'Green' satellite primed for blast-off

Envisat is the size of a bus

By BBC News Online's Helen Briggs in Kourou, French Guiana

The largest and most expensive satellite ever built in Europe is back on the launch pad and set for take-off, following a last-minute technical glitch.

All conditions are go-for-launch this evening

Jean-Yves Le Gall, Arianespace

A team worked all night to fix a problem that could have delayed Thursday's blast-off of the environmental satellite, called Envisat, from the Kourou spaceport in French Guiana.

Mission managers say high winds buffeting the giant rocket as it stood on the pad could have unfastened connections to the umbilical tower.

The Ariane 5 rocket, and its precious cargo, had to be rolled back along a railway line into the Final Assembly Building where engineers inspected a venting duct that regulates temperature on an important part of the launcher.

Looking good

But Jean-Yves Le Gall, general director of Arianespace, the company that operates the Ariane rocket programme, expressed his satisfaction with the checks and confirmed the launch would go ahead on schedule at 22:07 local time (01:07 GMT, Friday).

The launcher is back on its pad and ready to fly

"Obviously every check has to be made," Mr Le Gall told reporters. "But all conditions are go-for-launch this evening."

Bernhard Puygrenier, mission director for Flight 145, said the cryogenic fuel (oxygen and hydrogen) was being put into the rocket ready for blast-off.

"Everything is under control and going normally," he said. "Everything is as expected."

And Philippe Gilson, from the French space agency, said weather conditions were fair and looked good for launch.

Informing policy

Envisat will be the largest payload to be launched on an Ariane rocket. It weighs more than 8,000 kg and is 10 metres long.

The fairing - the part of the rocket that contains the satellite - is the longest ever for an Ariane rocket , at 17 metres, and has been specially built.

If all goes to plan, Thursday's launch will mark the beginning of the spacecraft's five-year journey around the Earth and the end of a decade-long development and construction effort.

Envisat facts

The size of a bus

8.2 tonnes in weight

Circles the Earth every 100 minutes from 800 km up

10 instruments will scan the planet for environmental changes

Built at cost of 2.3bn euros (£1.4bn)

The satellite cost about £1.4bn to build and is the joint investment of 13 member states of the European Space Agency (Esa), and Canada.

The UK has contributed £300m to the project, a record for a British contribution to one satellite and second only to France among the 14 collaborators.

Billed as a "unique flying environment station", Envisat will monitor the health of the Earth's oceans, ice caps, land and atmosphere.

Scientists hope that the data it gathers over the course of five or more years will justify its cost, by providing key environmental data that will feed into international policies like the Kyoto Protocol.