Fisheries Acoustics Research

The DEIMOS instrument package was deployed in Monterey Bay as part of the MARS ocean observatory during the last week in February 2009. Prior to deployment, the package was tested and calibrated at the Monterey Bay Aquarium Research Institute, or MBARI. When all testing was complete, the instrument was placed on the RV Point Lobos. Once on site, ROV Ventana transported, placed, and connected DEIMOS to the MARS node more than 870 meters beneath the ocean surface. After activation, DEIMOS immediately began transmitting data back to shore and continues to transmit and receive data once every 5 seconds.

Installation and Testing

After arriving at MBARI, we installed our rackmounted computers in the MARS control room.

Left: Ken Heller (MBARI IT specialist) helping us to negotiate computer firewalls, just one of many tasks.
Right: Our rackmounted computer system is shown just above Dick in this picture.

With the computer equipment connected to the MARS node simulator, we could now lower DEIMOS into the MBARI 10 m deep test tank. The tank is large enough to test field equipment such as remotely operated underwater (ROV) or autonomous underwater (AUV) vehicles and divers. It even has vewing windows from various rooms in the building.

Using a very large overhead crane, the instrument was gently lowered to the bottom. The simulated science port was powered up. We were off and running. Initial tests looked great.

David Barbee takes a brief break from work. DEIMOS and some testing equipment are visible.

Looking down on DEIMOS while it was on the bottom of the MBARI 10m deep test tank.

Calibration

Once the echosounder was running, David and Dick started to calibrate the system. When calibrating a reference target, a tungsten carbide or copper sphere, is placed within the transducer beam. The sphere is first aligned with the acoustic axis and then slowly swung through the entire "main lobe" of the beam. Unfortunately, the test tank began an ozone cleaning cycle about halfway through our first set of calibration measurements. Tiny ozone bubbles suspended in water are very good acoustical reflectors. We had to wait until the bubbles abated to resume our work.

Dick hard at work calibrating the transducer. A tungsten carbide sphere is attached to the fishing line.

This research was made possible by the University of Washington's School of Aquatic and Fishery Sciences, Kongsberg Simard, and the Monterey Bay Aquarium Research Institute.