Re-entry support system for deep sea drillings

So-called UWTV (Under Water TV) system is equipped on the drilling vessel Chikyu. The system has a role of eyes for drilling and/or observatory installing operations in the water of more than 3,000 meters deep, where the usual commercial ROVs (Remotely Operated Vehicles) are not available. The UWTV system includes winches, sheaves, an umbilical cable, controllers, and underwater assembly which consists of two under water cameras, two underwater lights, a sonar and guide sleeves. The guide sleeves are attached in the UWTV frame, and drill pipes goes in the sleeves. The UWTV cable is connected to the frame and an UWTV winch system haul in and lower the UWTV frame along the drill pipe through moon pool. This UWTV is available for up to 7,000 meters deep water operation. Two UWTV systems have constructed. The 1^st one was used in the operation in 2011 Tohoku earthquake research project and successfully worked. The 2^nd one was replaced with the 1^st one and now is under sea trials. It will be used in the next scientific drilling project, so-called T-Limit, off Shikoku. In this paper, the 1^st and the 2^nd UWTVs on Chikyu are introduced.