Washington - The space shuttle Atlantis is scheduled to launch September 6.

After returning from its Houston home base to the Kennedy Space Center September 2, the STS-115 six-member crew begins final preparations for launch on Wednesday.

Led by Commander Brent W. Jett Jr., the STS-115 crew consists of pilot Christopher J. Ferguson and mission specialists Heidemarie M. Stefanyshyn-Piper, Joseph R. Tanner, Daniel C. Burbank and Steven G. MacLean, who represents the Canadian Space Agency.

STS-115, regarded as one of the most challenging space missions ever, aims to resume building the International Space Station, according to NASA. During three spacewalks, the Atlantis crew will install the P3/P4 integrated truss - a segment weighing almost 16 metric tons - and a second set of solar arrays, both of which will double the station’s capacity to generate power from sunlight and allow for tracking of the sun.

“It’s a mission they’ve had four years to train for, and it’s still no cakewalk,” said Jett.

As in previous shuttle flights, the Atlantis crew will test safety inspection techniques and perform a shuttle back flip as it approaches the station so that the belly can be photographed and any damage on the shuttle’s heat shield can be detected. The other safety procedure includes inspecting the shuttle wings’ leading edges and nose cap.

According to NASA, STS-115 is the 116th space shuttle flight, making it the 27th flight for Atlantis and the 19th flight to the station.

The countdown for the Wednesday launch officially starts at 8 a.m. EDT September 3.

For more information about NASA and the U.S. space program, see Science and Technology.

For more information on the Atlantis' mission, visit NASA’s Web site.