Timeline: Atlas 5/NROL-79 launch events

Follow the unclassified portion of the Atlas 5 rocket’s ascent to space from California’s Vandenberg Air Force Base launch site with the U.S. National Reconnaissance Office’s NROL-79 satellite payload. Launch is scheduled for Wednesday at 9:50 a.m. local time (12:50 p.m. EST; 1750 GMT).

T+00:01.1: Liftoff

The United Launch Alliance Atlas 5 vehicle, designated AV-068, will lift off and begin a vertical rise away from Space Launch Complex 3-East at Vandenberg Air Force Base, California.

T+00:81: Mach 1 and Max Q

The Atlas rocket achieves Mach 1 some 81 seconds into the flight, then passes through the region of maximum dynamic pressure at 89 seconds.

T+04:03: Main Engine Cutoff

The RD-180 main engine completes its firing after consuming the load of RP-1 kerosene fuel and liquid oxygen supply in the Atlas first stage.

T+04:09: 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+04:19: Centaur Ignition No. 1

The Centaur RL10 engine ignites to inject the Centaur stage and NROL-79 spacecraft into orbit.

T+04:27: Nose Cone Jettison

The two-piece, 14-foot-diameter payload fairing that protected the NROL-79 craft during the atmospheric ascent is separated to reveal the satellite to space.

The mission now enters a news blackout to perform the orbit-shaping and payload deployment for the National Reconnaissance Office in secrecy.

After performing its mission, the Centaur will be de-orbited into the South Pacific, west of Chile.

See earlier NROL-79 coverage.

Our Atlas archive.