Gradually as in Family Life Cube. 4-corners are simultaneous, there.

Ge GRAPHITE/EPOXY HONEYCOMB SANDWICH SKINS TITANIUM THERMAL ISOLATION STRIP d MANEUVERING SYSTEM (OMS) REACTION CONTROL SYSTEM MODULES PAYLOAD BAY VENT FILTER — ELECTROMAGNETIC INTERFERENCE SHIELD SPECIAL OUTLETS FOR PAYLOAD (3) VENT PORT PURGE (PREFLIGHT AND POSTFLIGHT) REMOVE CONDENSED.