Advances in High-Frequency Active Sonars for Countering Asymmetric Threats in Littoral Waters

Sea mines and fast in-shore attack craft pose threats to maritime force vessels operating in littoral waters. Three advances in high-frequency (HF) active sonars that can be used to counter these threats are reviewed. First, a tomographic sonar is able to reconstruct the acoustic image of a sea mine by processing multi-aspect projection data acquired with a wideband monostatic sonar circumnavigating the mine at a safe standoff distance. Second, a single-snapshot adaptive beamforming algorithm can be applied to a wideband, small-aperture sector-scan sonar to enhance its azimuthal resolution, which improves the detection and localization of mines and underwater obstacles. Third, a HF active sonar is able to detect, localize and track automatically a small fast surface craft in a shallow water cluttered environment based on the evolution of the craft wake observed in the sonar image sequence