Filler Vratislav (Geodetic Observatory Pecny, VUGTK, Czech republic); Gunasekaran Barath Krsna (Technical University of Munich, Germany); Urs Hugentobler (Technical University of Munich, Germany); Bingbing Duan (Technical University of Munich, Germany)

This study investigates the introduction of GNSS-derived clocks into DORIS data processing for the satellites Sentinel-3A, Sentinel-3B, and Sentinel-6A. The work focuses on the integration of external clock products and the application of clock data smoothing, and evaluates their impact on the estimation of geodetic parameters. The motivation for this study stems from the need to enhance the reliability of DORIS-derived geodetic products, particularly in regions affected by systematic perturbations such as the South Atlantic Anomaly (SAA), which can influence broader solution stability.
Particular attention is given to the mitigation of the SAA effect, which is known to degrade the quality of DORIS observations and associated clock estimates through systematic errors caused by the frequency deviation of the onboard oscillator. By incorporating GNSS-derived clocks, we directly correct for this systematic effect.
The analysis is performed for both single-satellite and multi-satellite solutions, allowing assessment of the consistency and stability of the estimated parameters across different processing strategies. By systematically exploring different smoothing strategies and clock epoch intervals, the study aims to provide guidance on optimal processing settings for Sentinel DORIS observations. The study further investigates the role of clock data smoothing, including the selection of appropriate smoothing levels and their impact on station positioning and Earth Rotation Parameters (ERP) estimation. In addition, the influence of the temporal sampling interval between epochs used for clock determination is analyzed.

Keywords: DORIS, SAA, GNSS clocks, Sentinel-3, Sentinel-6
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