Advanced sonar technologies for high clearance rate mine countermeasures

Abstract

During 2014–2016 the office of Naval Research fielded two new wideband synthetic aperture sonar (SAS) systems: the third generation of the Small Synthetic Aperture Minehunter (SSAM III) and the Lightweight Conformal SAS (LC-SAS). These systems, collaboratively developed by the Naval Surface Warfare Center Panama City Division, the Applied Research Laboratory at Penn State University, and the Applied Research Laboratories at the University of Texas, were integrated on to REMUS 600 autonomous undersea vehicles (AUV) developed by the Woods Hole Oceanographic Institution. Designed to increase area coverage rate and reduce false contact calls, both systems operate over a wide range of wavelengths and aspects: where centimeter-scale wavelengths are used for fine-detail imaging of the seabed and small objects that lay proud on it, and longer wavelengths, which can propagate deeper into the sediment volume, are used for imaging and spectroscopic analysis of proud and buried objects. The SSAM III is the first multi-band sonar that combines techniques for high-resolution imaging and target analysis via acoustic spectroscopy. The LC-SAS is a dual-band sensor that represents the longest (and thus longest range) SAS incorporated on a lightweight AUV to date, and marks the first time that a SAS has been integrated onto such a platform with a high-quality forward look sonar - in this case the Autonomous Topographic & Large Area Survey (ATLAS) sonar. The SSAM III and LC-SAS systems are reviewed, along with associated technologies and sensor modalities, which include image and spectral based processing, tomographic imaging, automated target recognition and seabed changed detection, and advanced autonomy via situational awareness provided by the sensors.