Independent SAR System Calibration of Sentinel-1C

Sentinel-1 C is the third satellite of the Sentinel-1 mission. Launched in late 2024, it ensures seamless continuity of C-band SAR data for global monitoring of the Earth surface in the framework of the Copernicus program. In parallel to the commissioning of Sentinel-1 C by the European Space Agency (ESA), an independent verification of the system calibration has been performed by the German Aerospace Center (DLR) under an ESA contract. Based on an efficient calibration strategy, this paper describes the different activities performed and discusses in detail the results and main findings of DLR during the commissioning phase (CP) of Sentinel-1 C. The main goal is to provide a comprehensive compendium of the SAR calibration and performance status of S1C at the beginning of its operational mission: At the end of the commissioning phase we find that S1C achieves or even exceeds all SAR performance requirements put forth and is ready for its nominal mission operations.