Calibration of Compact Polarimetric SAR Images Using Distributed Targets and One Corner Reflector

Compact polarimetric (CP) synthetic aperture radar (SAR) systems are attracting increasing interest as they possess the ability to construct quad-polarimetric information with advantages of simpler system, lower data rate, and wider swath, compared to a fully polarimetric (FP) system. In order to get undistorted polarimetric information, calibration of CP measurements has to be performed. Freeman and Chen both proposed methods for CP SAR calibration using merely calibrators, which require at least three calibrators at a range line and would require many more calibrators when monitoring the change of the system across the swath is necessary. It has been proved that FP SAR calibration methods exploring scattering characteristics of natural distributed targets (DTs) can reduce the requirement of the number of deployed calibrators. However, it is much more complicated in the case of CP SAR calibration, as only two channels of CP measurements are available. This paper proposes a numerical CP calibration method using natural DTs and only one corner reflector (CR) for a reciprocal CP SAR system. The validity of the method for three typical CP modes is confirmed by simulations with Advanced Land Observing Satellite Phased Array L-band SAR data. Through sensitivity analysis, a dihedral at 0° is selected as the best CR for the calibration algorithm.