The mission crew enthusiastically greet the onlookers as they head to the Astrovan for the ride to Launch Pad 39B.

After suiting up, the STS-115 mission crew enthusiastically greet the onlookers as they head to the Astrovan for the ride to Launch Pad 39B. From left are Mission Specialist Heidemarie Stefanyshyn-Piper, Steven MacLean, Joseph Tanner, Pilot Christopher Ferguson and Daniel Burbank. Not seen is Commander Brent Jett. The crew is eager for another attempt at liftoff after the Sept. 8 scrub. The launch attempt on Sept. 8 was scrubbed due to an issue with a fuel cut-off sensor system inside the external fuel tank. This is one of several systems that protect the shuttle's main engines by triggering their shutdown if fuel runs unexpectedly low. 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