AUV Tri-TON 2: An intelligent platform for detailed survey of hydrothermal vent fields

The AUV Tri-TON 2 was built in 2013 under the governmental project to develop instruments to estimate ore reserves in underwater hydrothermal deposits, after the success of the prototype AUV Tri-TON [1]. The vehicle has two suites of imaging instruments looking forward and downward directions, in order to obtain dense, large-area 3D image of hydrothermal vent fields. The vehicle can follow rugged surface of hydrothermal vent fields at close range of less than 2.0 m. Although the vehicle is not equipped with an inertial navigation system (INS), the vehicle can estimate its position in real-time with a precision enough for rough photo-mosaicing, owing to the mutual acoustic positioning with a seafloor station. The vehicle has a strong ability of real-time path-planning to obtain a full-coverage 3D image of a rough, unknown seafloor in a single deployment [2]. The performance of the vehicle was verified through a series of sea experiments. At the first experiment, the vehicle succeeded in imaging seafloor with the area of 14 × 10 m. Then, the vehicle was deployed to hydrothermal vent field at Irabu Knoll in Okinawa Trough with the depth of 1,840m.