Developlment of super-deep instrumental housings.

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Deepest poritions over the earth are located in the western Notrh Pacific. Usually capcbilty depth of oceanic instruments in limited to be less than 600 m, however, the depth is obviously not enough for Japanese scientist. In this research project, we dovolopod we have developed instrumental nousings for depth greater then 12 km water by using titanium cylinder We developed acoustic release and current meter with titanium housing Acoustic characteristics of the release is improved by a narrow beam transducer pattern of directional, and has been proced the capability of more than 12 km signal transmission, A current meter with titanium housing has been proved to applicapable for a depth greater than 12 km. Deployments of the mooring was made on Jamary 28, and recoveres on mayll,1987. A 104 day long continuous record of current shows that inertial oscilation is increased at bottom layer. A mazimum current speed is greater than 10 cn/sec, which is first shown by the research for the depth of 9205 m in the Izu-Ogasawara Trench.