Space Shuttle Discovery sits on Launch Pad 39A after rollback of the rotating service structure or RSS.

Space Shuttle Discovery sits on Launch Pad 39A at NASA’s Kennedy Space Center in Florida, after rollback of the rotating service structure, or RSS. The oxygen vent hood, called the “beanie cap,” is positioned above the external fuel tank. It is designed to vent gaseous oxygen vapors away from the shuttle. The rollback is preparation for Discovery’s scheduled 1:36 a.m. EDT liftoff Aug. 25 on the STS-128 mission with a crew of seven. First motion was at 5:06 a.m. EDT and completed at 5:46 a.m. EDT. The service structure provides weather protection and access to the space shuttle at the launch pad. The 13-day mission will deliver a new crew member and 33,000 pounds of equipment to the International Space Station. The equipment includes science and storage racks, a freezer to store research samples, a new sleeping compartment and the COLBERT treadmill. STS-128 will be Discovery's 37th mission and the 30th shuttle flight dedicated to station assembly and maintenance. Photo credit: NASA/Troy Cryder