15 16 February is ATV Johannes Kepler launch day – it’s show time (again)! ATV lift-off is set for 23:13 22:50 CET on board Ariane 5 ES V200 (the 200th Ariane!) from Europe’s Spaceport in Kourou, French Guiana. Below, we’ve listed the most critical steps that will take place today in the mission of Ariane 5 and ATV – we’ll pin this post to the top of the blog so that you can refer back to it often.

Launch Day – Tuesday, 15 Wednesday, 16 February 2011
Intensive pre-launch activities continue at Kourou’s ELA3 launch site – including filling Ariane’s main stage with liquid Oxygen and Hydrogen.

Critical timings start at T-7 minutes
For the Ariane 5 ES launcher, the most critical lift-off timings begin with the start of the synchronized sequence 7 minutes before ignition (T-0), which implement the final operations on the launcher prior to launch and switches the vehicle over to flight configuration.

As its name indicates, it is fully automatic, and is performed concurrently by the on-board computer and by two redundant computers at the ELA3 launch complex (until T-4 seconds). The computers command the final electrical operations (start up of the flight programme, switching from ground power supply to on-board batteries, etc.) and associated checks. They also place the propellant and fluid systems into flight configuration and perform associated checks.

The computers also handle the final ground system configurations, namely:

  • Start of water injection in the flame trenches and jet guide (T-30 sec)
  • Hydrogen aspiration for chilldown of the Vulcain engine in the jet guide (T-18 sec)
  • Burnoff of hydrogen used for chilldown (T-5.5 sec)

At T-4 seconds, the on-board computer takes over control of final engine start-up and lift-off operations:

  • It starts the ignition sequence for the Vulcain main stage engine (T-0)
  • It checks engine operation (from T+4.5 to T+7.3 sec)
  • It commands ignition of the solid boosters for immediate lift-off at T+7.3 seconds

Any shutdown of the synchronized sequence after T-7 mn automatically places the launcher back in its T-7 min configuration.

Note: all times subject to change

[pdf http://blogs.esa.int/atv/files/2011/02/esa-atv2_launch_timeline_16022011.pdf 640 860]