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Atlas/DMSP launch timeline

T-00:02.7 Engine Start
The Russian-designed RD-180 main engine is ignited and undergoes checkout prior to launch.
T+00:01.1 Liftoff
The Atlas 5 vehicle, designated AV-017, lifts off and begins a vertical rise away from Vandenberg Air Force Base, California.
T+04:07 Main Engine Cutoff
The RD-180 main engine completes its firing after consuming its kerosene and liquid oxygen fuel supply in the Atlas first stage.
T+04:13 Stage Separation
The Common Core Booster first stage of the Atlas 5 rocket separates from the Centaur upper stage. Over the next few seconds, the Centaur engine liquid hydrogen and liquid oxygen systems are readied for ignition.
T+04:23 Centaur Ignition 1
The Centaur RL10 engine ignites for the sole firing needed to inject the upper stage and spacecraft into polar orbit.
T+04:31 Nose Cone Jettison
The payload fairing that protected the DMSP spacecraft during launch is separated once heating levels drop to predetermined limits.
T+15:20 Centaur Cutoff 1
The Centaur engine shuts down after arriving in a planned circular polar orbit of 462.8 nautical miles inclined 99 degrees to the equator.
T+18:09 DMSP Separation
The U.S. Air Force's Defense Meteorological Satellite Program 18 spacecraft is released from the Centaur upper stage to begin its mission.
T+2:58:07 Centaur Ignition 2
After moving away from the DMSP spacecraft, the Centaur will spend a couple of hours in demonstration mode and eventually re-ignite the RL10 engine for disposal.
T+3:01:47 Centaur Cutoff 2
At the conclusion of its second firing, the Centaur will have embarked on an Earth-escape trajectory.

Data source: United Launch Alliance.