Spaceborne GPS measurements are used at AIUB together with the final GPS orbit and clock products... more Spaceborne GPS measurements are used at AIUB together with the final GPS orbit and clock products of the CODE analysis center for kinematic and reduced-dynamic precise orbit determination
AIUB-CHAMP01S fact sheet The AIUB-CHAMP01S was, together with other gravity field models, validat... more AIUB-CHAMP01S fact sheet The AIUB-CHAMP01S was, together with other gravity field models, validated by Thomas Gruber from IAPG in Munich. From the terrestrial height data sets as well as from the gravity field models geoid heights and geoid slopes have been derived and compared. For further details concerning the method we refer to Gruber (2004). The external validation confirms the results of the internal validation and shows that the AIUB-CHAMP01S is one of the best gravity field models using only CHAMP data of one year (see comparison to the ITG-CHAMP01S). The results also show the strong impact of regularization (see ITG-CHAMP01E, which is regularized to theEGM96model). Table 2 also indicates the limitations of the terrestrial height data sets used for validation: For some terrestrial data sets the RMS error does not differ greatly when compared to very different gravity field models, e.g. models based on SLR,
Abstract. Kinematic positions of individual low Earth orbiting satellites equipped with spaceborn... more Abstract. Kinematic positions of individual low Earth orbiting satellites equipped with spaceborne GPS receivers have been used in the past to deter-mine the long wavelength static part of the Earth’s gravity field. In the near future GPS-derived rela-tive kinematic positions of present and upcoming for-mation flying satellites like COSMIC and SWARM could be used in addition to perform and improve the long wavelength static part of the gravity field also with non-dedicated satellites. Since space baselines between satellites can be determined more precisely from GPS than the individual positions, a correspond-ing improvement of the estimated gravity field co-efficients is commonly expected. We review and ex-tend the principles of gravity field determination from kinematic positions of single satellites and apply them to kinematic baseline data. Simulated as well as real data from the GRACE GPS receivers are used to evaluate our procedures and to assess the impact of different GPS ob...
Orbits from Global Navigation Satellite Systems (GNSS) are typically based on microwave observati... more Orbits from Global Navigation Satellite Systems (GNSS) are typically based on microwave observations. Satellite Laser Ranging (SLR) is therefore a fully independent technique to validate these orbits. All GLONASS, Galileo, BeiDou, and QZSS spacecraft carry retroreflectors and can thus be tracked by SLR. The two GPS satellites equipped with reflectors are meanwhile decommissioned. The Center for Orbit Determination in Europe (CODE) operationally computes SLR residuals w.r.t. CODE’s rapid and MGEX orbits and provides daily reports to the laser stations. At the same time, the residuals are used for internal orbit validation purposes.
1. Faculty of Science, Technology and Communication, University of Luxembourg, Luxembourg 2. Inst... more 1. Faculty of Science, Technology and Communication, University of Luxembourg, Luxembourg 2. Institute of Geodesy, University of Stuttgart, Germany 3. Lantmateriet, Sweden 4. Space Research Institute, Austrian Academy of Sciences, Austria 5. Astronomical Institute, University of Bern, Switzerland 6. Institute of Theoretical Geodesy and Satellite Geodesy, Graz University of Technology, Austria Sensitivity of GOCE to time-variable gravity
We derive gravity field parameters using a two step procedure: In a first step a kinematic trajec... more We derive gravity field parameters using a two step procedure: In a first step a kinematic trajectory of a LEO satellite is computed using the GPS data from the on-board receiver. In this step the orbits and clock corrections of the GPS satellites as well as the Earth orientation parameters are introduced as known. In the second step this kinematic orbit is represented by a gravitational force model and orbit parameters. Gravity field models based on kinematic positions of CHAMP and GRACE were generated by the AIUB using this approach. In order to ensure full model consistency the GPS satellite orbits and clock corrections, which have been used for the generation of the kinematic LEO trajectories, were taken from the CODE IGS analysis center, located at AIUB. In the recent years many improvements have taken place in the GNSS data processing, e.g., implementation of absolute antenna phase center modeling. These are good reasons to initiate a reprocessing of the GPS data to obtain sta...
