Space Shuttle Atlantis is illuminated on Launch Pad 39B surrounded by amber lights on the rotating and fixed service structures.

Space Shuttle Atlantis is illuminated on Launch Pad 39B, surrounded by amber lights on the rotating and fixed service structures. Seen above the golden external tank is the vent hood (known as the "beanie cap") at the end of the gaseous oxygen vent arm. Vapors are created as the liquid oxygen in the external tank boil off. The hood vents the gaseous oxygen vapors away from the space shuttle vehicle. Atlantis was originally scheduled to launch on Aug. 27, but a scrub was called by mission managers due to a concern with fuel cell 1. Atlantis is scheduled to lift off at 11:41 a.m. EDT Sept. 8. During the STS-115 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 ISS. STS-115 is scheduled to last 11 days with a planned landing at KSC. Photo credit: NASA/Ken Thornsley