Dr. Tom Grothues—or “Motz,” as he is known to his colleagues at the Rutgers University Marine Field Station in Tuckerton, just north of Atlantic City—studies the migration and habitats of fish off the Jersey coast; the salinity, temperature, currents, and oxygen level of the water itself; and the features of the ocean floor. In all this research he is aided immeasurably by a torpedo-shaped Autonomous Underwater Vehicle, or AUV, called the REMUS 100 (Remote Environmental Measuring Units).
Unlike a Remotely Operated Vehicle, or ROV (think opening scenes of the movie Titanic), the $320,000 REMUS 100 has no umbilical cord but is programmed in advance to follow a certain course, as simple or intricate as needed, and to gather mountains of data. It is just over 5 feet long, weighs less than 80 pounds, and can be walked out into the surf or placed in the water from the side of a small boat.
The REMUS was developed by the Woods Hole Oceanographic Institute and is manufactured by Hydroid Inc. There are about 120 REMUS 100’s in the world. Many are used by the Navy to scout minefields. Other models, some as long as trucks, are used to inspect underwater sections of bridges or survey conditions under ice shelves.
1. DRIVE TIME
With its three-blade propeller, the REMUS can reach speeds of up to 5 knots (roughly 6 mph). It can travel for as long as eighteen hours, periodically surfacing to check position and using GPS to navigate to a precise pickup location.
2. SWISS ARMY KNIFE
The REMUS packs a variety of tools. Sensors near the front measure conductivity, depth, and temperature of the water. An oxygen optode, which looks like a hockey puck, uses light beams to measure dissolved oxygen in the water, a crucial aid in mapping oxygen-depleted “dead zones,” which impede fish migration and repel life.
3. BOTH SIDES NOW
Running along each side of the REMUS is a high-frequency side-scan transducer, which emits sonar pulses that sweep the ocean floor and echo back to the REMUS. When the two views are stitched together, they yield a sharp image of the ocean floor.
4. CURRENT EVENTS
Four small, round sensors on top of the REMUS and four on the bottom use sonar to map water currents and direction, and to determine depth to the bottom.
5. NOSING AROUND
The Rutgers REMUS employs two specially designed nose cones. One is a ram scoop, which gathers plankton samples for analysis. The other is a hydrophone, or underwater microphone, which listens for signals from fish tagged with electronic transmitters.