Antares 100 Series Countdown Timeline

Time Event
L-8:00:00 Teams on Station
L-8:00:00 Call to Stations
L-8:00:00 Launch Window Determination
L-7:45:00 Begin Launch Checklist
L-7:30:00 Launch Team Voice Checks
L-7:00:00 CST Countdown Sequence (Combined Systems Test)
L-7:00:00 Range Safety Setup
L-6:30:00 Launch Pad Evacuation
L-6:05:00 Poll to Initiate Propellant Loading Sequencer
L-6:05:00 Start Warm Helium Flow
L-6:00:00 OCCS Sequencer Initiation
L-5:55:00 Start Launch Vehicle Activation
L-5:30:00 1st & 2nd Stage ECU Initialization
L-5:20:00 Initiate Helium Purge Flow
L-5:20:00 Hard Line Communications Checks
L-5:10:00 Space Integrated GPS/Inertial Navigation System Init
L-5:00:00 Launch Vehicle Activation Complete
L-5:00:00 Combined Systems Test
L-5:00:00 Open Loop C- and S-Band Testing
L-5:00:00 Telemetry Verification
L-5:00:00 Payload Checks
L-5:00:00 Mission Simulation Test
L-5:00:00 Red-Team Launch Pad Evacuation
L-4:45:00 Space Integrated GPS/Inertial Navigation System Align
L-4:00:00 Initiate Pre-Launch Processing
L-4:00:00 Start LOX Tank Purge
L-3:55:00 OCCS – Regulator Adjustment
L-3:40:00 Management Comm Checks, CDT Ops Pause
L-3:35:00 S- and C-Band Communications Checks complete
L-3:30:00 Management Call to Stations
L-3:15:00 LOX Ground Support Equipment Chilldown
L-3:05:00 Main Subcooler N2 Fill complete
L-3:00:00 Initiate Nitrogen Flow
L-3:00:00 Electrical Checks complete
L-2:45:00 FTS Open Loop Testing (Flight Termination System)
L-2:24:00 Enable Launch Vehicle Ordnances
L-2:00:00 Propellant Loading Operations
L-2:00:00 LOX Transfer Lines Chilldown
L-1:45:00 15-minute Ops Hold
L-1:30:00 LOX Tank Chilldown
L-1:30:00 LOX & RP-1 Loading of first Stage
L-1:30:00 Vehicle Tests
L-1:30:00 Range Verifications
L-0:45:00 Flight Sfotware Load
L-0:35:00 Rocket Cam Verification, Switch to chilled Helium
L-0:30:00 Launch Readiness Polls
L-0:25:00 AJ-26 Low Flow Chilldown
L-0:15:00 Propellants at Flight Level
L-0:12:00 GO/No GO for Launch Poll
L-0:10:00 AJ-26 Medium Flow Chilldown
L-0:05:00 Flight Termination System to Internal Power
L-0:05:00 Launch Vehicle to Internal Power
L-0:03:30 Initiate and Verify Countdown Auto Sequencer
T-0:03:00 Countdown Auto Sequence
T-0:02:45 Electrical System Verify, LOX Pre-Pressurization
T-0:02:35 SIGI Ready for Flight Verify
T-0:02:15 SIGI to Inertial Mode
T-0:02:00 Propellant Tank Pressurization
T-0:02:00 AJ-26 Nitrogen Purge
T-0:01:55 Main Engine Heater Deactivation
T-0:01:00 High-Speed Camera Start
T-0:00:15 Main Engine Slew Profile
T-0:00:05 TEL Retraction (Transporter, Erector & Launch Device)
T-0:00:01.5 Final Vehicle Health Check
T-0:00:00.5 Initiation of Launch Ordnance Train
T-0:00:00 AJ-26 Ignition
T-0:00:00 Throttle Up to 108%
T+0:00:01.5 AJ-26 Monitoring Complete
T+0:00:01.5 Launch Commit
T+0:00:01.5 Actuate LOX/RP-1 Propellant Line Pyros
T+0:00:01.5 Fire Hold Down Pyros
T+0:00:02 Liftoff