Spaceflight Now Home

Mission Briefing


Sign up for our NewsAlert service and have the latest news in astronomy and space e-mailed direct to your desktop.

Enter your e-mail address:

Privacy note: your e-mail address will not be used for any other purpose.

AC-167 launch timeline
Posted: August 24, 2004

T-00:02.4 Engine Start
Engine start Atlas booster and sustainer engines are ignited and undergo checkout prior to liftoff.
T+00:00 Launch
Liftoff The two ground-lit solid rocket boosters are ignited as the Atlas 2AS vehicle, designated AC-167, lifts off and begins a vertical rise away from launch pad 36A at Cape Canaveral Air Force Station, Florida. The rocket will head northeast to reach a highly inclined orbit.
T+00:58.9 Air-lit SRB Ignition
Air-lit 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, just seconds earlier.
T+01:17.0 Jettison Ground-Lit SRBs
Ground-lit sep The two spent solid rocket boosters that were ignited on the ground are jettisoned to fall into the Atlantic Ocean.
T+01:56.0 Jettison Air-Lit SRBs
Air-let sep 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+02:44.0 Booster Engine Cutoff
BECO BECO occurs when axial acceleration of 5.0 g is obtained on the rocket. Sustainer engine provides the continued boost toward orbit for the Atlas rocket.
T+02:47.0 Jettison Booster Package
Booster sep The bottom engine structure with the two booster engine nozzles is separated from the Atlas vehicle.
T+03:28.1 Jettison Payload Fairing
Fairing separation The 14-foot diameter aluminum payload fairing that protected the classified NRO spacecraft during launch is separated once heating levels drop to predetermined limits.
T+04:57.0 Sustainer Engine Cutoff
SECO SECO is commanded once minimum residual propellant is sensed inside the Atlas booster stage.
T+04:58.0 Atlas/Centaur Separation
Atlas separation The Atlas booster stage 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+05:15.0 Centaur Engine Start 1
MES-1 MES 1, the longer of the two Centaur firings begins to inject the upper stage and NRO spacecraft into a low-altitude parking orbit.
T+10:02.0 Centaur Engine Cutoff 1
Coast MECO 1 occurs the Centaur engines are shutdown, arriving in a planned parking orbit. The vehicle entered a lengthy coast period before arriving at the required location in space for the second burn.
T+68:35.0 Centaur Engine Start 2
MES-2 MES 2 occurs over the South Pacific to accelerate the payload into a dfferent orbit from the one achieved earlier in the launch sequence.
T+69:49.0 Centaur Engine Cutoff 2
MECO-2 At MECO 2, the Centaur completes the powered flight to deliver the NRO spacecraft into the targeted deployment orbit. The parameters for that orbit are classified.
T+73:50.0 Spacecraft Separation
Spacecraft separation The classified National Reconnaissance Office spacecraft is released into orbit from the Centaur upper stage to complete the AC-167 launch, the final flight for Lockheed Martin's Atlas 2AS rocket.

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