Google has requested imagery from Digital Globe, the satellite imagery firm in Longmont, Colo., to help in the search for missing Nevada aviator Steve Fossett.

Fossett disappeared after taking off at the controls of a small plane Monday from the Flying M Ranch airstrip about 70 southeast of Reno, Nev. He left no flight plan, and searchers have been combing a 10,000 square mile expanse of Nevada and California to no avail.

Digital Globe's QuickBird satellite scanned what is believed to be an 11-mile wide and 120-mile long strip of Nevada around the ranch, but Fossett could have flown beyond the boundaries of the satellite scan. Google declined to comment on the search but it's known to connect search and rescue teams to available satellite imagery. Digital Globe and other satellite company imagery companies routinely feed Google data that goes into its Google Earth software, but Google Earth image posting is typically three to six months behind when it was taken.

In a previous search, satellite images were used to try to track down the missing computer scientist Jim Gray, who disappeared in his sailboat off the coast near San Francisco. Digital Globe images were subdivided into tiles at Johns Hopkins University and inspected by astronomy faculty and graduate students. The effort proved that volunteers could identify 40-foot boats in the fuzzy gray images, but Gray's Tenacious was never found.

Fossett's U.K. financier and partner, Richard Branson, told the San Francisco Chronicle that he was coordinating the search for Fossett by working with Google and others interested in finding his missing plane. It was a blue and white Bellanca Citabria Super Decathlon, a plane capable of aerial aerobatics. It had orange strips on the fuselage and sunburst patterns on the wings.

Chuck Herrick, Digital Globe spokesman, said the firm will try for another scan Saturday as QuickBird passes over the region again. The satellite can capture objects the size of a car or smaller, and image enhancement software can sometimes filter out what isn't visible to the naked eye. But Herrick warns that a small plane can fly into a canyon or ravine, or hit the ground behind a hill that obscures it from the satellite's 45-degree angle view.

"You could see a plane, but it depends on the terrain and vegetation cover," he notes.

Even if satellite images don't contribute directly to locating a downed plane, they can be used to map the search area, highlight what's already been flown over by helicopter or search plane, and define the terrain where the missing aviator is most likely to be found, he points out.