A trihedral corner reflector is often used for SAR polarimetric calibration. However, the scattering property of the reflector used for the calibration may not be correct if the high frequency approximation is not satisfied or if an incident angle deviates from the symmetric axis of the reflector. In order to know the conditions for precise SAR polarimetric calibration, we evaluated the polarimetric response of the reflector by a numerical simulation using the method of moment (MoM). It is found that allowable incident angle deviation is 5 degree to azimuth direction and 4 degree to elevation direction for precise SAR polarimetric calibration when the size of the reflector is 7.5 times larger than the wavelength of an incident wave.

Polarimetric calibration of radar is indispensable for using radar data effectively. This paper proposes a polarimetric radar calibration algorithm using polarization-preserving and polarization-selective reflectors as reference targets. The algorithm assumes radar antenna reciprocity but allows different co-polarization transmission characteristics between horizontal and vertical polarization channels. In processing, the second order terms of small cross-talk factors in antenna polarization transfer characteristics are ignored. The major advantage of the present algorithm is that it does not need assumptions on the scattering characteristics of the background natural surface and is independent of external phase calibration. The results of error analysis show that the present algorithm has sufficient tolerance against errors of reference targets. The validity of the present algorithm was evaluated by analyzing the Spaceborne Imaging Radar C (SIR-C) data and the results were satisfactory.