USGS CMG Z-1-07-MB Metadata

Three AUV dives were planned in the Little Lucia channel system,
located offshore between Point Sur, CA and the offshore Santa Maria Basin.
The primary target was the transition from highly channelized to unconfined
sedimentation features. The areas mapped are in water depths of 975 to 1050 m.
 The primary objective of these dives is to obtain multibeam bathymetric data
and subbottom profiles. Processing and analysis of this data will be used to
study the sedimentary architecture of the area. Approximately 1.5-m-long
vibracores were taken using the MBARI ROV Tiburon during cruise W-4-06-MB.

Very high-resolution bathymetry and subbottom structure of the Little
Lucia channel and lobe system. Bathymetric maps are produced at a one-meter
contour interval.

~1600/JD071 R/V Zephyr departs Moss Landing.


~1411/JD072 Begin first successful AUV dive over Little Lucia


~2311/JD072 Complete first successful AUV Dive over Little Lucia


~1000/JD073 R/V Zephyr arrives in Moss Landing


A total of 2 AUV dives were completed. The first dive was unsuccessful because 
problems
with the acoustic modem prevented accurate tracking of the AUVs location.  
Releasing
the AUVs drop weight failed to cause the AUV to abort the dive, but the data 
collected
cannot be used for analysis.  A second dive covered the same area planned for 
the first
dive and successfully collected multibeam bathymetry and subbottom data.
The AUVs starting position was determined by GPS at the launch site. The vehicle 
then
dives in a USBL-nav-aided spiral to 50 meters above the seafloor.  The total 
survey
trackline was 42.5 km with 150 m line spacing.  The AUV can survey with the 
multibeam
sounding system and chirp sonar for ~9 hours; it then returns to the sea surface 
to be
picked by the R/V Zephyr.
Only one-third of the objectives of the cruise were attained because of weather. 
A second
cruise is planned to complete the two additional dives.

Used seafloor mapping AUV; MBARI's automated underwater vehicle (AUV)
for sea-floor mapping and subbottom profiles. The AUV has a high-resolution
Edgetech chirp sonar profiling system and a multibeam sounding system and uses
both Doppler sonar tracking of the sea floor and an inertial guidance system
for position control.  The AUV descends to 50 m above the seafloor with
USBL-nav-aided spiral descent.