[DONET Network Component Trial]
From November to late December 2009, the DONET system development group conducted several trials to confirm the function and the performance of science node and observatory measurement instruments. The major three science node functions 1) power distribution control 2) data transmission control, and 3) time synchronization control were evaluated by the bench test in the laboratory using node final prototype and then assembled to the pressure housings. The pressure housings are mounted on the titanium alloy chassis with 8 underwater mateable observatory interfaces, one high voltage backbone cable system interface and a sea ground for tank test.
Ground Motion Sensing System Experiment
Pressure Sensor Stability Test
The DONET standard observatory is composed of the ground motion sensing system and the pressure sensing system. The ground motion sensing component took a long term sensor evaluation in Matsushiro Seismological Observatory, Japan Meteorological Agency ( http://www.grn.janis.or.jp/~matu-jma/ ) where is the one of the quietest seismological observatory in Japan. The pressure sensing component also took an evaluation at the pressure sensor stability test facility in JAMSTEC. The sensing components pass the evaluation, were integrated as an observatory in the factory.
System Trial in Seawater Test Tank
Two network components meet together in the seawater test tank at National Research Institute of Fisheries Engineering ( http://nrife.fra.affrc.go.jp/index_e.html ). One week system trial was conducted from November 30. The following items were confirmed in the test.
1) System functions.
2) Hardware configuration of each component.
3) Communication and control between science node and observatory.
4) Property of integrated system in seawater.
5) System stability in consecutive operation.
The tank test was successfully concluded in this period and got a list of minor modification for final product. The measures against the list were immediately reflected to the manufacturing process after the test.
system assemble test
Right after the Christmas 2009, from 27-29 December, the SAT (system assemble test) was conducted in the submarine cable factory in Kita-Kyusyu, Fukuoka. The Observatory component passed the tank test was transport to the cable factory and set up to connect the 300km length of backbone cable system with repeaters branching interface and termination equipment. The all items confirmed in tank test were re-tested in the factory through the backbone cable system. The result of SAT had being very satisfactory to start the preparation of backbone cable system installation. The cable laying operation is scheduled to starts early January, 2010.