4:59 p.m. Begin 30-minute hold at T-4 Minutes
5:03 p.m. Weather Briefing
5:26 p.m. Status check to continue countdown
5:29:11 p.m. T-4 Minutes and counting
5:33:08 p.m. RD-180 engine ignition
5:33:11 p.m. Launch
5:33:29 p.m. Begin pitch/yaw/roll maneuver
5:34:33 p.m. Mach 1
5:34:44 p.m. Maximum Dynamic Pressure
5:37:26 p.m. Atlas booster engine cutoff (BECO)
5:37:32 p.m. Atlas booster/Centaur separation
5:37:42 p.m. Centaur first main engine start (MES1)
5:37:50 p.m. Payload Fairing jettison
5:51:27 p.m. Centaur first main engine cutoff (MECO1)
5:54:16 p.m. Cygnus spacecraft separation
~6:33 p.m. Cygnus solar array deploy
~7:30 p.m. Post-Launch News Conference on NASA Television