Baseline lengths and geocentric radii have been determined from GPS data without the use of fiduc... more Baseline lengths and geocentric radii have been determined from GPS data without the use of fiducial sites. Data from the first GPS experiment for the IERS and Geodynamics (GIG '91) have been analyzed with a no-fiducial strategy. A baseline length daily repeatability of 2 mm + 4 pans per billion was obtained for baselines in the northern hemisphere. Comparison of baseline lengths from GPS and the global VLBI solution GLB659 (Caprette et al. 1990) show rms agreement of 2.1 pans per billion. The geocentric radius mean daily repeatability for all sites was 15 cm. Comparison of geocentric radii from GPS and SV5 (Murray et al. 1990) show rms agreement of 3.8 cm. Given n globally distributed stations, the n(n -1)/2 baseline lengths and n geocentric radii uniquely define a rigid closed polyhedron with a we!l-defined center of mass. Geodetic information can be obtained by examining the structure of the polyhedron and its change with time.
IEEE International Frequency Control Sympposium and PDA Exhibition Jointly with the 17th European Frequency and Time Forum, 2003. Proceedings of the 2003, 2003
Abstract The two GRACE (gravity recovery and climate experiment) spacecraft were launched into a ... more Abstract The two GRACE (gravity recovery and climate experiment) spacecraft were launched into a near polar circular orbit around the earth in March of 2002. The two spacecraft serve as test masses to measure the earth's gravitational field. Both spacecraft ...
... Sumita Nandi is presently a Senior Member of Technical Staff in the Orbiter and Radiometrics ... more ... Sumita Nandi is presently a Senior Member of Technical Staff in the Orbiter and Radiometrics Systems Group at JPL. ... Larry J. Romans received his Ph.D. in Theoretical Physics from the California Institute of Technology in 1985. ...
We present strategies and results for near real time precise orbit determination (POD) for the GL... more We present strategies and results for near real time precise orbit determination (POD) for the GLONASS constellation. Our approach is to perform GLONASS-only POD aided by GPS-derived estimates of tropospheric delay and ground station receiver clock, and additionally estimate a bias between GPS and GLONASS time for each receiver. We utilize data from approximately 30 IGS and JPL ground stations
Reducing the uncertainty in locating the phase centers on both GPS transmitter and receiver anten... more Reducing the uncertainty in locating the phase centers on both GPS transmitter and receiver antennas has emerged as an area of active research in the GPS geodetic community. We have used on-orbit data from the Jason-1 (2001-) and GRACE (2002-) missions to develop estimates of GPS satellite antenna phase-center variations (PCV). These missions offer a number of advantages for this
The GRACE team at the Jet Propulsion Laboratory have over the past few years adapted the MIRAGE s... more The GRACE team at the Jet Propulsion Laboratory have over the past few years adapted the MIRAGE software used for deep space tracking data analysis and determination of the gravity field of planetary bodies such as Mars, Venus, the Moon, and 433 Eros, for GRACE applications. We have used this software to produce Earth gravity fields of unprecedented quality from a combination of the first GRACE K/Ka-band intersatellite tracking, GPS, accelerometer, and star camera data. In this paper we will present the results of that gravity field analysis, including the parameterization used, the spectral content of the residuals, the calibrated covariance, and performance in external tests such as orbit fits and sea surface topography. In addition, since the software and parameterization are independent of that used at the University of Texas and GFZ Potsdam, it provides a type of verification of the fields, and we will discuss the results of the intercomparison of the available gravity solutions.
The Mw 7.7 Tocopilla, Chile earthquake occurred within the CANTO (Central ANdean Tectonic Observa... more The Mw 7.7 Tocopilla, Chile earthquake occurred within the CANTO (Central ANdean Tectonic Observatory) geodetic network, with ten stations recording at 5Hz. Because of the magnitude and proximity of the event, many of the stations recorded the dynamic as well as the static displacement from the earthquake. In order to provide the best time series for source modeling studies (see Minson et al, Fall AGU 2008), we have tested several high-rate analysis strategies. The high-rate solutions were analyzed in a baseline mode, fixing the position and clocks of a remote reference site, and estimating satellite clocks, tropospheric parameters, as well as the station position and clock of the non-stationary site. The station position was estimated at longer time intervals leading up to the onset of earthquake displacement (e.g., 10 minutes) to allow for a more robust position and troposphere estimate. During the earthquake, station positions were estimated at 5Hz. The station position estimates...
