Today, 12 Nov 2012, around 16:00 GMT, after a 6 or 7 hour journey from the Rosetta mothership, the Philae lander is due to touch down on Comet 67P/Churyumov–Gerasimenko, in (I think) the red circle shown below:
At launch, the Rosetta mothership will be about 22 km from the comet, and since the lander will approach it at a speed of 1 metre/second, it will take it 6 or 7 hours to cover the distance.
As you can see, the comet has a narrow waist between two lobes. The landing site is on the smaller lobe, which is 2.5×2.5×2 km. So it looks like the ‘plateau’ with the landing site on it is 2.5×2 km. And the landing site doesn’t look very flat:
I think the above photo shows an area approximately 1 km x 1 km. The deep crater next to the landing site is partly shown at the bottom.
And the lander doesn’t have a motor. So it seems that it’s just going to be given a shove to get it up to speed, hopefully in the right direction.
And the comet is spinning end over end with a rotation period of 12.4 hours. So that when it’s launched, the landing site will be on the other side of the comet.
And they don’t know what the surface is like. They’re going to try and fire a couple of harpoons into it to hold on with, given that escape velocity from the comet is 0.5 metres/second. So if it lands and bounces off, it’ll never be able to land again.
If they completely miss the target smaller node, they’re going to try to land on the larger node instead.
The scientific goals of the mission focus on “elemental, isotopic, molecular and mineralogical composition of the cometary material, the characterization of physical properties of the surface and subsurface material, the large-scale structure and the magnetic and plasma environment of the nucleus.
It also has cameras on board.
There’s going to be a webcast tomorrow covering the mission.
On 11 & 12 November, all segments broadcast by ESA TV will also be webcast here. These include: Media briefing 11.11-20:00CET || GO/NOGO decision points 1-4 (11-12 Nov) || Separation, science updates & landing (12 Nov). The webstream will remain live all the way until 19:00 GMT / 20:00 CET on 12 November with a permanent view of ESOC Mission Control Room in between the listed sequences. Complete list is available via: http://www.esa.int/esatv/Television
I’m sure they were expecting something a bit easier to land on than this. Last I heard, comets were supposed to be ‘dirty snowballs’. It doesn’t look a bit like a snowball to me. It looks like solid rock, with sand here and there. But if it is rock, it’s apparently as light as pumice stone. If you put it in a tub of water, it would float.
I read a few days ago that they reckon they have a 70% chance of a successful landing. I think that’s a bit optimistic. There seem to me to be any number of things that could go wrong. To me it looks like trying to land a glider on a very lumpy deck of a spinning aircraft carrier, blindfolded