(12/03/2001) -- The Rotating Service Structure on Launch Pad 39B rolls away from Space Shuttle Endeavour atop the Mobile Launcher Platform. The Space Shuttle comprises the orbiter and an external tank flanked by twin solid rocket boosters. Above the external tank is the Gaseous Oxygen Vent Arm that vents gaseous oxygen vapors away from the Shuttle. The vent hood assembly at the end is often referred to as the 'beanie cap.' On either side of the orbiter's tail and main engines are two tail masts that support the fluid, gas and electrical requirements of the orbiter's liquid oxygen and liquid hydrogen aft T-0 umbilicals. . Each tail mast is 31 feet (9.4 meters) high, 15 feet (4.6 meters) long and 9 feet (3.1 meters) wide. Endeavour is scheduled to launch on mission STS-108 Dec. 4 at 5:45 p.m. EST. On this 12th flight to the International Space Station, known as a Utilization Flight, Endeavour will carry a crew of four plus the Expedition 4 crew, who will replace Expedition 3 aboard the ISS. The payload includes the Multi-Purpose Logistics Module Raffaello, filled with supplies, equipment and experiments