Spaceflight Now: Atlas launch report

AC-138 launch timeline
Posted: Jan. 19, 2000

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 Rocket lifts off and begins a vertical rise away from launch pad 36A at Cape Canaveral Air Station.
T+00:02 Roll Program
Roll During vertical ascent, Atlas begins a 13-second roll maneuver to align itself with proper flight azimuth of 104 degrees. Following the roll, the vehicle begins open-loop pitch and yaw steering under control of the Centaur inertial guidance system.
T+02:44.7 Booster Engine Cutoff
BECO BECO occurs when axial acceleration of 5.5 g is obtained. Sustainer engine provides the continued boost toward orbit for the Atlas rocket.
T+02:47.8 Jettison Booster Package
Booster sep The bottom engine structure with the two booster engines is separated from the Atlas vehicle.
T+03:53.5 Jettison Payload Fairing
Fairing separation The 11-foot diameter aluminum payload fairing that protected the DSCS B8 satellite during launch is separated once heating levels drop to predetermined limits.
T+04:41.6 Sustainer Engine Cutoff
SECO SECO is commanded once minimum residual propellant is sensed inside the Atlas booster stage.
T+04:43.6 Atlas/Centaur Separation
Atlas separation Two seconds after the Atlas sustainer engine shuts down, the Atlas booster stage separates from the Centaur upper stage.
T+05:00.1 Centaur 1st Main Engine Start
MES-1 MES 1, the longer of the two Centaur firings begins to inject the upper stage and DCSC B8 spacecraft into a low-altitude parking orbit around Earth. Guidance steering in the burn will result in an inclination of 29.3 degrees.
T+10:07.1 Centaur Main Engine Cutoff
Coast MECO 1 occurs the Centaur engines are shutdown, arriving in a planned 80 x 485 nautical mile orbit. The vehicle begins a coast period over the mid-Atlantic before arriving at the required location in space for the second burn.
T+22:17.0 Centaur 2nd Main Engine Start
MES-2 MES 2 occurs over the Atlantic Ocean near the African Ivory Coast as the rocket passes over the equator. The burn accelerates the vehicle and satellite into the required subsynchronous transfer orbit.
T+23:43.4 Centaur Main Engine Cutoff
MECO-2 At the point of MECO 2, the Centaur/DSCS B8 vehicle should be in the required transfer orbit.
T+25:17.4 Start Spinup
Spinup The Centaur's reaction control system thrusters initiate the required spinup of the DSCS B8 satellite to 4.7 rpm.
T+26:38.4 Spacecraft Separation
Spacecraft separation The Defense Satellite Communications System B8 spacecraft is released into orbit from the Centaur upper stage to complete the AC-138 launch.

Image and data source: International Launch Services and Lockheed Martin Astronautics.
Flight data file
Vehicle: Atlas 2A
Payload: DSCS B8
Launch date: Jan. 21, 2000
Launch window: 0015-0139 GMT (7:15-8:39 p.m. EST on 20th)
Launch site: SLC-36A, Cape Canaveral Air Station, Fla.

Pre-launch briefing
Atlas vehicle data - Overview of the rocket that will launch DSCS B8 into space.

Launch windows - Available windows for future launch dates of AC-138.

DSCS B8 - Overview of the U.S. Air Force DSCS satellite program.

Atlas index - Listing of our previous Atlas coverage.

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