New system could provide detailed images — even of soft tissue — from a lightweight, portable device.
Despite a wind chill index of -80oF and an emergency ice camp evacuation, the MIT Sea Grant Underwater Vehicles Laboratory successfully deployed its newest autonomous underwater vehicle beneath the Arctic ice. The nine-day expedition beginning March 22 was the Odyssey II's first major scientific operation.
Odyssey II's launch from a hole cut through five-foot-thick ice at a camp approximately 170 miles offshore of Prudhoe Bay on the northern coast of Alaska was a major validation of a new generation of low-cost vehicles that should revolutionize studies of the world's oceans.
Odyssey II is the most recent addition to a fleet of small, adaptable autonomous underwater vehicles (AUVs) built to run oceanographic missions on nonmilitary-sized budgets. With components costing less than $75,000, the 360-pound Odyssey II can travel 170 miles at depths up to 3.7 miles and is the first deep-diving AUV to carry a sonar system and two acoustic navigation systems.
Led by the Underwater Vehicle Laboratory's manager, James G. Bellingham, the MIT Sea Grant team conducted vehicle operations paving the way for inexpensive surveys of the previously unmappable underside of Arctic ice.
Three of the four other team members focused on different, critical aspects of the vehicle's underwater navigation system. These researchers included postdoctoral fellows: Donald K. Atwood, who developed state-of-the-art technology for acoustic navigation; John J. Leonard, who specialized in navigation relative to underwater features; and Jerome Vaganay, affiliated with the French agency Ifremer, who concentrated on merging navigation information from various sensors. Clifford A. Goudey, MIT Sea Grant fisheries engineer, contributed engineering expertise and assisted in operations.
During the Arctic expedition, the vehicle made several runs beneath the ice, conducting preliminary tests of under-ice mapping and obtaining data on conductivity, temperature and depth before piloting itself back into a capture net at its point of entry. Thanks to an innovative navigational system, the AUV was able to maneuver successfully beneath the irregularly shaped icepack and return home with pinpoint accuracy.
To help scientists communicate directly with the vehicle in future missions, preliminary acoustic communication tests were conducted with members of the Woods Hole Oceanographic Institution, with listening posts set up at various sites around the ice flow.
"The trip was a big success," Dr. Bellingham said. "This was the first round of tests of the critical components of the autonomous ocean sampling network."
A network in which many low-cost AUVs operate interactively from remote sites opens up the possibility of collecting oceanographic data over greater areas and for longer periods. The high costs of oceanographic vessels had previously prohibited this scope of data collection.
The need for a better understanding of sea-ice mechanics was powerfully illustrated when two grinding ice shelves opened a fissure through the middle of the ice camp, prompting a speedy evacuation of the Sea Grant team and other researchers working with the Sea Ice Mechanics Initiative. "Ultimately, it was the ice itself that cut short our effort," Dr. Bellingham said.
Odyssey II provides a unique capability for responding to transient events in the ice. Because the Arctic ice plays a significant role in air and sea interactions, understanding its mechanics will figure prominently in predictions regarding global climate. AUVs provide an affordable means for exploring unmapped environments otherwise unreachable by humans.
Because they do not rely on tethers, as do more widely known remotely operated underwater vehicles, AUVs need not be tended by a surface ship and are not subject to the problems associated with miles of underwater cables.
"Because of their low cost and long range, these AUVs could revolutionize the way we measure fish abundance," Dr. Goudey added.
Along with support from the Office of Naval Research for the Arctic expedition, AUV research at MIT Sea Grant has been sponsored by a number of agencies, including the National Science Foundation, the National Undersea Research Program and the Advanced Research Projects Agency, as well as numerous industrial supporters.
In upcoming missions, plans call forOdyssey II to study hydrothermal vent systems on the Juan de Fuca Ridge off the coast of Washington state in August and on the East Pacific Rise west of Central America next October.
A version of this article appeared in the April 13, 1994 issue of MIT Tech Talk (Volume 38, Number 29).