Multi-disciplinary VENUS observation at the Ryukyu Trench using Guam-Okinawa geophysical submarine cable

A multi-disciplinary VENUS (versatile eco-monitoring network by undersea-cable system) observatory, which equips seven geophysical instrument groups, was installed at the depth of 2,170 meters on the slope of the Rukyu Trench. Prior to the installation of the VENUS multi-disciplinary ocean bottom (MDOBO) observatory, an ocean-bottom telemetry system, which has functions to supply electrical power to the MDOBO, and the submarine coaxial cable were installed at ocean bottom. The installation of the multi-disciplinary ocean bottom observatory was done by use of deep-towing unit and ROV Kaiko-10K. During the period of August-September 1999, seven instrument groups of MDOBO were deployed at the target position, at 80-100 meter distances from the telemetry system, with several meters allowances using a deep-towing unit. To install the instrument at the exact location, the mother ship of deep-towing unit was precisely navigated. The extension cables were also dropped from the deep-towing unit. The ROV Kaiko-10K extended multi-conductor extension cables from instrument units towards the ocean-bottom telemetry system and connected them to undersea mateable connectors on the junction box. The MDOBO collected one and half month records. Some useful data were observed since the installation.