| Summary: | ESA’s POLarimetric Airborne Radar Ice Sounder demonstrator (POLARIS) – built, maintained and deployed by the Technical University of Denmark (DTU) - operates at P-band and features a multi-phase-center antenna for the purpose of surface clutter suppression. The first data suitable for the development and demonstration of surface clutter cancellation methods were acquired in February 2011 during the IceGrav campaign in Antarctica. The purpose of the present study was to investigate and compare different methods for surface clutter cancellation and to implement a Processing Tool to augment the along-track POLARIS processor developed by ESA, thus improving bedrock detectability. Five algorithms have been selected for implementation and analysis: the standard beamformer, two different clutter nulling algorithms, the optimum beamformer and the MVDR beamformer. Prior to the analysis with real POLARIS data the algorithms have been implemented in a simulation environment, allowing for a performance analysis concerning the different input parameters. These included pulse bandwidth, aircraft roll, cross-track terrain slopes, as well as POLARIS antenna patterns. The improved performance of the nulling, MVDR and optimum beamformer techniques for surface clutter suppression compared to standard beamformer has been demonstrated and requirements on the knowledge of slope and roll parameters have been quantified for nulling and optimum beamformer algoorithms. By means of simulation it was shown that the relatively large separation of the POLARIS phase centers (~lambda) is responsible for regions of high noise scaling around +/- 45deg off-nadir angle, which turned out to be annoying in particular for the application of the nulling techniques. The optimum beamformer and the MVDR instead are able to better handle these angular regions. The clutter suppression performance has also been demonstrated with the available POLARIS data from the IceGrav 2011 campaign. For all 4 available data takes a clear improvement in clutter ...
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