Requirements on the calibration of Hybrid-Compact SAR

The state of the art in compact SAR calibration is reconsidered. It is shown that all the existing Compact calibration methods are built on the assumption that the Compact transmits a perfect circular polarization (CP). Unfortunately, the actual technology does not permit the generation of a perfect CP wave. The impact of non circularity of the transmitted polarization on Compact polarization information is assessed. The variations with incidence angles of the helicity and ellipticity of the transmitted polarization are simulated for C-band and L-band Compact SAR using Radarsat-2 and Alos data. This permits quantification of the resulting radiometric error on RH and RV dual-pol measurements. The impact of the non circularity of the transmitted polarization on the degree of polarization (DoP) and Compact polarization synthesis is also quantified. The requirements on the calibration of compact SAR for the extraction of a meaningful polarimetric SAR information from compact, are then setup.