Reprocessing of Copernicus Sentinel POD solutions with COST-G geopotential models

Abstract

The Copernicus Precise Orbit Determination (CPOD) Service generates routinely precise orbital products of Sentinel-1, -2, -3 and -6 for its operational use by ESA and EUMETSAT. The accuracy of these products depends on the quality of the inputs used, particularly the gravity field and the GNSS orbits and clocks. This abstract focusses on the impact of the gravity field using the COST-G geopotential models.Currently, the CPOD Service is using the EIGEN-GRGS-RL04 mean gravity field model, which dates back in 2019. In the framework of COST-G (Combination Service for Time-variable Gravity Fields) a new series of gravity fields is being generated quarterly by AIUB (Astronomical Institute, University of Bern), as a fit to a weighted combination of monthly gravity fields generated by different analysis centres. The monthly gravity fields models are generated based on GRACE-FO data, so they are capable of accurately catching up the recent changes in the gravity field. These models improve the operational orbit results significantly. Since these fitted signal models (FSM) only cover the GRACE-FO period they are not suitable for consistent reprocessing of entire mission times beyond 2018. In order to support such reprocessing activities an additional COST-G FSM has been generated covering the GRACE and GRACE-FO period. The use of the COST-G products has been proposed to substitute the current EIGEN-GRGS-RL04 mean gravity field model within the Copernicus Precise Orbit Determination (CPOD) Service. Based on limited reprocessing campaigns (from 2019 onwards) of Sentinel-3 A&B using both geopotentials (EIGEN and COST-G), it has shown that the COST-G FSMs represent improvements on the orbital accuracy and yields smaller dispersion of empirical accelerations.Thanks to the recent availability of a new full COST-G FSM covering the GRACE and GRACE-FO period, the present work will extend this analysis to the Sentinel-1, -2 and -6 missions as well, including the full mission (e.g., from 2014 in the case of Sentinel-1A), to confirm the potential benefits of COST-G FSMs.It is worth mentioning that this analysis will be performed with FocusPOD, a new GMV state-of-the-art POD SW.