The National Aeronautics and Space Administration said the primary goal of the six-hour, 53-minute excursion was the completion of the outfitting of Dextre, the Canadian-produced mobile servicing system on the International Space Station. Linnehan and Behnken installed a spare parts platform and tool handling assembly for Dextre and, among other tasks, attached critical spare parts to an external stowage platform.

NASA controllers in Houston said Behnken and astronaut Mike Foreman are to begin the mission's fourth spacewalk at 6:28 p.m. EDT Thursday. They were to perform tasks that include a shuttle tile repair test and replacement of a space station circuit breaker.