Assessment of SWOT Systematic Errors and Calibration Strategy

Clement Ubelmann , cecile anadon, antoine delepoulle, Gérald Dibarboure, matthias raynal

The SWOT KaRIN instrument provides wide-swath Sea Surface Height measurements
affected by cross-swath systematic errors largely driven by thermo-elastic distortions and attitude knowledge errors. Using more than two years of science-orbit data, we evaluate a calibration procedure structured in two principal steps to estimate the systematic errors. The first step applies an empirical modeling approach—combining a solar–orbital model and a geographically fixed model. This empirical phase reduces the dominant linear swath-tilt variability from 17cm to 7cm. The second step implements a localized Optimal Interpolation framework that exploits the k-2 power-law behavior of the remaining attitude errors to isolate them from actual SLA signal to preserve. This combined approach reduces the final residual formal error of the linear term to ~1cm over open oceans and~3cm over continental regions, providing a calibration scheme for global oceanographic and hydrological applications.