STS-115 Mission Specialist Joseph Tanner waits to complete suiting up before heading to the launch pad.

In the Operations and Checkout Building at NASA Kennedy Space Center, STS-115 Mission Specialist Joseph Tanner waits to complete suiting up before heading to the launch pad. Tanner is making his fourth shuttle flight on this mission to the International Space Station aboard Space Shuttle Atlantis. On its second attempt for launch, Atlantis is scheduled to lift off at 11:41 a.m. EDT today from Launch Pad 39B. 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/Kim Shiflett