STS-115 Mission Specialist Steven MacLean tests the fit of his helmet before launching.

STS-115 Mission Specialist Steven MacLean tests the fit of his helmet before launching on Aug. 27. MacLean, who represents the Canadian Space Agency, will be making his second flight on a shuttle. Mission STS-115 is scheduled to lift off about 4:30 p.m. Aug. 27 on Space Shuttle Atlantis. The crew will deliver and install the P3/P4 segment to the port side of the integrated truss system on the International Space Station. The truss includes a new set of photovoltaic solar arrays. When unfurled to their full length of 240 feet, the arrays will provide additional power for the station in preparation for the delivery of international science modules over the next two years. The mission is expected to last 11 days and includes three scheduled spacewalks. Photo credit: NASA/Kim Shiflett