The STS-115 crew members walk toward the Astrovan that will take them to Launch Pad 39B.

The STS-115 crew members walk toward the Astrovan that will take them to Launch Pad 39B. Seen left to right are Mission Specialists Heidemarie Stefanyshyn-Piper, Steven MacLean, Joseph Tanner and Daniel Burbank; Pilot Christopher Ferguson; and Commander Brent Jett. This is the second attempt at launch after a week's postponement due to weather and technical concerns. Atlantis is scheduled to lift off at 11:41 a.m. EDT on this date 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