Quad-polarimetry and interferometry from repeat-pass dual-polarimetric SAR imagery

New space-borne polarimetric SAR systems employ, or will employ, dual-pol imaging modes as well as full quad-pol imaging, e.g. PALSAR, RADARSAT-2, TERRASAR-X. Therefore questions arise as to the capabilities (and limitations) of these various dual-pol SAR imaging modes. One novel offshoot of our work on dual-pol SAR image analysis and polarimetric decompositions of dual-pol data was the idea to collect two dual-pol images employing geometry appropriate for parallel repeat-pass interferometry. The polarizations of the dual-pol collections differ, e.g. one is (HH, HV) and the other (VV, VH). Using the example of transmitting either horizontal (H) or vertical (V) polarizations, one collects all four polarimetric channels, but only two per pass. Except for the interferometric repeat-pass nature of the SAR image collections the polarimetric information should be identical to standard quad-pol SAR imagery. The relevant open questions concern the interferometric baseline and temporal decorrelations between the repeat-pass dual-pol images.