Study of Phase Calibration for GEOSAR Based on Chinese Area Positioning System

GEOSAR (synthetic aperture radar on geosynchronous satellite) has become a very potential method of space-borne geoscience remote sensing for its excellent performances such as imaging with large observing area and high time-resolution, high precision repeat orbit interferometric measurement, rapid response to emergency and so on. However, the long synthetic aperture time will result in extra phase error for GEOSAR, which will lead to degradation in image quality. In the absence of GEOSAR in-orbit, a method of phase calibration based on CAPS (Chinese Area Positioning System) for GEOSAR is proposed. An experiment system including an ISAR and CAPS was established. In this experiment system, ISAR acts as the GEOSAR and CAPS acts as transponder for calibration, which can be seen the reverse of calibration for GEOSAR using transponder on ground. By use of the experiment system, the phase error induced by ionosphere and range can be calibrated.