The series of calibration experiments with ERS-1/2 SAR were conducted in 1995 and 1999-2000 at the Bear Lakes calibration site near Moscow. Since very beginning a number of calibration scenarios with new passive calibration targets based on parabolic antennas was exploited. Some results of a study of the scatterers stability and ideas about a way to broaden scatterer pattern were reported earlier. Experiments of the year 1999-2000 were conducted under AO3-343 project and devoted to the continuation of the study of the temporal stability of parabolic antennas scattering, antenna pattern shape and a way to control their polarization properties and radar cross section. Three parabolic antennas, used in the experiment, were located at the corners of the rectangular triangle with 50 m legs. Two antennas were used as a reference, and another one was a calibration target with polarization grid in focal area. The use of the polarization grid allowed us to modify scattering matrix of the antenna. As a result, changing the angle 6 between the SAR polarization plane and the grid polarization plane, we were able to change the target's RCS for a single polarization system, like as ERS SAR. The SLCI data obtained under AO3-343 project were used usually for the measurements of the scatterers RCS. The measurements show, that reference antennas have very stable and very large ∼ 55 dBm2 radar cross-section. The cross-section of the antenna could be controlled by the orientation of the polarization grid with respect to ERS-2 polarization plane. The results are in good agreement with theoretical predictions and laboratory measurements except for the orthogonal orientation, where instead of 20 dBm2 decrease of RCS we observe 16 dBm2 decrease only. The reason is an interfering backscatter from the antenna structure and a layer of polarization grid. The study conducted with a use of ERS SAR data confirms high stability of the parabolic antennas and the possibility to control the polarization plane (and, respectively, RCS for a single polarization SAR system) of the backscattered signal.
|Number of pages||8|
|Publication status||Published - 1 Dec 2000|
|Event||ERS-Envisat Symposium 'Looking Down to Earth in the New Millennium' - Gothenburg, Sweden|
Duration: 16 Oct 2000 → 20 Oct 2000