The target of the R1 Project is to construct a long endurance autonomous underwater free swimming robot equipped with a Closed Cycle Diesel Engine (CCDE) for long term servey of mid-ocean ridges. The distinctive feature of CCDE is robustness and low cost for construction and operation. The robot swims for one day without terminating its mission and surveys a wide area of ridge systems including measurement of CTDO in the vicinity of the seabed. It is anticipated to make detailed research when abnormalities in temperature, etc., are detected.