Design and deployment of a four-degrees-of-freedom hovering autonomous underwater vehicle for sub-ice exploration and mapping

This paper describes the 2008 and 2009 Antarctic deployments of the National Aeronautics and Space Administration ENDURANCE autonomous underwater vehicle (AUV). The goal of this project was to conduct three autonomous tasks beneath the ice cap 4 m thick of West Lake Bonney: first, to measure the three-dimensional (3D) water chemistry of the lake at prespecified coordinates; second, to map the underwater face of the Taylor Glacier; third, to chart the bathymetry of the lake bottom. At the end of each mission the AUV had to locate and return through a hole in the ice slightly larger than the outer diameter of the vehicle. During two 10-week deployments to Antarctica, in the austral summers of 2008 and 2009, ENDURANCE logged 243 h of sub-ice operational time, conducted 275 aqueous chemistry sonde casts, completed a 3D bathymetry survey over an area of 1.06 km at a resolution of 22 cm, and traversed 74 km beneath the ice cap of West Lake Bonney. Many of the characteristics and capabilities of ENDURANCE are similar to the behaviours that will be needed for sub-ice autonomous probes to Europa, Enceladus, and other outer-planet icy moons. These characteristics are also of great utility for terrestrial operations in which there is a need for an underwater vehicle to manoeuvre precisely to desired positions in 3D space or to manoeuvre and explore complicated 3D environments.