Analyzing the Impact of GPS Clock as the modelled DORIS USO on Station Position Estimation for Sentinel Satellites

The DORIS Ultra-Stable Oscillators (USO) onboard Sentinel satellites are sensitive to the South Atlantic Anomaly (SAA) effect. While this sensitivity is not particularly significant for the precise orbit determination (POD) of the Sentinel-3A, Sentinel-3B, and Sentinel-6A satellites, it becomes crucial when estimating station positions. Previous studies have shown notable degradation in station position accuracy for stations located within the SAA region when using single-satellite solutions.
This study aims to evaluate the impact of using GPS clock as the modelled DORIS USO, provided by the CNES POD team, on station position estimation derived from single-satellite solutions of Sentinel-3A and Sentinel-6A. Single-satellite solutions were computed both with and without GPS clock corrections and were compared to the SARAL single-satellite solution, which serves as a reference due to its USO being minimally or not at all affected by the SAA. Our analysis investigates whether incorporating GPS clock corrections as a modeled DORIS USO can effectively mitigate the impact of the SAA on station position estimations in the affected regions.