Before the sun sets on Launch Pad 39A shuttle Discovery is concealed by the pad's rotating service structure.

Before the sun sets on Launch Pad 39A at NASA's Kennedy Space Center in Florida, space shuttle Discovery is concealed by the pad's rotating service structure. The structure provides weather protection and access to the shuttle. RSS "rollback," as it's called, is a significant milestone in the launch countdown.

Launch of Discovery on the STS-133 mission to the International Space Station is set for 3:29 p.m. on Nov. 4. During the 11-day mission, Discovery and its six crew members will deliver the Permanent Multipurpose Module, packed with supplies and critical spare parts, as well as Robonaut 2, to the orbiting laboratory. Discovery, which will fly its 39th mission, is scheduled to be retired following STS-133. This will be the 133rd Space Shuttle Program mission and the 35th shuttle voyage to the space station. For more information on STS-133, visit www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts133/. Photo credit: NASA/Kim Shiflett