Development of polarization selective corner reflectors and its experiment for calibration of airborne polarimetric synthetic aperture radar

As a part of polarimetric calibration efforts of CRL/NASDA airborne synthetic aperture radar system (Pi-SAR), we have developed corner reflectors to reflect a specific polarization channel. They include a 45° rotated dihedral, a 22.5° rotated dihedral, and a dihedral made of thin wires placed in the direction of polarization to be reflected, horizontal (H) or vertical (V). The wire-aligned dihedral we proposed has a thin dielectric frame to hold the wires, requiring no base material. In October 2000 we made a polarimetric calibration experiment of the X-band synthetic aperture radar, a part of the Pi-SAR. Those polarization selective dihedrals, together with conventional trihedrals, were deployed in the experiment. Preliminary results of the image data analysis showed that they were of practical use for polarimetric calibration, while there were some errors in reflected power probably due to their structure and their misalignment. It also showed that the corner reflectors were useful to determine phase calibration coefficients that is phase imbalances between polarimetric channels in the radar hardware