Comet chaser seeks launch

A rocket failure cast a shadow on the Rosetta launch

Europe's ambitious mission to land a probe on the surface of a comet is likely to launch on 22 January.

Scientists working on the Rosetta mission told journalists in London on Monday they were hopeful of meeting the date - or one just a few days later.

A final decision is expected in the next 48 hours.

"I hope we will get Rosetta soon off the ground and we don't have to wait for much longer to get the return on our investment in this excellent science," said Dr Gerhard Schwehm, Rosetta's project scientist.

He said the chance of a successful mission, including launch, was "above 90%".

Standard rocket

The spacecraft should have flown at the weekend but the high-profile failure of Europe's new super rocket, the Ariane 5-ECA, led to all Rosetta preparations being suspended.

Although investigators think they know the cause of the failure, they wanted to satisfy themselves that there were no implications for the £600m (one billion euros) comet mission, which is due to launch on a standard version of the vehicle.

Engine glitch brought down rocket

All inquiries should be complete by tomorrow and the European Space Agency (Esa) is expected to give Rosetta the formal green light on Wednesday.

The agency is under immense pressure to get the comet mission up.

High speed

The spacecraft must perform a complex series of manoeuvres around Earth and Mars to achieve the speed it needs to catch up with Comet Wirtanen.

Even then, it will be 2011 before Rosetta reaches Wirtanen and 2012 before it places a lander on the surface of the comet.

But the narrow launch window closes at the end of January. If Rosetta fails to fly, Esa will have to find an alternative target, which may not be possible.

Dr Schwehm said 22 January was the earliest Rosetta could launch.

He told the BBC there were three other options to go on the 23rd, 26th or 29th - but after that it would be too late.

Moon mission

It emerged on Monday that another Esa space venture could be delayed by the rocket set-back.

Europe is sending an unmanned spacecraft to map the Moon early in 2003. The mission, Smart-1, is due to be launched in March.

A British scientist on the project, Professor Manuel Grand of the Rutherford Appleton Laboratory in Oxfordshire, said the take-off date might slip because of the Ariane 5 problems.

"We're still officially launching on 21 March but I wouldn't be surprised if we had a couple of months' delay," he told BBC News Online.