Polarimetric Calibration of Spaceborne SAR Data by means of PARCs in the Presence of the Ionosphere

Abstract

Abstract: Ionosphere imposes critical difficulties in the calibration of space-borne SAR systems operating at low frequencies. It degrades the focusing quality, induces positioning error, adds phase screen, and often undulates amplitude at low latitudes. The spatial inhomogeneity of the ionosphere imposes additional complicacy into the system calibration. Most of all, the Faraday rotation through the ionosphere contaminates the polarimetric signature. The correct geo-/biophysical parameter retrieval using SAR polarimetry requires the accurate polarimetric calibration of the SAR system. This paper discusses the requirement of polarimetric SAR system calibrations based on the recent studies of ionospheric parameter estimation methods using SAR. It uses the variability of antenna system across the sub-band space both in range and azimuth directions. The separation of FR from cross-talk is its corollary.