In the payload changeout room on Launch Pad 39B a worker helps with the door opening on the payload canister.

In the payload changeout room on Launch Pad 39B, a worker (at left) helps with the door opening on the payload canister. Inside is the Port 3/4 truss segment for mission STS-115. The payload will be removed from the canister and later installed in Space Shuttle Atlantis' payload bay. Atlantis' launch window begins Aug. 28. During its 11-day mission to the International Space Station, the STS-115 crew of six astronauts will install the truss, a 17-ton segment of the space station's truss backbone. Photo credit: NASA/Jack Pfaller