ATV Johannes Kepler mounted under the fairing of Ariane 5

ATV Johannes Kepler mounted under the fairing of Ariane 5

Here at ATV-CC Toulouse, we’re in ‘wait mode’ for tonight’s big event, but in Kourou, teams are busy now with final Ariane 5 launch preparations. It will be the 200th Ariane flight, lofting the sophisticated ATV Johannes Kepler into orbit. ATV-2 is the biggest and heaviest payload ever launched by Europe: Supplies to astronauts aboard the International Space Station and a huge rocket roaring up into the sky has to be one of the greatest shows on Earth!

Just couple of minutes ago, the launch preparations reached the moment when Ariane’s electrical systems were checked. The countdown is a very carefully orchestrated sequence of tasks heading down to the ignition of the main stage engine – followed by the two boosters – for a liftoff at the targeted time. Read more about the launch countdown after the jump (and there’s a perma link at top-right in the blog now to the detailed count-down timeline).
The countdown culminates in a ‘synchronized sequence’, which is managed by the Launcher Control Centre (from the Jupiter Control Room) and by on-board computers starting at T-7 minutes. 
If an interruption in the countdown means that T-0 falls outside the launch window, then the launch will be delayed by one, two or more days, depending on the problem involved, while a solution is developed (due to orbital mechanics, delays come in ~24-hour chunks).  Hopefully, ATV Johannes Kepler will fly today – at least now all status bars are green!
This is the launch countdown (by main events – detailed timline is available here):
Time
–11h 30 m: Start of final countdown
–7h 30 m:  Check of electrical systems
–4h 50 m: Start of filling of main cryogenic stage with liquid oxygen and hydrogen
–3h 20 m:  Chilldown of Vulcain main stage engine
–1h 10 m:  Check of connections between launcher and telemetry, tracking and command systems
–7m 00s:  “All systems go” report, allowing start of synchronized sequence
–4m 00s:  Tanks pressurized for flight
–1m 00s:  Switch to onboard power mode
–04s:  Onboard systems take over
–03s:  Unlocking of guidance systems to flight mode
HO Ignition of the cryogenic main stage engine (EPC)
+ 7,0 s:  Ignition of solid boosters
+ 7,3 s:  Liftoff
+ 12,5 s:  End of vertical rise, beginning of pitch motion
+ 17 s:   Beginning of roll manoeuvre
+2m 29s:  EAP separation
+3m 29s:  Fairing jettisoning
+8m 52s:  End of EPC thrust phase
+8m 58s:  EPC separation
+9m 04s:  Beginning of EPS first thrust phase
+17m 17s:  End of EPS first thrust phase
+17m 19s:  Beginning of ballistic phase
+53m 46s:  End of ballistic phase
+59m 28s:  Beginning of EPS second thrust phase
+59m 55s:  End of EPS second thrust phase
+59m 57s:  ATV orientation phase
+1h 3m 54s:  ATV separation
+1h 4m 04s:  Avoidance and distancing manœuvres
+2h 24m 12s:  EPS third boost for deorbitation
2h 44m 39s:  End of launch vehicle mission