Rosetta, Philae and Comet 67P/Churyumov-Gerasimenko.

[KerikBalm]

"If it bounces, it will enter a suborbital trajectory and later smack into one of the lobes of a rotating comet"

Not knowing the exact speed its going when landing, and the escape velocity of the comment (perhaps you do), its possible that the bounce will send it on an escape trajectory, if it hits the comet at higher than escape velocity

but I doubt it... you are probably right

[lajoswinkler]

I've heard the departure speed was less than 0.2 m/s. I'm not sure about escape velocity as it's so oddly shaped.

[Tommygun]

If it bounces, it will enter a suborbital trajectory and later smack into one of the lobes of a rotating comet. Anyhow, it's gonna be interesting.

Sounds like the two lobes could end up playing pong with poor little Philae.

[Meithan]

I seriously still can't believe they're gonna land a probe on a comet!!

[Ralathon]

I seriously still can't believe they're gonna land a probe on a comet!!

Its more like a controlled lawn dart than a 'landing' to be fair. Still very impressive though.

[Streetwind]

I think it's almost more impressive than using a fully autonomous and steerable vehicle. I mean, anyone can catch a KSP asteroid with RCS and reaction wheels, but now try getting a hold with your claw by flinging it at the asteroid from 14 kilometers away...

Meanwhile, the 24-hour livestream starts in 3 hours, at 19:000 UTC.

And here's a video from last month, for those who missed it, talking about Philae:

[Frida Space]

Philae had some troubles sending the telemetry data back to Rosetta yesterday night (here in Europe), but everything has been fixed now and the lander is operating well. go philae!

[tutrakan4e]

(Thinking of Space X and the Antares Rocket failure)

Third one's a charm!

[AbortButton]

Can't wait!

[Ikaneko]

Hmm...

If they pull this off, I think they'll move up one on my sig!!

In any case, what they're doing is a major step forward in space exploration and will contribute to Science!

[Geneborg]

I'm starting to get excited now...man if this works...i will be so sad if it doesn't, but i know its really really difficult and they will need alot of luck.

[rkman]

The comet is singing

https://soundcloud.com/esaops/a-singing-comet

"Rosetta’s Plasma Consortium (RPC) has uncovered a mysterious ‘song’ that Comet 67P/Churyumov-Gerasimenko is singing into space. The comet seems to be emitting a ‘song’ in the form of oscillations in the magnetic field in the comet’s environment. It is being sung at 40-50 millihertz, far below human hearing, which typically picks up sound between 20 Hz and 20 kHz. To make the music audible to the human ear, the frequencies have been increased in this recording."

[hugix]

All this talk about SOI, orbit and escape velocity are a bit meaningless in this scenario. 76p has almost no gravity, at least not enough for a stable orbit. Rosetta constantly adjusts her trajectory in order to stay around the comet(these triangle shaped orbits in the videos). When close enough Rosetta does orbit the comet but when the gravitational distortions from the sun, Jupiter and whatnot become to much and it has to alter it's trajectory.

The best analogy in KSP is to fly to a comet, distance yourself to something like 5-10 kilometers from it. do an EVA, line your kerbal up to the comet and push prograde once(!) and see if the kerbal hits the comet.

[Frida Space]

When it came down <30 km from the comet, Rosetta entered a pretty stable orbit. The only manouvers it did since then where to actually change orbit, not to keep it stable. The triangular orbits were before the 30 km mark.

[Camacha]

I know these guys know what they are doing, but as the time of the manoeuvre creeps closer I am really starting to get jittery about the throw and wait approach I am sure it is going to be all fine and dandy, but the way I am feeling now I would prefer a good old fashioned wasteful powered descent. Moar power and all will be well.

[Sky_walker]

Philae landing live online stream is now set up & running: http://new.livestream.com/ESA/cometlanding

[Jenteb07]

First go/nogo passed successfully

[AbortButton]

Fingers crossed for a successful maneuver!

[Mitchz95]

How long do they think until it lands? I'm in class right now and can't watch it.

[Streetwind]

All this talk about SOI, orbit and escape velocity are a bit meaningless in this scenario. 76p has almost no gravity, at least not enough for a stable orbit. Rosetta constantly adjusts her trajectory in order to stay around the comet(these triangle shaped orbits in the videos). When close enough Rosetta does orbit the comet but when the gravitational distortions from the sun, Jupiter and whatnot become to much and it has to alter it's trajectory.

When it came down <30 km from the comet, Rosetta entered a pretty stable orbit. The only manouvers it did since then where to actually change orbit, not to keep it stable. The triangular orbits were before the 30 km mark.

^--- This. Rosetta can orbit on gravity alone just fine (very very slowly, Gilly style). The triangle trajectories were used to obtain a comprehensive, multi-angle surface map of the constantly rotating comet nucleus and to perform some scientific experiments. They also wanted to make really sure that nothing would endanger the spacecraft in close proximity, so they kept creeping closer and closer only very slowly, with lots of small manual adjustments.

And yes, other gravity sources will interfere with Rosetta's orbit, making stationkeeping maneuvers necessary. This is true for all orbits in an N-body environment. Even spacecraft in lunar orbit for example must regularly make correction burns to stay where they want to be. Or commsats in geostationary Earth orbit. Or the science craft around Mars. And so on.

How long do they think until it lands? I'm in class right now and can't watch it.

Landing confirmation is not expected until 17:00 16:00 UTC on Wednesday, IIRC.

Edited November 11, 2014 by Streetwind

[Kryten]

How long do they think until it lands? I'm in class right now and can't watch it.

About 21 hours. The release of Philae isn't scheduled until tomorrow.

[hugix]

When it came down <30 km from the comet, Rosetta entered a pretty stable orbit. The only manouvers it did since then where to actually change orbit, not to keep it stable. The triangular orbits were before the 30 km mark.

It did orbit the comet, but it's no stable orbit. Just let it fly long enough and the orbit will deteriorate and escape the comet once again.

[Sky_walker]

Oh, they put the stream up to the Rosetta website - http://rosetta.esa.int/ - includes the count-down clock to the separation.

Fingers crossed for a successful maneuver!

For the sake of ESA - it better would. Otherwise it's going to be a huge PR disaster for them, as it's pretty much the first such a huge event for ESA in a public relations department. (Sorry for being so pragmatic instead of looking at the scientific benefits, but having successful mission like that, right now, with public caring so much, will give ESA a strong argument to further increase it's budget)

It did orbit the comet, but it's no stable orbit. Just let it fly long enough and the orbit will deteriorate and escape the comet once again.

Eventually, yes, but overall it's relatively stable.

[Streetwind]

Deep Space Network antenna DSS-25 in Goldstone is passively tracking Rosetta right now:

They're probably going to keep at least one antenna locked onto it constantly for the next 24 hours at minimum to facilitate prompt exchange of information, particularly uploading commands.

If you stalk the DSN website, you may occasionally catch the communication graphics light up.

[Meithan]

Its more like a controlled lawn dart than a 'landing' to be fair. Still very impressive though.

In fact I think the very low gravity is what makes it so impressive. Just the kick from releasing the lander will probably impart a change of speed comparable to orbital speed. And they have to calculate trajectories using the mass distribution and rotation pattern they just learned a few weeks ago from in situ measurements. Very impressive navigation skills.