Note: The animation images used below are NOT meant to depict the classified NRO payload being launched on this mission. Rather it is to illustrate a generic Atlas cargo.

T-00:02.4	Engine start
	Atlas booster and sustainer engines are ignited and undergo checkout prior to liftoff. The two ground-start boosters will light a half-second before launch.
T+00:00	Launch
	The Atlas 2AS rocket, designated AC-157, lifts off and begins a vertical rise away from launch pad 36A at Cape Canaveral Air Force Station, Florida.
T+00:08	Roll Program
	During vertical ascent, Atlas begins a seven-second roll maneuver to align itself with proper flight azimuth. Following the roll, the Centaur inertial guidance system controls pitch and yaw programs.
T+00:58.5	Air-lit SRB Ignition
	The remaining two solid rocket boosters strapped to the Atlas are ignited once onboard computer software determines the two ground-start SRBs have burned out, about two seconds earlier.
T+01:08.9	Jettison Ground-Lit SRBs
	The two spent solid rocket boosters that were ignited on the ground are jettisoned to fall into the Atlantic Ocean.
T+01:56.6	Jettison Air-Lit SRBs
	Computer software will determine the air-start solid rocket boosters have burned all their propellant and should be jettisoned from the Atlas vehicle. The two SRBs will fall into the Atlantic Ocean.
T+02:44.9	Booster Engine Cutoff
	BECO occurs when axial acceleration of 5.0 g is obtained. Sustainer engine provides the continued boost toward orbit for the Atlas rocket.
T+02:47.91	Jettison Booster Package
	The bottom engine structure with the two booster engines is separated from the Atlas vehicle.
T+03:25.2	Jettison Payload Fairing
	The 14-foot diameter aluminum payload fairing that protected the NRO satellite during launch is separated once heating levels drop to predetermined limits.
T+04:58.0	Sustainer Engine Cutoff
	SECO is commanded once minimum residual propellant is sensed inside the Atlas booster stage.
T+04:59.9	Atlas/Centaur Separation
	The Atlas booster stage separates from the Centaur upper stage. Over the next few seconds, the Centaur liquid hydrogen and liquid oxygen systems are readied for engine ignition.
T+05:16.5	Centaur 1st Main Engine Start
	MES 1, the longer of the two Centaur firings begins to inject the upper stage and NRO spacecraft into a parking orbit with a perigee of 95 nautical miles and apogee of 466 nautical miles inclined 28.2 degrees.
T+09:54.2	Centaur Main Engine Cutoff
	MECO 1 occurs the Centaur engines are shutdown, arriving in a planned parking orbit. The vehicle begins a coast period over the mid-Atlantic before arriving at the required location in space for the second burn.
T+24:17.8	Centaur 2nd Engine Start
	MES 2 occurs over the Atlantic Ocean between the African Ivory Coast and Ascension Island before the rocket passes over the equator. The burn lasts until all the Centaur fuel is used, placing the NRO payload into a geosynchronous transfer orbit.
T+25:48.8	Centaur Main Engine Cutoff
	At the point of MECO 2, the Centaur/NRO vehicle should be in the required transfer orbit with a perigee of 146 naut. miles, apogee of 20,247 naut. miles, inclined 26.5 deg. Moments later, the stage begins aligning to the satellite separation attitude.
T+29:35.8	Spacecraft Separation
	The classified payload for the U.S. National Reconnaissance Office is released into orbit from the Centaur upper stage to complete the AC-157 launch.

Image and data source: International Launch Services and Lockheed Martin Astronautics.