Ministry of the Environment of Japan started the national demonstration project of Floating Offshore Wind Turbine (FOWT) in 2010 FY. In this project two SPARs with different scales are used. The first half-sized model, supporting a 100kW wind turbine, was installed in 2012 and is currently in operation. It is characteristic that the floater has a hybrid structure, i.e., the upper part is constructed of steel and the lower part of pre-stressed concrete and that the turbine is downwind type of horizontal axis.
The FOWT is equipped with many sensors for measuring motions of 6 DOF, the strain of the steel / concrete parts and other factors. In this paper the measuring system is presented. In September 2012, the FOWT was attacked by a huge typhoon and it survived, although the measured wave height exceeded the designed value. The measured record of the floater in the storm is also presented.