Published: 09.18 Europe/London, April 20, 2011

Arianespace has said it is on track for the rescheduled April 22 liftoff of its Ariane 5mission with the Yahsat 1A and Intelsat New Dawn satellite payloads after replacement of actuators on the heavy-lift launcherís Vulcain 2 cryogenic main engine.

The replacement was made following an interruption of the original final countdown on March 30, when an incorrect displacement of one of the Vulcain2 engineís actuators was detected.

This anomaly was reported at 6.65 seconds into the Vulcain 2′s ignition procedure, and it occurred during the pre-planned automatic checkout sequence of 7.05 seconds Ė when the cryogenic engineís operation is verified before the Ariane 5′s two large solid propellant boosters are commanded to ignite.

Once the anomaly was detected, a shut-down of the Vulcain 2 engine was ordered Ė with Ariane 5, its two satellites, and the Spaceportís launch installation immediately put in safe conditions using identified and qualified procedures.

The launcher was transferred back to the Spaceportís Final Assembly Building on April 1, where the actuator replacement was implemented and the Ariane 5 was returned to its flight configuration.

New mission planning calls for Ariane 5′s rollout to the ELA-3 launch zone on Thursday, April 21, followed by the April 22 liftoff during a launch window that opens at 6:37 pm local time in French Guiana and continues to 7:41 pm.

WATCH THE LAUNCH LIVE Ė You can follow the launch on the special video site of Arianespace. At the moment, an informaitonal video is available on this site.