Principal characteristics of the up-to-date Japanese oceanographic research vessels

The principal requirements of scientific research for medium to large oceanographic vessels for various types of sea-going works of different disciplines are described with particular emphasis on the Hakuho Maru of the Ocean Research Institute, University of Tokyo (100 m long, launched in 1989) and Yokosuka (105 m long, launched in 1990) belonging to JAMSTEC. The former has already accomplished a round-the-world cruise and joined several international scientific programs. Such as the InterRidge and KAIKO. The latter was originally designed as a tender ship for research submersible Shinkai 6500 but recently used also for general geophysical survey while the submersible is under maintenance on board. These vessels are operated in world oceans including the Pacific, Atlantic and Indian Oceans. Extensive on-board scientific studies are carried out during the cruises. Local area network using fibre-optical cable is an excellent system for information handling on the vessel. Good maneuvering ability is required for oceanographic work in high seas and strong wins. Precise acoustic measurements such as dynamic positioning, acoustic image and data transmission as well as multi-narrow beam bathymetry, seismic profiling and side-scanning sonar observation require abatement of both waterborne noises due to propeller cavitation and mechanical vibration of the hull. Reduction of rolling and pitching has been one of great tasks for oceanographic ships, although these two vessels are not equipped with any anti-rolling device. The results will be fully used for the design of new ships.