T-5 minutes and counting
-Start auxiliary power units
-Arm solid rocket booster range safety safe and arm devices
-Start orbiter aerosurface profile test, followed by main engine gimbal profile test (T-3 minutes, 55 seconds)
-Retract gaseous oxygen vent arm, or "beanie cap" (T-2 minutes, 50 seconds)[6]
-Crew members close and lock their visors (T-2 minutes, 0 seconds)
-Orbiter transfers from ground to internal power (T-50 seconds)
-Ground launch sequencer is go for auto sequence start (T-31 seconds)
-Activate launch pad sound suppression system (T-16 seconds)