With the Service Structure rolling back Space Shuttle Atlantis is revealed on the Mobile Launcher Platform.

With the Rotating Service Structure rolling back, Space Shuttle Atlantis is revealed on the Mobile Launcher Platform. At the top is the 13-foot-wide “beanie cap,” at the end of the Gaseous Oxygen Vent Arm, designed to vent gaseous oxygen vapors away from the Space Shuttle. Lower is the Orbiter Access Arm with the environmental chamber, known as the “white room,” extended to the orbiter. The chamber provides entry for the crew into the orbiter and also serves as emergency egress up to 7 minutes 24 seconds before launch