Treating the GRACE tandem mission as an orbiting fiducial laboratory, we have developed new estim... more Treating the GRACE tandem mission as an orbiting fiducial laboratory, we have developed new estimates of the phase and group-delay variations of the GPS transmitter antennas. Application of these antenna phase variation (APV) maps have shown great promise in reducing previously unexplained errors in our realization of GPS measurements from the TOPEX/POSEIDON (T/P; 1992--2005) and Jason-1 (2001--) missions. In particular, a 56 mm vertical offset in the solved-for position of the T/P receiver antenna is reduced to insignificance (less than 1 mm). For Jason-1, a spurious long-term (4-yr) drift in the daily antenna offset estimates is reduced from +3.7 to +0.1 mm/yr. Prior ground-based results, based on precise point positioning, also hint at the potential of the GRACE-based APV maps for scale determination, reducing the spurious scale rate by one half. In this paper, we report on the latest APV estimates from GRACE, and provide a further assessment of the impact of the APV maps on real...
The Jet Propulsion Laboratory (JPL) has a long history of processing global GPS data for various ... more The Jet Propulsion Laboratory (JPL) has a long history of processing global GPS data for various geodetic and orbit determination applications, and serves as an Analysis Center for the International GNSS Service. In this paper, we describe recent developments in the GPS data processing software system at JPL, GIPSY-OASIS, and the derived GPS data products. We detail the resulting improvements in accuracy of the primary products, namely the estimates of the precise GPS orbits and clocks, Earth orientation parameters, and zenith troposphere at the GPS sites, as well as the impact on various geodetic and orbit determination applications. We provide details of the changes to the models and capabilities of the GIPSY-OASIS software system, and describe modifications to the JPL products that are provided to the international community.
As one of the Analysis Centers for the International GNSS Service (IGS), the Jet Propulsion Labor... more As one of the Analysis Centers for the International GNSS Service (IGS), the Jet Propulsion Laboratory (JPL) is participating in the 2009 campaign to reprocess the historical time series of Global Positioning System (GPS) data. We present results from our reprocessed solutions by providing internal and external metrics on the accuracy of the orbit and clock solutions for the GPS constellation, as well as the observed variations in the terrestrial reference frame and Earth orientation parameters. We discuss various analyses that were used to define our overall reanalysis approach, emphasizing those aspects of our estimation strategy and force models for the GPS constellation that may differ from other IGS centers. In addition, we present results from some preliminary analyses that have been performed as a precursor for future reanalysis of the historical GPS data, such as the impact of recently available models for tidal variations in the Earth orientation parameters and alternative ...
2008 IEEE/ION Position, Location and Navigation Symposium, 2008
Abstract Each of the six COSMIC satellites carries one GPS receiver with two antennas for orbit d... more Abstract Each of the six COSMIC satellites carries one GPS receiver with two antennas for orbit determination (OD) and another two antennas for radio occultation. In this paper we describe the features of the GPS data associated with COSMIC satellite attitude. Method ...
ABSTRACT An estimated orbit error budget for the Jason-1 and Jason-2 GDR-D solutions is construct... more ABSTRACT An estimated orbit error budget for the Jason-1 and Jason-2 GDR-D solutions is constructed, using several measures of orbit error. The focus is on the long-term stability of the orbit time series for mean sea level applications on a regional scale. We discuss various issues related to the assessment of radial orbit error trends; in particular this study reviews orbit errors dependent on the tracking technique, with an aim to monitoring the long-term stability of all available tracking systems operating on Jason-1 and Jason-2 (GPS, DORIS, SLR). The reference frame accuracy and its effect on Jason orbit is assessed. We also examine the impact of analysis method on the inference of Geographically Correlated Errors as well as the significance of estimated radial orbit error trends versus the time span of the analysis. Thus a long-term error budget of the 10-year Jason-1 and Envisat GDR-D orbit time series is provided for two time scales: interannual and decadal. As the temporal variations of the geopotential remain one of the primary limitations in the Precision Orbit Determination modeling, the overall accuracy of the Jason-1 and Jason-2 GDR-D solutions is evaluated through comparison with external orbits based on different time-variable gravity models. This contribution is limited to an East–West “order-1” pattern at the 2 mm/y level (secular) and 4 mm level (seasonal), over the Jason-2 lifetime. The possibility of achieving sub-mm/y radial orbit stability over interannual and decadal periods at regional scales and the challenge of evaluating such an improvement using in situ independent data is discussed.
