Atlas Countdown Timeline

T- L- Event
12:00 Countdown Begins
12:00 MLP Clear of non essential personnel
12:00 Launch Pad Environmental Control System Preps
12:00 Nitrogen Purge
12:00 Weather Briefing
12:00 Search Light Power Up
12:00 SLC41 warning lights on
08:30 Atlas System Start in preparation for Tanking
08:30 Instrument Checks
08:30 Lox System Preparations
08:30 Gas Detection System Preparations
08:30 Internal Battery Checks
08:30 LH2 System Preparations
07:05 Set Roadblocks
07:00 Atlas V Power-Up
05:25 Weather Briefing
05:15 Communication Checks
05:15 C-Band Communication Checks
04:50 Weather Balloon Release
04:20 S-Band Communication Checks
04:00 L-4HR Commanding
04:00 Polls
03:35 Initiation of Nitrogen Flow
03:34 Set Spacecraft Clock
03:00 SLC Clear of all Personnel
02:00 03:00 Launch Conductor Briefing on Vehicle Conditions
HOLDING 02:40 GO/No GO for Tanking Poll
30min Hold 02:33 Pre-Test Tanking Briefing
02:00 02:30 Centaur LOX Tank Chilldown
COUNTING 02:30 Atlas LOX Vault & MLP Chilldown
02:30 Centaur Helium Storage Bottle Pressurization
02:30 Atlas Pressure Vessels Charge
02:30 Atlas V RP-1 Fuel Tank Press
01:55 02:25 Safe Arm Device Cycle Test
01:50 02:20 Centaur LOX Transfer Line Chilldown
01:45 02:15 Launch Hazard Area in Effect
01:43 02:13 Centaur LOX Tanking begins
01:40 02:10 Weather Balloon Release
01:33 02:03 Centaur LH2 Tank Press to Chilldown Level
01:30 02:00 Atlas V LOX Tanking begins
01:25 01:55 Centaur LOX at 75%
01:25 01:55 Centaur LH2 Transfer Lines Chilldown
01:20 01:50 Centaur LH2 Loading
01:00 01:30 Centaur Engine Chilldown
00:55 01:25 Flight Control Final Preparations for Hydraulic Press
00:45 01:15 Main Engine Pneumatic System Press to Flight Level
00:40 01:10 Heater Activation
00:40 01:10 FTS Test
00:35 01:05 FGM Activation
00:25 00:55 Load Boost Block
00:20 00:50 Fault Protection Validation
00:17 00:27 Polls for Terminal Countdown
00:16 00:46 Fuel Fill Sequence Initiation
00:15 00:45 History Data Dump
00:15 00:45 Term CT Configuration complete
00:04 00:34 T-4-Minute HOLD
HOLDING 00:30 Weather Briefing
Variable Hold 00:25 Fuel Fill Sequence Complete
00:17 Range Clear Poll
00:16 Spacecraft GO/No GO Poll
00:16 NAM Poll
00:16 SMD Poll
00:15 Water Deluge System actuation Pressure Adjustment
00:15 Centaur LOX at Flight Level
00:15 Centaur LH2 at Flight Level
00:13 Spacecraft Poll
00:07 Launch Director Final Poll
>>>> SAFE L-9MIN CONFIGURATION FOR EXTENDED HOLDS
00:07 Spacecraft Status Check
00:06 Spacecraft on internal Power
00:06 LD GO to Launch
00:05 Range Clear Validation
COUNTING 00:04 Hazardous Gas Monitoring Complete
00:04 00:04 Automatic Sequence Begins
00:04 00:04 Atlas LOX Replenish Terminated
00:04 00:04 Atlas LOX Tank Pressurization
00:03 00:03 Atlas Tanks at Flight Pressure
00:02 00:02 Atlas and Centaur switch to internal Power
00:01:55 00:01:55 CMD Sequence
00:01:50 00:01:50 Centaur Topping Sequence complete
00:01:30 00:01:30 Launch Control System Enabled
00:00:16 00:00:16 Launch Verification
00:00:02.7 00:00:02.7 Main Engine Start
00:00:00.0 00:00:00.0 Booster Ignition
+00:00:01.1 +00:00:01.1 Liftoff