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In October,
1990, the Navy granted approval to NOAA/PMEL to access the SOSUS arrays
in the North Pacific to assess their value in ocean environmental monitoring,
as part of the U.S. government's dual-use initiative.
The data
collection systems developed by NOAA's VENTS Program have been in place
since August 29, 1991. Acoustic signals from the north Pacific Ocean are
monitored and recorded at the Newport, Oregon facility of NOAA/PMEL. This
is the primary tool for both continuous monitoring of low-level seismicity
around the northeast Pacific Ocean and real-time detection of volcanic
activity along the northeast Pacific spreading centers in support of the
VENTS research program in ocean hydrothermal systems. Real-time ridge
crest monitoring potentially permits the timely on-site investigation
of hydrothermal and magmatic emissions.
Data
acquisition is accomplished by combining portions of the Navy's
processing facilities with NOAA-designed systems installed
at the U.S. Naval Ocean Processing Facility (NOPF) at Whidbey
Island, Washington. Analog outputs from each hydrophone element
are available either through direct cabling or remote data
linkage. Navy systems perform adaptive beam forming on digitized
hydrophone signals, with the outputs converted back to analog
electrical signals. These analog hydrophone and beam-former
outputs are accessed by the NOAA-supplied systems, where the
signals are low-pass filtered, digitized, and temporarily
buffered on hard disk. The digital data are provided to a
wide-area network (WAN) based on Network File System (NFS)
protocol, linking (by encrypted, dedicated telephone line)
the acquisition computer to an analysis system located at
NOAA laboratories in Newport, Oregon.
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