Daniel Burbank left and Steven MacLean get help with their launch suits from the closeout crew before entering Space Shuttle Atlantis.

STS-115 Mission Specialists Daniel Burbank (left) and Steven MacLean get help with their launch suits from the closeout crew before entering Space Shuttle Atlantis. Both astronauts are making their second shuttle flights. MacLean is with the Canadian Space Agency. 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 landing at KSC