Development of an Underwater Towed Exploration System for Archaeological Relics

Many archaeological relics such as a wreck of an ancient ship are remains under the sea bottom and most of them are untouched because of difficulties of underwater exploration. Usual sub-bottom explorations for offshore resources such as oil and gas are carried out using seismic and sonic prospecting instruments and it is high cost and time consuming. On the other hand, archaeological relics in the relatively shallow water are explored by a sub-bottom profiler and by divers so the area which can be investigated is very limited. The authors have been developing underwater towed vehicles and autonomous underwater gliders in the previous studies. These vehicles equip various types of instruments including an OBEM (Ocean Bottom Electro-Magnetometer). They are promising instruments for marine environment survey and ocean floor resources exploration. In this report, a towed exploration system for archaeological relics exploration is proposed and the development of the vehicle including a motion controller is discussed. The vehicle is towed near the sea bottom to improve the accuracy of the measurement using a sonic prospector. The performance of the towed system and its motion control system are assessed by tank experiments and numerical simulations.