Towards an Autonomous Sampling System for the Hadal Zone

We present a vehicle system combining a small autonomous underwater vehicle (AUV) with an underwater lander for use in an autonomous sampling system for hadal zone (depth of more than 6,000m) applications. When developing an ultra-deep sea vehicle system, the long vertical movement, the increased weight and size to withstand high water pressure or special equipment for hadal, the limitations of commercially available sensors, and underwater communication represent high barriers. We aim to overcome these challenges by sharing functions effectively between the AUV and the lander. The lander can be equipped with adequate flotation to move vertically, with large-capacity batteries and acoustic communication devices to support vessels, all of which can contribute to reduce the AUV weight, and offer good maneuverability and payload for sampling capabilities despite the hadal applications. We also assume that acoustic positioning of the AUV from the lander provides a solution to sensor-limited AUV navigation. In addition to describing the concept, this paper presents preliminary experiments conducted using a prototype AUV for vehicle navigation assisted by acoustic positioning from a lander, and visual feed-back control assuming docking to the lander. These results support the benefits and feasibility of this concept and clarify future works to produce an autonomous sampling system.