POLARIMETRIC CALIBRATION OF SIR-C USING POINT AND DISTRIBUTED TARGETS

In preparation for the Shuttle Imaging Radar-C/XSAR (SIR-C/XSAR) fligh ts, the University of Michigan has been involved in the development of calibration procedures and precision calibration devices to quantify the complex radar images with an accuracy of 0.5 dB in magnitude and 5 degrees in phase, In this paper, the preliminary results of the SIR-C calibration and a summary of the University of Michigan's activity in the Raco calibration super-site is presented. In this calibration cam paign an array of point calibration targets including trihedral corner reflectors and polarimetric active radar calibrators (PARC's) in addi tion to a uniform distributed target were used for characterizing the radiometric calibration constant and the distortion parameters of the C-band SAR, Two different calibration methods, one based on the applic ation of point targets and the other based on the application of the d istributed target, are used to calibrate the SIR-C data and the result s are compared with calibrated images provided by JPL, The distributed target used in this experiment was a held of grass, sometimes covered with snow, whose differential Mueller matrix was measured immediately after the SIR-C overpass using The University of Michigan polarimetri c scatterometer systems, The scatterometers were calibrated against a precision metallic sphere and measured 100 independent spatial samples for characterizing the differential Mueller matrix of the distributed target to achieve the desired calibration accuracy, The L-band SAR ha s not yet been adequately calibrated for inclusion here.