SAR characterization through amplitude and phase measure of transmit-receive modules

This paper discusses the instrument calibration approach of the COSMO-SkyMed SAR antenna, developed by Thales Alenia Space Italia under contract of Italian Space Agency and Italian Ministry of Defence. The SAR is equipped with a phased array antenna composed of 1280 transmit and receive modules (TRM) allocated on five electrical panel, each panel is composed by eight tiles for a total of four columns and 64 rows. Although the active phased array antenna is fully characterised using on ground nearfield measurements, the antenna performance would change over time due to changes in the characteristics of active devices. To this reason the antenna calibration is necessary to test the amplitude and phase value of the TRMpsilas and checking the possible TRMpsilas failures. In this paper we present a brief description of the COOSMO-SkyMed SAR internal calibration subsystem, the TRM calibration mode, and the processing algorithm to estimate the amplitude and phase of the TRMpsilas and the limits of the estimator.