Comparison of Digital Beamforming Techniques for Enhanced Ice Sounding Radar Data Processing

Ice sounding radar from high altitudes is compromised by off-nadir ice surface reflections (clutter), which overlays the nadir signal of interest originating from the bedrock and/or internal ice layers. Multi-aperture antenna radar systems were developed to mitigate the impact of surface clutter allowing spatially variant digital beamforming (DBF) processing of the data received from the individual spatially separated apertures. This paper investigates four different beamforming algorithms: conventional beamsteering, nulling of clutter angles, optimum beamformer and the MVDR beamformer. Comparisons are performed based on simulations for an airborne ice sounding scenarios. In addition, real echograms are computed from data acquired by the P-band POLARIS sensor. Relevant conclusions are drawn with respect to the implementation of a future space-based ice sounding mission.