DLR's Independent Calibration of the Sentinel-1D SAR System: First Results with an Initial Comparison to Sentinel-1C

Abstract

Sentinel-1D is the fourth satellite of the Sentinel-1 mission. Successfully launched on November 4, 2025, it joins its sibling Sentinel-1C to ensure seamless continuity of C-band SAR data for global monitoring of the Earth surface in the framework of the Copernicus program. As for previous Sentinel-1 missions, in parallel to the commissioning of Sentinel-1D by the European Space Agency (ESA), an independent end-to-end SAR system calibration is performed by DLR under an ESA contract. Based on an efficient calibration strategy, this paper describes the different activities performed by DLR during the commissioning phase (CP) of Sentinel-1D and discusses the results achieved. We focus on the implementation of lessons learnt from the recently completed CP activities of its predecessor, Sentinel-1C and briefly compare exemplary results achieved for the two systems.