The rotating service structure left on Launch Pad 39B begins rolling back to reveal Space Shuttle Atlantis.

The rotating service structure (left) on Launch Pad 39B begins rolling back to reveal Space Shuttle Atlantis. The RSS provides protected access to the orbiter for changeout and servicing of payloads at the pad and then is rolled away before liftoff. Atlantis is scheduled to launch Sept. 6 at 12:29 p.m. EDT on mission STS-115. During the mission, Atlantis' astronauts will deliver and install the 17.5-ton, bus-sized P3/P4 integrated truss segment on the station. The girder-like truss includes a set of giant solar arrays, batteries and associated electronics and will provide one-fourth of the total power-generation capability for the completed station. This mission is the 116th space shuttle flight, the 27th flight for orbiter Atlantis, and the 19th U.S. flight to the International Space Station. STS-115 is scheduled to last 11 days with a planned KSC landing at about 8:03 a.m. EDT on Sept. 17. Photo credit: NASA/George Shelton