A multidisciplinary deep sea long-term observatory in Japan

Described is an effort to deploy off the coast of Japan, a system designed to collect and transmit data from the deep sea floor, sensors placed in boreholes, as well as water column and air-sea interface sensors and transmit this data back to shore in real-time. A variety of sea floor and buoy based sensors provide oceanographic, atmospheric and geophysical data. Transmission of highspeed data (to 2 Mbps) is effected by means of a moored surface buoy that is tethered to the sea floor by a cable carrying both optical fibers and copper power conductors. The data link to shore is facilitated by an inertially stabilized and steered C-Band antenna pointed at a geosynchronous satellite. Redundant 20 kW diesel generators onboard the 5-m diameter buoy both power this telemetry system and supply up to 1 kW of electrical power to seafloor sensors. This Ocean Net buoy, designed by Harris Corporation, carries on board sufficient fuel and electronic redundancy to support 6 months of unmanned operation. Areas around Japan are regions particularly well suited for such a high bandwidth observatory. Broadband seismometers, strain gauges and other sensors deployed in nearby boreholes, drilled to study seismogenic zones, provide vital data for the for scientific community. The mooring riser of the surface buoy is terminated at a sea floor Junction Box equipped with ROV-wet-mateable connectors. These connectors facilitate the continual addition of future sensors and experiments