Silicon Valley continues its search for Microsoft researcher Jim Gray, who hasn't returned from a Jan. 28 solo trip in his 40-foot sailboat off San Francisco. In the effort to find him, technologists are using the latest tools, some of which Gray himself helped develop: advanced satellite imaging, ocean drift modeling, and large database searching techniques.

Within days of his disappearance, the U.S. Coast Guard ran grid searches by ship and air over 132,000 square miles of ocean from the Channel Islands off Los Angeles to Humboldt Bay in Northern California. Unable to find any sign of Gray's red-hulled Tenacious or debris that might indicate a wreck, the Coast Guard discontinued its search on Feb.1.

The odds get longer each day, but a network of colleagues, peers, and acquaintances has picked up where the Coast Guard left off. Jim Frew, an expert at using satellite imagery in environmental science and an associate professor at the University of California at Santa Barbara, and others quickly concluded that with the right imagery and enough eyeballs, a 40-foot boat could be found on the ocean. In addition, Gray's boat has a standard piece of equipment for Bay Area sailors, a pie-plate-like radar reflector, good for alerting container ships to a sailboat's presence. That could yield a characteristic signature if it comes within range of a radar satellite, potentially functioning as a second data source, they reason.

IMAGES, DRIFT
On the day before the Coast Guard search ended, Joseph Hellerstein, a computer science professor at the University of California at Berkeley, established a Web site devoted to the ongoing civilian effort, and researchers at the Ames Research Center, a NASA unit at Moffett Field in the valley, persuaded a high-altitude aircraft pilot to change his flight plan and take high-resolution imagery of the search area. And, at the request of the group and the Coast Guard, DigitalGlobe, a satellite imaging company, redirected its satellites to capture more imagery of the search area.

One of the people volunteering to help is Werner Vogels, CTO of Amazon.com, who has written several research papers with Gray. Vogels arranged for satellite images to be uploaded to Amazon, where its engineers subdivided the huge images into smaller 400-by-400-pixel tiles that were posted to Amazon's Mechanical Turk site, which divvies up routine tasks among many people. Twelve thousand volunteers viewed blown-up versions of the tiles and in a few days inspected all of them for objects that might be a boat.

Coordinating that effort was Oracle VP Mike Olson, a veteran open source project leader and a friend of Gray's. As the image review proceeded, Olson found other volunteers at the Jet Propulsion Lab to apply the latest ocean surface modeling techniques to data obtained from a buoy dropped by the Coast Guard. Their objective: to determine where a boat might drift under prevailing conditions. Olson, in a Feb. 8 Web site posting, called the work done by the image and drift teams unprecedented and said it produced valuable information.

Based on the modeling, the Coast Guard went out again to search the shoreline north of San Francisco and Drakes Bay. If Gray had gotten into trouble in San Francisco's northern offshore shipping lane, the model indicated, the boat or debris would wash ashore in that area. If he were drifting south, he would be far offshore and driven by the wind, it showed. Private planes headed south.

Thus far, they have come up empty handed. The search for Jim Gray continues.

WHERE'S JIM GRAY?
FEB. 8 Limited visibility off the coast hampers the air search	FEB. 7 Search extends south along the coast of Baja California and Mexico	FEB. 6 Searchers rule out possibility of collision between Tenacious and a major vessel in north shipping channel	FEB. 5 Distribution of "missing sailor" fliers expands to 65 West Coast marinas
Data: Tenacious Search Web site