Endeavour Crew Rests Before Trip Home

In this image provided by NASA astronaut Robert L. Behnken, participates in the mission's fourth spacewalk Thursday March 20, 2008 as construction and maintenance continue on the International Space Station. During the 6-hour, 24-minute spacewalk, Behnken and astronaut Mike Foreman (out of frame), replaced a failed Remote Power Control Module -- essentially a circuit breaker -- on the station's truss. The spacewalkers also tested a repair method for damaged heat resistant tiles on the space shuttle. The sample tiles will be returned to Earth to undergo extensive testing on the ground. (AP Photo/NASA)