The payload canister arrives under the payload changeout room in the rotating service structure at NASA's Kennedy Space Center.

The payload canister arrives under the payload changeout room in the rotating service structure on Launch Pad 39B at NASA's Kennedy Space Center. The canister holds the payloads for mission STS-121: the multi-purpose logistics module Leonardo, with supplies and equipment for the International Space Station; the lightweight multi-purpose experiment support structure carrier; and the integrated cargo carrier, with the mobile transporter reel assembly and a spare pump module. The payload canister will be lifted into the changeout room where the payloads will be transferred to Space Shuttle Discovery's payload bay. Discovery is scheduled to launch on mission STS-121 from Launch Pad 39B in a window that opens July 1 and extends to July 19. Photo credit: NASA/Kim Shiflett