Under-ice seabed mapping with AUVs

In the past few years, there has been increasing interest in the use of the Arctic, both as an ocean waterway and as a source of natural resources and food. In support of these objectives, scientific studies and research to characterise the Arctic environment are being initiated. At the same time, northern nations have begun to collect the data that is necessary to assert their sovereignty claims under Article 76 of the United Nations Law of the Sea Convention (UNCLOS). With an Arctic landmass second only in area to that of Russia, Canada has a major interest in these activities. To support some of the effort, it has started to use Autonomous Underwater Vehicles (AUVs) to aid in the collection of under-ice seabed imagery. Remotely Operated Vehicles have been used fairly routinely for under-ice observation since the 1970's and the procedures associated with their use are straightforward. However, the coverage that an ROV can achieve is limited. In terms of mobility, the Autonomous Underwater Vehicle (AUV) is far more versatile. Operating without a tether, it can make undersea transits or surveys hundreds of kilometres in length. So far, use of the AUV in polar regions has been sparse and there is not a lot of operational experience with under-ice operations. In 1995 and 1996, however, the Canadian Department of National Defence (DND) and International Submarine Engineering Ltd. (ISE), operated a large AUV through ice in the Lincoln Sea, north of Alert, NWT, conducting missions in excess of 450 km. ISE is now using this experience to adapt the smaller 3000 m depth Explorer AUV for Antarctic missions with Memorial University and the University of Tasmania, in south polar regions. The company is also working with DND, Memorial University and the NRC, to ready two 5000 m depth AUVs for sea-floor mapping operations in 2010-11, in support of Canada's submission to UNCLOS. Mission lengths are again expected to be lengthy, up to 450 km under ice. The paper will review experience gained on earlier Arctic operations and outline the considerations and decisions that have so far been made to adapt AUV technology and procedures for the upcoming Arctic missions. Pre-deployment aspects include training, fail-safe provisions, mission planning and simulation, mission logistics and finally, loss provisions and insurance coverage for the vehicle. Operational aspects include dealing with extremely cold, ice-surface temperatures, the challenge of high latitude, inertial navigation, under-ice acoustic positioning, throughand under-ice communications with the AUV, acoustic homing to the recovery site and the procedures for recovery. Procedures for turning the vehicle around between missions including underwater docking options for battery charging, data download and mission upload will also be presented.