Ingestion of GNSS-derived clock parameters into DORIS data analysis

DORIS data processing is sensitive to the short-term clock variations, but the onboard clock corrections can be obtained from DORIS pseudoranges alone only as a polynomial model covering a couple of days. The Sentinel -3A and -3B satellites are the very first ones where the DORIS and the GNSS equipment are running on the same onboard oscillator. This offers the unique opportunity to synchronize the onboard clocks epoch-wise using GNSS and thus to measure clock behavior in detail and to make use of the short-term clock behavior in the DORIS data analysis. A similar approach can be applied also for Sentinel-6A on Jason orbit.

GPS-derived epoch-wise clock corrections are computed for the ultra-stable oscillator (USO) and introduced as fixed into the DORIS data processing making DORIS processing capable of considering the short-term variations of the satellite clock. This approach is very promising for studying the South Atlantic Anomaly (SAA) effect. In addition, the tandem phase of the satellite pairs Sentinel-3A and 3B (130 days) and Sentinel -6A and Jason -3 (~330 days) offer additional opportunities to perform closure measurements using same beacons observed synchronously by both satellites.

This poster will visually illustrate these concepts and techniques along with the results of Sentinel -6 with integrated GNSS clocks, the mapping of the SAA effect, the tandem phase analysis results and the near future plans and benefits of GNSS-DORIS combination for precise orbit determination.