Rosetta: Date fixed for historic comet landing attempt

The date has been fixed for Europe's daring attempt to land on a comet: Wednesday 12 November, the BBC reported.

It will see the Rosetta satellite, which is currently orbiting the huge "ice mountain" known as 67P, drop a small robot from a height of 20km.

If all goes well, the lander will free-fall towards the comet, making contact with the surface somewhere in a 1km-wide zone at roughly 15:35 GMT.

The European Space Agency (Esa) says the challenges ahead are immense.

Imagine pushing a washing machine out the back of an airliner at twice cruising altitude and expecting it to hit Regent's Park in London - all while the ground is moving underneath.

Although not really analogous for many reasons, this scenario does give a sense of the difficulties involved. The chances of failure are high.

Esa's confirmed date is actually a day later than the one that had been discussed in provisional planning in recent months.

The extra time will give flight controllers a bit more latitude as they try to get Rosetta into just the right position to deliver the 100kg lander, which goes by the name of Philae.

This requires careful "phasing" of Rosetta's path around 4km-wide 67P so that the satellite turns up at the precise, pre-determined ejection point, 22.5km from the centre of the comet at 08:35 GMT.

Because the whole event will be taking place 509 million km from Earth, any radio signal will take 28 minutes and 20 seconds to reach Esa's ground station network.

It means confirmation of success or failure will not come until perhaps just after 16:00 GMT.

The chosen landing site is on the "head" of the rubber-duck-shaped comet and is currently referred to simply as "J", the designation it was given in a list of possible destinations in the selection process.

It is far from ideal. It contains some terrifying cliffs, but is the flattest, most boulder-free location the mission team could find in its survey of the icy object.