Sentinel-1A Calibration Support during Routine Operation

Abstract

Sentinel-1A (S-1A) is the first of two satellites for global Earth monitoring in C-band in the frame of the COPERNI-CUS program of the European Commission and the European Space Agency (ESA). After launch in April 2014, the calibration of the SAR instrument was performed by ESA and their partners during the commissioning phase. Addi-tionally an independent verification of the Sentinel-1A instrument calibration was undertaken by the German Aero-space Center (DLR) on behalf of ESA [1]. However, as the commissioning phase was executed under non-ideal con-ditions the strong requirement for the absolute radiometric accuracy of 1 dB (3σ) could not be achieved. In order to improve the radiometric and polarimetric performance of S-1A, further support has been given by the DLR for addi-tional calibration activities executed during routine operation. Based on the DLR SAR calibration facility and rain-forest acquisitions, the paper describes the different effects observed and gives recommendations to solve the out-standing issues. Furthermore, it is shown, that the strong radiometric requirement of Sentinel-1A is achievable.