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Photos: Alison Scott

Features

September, 2014

Adventures with an Autonomous Underwater Vehicle
at Gray's Reef

Alison Scott,
Intern,
Gray's Reef National Marine Sanctuary

Gray's Reef National Marine Sanctuary is currently collaborating with Dr. Catherine Edwards from the Skidaway Institute of Oceanography and PhD students from Georgia Tech on a research project to determine how accurately an Autonomous Underwater Vehicle (AUV) carrying acoustic receivers can detect acoustic transmitters within a selected array.

Team Ocean Volunteer Randy Rudd helping in the water.

Team Ocean Volunteer Randy Rudd helping in the water.
Photo: Alison Scott

The staff at Gray's Reef National Marine Sanctuary deployed 8 transmitters on buoy lines within a 1500 by 1500 meter area. During the two week study, the AUV glides past each of the transmitters multiple times while flying a set course. The acoustic receivers attached to the glider should establish a record of the encountered transmitters as it flies past the buoy lines (see diagram below). The team is interested in determining how well it detects the transmitters as it flies past at different angles and depths. Ultimately scientists will use the AUV to track fish tagged with similar transmitters.

In addition to detecting transmitters, the AUV measures other environmental factors such as dissolved oxygen, temperature and depth in real time. Surfacing at regular intervals, the AUV uploads collected data via a satellite transmission and relays the planned next path. The engineers at Georgia Tech can then manipulate this path if required.

Modena ready to be deployed! Modena down under!

Modena ready to be deployed!
Photo: Alison Scott

Modena down under!
Photo: Jaren Halonen

Some of the challenges in the deployment of the AUV Modena have included setting the correct ballast to establish neutral buoyancy in the dense seawater at Gray's Reef and stronger than predicted currents due to a storm system. The engineers are currently evaluating the best approach for modulating the speed of the AUV for variable currents.

AUV Deployment Process.

Photo: Alison Scott


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