Abstract: We will describe a mine-hunting sonar system, which is carried on an untethered Autonomous Underwater Vehicle (AUV): the Hugin. The Hugin Autonomous Underwater Vehicle (AUV) carries a wide-band sonar system. The AUV-borne sonar preprocessing includes output from beam-former + matched filter on a distance, bearing (r, θ) format. Further post-processing is performed in the equipment on board the surface vessel.