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KENNEDY SPACE CENTER, FLA. -- On top of Launch Pad 39A at NASA's Kennedy Space Center, space shuttle Endeavour waits for liftoff on the STS-123 mission. The rotating service structure was rolled back starting at 8:23 a.m. and complete at 8:55 a.m. At far right is the 300,000-gallon water tank that provides the water for sound suppression during liftoff. Signs on the gate across the pad illustrate the primary payloads on the mission: the Japan Aerospace Exploration Agency's Kibo laboratory and the Canadian Space Agency's two-armed robotic system, Dextre. The rotating structure provides protected access to the orbiter for changeout and servicing of payloads at the pad. The structure is supported by a rotating bridge that pivots about a vertical axis on the west side of the pad's flame trench. After the RSS is rolled back, the orbiter is ready for fuel cell activation and external tank cryogenic propellant loading operations. The pad is cleared to the perimeter gate for operations to fill the external tank with about 500,000 gallons of cryogenic propellants used by the shuttle’s main engines. This is done at the pad approximately eight hours before the scheduled launch. Liftoff is scheduled for 2:28 a.m. EDT March 11. Photo credit: NASA/Kim Shiflett