Formulation of Radiometric Calibration for Azimuthal Multi-Angle Observation Space-Borne SAR

A novel space-borne SAR technique, azimuthal multi-angle observation (AMAO), has recently been proposed. It has highly flexible working modes and powerful capability of target information acquisition, but has challenges in achieving radiometric measurement accuracy. The larger the squint angle, the higher the resolution and the more variations involved. Radiometric calibration is a necessary approach to consistent and accurate SAR measurements, but has so far not been carefully considered for AMAO space-borne SAR. This paper addressed the new issues in radiometric calibration arising from the AMAO space-borne SAR system. The AMAO imaging modes are firstly been illustrated, based on which the influences of the AMAO on radiometric calibration are analyzed. To guarantee the accuracy of the radiometric calibration, an appropriate form of the SAR radar equation is derived for AMAO space-borne SAR. On these bases, the calibration models can be obtained by reformulating the novel AMAO SAR equation, and the corresponding normalization method is then proposed. The good experimental performance indicators verify the correctness of proposed models and the effectiveness of the correction method.