4 research outputs found
OBSAPS data acquisition system : operator's manual and system overview
On the Ocean Bottom Seismometer Augmentation to the Philippine Sea Experiment
(OBSAPS, April-May, 2011, R/V Revelle), a VLA and six OBSs were deployed to listen to
an active acoustic source, a J15-3. This report describes the hardware and software used to
control and record the acoustic transmissions from the source. Some significant features of
the system are: 1) The system transmits general user-defined source functions, such as Msequences
(.SIO files). 2) In addition to controlling the source waveform, the system also
records six real-time channels in binary files with user-selectable lengths: the monitor
hydrophone mounted near the source, the power amplifier voltage and current, the depth of
the source, sonobuoy data (when deployed) and an IRIG-B time reference. Files are output
in .AUV format with a precision GPS-based time stamp in the file name. 3) The
transmission start time along with ADC and DAC sample rates are disciplined to GPS time.
4) A convenient, Labview based, user interface provides real-time source control and
monitoring. 5) The software provides parsing and logging of gyro and GPS NMEA
sentences. The system, which was based on an earlier system from Scripps MPL, worked
well on OBSAPS and is available for future projects.Funding was provided by the Office of Naval Research under Contract Nos. N00014-10-1-0994
and N00014-10-1-0987
OBSANP data acquisition system : operator's manual and system overview
On the Ocean Bottom Seismometer Augmentation in the North Pacific Experiment (OBSANP,
June-July, 2013, R/V Melville), a VLA and twelve OBSs were deployed to listen to an active
acoustic source, a J15-3. This report describes the hardware and software used to control and
record the acoustic transmissions from the source. Some significant features of the system are:
1) The system transmits general user-defined source functions, such as M-sequences (.SIO files).
2) In addition to controlling the source waveform, the system also records six real-time channels
in binary files with user-selectable lengths: the monitor hydrophone mounted near the source, the
power amplifier voltage and current, the depth of the source, Vref signal driving the power
amplifiers and an IRIG-B time reference. Files are output in .AUV format with a precision GPSbased
time stamp in the file name. 3) The transmission start time along with ADC and DAC
sample rates are disciplined to GPS time. 4) A convenient, Labview based, user interface
provides real-time source control and monitoring. 5) The software provides parsing and logging
of gyro and GPS NMEA sentences. The system, which was based on an earlier system from
Scripps MPL, worked well on OBSANP and is available for future projects.Funding was provided by the Office of Naval Research
under contract N00014-10-1-0987 and N00014-10-1-0510
Ocean Bottom Seismometer Augmentation in the North Pacific (OBSANP) - cruise report
The Ocean Bottom Seismometer Augmentation in the North Pacific Experiment (OBSANP,
June-July, 2013, R/V Melville) addresses the coherence and depth dependence of deep-water
ambient noise and signals. During the 2004 NPAL Experiment in the North Pacific Ocean, in
addition to predicted ocean acoustic arrivals and deep shadow zone arrivals, we observed "deep
seafloor arrivals" (DSFA) that were dominant on the seafloor Ocean Bottom Seismometer (OBS)
(at about 5000m depth) but were absent or very weak on the Distributed Vertical Line Array
(DVLA) (above 4250m depth). At least a subset of these arrivals correspond to bottomdiffracted
surface-reflected (BDSR) paths from an out-of-plane seamount. BDSR arrivals are
present throughout the water column, but at depths above the conjugate depth are obscured by
ambient noise and PE predicted arrivals. On the 2004 NPAL/LOAPEX experiment BDSR paths
yielded the largest amplitude seafloor arrivals for ranges from 500 to 3200km. The OBSANP
experiment tests the hypothesis that BDSR paths contribute to the arrival structure on the deep
seafloor even at short ranges (from near zero to 4-1/2CZ). The OBSANP cruise had three major
research goals: a) identification and analysis of DSFA and BDSR arrivals occurring at short
(1/2CZ) ranges in the 50 to 400Hz band, b) analysis of deep sea ambient noise in the band 0.03
to 80Hz, and c) analysis of the frequency dependence of BR and SRBR paths. On OBSANP we
deployed a 32 element VLA from 12 to 1000m above the seafloor, eight short-period OBSs and
four long-period OBSs and carried out a 15day transmission program using a J15-3 acoustic
source.Funding was provided by the Office of Naval Research under contract #'s N00014-10-1-0987
and N00014-10-1-051
Ocean Bottom Seismometer Augmentation of the Philippine Sea Experiment (OBSAPS) cruise report
The Ocean Bottom Seismometer Augmentation to the Philippine Sea Experiment
(OBSAPS, April-May, 2011, R/V Revelle) addresses the coherence and depth dependence of
deep-water ambient noise and signals. During the 2004 NPAL Experiment in the North Pacific
Ocean, in addition to predicted ocean acoustic arrivals and deep shadow zone arrivals, we
observed "deep seafloor arrivals" that were dominant on the seafloor Ocean Bottom Seismometer
(OBS) (at about 5000m depth) but were absent or very weak on the Distributed Vertical Line
Array (DVLA) (above 4250m depth). These "deep seafloor arrivals" (DSFA) are a new class of
arrivals in ocean acoustics possibly associated with seafloor interface waves. The OBSAPS
cruise had three major research goals: a) identification and analysis of DSFAs occurring at short
(1/2CZ) ranges in the 50 to 400Hz band, b) analysis of deep sea ambient noise in the band 0.03
to 80Hz, and c) analysis of the frequency dependence of BR and SRBR paths as a function of
frequency. On OBSAPS we deployed a fifteen element VLA from 12 to 852m above the
seafloor, four short-period OBSs and two long-period OBSs and carried out an 11.5day
transmission program using a J15-3 acoustic source.Funding was provided by the Office of Naval Research under Contract Nos. N00014-10-1-0994
and N00014-10-1-0987