CALIBRATION OF A POLARIMETRIC IMAGING SAR

Calibration of polarimetric imaging SAR's using point calibration targets is discussed in this paper. The four-port network calibration technique [5] is used to describe the radar error model. The processor ambiguity function and the radar distortion matrices are then combined to form a generalized polarimetric ambiguity function. The polarimetric ambiguity function of the SAR is then found using a single point target, namely a trihedral corner reflector. Based on the resultant polarimetric ambiguity function, an estimate for the backscattering coefficient of the terrain is found using a modified version of the STCT technique [5]. A radar image recorded by the JPL aircraft SAR, which includes a variety of point targets, is used for verification of the new calibration method. The calibrated responses of the point targets are compared both with theory and responses based on the POLCAL technique [8]. Also, using a uniform area of the imaged scene, responses of a distributed target are compared using the modified STCT and POLCAL techniques.