Live Coverage Begins for STP-3

STP-3 Launch Pad
The United Launch Alliance (ULA) Atlas V rocket and the United States Space Force’s STP-3 mission on launch day. The mission hosts NASA’s Laser Communications Relay Demonstration (LCRD) and the NASA-U.S. Naval Research Laboratory Ultraviolet Spectro-Coronagraph (UVSC). Photo Credit: NASA

Hello, and welcome from NASA’s Kennedy Space Center in Florida! A United Launch Alliance (ULA) Atlas V 551 rocket stands ready for liftoff at Launch Complex 41 on Cape Canaveral Space Force Station (CCSFS) for the U.S. Space Force’s (USSF) Space Systems Command (SSC) Space Test Program 3 (STP-3) mission, which hosts NASA’s Laser Communications Relay Demonstration (LCRD) and the NASA-U.S. Naval Research Laboratory Ultraviolet Spectro-Coronagraph (UVSC) Pathfinder.

Launch is scheduled for 4:04 a.m. EST this morning, with a two-hour launch window. Follow along on NASA Television for the live broadcast.

Meteorologists with the U.S. Space Force 45th Weather Squadron predict a more than 90% chance of favorable weather for liftoff.

Here’s a look at some of today’s countdown and ascent milestones. All times are approximate:

Hr/Min/Sec    Event
– 00:55:00      Start flight control final preparations to raise hydraulic pressures
– 00:45:00      Pressurize Main Engine Pneumatic System to flight pressure
– 00:16:00      Initiate fuel fill sequence
– 00:10:00      Weather briefing with Atlas Launch Weather Officer
– 00:05:00      Fuel fill sequence is complete; water deluge system actuation pressure adjustment is performed; Atlas L02 at flight level; Centaur L02 at Flight level; Centaur LH2 at flight level
– 00:04:00      Hazardous gas monitoring is complete; automatic computer sequencer takes control for all critical events through liftoff; Atlas first stage LO2 replenishment is secured, allowing the tank to be pressurized for flight
– 00:03:00      Atlas tanks reach flight pressure
– 00:02:00      Atlas first stage and Centaur upper stage switch to internal power; L02 and LH2 topping for Centaur will stop in 10 seconds
– 00:01:30      Launch control system is enabled

All Times Approximate
Hr/Min/Sec    Event
00:00:00.1     RD-180 Engine Ignition
00:00:01.1     Liftoff of the Atlas V
00:00:03.9     Begin Pitch/Yaw Maneuver
00:00:34.7     Mach 1
00:00:48.7     Max Q (moment of peak mechanical stress on the rocket)
00:01:46.7     Solid rocket booster jettison
00:03:30.2     Payload fairing jettison
00:04:27.4     Atlas booster engine cutoff (BECO)
00:04:33.4     Atlas Centaur separation
00:04:43.3     Centaur first main engine start (MES-1) 
00:10:38.4     Centaur first main engine cutoff (MECO-1) 
01:07:22.1     Centaur second main engine start (MES-2)
01:12:25.6     Centaur second main engine cutoff (MECO-2)
06:24:48.2     Centaur third main engine start (MES-3)
06:27:26.3     Centaur third main engine cutoff (MECO-3)
06:30:15.4     STPSat-6 Separation
07:10:02.4     LDPE-1 Separation
08:08:02.3     End of mission

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