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KENNEDY SPACE CENTER, FLA. -- Afternoon clouds have rolled in, serving as a background for space shuttle Discovery after rollback of the rotating service structure, at far left. Seen above the golden external tank is the vent hood (known as the "beanie cap") at the end of the gaseous oxygen vent arm, extending from the fixed service structure. Vapors are created as the liquid oxygen in the external tank boil off. The hood vents the gaseous oxygen vapors away from the space shuttle vehicle. Below it, also extending toward Discovery from the structure, is the orbiter access arm with the White Room at the end. The crew gains access into the orbiter through the White Room. At right is the 300,000-gallon water tank that provides water for sound suppression during liftoff. Rollback of the RSS started at 3:34 p.m. EDT and was complete at 4:20 p.m. The RSS provides protected access to the orbiter for changeout and servicing of payloads at the pad. Rollback of the pad's RSS is one of the milestones in preparation for the launch of mission STS-120. Discovery is scheduled for liftoff at 11:38 a.m. EDT on Oct. 23. The mission will be the 23rd assembly flight to the International Space Station and the 34th flight for Discovery. Payload on the mission is the Italian-built U.S. Node 2, called Harmony. The 14-day mission will install Harmony and move the P6 solar arrays to their permanent position and deploy them. Discovery is expected to complete its mission and return home at 4:47 a.m. EST on Nov. 6. Photo credit: NASA/Kim Shiflett