Baseline lengths and geocentric radii have been determined from GPS data without the use of fiduc... more Baseline lengths and geocentric radii have been determined from GPS data without the use of fiducial sites. Data from the first GPS experiment for the IERS and Geodynamics (GIG '91) have been analyzed with a no-fiducial strategy. A baseline length daily repeatability of 2 mm + 4 pans per billion was obtained for baselines in the northern hemisphere. Comparison of baseline lengths from GPS and the global VLBI solution GLB659 (Caprette et al. 1990) show rms agreement of 2.1 pans per billion. The geocentric radius mean daily repeatability for all sites was 15 cm. Comparison of geocentric radii from GPS and SV5 (Murray et al. 1990) show rms agreement of 3.8 cm. Given n globally distributed stations, the n(n -1)/2 baseline lengths and n geocentric radii uniquely define a rigid closed polyhedron with a we!l-defined center of mass. Geodetic information can be obtained by examining the structure of the polyhedron and its change with time.
IEEE International Frequency Control Sympposium and PDA Exhibition Jointly with the 17th European Frequency and Time Forum, 2003. Proceedings of the 2003, 2003
Abstract The two GRACE (gravity recovery and climate experiment) spacecraft were launched into a ... more Abstract The two GRACE (gravity recovery and climate experiment) spacecraft were launched into a near polar circular orbit around the earth in March of 2002. The two spacecraft serve as test masses to measure the earth's gravitational field. Both spacecraft ...
... Sumita Nandi is presently a Senior Member of Technical Staff in the Orbiter and Radiometrics ... more ... Sumita Nandi is presently a Senior Member of Technical Staff in the Orbiter and Radiometrics Systems Group at JPL. ... Larry J. Romans received his Ph.D. in Theoretical Physics from the California Institute of Technology in 1985. ...
We present strategies and results for near real time precise orbit determination (POD) for the GL... more We present strategies and results for near real time precise orbit determination (POD) for the GLONASS constellation. Our approach is to perform GLONASS-only POD aided by GPS-derived estimates of tropospheric delay and ground station receiver clock, and additionally estimate a bias between GPS and GLONASS time for each receiver. We utilize data from approximately 30 IGS and JPL ground stations
Reducing the uncertainty in locating the phase centers on both GPS transmitter and receiver anten... more Reducing the uncertainty in locating the phase centers on both GPS transmitter and receiver antennas has emerged as an area of active research in the GPS geodetic community. We have used on-orbit data from the Jason-1 (2001-) and GRACE (2002-) missions to develop estimates of GPS satellite antenna phase-center variations (PCV). These missions offer a number of advantages for this
The GRACE team at the Jet Propulsion Laboratory have over the past few years adapted the MIRAGE s... more The GRACE team at the Jet Propulsion Laboratory have over the past few years adapted the MIRAGE software used for deep space tracking data analysis and determination of the gravity field of planetary bodies such as Mars, Venus, the Moon, and 433 Eros, for GRACE applications. We have used this software to produce Earth gravity fields of unprecedented quality from a combination of the first GRACE K/Ka-band intersatellite tracking, GPS, accelerometer, and star camera data. In this paper we will present the results of that gravity field analysis, including the parameterization used, the spectral content of the residuals, the calibrated covariance, and performance in external tests such as orbit fits and sea surface topography. In addition, since the software and parameterization are independent of that used at the University of Texas and GFZ Potsdam, it provides a type of verification of the fields, and we will discuss the results of the intercomparison of the available gravity solutions.
The Mw 7.7 Tocopilla, Chile earthquake occurred within the CANTO (Central ANdean Tectonic Observa... more The Mw 7.7 Tocopilla, Chile earthquake occurred within the CANTO (Central ANdean Tectonic Observatory) geodetic network, with ten stations recording at 5Hz. Because of the magnitude and proximity of the event, many of the stations recorded the dynamic as well as the static displacement from the earthquake. In order to provide the best time series for source modeling studies (see Minson et al, Fall AGU 2008), we have tested several high-rate analysis strategies. The high-rate solutions were analyzed in a baseline mode, fixing the position and clocks of a remote reference site, and estimating satellite clocks, tropospheric parameters, as well as the station position and clock of the non-stationary site. The station position was estimated at longer time intervals leading up to the onset of earthquake displacement (e.g., 10 minutes) to allow for a more robust position and troposphere estimate. During the earthquake, station positions were estimated at 5Hz. The station position estimates...
