In the Orbiter Processing Facility bay 3, space shuttle Discovery's robotic arm is moved into place for installation in the payload bay. Scheduled to launch on the STS-119 mission, Discovery will carry the S6 truss segment to complete the 361-foot-long backbone of the International Space Station. The truss includes the fourth pair of solar array wings and electronics that convert sunlight to power for the orbiting laboratory. A launch date has not yet been determined. Photo credit: NASA/Jim Grossmann