Spaceflight Now: Atlas launch report

AC-139 launch timeline
Posted: June 27, 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 The Atlas 2A rocket, designated AC-139, lifts off and begins a vertical rise away from launch pad 36A at Cape Canaveral Air Force Station, Florida.
T+00:08 Roll Program
Roll During vertical ascent, Atlas begins a 7-second roll maneuver to align itself with proper flight azimuth. Following the roll, the Centaur inertial guidance system controls pitch and yaw programs.
T+02:45 Booster Engine Cutoff
BECO BECO occurs when axial acceleration of 5.0 g is obtained. Sustainer engine provides the continued boost toward orbit for the Atlas rocket.
T+02:48 Jettison Booster Package
Booster sep The bottom engine structure with the two booster engines is separated from the Atlas vehicle.
T+03:37 Jettison Payload Fairing
Fairing separation The 14-foot diameter aluminum payload fairing that protected the TDRS-H satellite during launch is separated once heating levels drop to predetermined limits.
T+04:35 Sustainer Engine Cutoff
SECO SECO is commanded once minimum residual propellant is sensed inside the Atlas booster stage.
T+04:37 Atlas/Centaur Separation
Atlas separation The Atlas booster stage separates from the Centaur upper stage. Over the next few seconds, the Centaur liquid hydrogen and liquid oxygen systems are readied for engine ignition.
T+04:53 Centaur 1st Main Engine Start
MES-1 MES 1, the longer of the two Centaur firings begins to inject the upper stage and TDRS-H spacecraft into a low-altitude parking orbit around Earth.
T+09:46 Centaur Main Engine Cutoff
Coast MECO 1 occurs the Centaur engines are shutdown, arriving in a planned parking orbit. The vehicle begins a coast period over the mid-Atlantic before arriving at the required location in space for the second burn.
T+24:48 Centaur 2nd Main Engine Start
MES-2 MES 2 occurs over the Atlantic Ocean between the African Ivory Coast and Ascension Island before the rocket passes over the equator. The burn lasts until all the Centaur fuel is used, placing TDRS-H into the highest energy transfer orbit possible.
T+26:08 Centaur Main Engine Cutoff
MECO-2 At the point of MECO 2, the Centaur/TDRS-H vehicle should be in the required transfer orbit. About four seconds later, the stage begins aligning to the satellite separation attitude.
T+28:08 Start Spinup
Spinup The Centaur's reaction control system thrusters initiate the required spinup of the TDRS-H satellite to 5 rpm.
T+29:55 Spacecraft Separation
Spacecraft separation NASA's Tracking and Data Relay Satellite-H communications satellite is released into orbit from the Centaur upper stage to complete the AC-139 launch.

Image and data source: International Launch Services and Lockheed Martin Astronautics.
Next launch
Vehicle: Atlas 2A (AC-139)
Payload: NASA's TDRS-H
Launch date: June 30, 2000
Launch window: 1238-1318 GMT (8:38-9:18 a.m. EDT)
Launch site: SLC-36A, Cape Canaveral, Fla.

Flight profile
Track the major launch events for the Atlas 2A rocket carrying the TDRS-H satellite on Spaceflight Now's interactive flight profile page (requires JavaScript).

Pre-launch briefing
Atlas 2A vehicle data - Overview of the rocket that will launch TDRS-H into space.

TDRS-H - Description of the satellite to be launched on AC-139.

History of TDRSS - Past launches of TDRS satellites and their current status.

Launch windows - Available windows for possible future launch dates of AC-139.

Launch danger zone - Map shows restricted safety area off Cape Canaveral for this launch.

Video vault
Watch a movie about the planned sequence of events as the Atlas 2A rocket carries the TDRS-H communications satellite into orbit.
  PLAY (789k, 1min 51sec QuickTime file)
Animation shows NASA's Tracking and Data Relay Satellite-H working in geostationary orbit above Earth.
  PLAY (285k, 24sec QuickTime file)
Satellite builder Hughes tests the 15-foot diameter graphite shaped springback reflector antennas on TDRS-H.
  PLAY (169k, 12sec QuickTime file)
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Inside the blockhouse

Step inside the historic Complex 36 Blockhouse where the 120 members of the launch team control every countdown and liftoff of Atlas rockets from Cape Canaveral.
  VIEW (286k QuickTime file)
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