Ariane 5 Countdown Timeline

Time Event
L-11:43:00 Countdown Initiation
L-10:23:00 Ariane 5 Power-Up
L-09:30:00 Electrical Systems Checks
L-07:30:00 Vehicle in Fueling Configuration
L-06:00:00 Launch Pad Close-Outs
L-06:00:00 Flight Software Load
L-06:00:00 Communication Checks
L-06:00:00 Inertial Guidance System Alignment
L-05:00:00 Launch Pad Evacuation
L-05:00:00 Attitude Control System Pressurization
L-04:50:00 Propellant Loading Ops
L-04:50:00 GSE LOX and LH2 Tank Pressurization
L-04:30:00 Propellant Transfer Lines Chilldown
L-04:23:00 First Stage Propellant Loading
L-03:43:00 Second Stage Propellant Loading
L-03:33:00 Vulcain Main Engine Chilldown
L-02:00:00 Propellant Topping Sequence
L-01:15:00 Telemetry, Tracking, Command Systems Checkouts
L-00:30:00 Prepare for Synchronized Sequence
L-00:10:00 GO/No GO for Launch
L-00:08:00 Payloads to internal Power
L-00:07:00 Countdown Hold&Recycle Point
T-00:06:30 Propellant Topping Termination
T-00:06:30 LOX & LH2 at Flight Level
T-00:06:30 Launch pad safety flood valves opened
T-00:06:30 Pyrotechnic Safety Barrier Arming
T-00:06:00 Launcher Ordnances armed
T-00:06:00 First Stage Helium Loading Termination
T-00:04:00 First Stage Propellant Tank Pressurization
T-00:04:00 Propellant GSE Interface Purge
T-00:04:00 Second Stage LOX Load Termination
T-00:04:00 Second Stage LOX Pressurization
T-00:03:40 Second Stage LH2 Load Termination
T-00:03:30 Launch Time Calculation
T-00:03:10 Second Stage LH2 Pressurization
T-00:03:00 Final T0 loaded into Onboard Computers
T-00:02:30 First Stage, VEB Battery Heating Termination
T-00:02:30 Vulcain Ignition System Heater Shutdown
T-00:02:00 Vulcain 2 Bleeder Valves Open
T-00:02:00 Chilldown Valves closed
T-00:01:50 Pre-Deflection of HM-7B Engine
T-00:01:05 Transition to internal Power
T-00:01:05 Second Stage Isolation from GSE, Tightness Check
T-00:00:37 Ignition Sequence Start
T-00:00:37 On-Board Recorder Activation
T-00:00:37 Arming of pyrotechnic line electric safety barriers
T-00:00:30 Verification of Propellant System Purge
T-00:00:30 First Stage Flood Valves Open
T-00:00:22 First Stage Attitude Control System enabled
T-00:00:16.5 POGO Pressurization
T-00:00:16.5 Fairing Ventilation Termination
T-00:00:12 Flood Valves Opening Command
T-00:00:06 Cryogenic Umbilicals Retraction
T-00:00:06 Start Hydrogen Burn Off System
T-00:00:05.5 Transfer to On-Board Control
T-00:00:03 Guidance System Transition to Flight Mode
T-00:00:03 Computer Status Check
T-00:00:03 Helium Pressurization System Active
T-00:00:02.5 Verification of HM-7B Nozzle Deflection
T-00:00:02 Launch Pad Water System Activation
T-00:00:01.4 Engine Purge Valve Closed
T-00:00:00.2 Arm Retraction Confirmation
T-00:00:00 Vulcain 2 Main Engine Ignition
T+00:00:06.90 End of Vulcain Checkout
T+00:00:07.05 Solid Rocket Booster Ignition
T+00:00:07.30 LIFTOFF