Coastguards in northern California are planning to call off the search for missing Microsoft researcher Jim Gray early on Thursday. He went missing on a sailing trip off San Francisco Bay on Sunday.

Associated Press reports a helicopter, six patrol boats, and a plane have been scouring the area since Monday to no avail. Coastguard spokesman Jonathan Cilley said: "If they were to even find a life raft, they would have located him in their search patterns."

Google co-founder Sergey Brin was reportedly inquiring into the possibility of using his firm's access to recent high resolution satellite imagery to find Turing Prize winner Gray, who was instrumental in the development of databases. Engineers at Amazon were exploring whether their software could be used to perform fast searches of the satellite images.

An experienced sailor, Gray had told family he was sailing to the Farallon islands 27 miles offshore to scatter the ashes of his recently-deceased mother, and was due home Sunday evening. The weather and sea conditions were reportedly fine.

University of Washington computer scientist Ed Lazowska, who had email contact with Jim Gray on Saturday, said: "Everyone's unbelievably distressed. I can't imagine this is anything other than an accident of some sort." ®

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