Space Shuttle Endeavour waits on Launch Pad 39B for launch on mission STS-97.

Space Shuttle Endeavour waits on Launch Pad 39B for launch on mission STS-97. Behind it are the orange external tank flanked by two solid rocket boosters. On either side of Endeavour’s tail are the tail service masts, which support the fluid, gas and electrical requirements of the orbiter’s liquid oxygen and liquid hydrogen aft T-0 umbilicals. The masts also protect the ground half of those umbilicals from the harsh launch environment. At launch, the masts rotate backward, triggering a compressed-gas thruster and causing a protective hood to move into place and completely seal the structure from the main engine exhaust. At the end of the orbiter access arm, near the nose of Endeavour, is the White Room, an environmental chamber that provides both entrance to the orbiter and emergency egress, if needed. The arm remains extended until 7 minutes, 24 seconds before launch. The arm extends from the Fixed Service Structure. In the center of Endeavour are the payload bay doors. Endeavour is scheduled to launch Nov. 30 at 10:06 p.m. EST