The phase calibration problem for polarimetric radars is discussed. More specifically, the assumption that the copolar vertical and horizontal returns from a slightly rough surface are in phase is critically reviewed. It is concluded by means of a theoretical analysis that the phase difference for moist soil targets can reach up to 10/spl deg/ at 15 GHz and for incidence angles of 50/spl deg/. However the assumption of zero phase difference is a good approximation for dry soils, lower frequencies, and low incidence angles. >
['Albert Guissard']
Phase calibration of polarimetric radars from slightly rough surfaces