actual footage of spacecraft preparations at Kennedy Space Center and slides of mission timelines. Dr. Yeates discusses the Galileo mission in chronological order and includes slides of the interplanetary trajectory, encounter geometry, propellant margins vs. launch date, and planned earth images.
G. Singh - One of the best experts on this subject based on the ideXlab platform.
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Galileo attitude determination: Experiences with a rotating star scanner
1991Co-Authors: L. Merken, G. SinghAbstract:The Galileo experience with a rotating star scanner is discussed in terms of problems encountered in flight, solutions implemented, and lessons learned. An overview of the Galileo Project and the attitude and articulation control subsystem is given and the star scanner hardware and relevant software algorithms are detailed. The star scanner is the sole source of inertial attitude reference for this spacecraft. Problem symptoms observed in flight are discussed in terms of effects on spacecraft performance and safety. Sources of thse problems include contributions from flight software idiosyncrasies and inadequate validation of the ground procedures used to identify target stars for use by the autonomous on-board star identification algorithm. Problem fixes (some already implemented and some only proposed) are discussed. A general conclusion is drawn regarding the inherent difficulty of performing simulation tests to validate algorithms which are highly sensitive to external inputs of statistically 'rare' events.
Erik Kroon - One of the best experts on this subject based on the ideXlab platform.
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Analysis of One Year of Zero-Baseline GPS Common-View Time Transfer and Direct Measurement Using Two Co-Located Clocks
2002Co-Authors: Gerrit De Jong, Erik KroonAbstract:Abstract : As part of the Galileo Project of Early Trials on Time Synchronization Techniques and Calibration Issues, the (near) zero-baseline GPS Common-View Time Transfer and Direct Measurement (using a Time Interval Counter) results between the time scales of two co-located clocks during 2001 were analyzed. This was done to identify the obtainable uncertainty levels with these techniques. The result of the analysis is presented. The baseline of the antennas of the two single-channel NBS-type GPS C-V receivers was 2 m, so multi-path influence is not excluded. The uncertainties from statistical origin "Type A evaluation" were determined by means of MDEV and TDEV. The uncertainties from other sources "Type B evaluation" were determined from calibrations. The TDEV of the GPS C-V result was less than 0.4 ns at averaging times > 1 day, and at shorter averaging times TDEV was about 1 ns.
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Analysis of One Year of GPS And Two-Way Time Transfer Results Between PTB, NPL, and VSL
2002Co-Authors: Gerrit De Jong, Erik KroonAbstract:As part of the Galileo Project of Early Trials on Time Synchronization Techniques and Calibration Issues, the GPS Common-View and Two-Way Satellite Frequency and Time Transfer (TWSTFT) results between the time scales of PTB, NPL, and VSL during 2001 were analyzed. This was done to identify the obtainable uncertainty levels with these techniques. These will be used for the future connection between the Galileo System Time (GST) and TAI and UTC. The results of the analysis are presented. The baseline of the stations is 400 to 900 km. The uncertainties from statistical origin (Type A evaluation) were determined by means of MDEV and TDEV. The uncertainties from other sources (Type B evaluation) were determined from calibration trips. The stabilities of the clocks dominate at averaging times > 5 days; at shorter averaging times TWSTFT shows better TDEV and MDEV. In the combined uncertainty, the contribution of the uncertainty in the calibration results dominates in both the GPS and TWSTFT results.
Gerrit De Jong - One of the best experts on this subject based on the ideXlab platform.
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Evaluation and Improvements of the Calibration of a TWSTFT Station Using SATSIM
2002Co-Authors: Gerrit De Jong, Roland Van BemmelenAbstract:Abstract : As part of the Galileo Project of Early Trials on Time Synchronization Techniques and Calibration Issues, the TWSTFT automated station delay calibration system using a special Satellite Simulator developed by VSL (SATSIM) at NMi-VSL was evaluated. This was done to verify the obtainable uncertainty level with this technique. The results of the evaluation will be presented. The stability of the station delay calibration has been reported earlier. The problem of reflection in cables used for GPS, Glonass, and TWSTFT has been reported earlier and may cause systematic errors and temperature sensitivity. The SATSIM system has now been checked for these reflections by revealing them by a new method with varying frequencies. Some imperfections were found and corrected; the final uncertainty results are now at the nanosecond level.
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Analysis of One Year of Zero-Baseline GPS Common-View Time Transfer and Direct Measurement Using Two Co-Located Clocks
2002Co-Authors: Gerrit De Jong, Erik KroonAbstract:Abstract : As part of the Galileo Project of Early Trials on Time Synchronization Techniques and Calibration Issues, the (near) zero-baseline GPS Common-View Time Transfer and Direct Measurement (using a Time Interval Counter) results between the time scales of two co-located clocks during 2001 were analyzed. This was done to identify the obtainable uncertainty levels with these techniques. The result of the analysis is presented. The baseline of the antennas of the two single-channel NBS-type GPS C-V receivers was 2 m, so multi-path influence is not excluded. The uncertainties from statistical origin "Type A evaluation" were determined by means of MDEV and TDEV. The uncertainties from other sources "Type B evaluation" were determined from calibrations. The TDEV of the GPS C-V result was less than 0.4 ns at averaging times > 1 day, and at shorter averaging times TDEV was about 1 ns.
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Analysis of One Year of GPS And Two-Way Time Transfer Results Between PTB, NPL, and VSL
2002Co-Authors: Gerrit De Jong, Erik KroonAbstract:As part of the Galileo Project of Early Trials on Time Synchronization Techniques and Calibration Issues, the GPS Common-View and Two-Way Satellite Frequency and Time Transfer (TWSTFT) results between the time scales of PTB, NPL, and VSL during 2001 were analyzed. This was done to identify the obtainable uncertainty levels with these techniques. These will be used for the future connection between the Galileo System Time (GST) and TAI and UTC. The results of the analysis are presented. The baseline of the stations is 400 to 900 km. The uncertainties from statistical origin (Type A evaluation) were determined by means of MDEV and TDEV. The uncertainties from other sources (Type B evaluation) were determined from calibration trips. The stabilities of the clocks dominate at averaging times > 5 days; at shorter averaging times TWSTFT shows better TDEV and MDEV. In the combined uncertainty, the contribution of the uncertainty in the calibration results dominates in both the GPS and TWSTFT results.
