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).
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.