"Loneliness and the Long Distance Glider," ME Online Exclusive, Companion to "A Model Mission" story, December 2004

loneliness and the long distance glider

by Gayle Ehrenman, Associate Editor

A small ocean glider named Spray has become the first autonomous underwater vehicle to cross the Gulf Stream underwater.

Launched on Sept. 11, 2004, about 100 miles south of Nantucket Island, Mass., the 6-foot-long orange glider with a 4-foot wingspan looks like a model airplane with no visible moving parts. It made its way slowly toward Bermuda at about one-half knot, roughly half a mile an hour or 12 miles per day, measuring various properties of the ocean as it glided up to the surface and then back down to 1,000-meters depth three times a day. Scientists recovered the vehicle in early November north of Bermuda.

"It has been exciting, to say the least," said Breck Owens, one of the developers of the robot for Woods Hole Oceanographic Institution. "This trip proved we can use gliders to monitor circulation patterns and major current." Other collaborators on the project include the Scripps Institution of Oceanography at the University of California, San Diego, and the Office of Naval Research.

The Spray autonomous underwater vehicle measures roughly 6.5 feet long and 8 inches in diameter.

Spray was developed to provide a small, long-range autonomous platform for long-term ocean measurements. The underwater glider uses lithium batteries and a hydraulic pump to periodically change its volume to alternately glide upward and downward.

Spray has a range of about 3,500 miles, which means it could potentially cross the Atlantic Ocean. Its mission is to provide a relatively low-cost way for scientists to observe large-scale changes under the ocean surface that might otherwise go unobserved, according to Owens.

The glider follows a preprogrammed course, and surfaces every seven hours to relay its position and information about ocean conditions via satellite back to the team in Woods Hole, Mass., and San Diego. On this mission, it was equipped with an instrument for measuring the temperature, salinity, and pressure of the ocean, and with an optical sensor for measuring the turbidity in the water. Its next mission is slated for early 2005.

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