Treating the GRACE tandem mission as an orbiting fiducial laboratory, we have developed new estim... more Treating the GRACE tandem mission as an orbiting fiducial laboratory, we have developed new estimates of the phase and group-delay variations of the GPS transmitter antennas. Application of these antenna phase variation (APV) maps have shown great promise in reducing previously unexplained errors in our realization of GPS measurements from the TOPEX/POSEIDON (T/P; 1992--2005) and Jason-1 (2001--) missions. In particular, a 56 mm vertical offset in the solved-for position of the T/P receiver antenna is reduced to insignificance (less than 1 mm). For Jason-1, a spurious long-term (4-yr) drift in the daily antenna offset estimates is reduced from +3.7 to +0.1 mm/yr. Prior ground-based results, based on precise point positioning, also hint at the potential of the GRACE-based APV maps for scale determination, reducing the spurious scale rate by one half. In this paper, we report on the latest APV estimates from GRACE, and provide a further assessment of the impact of the APV maps on real...
The Jet Propulsion Laboratory (JPL) has a long history of processing global GPS data for various ... more The Jet Propulsion Laboratory (JPL) has a long history of processing global GPS data for various geodetic and orbit determination applications, and serves as an Analysis Center for the International GNSS Service. In this paper, we describe recent developments in the GPS data processing software system at JPL, GIPSY-OASIS, and the derived GPS data products. We detail the resulting improvements in accuracy of the primary products, namely the estimates of the precise GPS orbits and clocks, Earth orientation parameters, and zenith troposphere at the GPS sites, as well as the impact on various geodetic and orbit determination applications. We provide details of the changes to the models and capabilities of the GIPSY-OASIS software system, and describe modifications to the JPL products that are provided to the international community.
As one of the Analysis Centers for the International GNSS Service (IGS), the Jet Propulsion Labor... more As one of the Analysis Centers for the International GNSS Service (IGS), the Jet Propulsion Laboratory (JPL) is participating in the 2009 campaign to reprocess the historical time series of Global Positioning System (GPS) data. We present results from our reprocessed solutions by providing internal and external metrics on the accuracy of the orbit and clock solutions for the GPS constellation, as well as the observed variations in the terrestrial reference frame and Earth orientation parameters. We discuss various analyses that were used to define our overall reanalysis approach, emphasizing those aspects of our estimation strategy and force models for the GPS constellation that may differ from other IGS centers. In addition, we present results from some preliminary analyses that have been performed as a precursor for future reanalysis of the historical GPS data, such as the impact of recently available models for tidal variations in the Earth orientation parameters and alternative ...
2008 IEEE/ION Position, Location and Navigation Symposium, 2008
Abstract Each of the six COSMIC satellites carries one GPS receiver with two antennas for orbit d... more Abstract Each of the six COSMIC satellites carries one GPS receiver with two antennas for orbit determination (OD) and another two antennas for radio occultation. In this paper we describe the features of the GPS data associated with COSMIC satellite attitude. Method ...
ABSTRACT An estimated orbit error budget for the Jason-1 and Jason-2 GDR-D solutions is construct... more ABSTRACT An estimated orbit error budget for the Jason-1 and Jason-2 GDR-D solutions is constructed, using several measures of orbit error. The focus is on the long-term stability of the orbit time series for mean sea level applications on a regional scale. We discuss various issues related to the assessment of radial orbit error trends; in particular this study reviews orbit errors dependent on the tracking technique, with an aim to monitoring the long-term stability of all available tracking systems operating on Jason-1 and Jason-2 (GPS, DORIS, SLR). The reference frame accuracy and its effect on Jason orbit is assessed. We also examine the impact of analysis method on the inference of Geographically Correlated Errors as well as the significance of estimated radial orbit error trends versus the time span of the analysis. Thus a long-term error budget of the 10-year Jason-1 and Envisat GDR-D orbit time series is provided for two time scales: interannual and decadal. As the temporal variations of the geopotential remain one of the primary limitations in the Precision Orbit Determination modeling, the overall accuracy of the Jason-1 and Jason-2 GDR-D solutions is evaluated through comparison with external orbits based on different time-variable gravity models. This contribution is limited to an East–West “order-1” pattern at the 2 mm/y level (secular) and 4 mm level (seasonal), over the Jason-2 lifetime. The possibility of achieving sub-mm/y radial orbit stability over interannual and decadal periods at regional scales and the challenge of evaluating such an improvement using in situ independent data is discussed.
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Papers by W. Bertiger