Computer cooling glitch hits Envisat launch

28 February 2002

The launch of Europe’s £1.4 billion Earth-monitoring satellite Envisat was struck by a glitch just 24 hours before take-off from Kourou in French Guyana.

An undisclosed problem with the ventilation system used to cool the computers aboard the rocket launcher Ariane 5 meant that it had to be returned from the launch pad to its assembly hanger at about 1030 GMT on Thursday.

However European Space Agency officials said that the problem was not expected to delay the launch. “It’s not exceptional. It’s known and can be mastered,” said ESA spokesman Franco Bonacini.

The rocket is currently scheduled to take off at 0107 GMT on Friday morning. But if engineers decide to go ahead, they will have to make the decision nine hours before the scheduled take-off time in order to prepare the rocket.


The on-board computer is located in the upper section of the rocket, below the rocket’s nose where the satellite is stowed. A tube from the launch scaffolding to the rocket provides ventilation to keep the computer control system at the correct temperature while it stands on the launch pad.

Back to base

Arianespace engineers found evidence late on Thursday that the ventilation system was not functioning correctly and decided to return the rocket to its assembly chamber. There the functioning of the ventilation system can be checked in more detail. The assembly chamber is located a short distance from launch pad and housed the rocket until three days ago.

This new problem has never occurred on Ariane 5 before, but a similar problem has affected the rocket’s smaller and highly successful predecessor Ariane 4.

The launch does not require any added drama. Both ESA’s largest ever satellite and the reputation of the Ariane 5 launcher are riding on the launch. It has taken 10 years and £1.4bn to develop the 8.5 tonne Envisat and scientists say it is irreplaceable. Arianespace is also keen to re-establish the reliability of Ariane 5 after its last launch ended in calamity in July 2001. The rocket placed two rockets worth £500m in the incorrect orbit after suffering engine difficulties. These were traced to water droplets in the second-stage engine and Arianespace has spent months testing modifications designed to prevent this re-occurring.