As you’ve probably noticed, AUVs are getting a lot of attention recently. AUVs, or Autonomous Underwater Vehicles, are on the cutting edge of ocean exploration and science. AUVs have been used to explore Arctic & Antarctic waters beneath the ice, deep ocean depths below 1,000 meters, near shore fish and benthic habitats. There are even plans to use them in future space exploration missions.
The SeaBED-class AUV used on this research cruise is designed by Woods Hole Oceanographic Institution (WHOI) and is jointly owned and operated by NOAA’s Northwest Fisheries Science Center (NWFSC) and the Pacific Islands Fisheries Science Center (PIFSC). SeaBED effectively samples across a wide range of habitat types at depths of 20 to 2,000 meters. Unlike other more traditional AUVs, SeaBED is designed to autonomously follow the sea floor at a close, fixed height (10 m above the sea floor for this project), collecting high-resolution imagery (e.g., color, black-and-white, mono, stereo, still photographs, and/or video) data, while maintaining a forward speed of approx. 0.5 knots. PIFSC and NWFSC are focused on developing this tool as part of an integrated multi-gear fishery-independent survey that will provide information on fish assemblages across their full range, including in complex benthic environments and within marine protected areas that cannot be sampled by trawl surveys or other extractive methods.
On project SE14-02, the AUV’s mission is to descend to depths between 100-250 meters and run a series of 500 meter transects through designated sampling grid cells. The sampling grid cells were selected using a stratified random design using depth, slope, and substrate characteristics. Other sampling “gears” (e.g., stationary, dropped cameras (BotCam) and cooperative research fishing) also occur in these sampling grid cells. The SeaBED is collecting high-resolution stereo video data without the use of external lighting in an effort to minimize alterations to fish behavior during the survey. High-resolution, forward-looking sonar data are simultaneously being collected by the AUV. The video and sonar data will be analyzed for bottomfish species identification and abundance, and compared to BotCam and fishing data obtained from the same grid cells.
SeaBED is programmed with a mission plan based on GIS bathymetry data while still aboard the ship. Programming parameters include navigational waypoints, speed, and altitude to maintain above the sea floor. Once submerged, the AUV does not resurface until the end of its mission. Several onboard sensors provide the data necessary for the vehicle’s autonomous navigation. SeaBED frequently reports its position (as well as information such as battery status, depth, and altitude) to the ship in telemetry messages via acoustic MODEM. An additional tracking sensor shows range and bearing between the ship and SeaBED during the mission. If any of these telemetry messages indicate an unexpected change in SeaBED’s planned mission, the mission can be aborted via acoustic MODEM message, resulting in the AUV returning to the surface for recovery. If needed, the AUV can be controlled from the surface using the acoustic modem to change parameters such as the start point of the mission plan or to turn the vehicle. Research is underway at WHOI to allow subsampled images to also be sent to the surface via acoustic MODEM.
Once the AUV completes its mission and returns to the surface, it is picked up by the ship and the collected data are downloaded. The video collected is saved for later viewing in the lab for fish enumeration and identification. The navigational data are saved for later mapping of the AUV’s true path and evaluating operational performance of the AUV. The AUV batteries are recharged overnight to prepare for the next day’s operations.
The PIFSC/NWFSC AUV team is led by Jeff Anderson and Elizabeth Clarke, and includes Erica Fruh, Curt Whitmire and Jeremy Taylor.