Abstract's details
Assessment of the Impact of Using GPS Clocks as a Proxy for the DORIS Onboard USO and Ground-Based GPS Clocks at Co-Located Stations on POD and Station Position Estimation for Sentinel Satellites
Event: 2026 IDS Workshop
Session: Earth Rotation, Atmosphere, and Clock Products
Presentation type: Oral
The DORIS Ultra-Stable Oscillators (USOs) onboard Sentinel satellites are sensitive to the effects of the South Atlantic Anomaly (SAA). While this sensitivity has a limited impact on the precise orbit determination (POD) of the Sentinel-3A, Sentinel-3B, and Sentinel-6A satellites, it becomes critical for station position estimation. Previous studies have reported significant degradation in station position accuracy for stations located within the SAA region when single-satellite solutions are used.
The objective of this study is to address DORIS clock-related issues by exploiting clock co-locations both in space and on the ground. Sentinel satellites equipped with a GNSS (Global Navigation Satellite System) receiver share the same Ultra-Stable Oscillator (USO) as the DORIS system, offering the possibility to correct DORIS clock errors using clock information derived from GNSS observations. This study primarily focuses on evaluating the impact of using GPS clocks as the modelled DORIS USO, as provided by the CNES POD team, on POD, and in particular on station position estimation derived from single-satellite solutions for Sentinel-3A, Sentinel-3B, and Sentinel-6A. Single-satellite solutions were computed with and without GPS clock corrections and compared with the latest version of DPOD2020. The analysis investigates whether the use of GPS clock corrections as a proxy for the DORIS USO can mitigate the impact of the SAA on station position estimation in affected regions. The impact of these corrections on stations located outside the SAA region is also assessed.
In addition, the use of ground-based clock co-locations, such as those available at five stations of the GNSS REGINA network, provides highly accurate knowledge of the station frequency. This allows us to assess whether the estimation of the station frequency offset can be avoided, potentially leading to improved accuracy of the DORIS orbits and station position estimation.
key words: SAA, USO DORIS, Clock GPS, POD, DORIS solutions
presentation in person
Back to the list of abstractThe objective of this study is to address DORIS clock-related issues by exploiting clock co-locations both in space and on the ground. Sentinel satellites equipped with a GNSS (Global Navigation Satellite System) receiver share the same Ultra-Stable Oscillator (USO) as the DORIS system, offering the possibility to correct DORIS clock errors using clock information derived from GNSS observations. This study primarily focuses on evaluating the impact of using GPS clocks as the modelled DORIS USO, as provided by the CNES POD team, on POD, and in particular on station position estimation derived from single-satellite solutions for Sentinel-3A, Sentinel-3B, and Sentinel-6A. Single-satellite solutions were computed with and without GPS clock corrections and compared with the latest version of DPOD2020. The analysis investigates whether the use of GPS clock corrections as a proxy for the DORIS USO can mitigate the impact of the SAA on station position estimation in affected regions. The impact of these corrections on stations located outside the SAA region is also assessed.
In addition, the use of ground-based clock co-locations, such as those available at five stations of the GNSS REGINA network, provides highly accurate knowledge of the station frequency. This allows us to assess whether the estimation of the station frequency offset can be avoided, potentially leading to improved accuracy of the DORIS orbits and station position estimation.
key words: SAA, USO DORIS, Clock GPS, POD, DORIS solutions
presentation in person