Rosetta mission: 'Looking good' for comet landing bid

Navigators must design a perfect delivery manoeuvre so that Philae's chances of success are maximised

European Space Agency officials say all looks good ahead of this week's historic bid to land on a comet.

Esa's Rosetta satellite will despatch its piggybacked Philae probe to the surface of the "ice mountain" known as 67P on Wednesday.
Controllers report both mothership and descent robot to be in excellent shape.
The landing commands on Philae have already been loaded, and an instruction was sent up on Monday evening to switch on and warm the probe.
The intention now is to leave it in an active state, ready for the separation. This is timed to occur at 08:35 GMT on Wednesday.
Touchdown should follow about seven hours later, with a confirmation signal expected back on Earth around 16:00 GMT.
But before the mission can get to this milestone, Rosetta must be primed to make its delivery run.

The satellite is currently moving on a long, slow arc around 67P at a height of about 30km.

At a predetermined time on Wednesday morning, it has to turn and head in towards the comet, releasing Philae on the path that will take it down to the targeted landing zone.
Executing this pre-delivery manoeuvre with high precision is the one really big issue vexing controllers.
They know their calculations for the thruster burn must be spot on. They know also that they will have very little time to assess its performance before giving the final "go" for separation.
"The point of separation is fixed in time, in space, velocity and attitude; and we have to reach exactly that point," explained Esa flight director Andrea Accomazzo.
"So, wherever Rosetta is, we have to design a manoeuvre to reach that point."