Spaceborne GPS measurements are used at AIUB together with the final GPS orbit and clock products... more Spaceborne GPS measurements are used at AIUB together with the final GPS orbit and clock products of the CODE analysis center for kinematic and reduced-dynamic precise orbit determination
AIUB-CHAMP01S fact sheet The AIUB-CHAMP01S was, together with other gravity field models, validat... more AIUB-CHAMP01S fact sheet The AIUB-CHAMP01S was, together with other gravity field models, validated by Thomas Gruber from IAPG in Munich. From the terrestrial height data sets as well as from the gravity field models geoid heights and geoid slopes have been derived and compared. For further details concerning the method we refer to Gruber (2004). The external validation confirms the results of the internal validation and shows that the AIUB-CHAMP01S is one of the best gravity field models using only CHAMP data of one year (see comparison to the ITG-CHAMP01S). The results also show the strong impact of regularization (see ITG-CHAMP01E, which is regularized to theEGM96model). Table 2 also indicates the limitations of the terrestrial height data sets used for validation: For some terrestrial data sets the RMS error does not differ greatly when compared to very different gravity field models, e.g. models based on SLR,
Abstract. Kinematic positions of individual low Earth orbiting satellites equipped with spaceborn... more Abstract. Kinematic positions of individual low Earth orbiting satellites equipped with spaceborne GPS receivers have been used in the past to deter-mine the long wavelength static part of the Earth’s gravity field. In the near future GPS-derived rela-tive kinematic positions of present and upcoming for-mation flying satellites like COSMIC and SWARM could be used in addition to perform and improve the long wavelength static part of the gravity field also with non-dedicated satellites. Since space baselines between satellites can be determined more precisely from GPS than the individual positions, a correspond-ing improvement of the estimated gravity field co-efficients is commonly expected. We review and ex-tend the principles of gravity field determination from kinematic positions of single satellites and apply them to kinematic baseline data. Simulated as well as real data from the GRACE GPS receivers are used to evaluate our procedures and to assess the impact of different GPS ob...
Orbits from Global Navigation Satellite Systems (GNSS) are typically based on microwave observati... more Orbits from Global Navigation Satellite Systems (GNSS) are typically based on microwave observations. Satellite Laser Ranging (SLR) is therefore a fully independent technique to validate these orbits. All GLONASS, Galileo, BeiDou, and QZSS spacecraft carry retroreflectors and can thus be tracked by SLR. The two GPS satellites equipped with reflectors are meanwhile decommissioned. The Center for Orbit Determination in Europe (CODE) operationally computes SLR residuals w.r.t. CODE’s rapid and MGEX orbits and provides daily reports to the laser stations. At the same time, the residuals are used for internal orbit validation purposes.
1. Faculty of Science, Technology and Communication, University of Luxembourg, Luxembourg 2. Inst... more 1. Faculty of Science, Technology and Communication, University of Luxembourg, Luxembourg 2. Institute of Geodesy, University of Stuttgart, Germany 3. Lantmateriet, Sweden 4. Space Research Institute, Austrian Academy of Sciences, Austria 5. Astronomical Institute, University of Bern, Switzerland 6. Institute of Theoretical Geodesy and Satellite Geodesy, Graz University of Technology, Austria Sensitivity of GOCE to time-variable gravity
We derive gravity field parameters using a two step procedure: In a first step a kinematic trajec... more We derive gravity field parameters using a two step procedure: In a first step a kinematic trajectory of a LEO satellite is computed using the GPS data from the on-board receiver. In this step the orbits and clock corrections of the GPS satellites as well as the Earth orientation parameters are introduced as known. In the second step this kinematic orbit is represented by a gravitational force model and orbit parameters. Gravity field models based on kinematic positions of CHAMP and GRACE were generated by the AIUB using this approach. In order to ensure full model consistency the GPS satellite orbits and clock corrections, which have been used for the generation of the kinematic LEO trajectories, were taken from the CODE IGS analysis center, located at AIUB. In the recent years many improvements have taken place in the GNSS data processing, e.g., implementation of absolute antenna phase center modeling. These are good reasons to initiate a reprocessing of the GPS data to obtain sta...
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