Saoussen Belhadj-Aissa (Jet Propulsion Laboratory, California Institute of Technology Pasadena, CA, USA); Alex Conrad (Jet Propulsion Laboratory, California Institute of Technology Pasadena, CA, USA); Shailen Desai (Jet Propulsion Laboratory, California Institute of Technology Pasadena, CA, USA); Bruce Haines (Jet Propulsion Laboratory, California Institute of Technology Pasadena, CA, USA); Andy Wu (Jet Propulsion Laboratory, California Institute of Technology Pasadena, CA, USA)

The Sentinel-6B mission was launched successfully from Vandenberg Air Force Base on November 16, 2025 with the goal of continuing the more than 30-year record of global ocean surface topography measurements. Prior to assuming its role as the new reference mission, Sentinel-6B has been operating in tandem formation with Sentinel-6 Michael Freilich along the reference ground track since December 15, 2025. This tandem formation enables direct comparison of near-coincident observations in both space and time.
We present a summary of calibration and validation results obtained during this tandem phase, with a focus on system performance and the Sea Surface Height error budget. Global S6B-S6MF Sea Surface Height Anomaly differences show an average bias of -0.5 cm with a standard deviation of 3.0 cm. The analysis further includes an evaluation of the performance based on JPL’s GPS-based precise orbit solutions. Global inter-satellite range bias results are consistent with observation from the dual-frequency transponder on Catalina Island with range bias of 0.6 cm for Ku-band and -3.3 cm for C-band. The results demonstrate that Sentinel-6’s altimetry products maintain high quality and consistency, highlighting their continued value for oceanographic applications at the mesoscale level and for climate studies.