sea states, including rather rough seas. Immediately after delivery, the Ryofu Maru ?, the flagship of the six vessels, was put into service to engage in intensive observations of oceans and atmosphere in the western North Pacific, including its western equatorial waters. Deployment of the Ryofu Maru ? has significantly improved and expanded the JMA's ocean survey capabilities in several ways. These include an increase in the number of observation parameters, improved reliability of measurements, and expanded geographical coverage of observations.
High-tech Operation Systems
The Ryofu Maru ? is equipped with a state-of-the- art navigation system and a number of modern scientific apparatuses and sophisticated observation facilities, including six winches to lower instruments and water samplers into the sea. The vessel's medium-speed diesel engine of 4,000 PS with a reduction gear drives a four-bladed control pitch, high-skewed propeller to allow operation at both extremely low speeds and up to a 14-knot cruising speed for 10,000 miles. A set of Beck twin rudders controlled with a joystick control system on the bridge, an aft control station, and a bow thruster (thrust of 4 tons) enable the ship to easily maneuver to carry out observations.
Advanced Equipment for Observations
Scientific apparatuses on board include the observation instruments described below and a Local Area Network, which, through INMARSAT telecommunication, provides linkage between the apparatuses, and a remote terminal at JMA Headquarters in Tokyo to forward the observational data from the vessel to the shore.
(1)Conductivity, Temperature and Depth profiler (CTD) with rosette samplers:
The CTD operates from the sea surface to 6,000 m to measure vertical profiles of water temperature and salinity and to obtain sea water samples at intended depths indicated by commands from the deck unit.
(2)Acoustic current profiler:
During cruising and at stations, the acoustic current profiler makes continuous measurements of ocean currents from the sea surface up to depths of 600 m. It does this by emitting ultrasonic waves from the ship's bottom and receiving their reflections from water columns to detect the Doppler shift of ultrasonic waves caused by the
