ESA/ESOC - Precise Orbit Determination for Sentinel-6 Michael Freilich Based on Galileo and GPS Observations

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With global mean sea level rising because of climate change, Copernicus Sentinel-6 is the radar altimetry reference mission to extend the legacy of sea-surface height measurements until at least 2030. The satellite carries a Poseidon-4 radar altimeter and a microwave radiometer. The analysis of the altimeter data relies on highly-accurate knowledge of the orbital position, in particular in the radial component, with errors below 1.5 cm. For this reason, Sentinel-6 carries several instruments, e.g., Laser Retroreflector Array, Doppler Orbitography and Radiopositioning Integrated By Satellite (DORIS) and also a dedicated GNSS receiver for generation of data, which allows to perform Precise Orbit Determination (POD) with the highest possible accuracy. For this reason, the GNSS receiver and respective GNSS observations is of particular interest for this paper because it is the first time that a high-quality dual frequency Galileo/GPS receiver is flown on-board of a Sentinel satellite. ESA’s Navigation Support Office (NavSO), located at the European Space Operations Centre (ESOC) in Darmstadt, Germany is providing an independent Precise Orbit Determination solution for all Sentinel satellites. As part of this activity, the office has been operationally computing and delivering the POD products, including the Sentine-6 multiGNSS-based precise orbits since its launch in November 2020. This presentation will describe the processing techniques adopted at ESOC, with a particular focus on the POD aspects and the related processing of the Galileo and GPS observations and their interoperability. The latest results and their validation are addressed in this paper.