Sentinel-1A Calibration Support during Routine Operation using innovative Point Targets

Abstract

Sentinel-1A was launched in April 2014 to operate a SAR instrument in C-band as part of the COPERNICUS program of the European Commission and the European Space Agency (ESA) for global Earth monitoring. The calibration of the SAR instrument was performed by ESA and their partners during the commissioning phase until end of September 2014. Additionally an independent verification of the Sentinel-1A instrument calibration has been undertaken by the German Aerospace Center (DLR) on behalf of ESA. For this purpose innovative active and passive point targets were developed. Three corner reflectors and three transponders are permanently installed in Southern Germany covering an east-west range of about 80 kilometres. The targets are remote controlled and have been operated since launch of Sentinel-1A. The paper describes the characteristics of the point targets and gives a detailed view on the Sentinel-1A system calibration using these targets. The analysis includes the geometric calibration, the antenna pointing determination and the radiometric calibration, altogether characterizing the performance for different acquisition modes.