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The AUV is constructed of two horizontal bodies configured one above the other, connected by struts, and weighs approximately 400 lb in air. The SeaBED AUV is designed to precisely navigate survey tracks at altitudes as low as 2.5 m above the sea floor. Propellers oriented in different planes allow the AUV to maintain course and altitude while avoiding obstacles.
On launch, the vehicle propels itself vertically downward until its navigation system locks onto the seabed at 30-m altitude and it can begin its programmed survey. It can acquire digital color photographs, sidescan-sonar imagery, high-resolution swath topography, and current-meter data.
In its present configuration, the AUV can remain submerged for as long as 3 hours (to be increased to 8 hours in the near future) and can acquire 1,200 photographs per hour, with varying degrees of overlap as determined by vehicle speed (0.5-2 knots). Processing of the images provides stunning views of the sea floor.
The SeaBED AUV is preprogrammed to perform various functions during its dive. Vehicle speed, altitude, photograph timing, and use of camera and sidescan sonar all can be varied during a single deployment. For example, the AUV can acquire photographs (2.5-m altitude) along separate transects, or along overlapping transects to make a mosaic of the seabed, and it can perform a sidescan-sonar survey (10-m altitude). Maximum water depth for the AUV at present is 2,000 m.
The vehicle successfully conducted several long (3 km) photographic surveys across various habitats and major topographic features; it also performed a tight grid survey of a boulder ridge to obtain a mosaic of the seabed. The lines of the grid survey were spaced 1.4 m apart to ensure adequate overlap of digital photographs.
In addition, the SeaBED AUV performed a survey of the sea floor in tandem with the REMUS AUV (deployed from a different ship), which surveyed the water column by using a CTD (conductivity-temperature-depth sensor) and a video plankton recorder.
The SeaBED AUV proved to be a valuable tool for acquiring sea-floor data for a range of purposes, from the making of detailed mosaics of specific features to conducting long photographic and sidescan-sonar transects for describing surficial geology and benthic habitats. Cruise participants included chief scientist Hanumant Singh (WHOI), Page Valentine and Soupy Alexander (USGS), James Lindholm (Stellwagen Bank National Marine Sanctuary), and Ryan Eustice, Oscar Pizzaro, Ali Can, and Ken Foote (WHOI).
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