The Rosetta probe has woken up ...

[anglolawyer]

They said it might wake up again as the comet approached the Sun. I was half asleep but I think they also said they might find DNA on it (if they do, I bet it turns out to be Amanda Knox's).

 

[Gawdzilla Sama]

They said it might wake up again as the comet approached the Sun. I was half asleep but I think they also said they might find DNA on it (if they do, I bet it turns out to be Amanda Knox's).

Not DNA, but "the basic building blocks of life", i.e., beer and nachos.

 

[ThunderChunky]

Not DNA, but "the basic building blocks of life", i.e., beer and nachos.

They were probably talking about nucleobases, which have been found in meteorites.

 

[Gawdzilla Sama]

They were probably talking about nucleobases, which have been found in meteorites.

Yep, that would be one of the most important finds on the comet.

 

[BenBurch]

Here is where having a really large laser in space would be useful. We'd just shine a light on the comet and fill in some of the shadows.

 

[Southwind17]

Said in the latest briefing: "We didn't land once, we landed twice!"

Some of the telemetry indicates that Philae slowly bounced once.

It sounds like the gravity is so weak on the comet that almost anything could cause the lander to drift off the surface if it wasn't attached so I hope the screws worked.

But anyone who's ever landed a probe on Bop in KSP knows what Philae's gone through: "Oh crap oh crap we just bounced we're in the air again oh crap go back down go down don't tip over DON'T TIP OVERRROOKAY WE'RE SETTLING!"

Here's the bit I don't get ... according to "Comet Catcher: The Rosetta Landing" aired on Foxtel in Australia on Thursday (and produced before the actual landing), the gravitational force of Comet 67P is so weak that if a human standing on it were to jump they would have escape velocity. How come, then, the Philae lander managed to bounce and land again? Must have been a very gentle bounce indeed - to accelerate away and still be pulled back by just the gravitational force!

 

[rjh01]

Here's the bit I don't get ... according to "Comet Catcher: The Rosetta Landing" aired on Foxtel in Australia on Thursday (and produced before the actual landing), the gravitational force of Comet 67P is so weak that if a human standing on it were to jump they would have escape velocity. How come, then, the Philae lander managed to bounce and land again? Must have been a very gentle bounce indeed - to accelerate away and still be pulled back by just the gravitational force!

Yes you are right, it would have been a very gentle bounce by something that would have been designed not to bounce for the reason you said.

 

[davefoc]

New forum glitch here and maybe operator error. deleting the post

 

[davefoc]

Here's the bit I don't get ... according to "Comet Catcher: The Rosetta Landing" aired on Foxtel in Australia on Thursday (and produced before the actual landing), the gravitational force of Comet 67P is so weak that if a human standing on it were to jump they would have escape velocity. How come, then, the Philae lander managed to bounce and land again? Must have been a very gentle bounce indeed - to accelerate away and still be pulled back by just the gravitational force!

From: https://en.wikipedia.org/wiki/Rosetta_(spacecraft)

The lander, named Philae, approached Churyumov–Gerasimenko at a relative speed of around 1 m/s (3.6 km/h; 2.2 mph) and on contact with the surface, two harpoons were to be fired into the comet to prevent the lander from bouncing off because the comet's escape velocity is only around 0.5 m/s (1.8 km/h; 1.1 mph).
​

It sounds like if the impact had been an elastic collision Philae would rebounded back into space. But the collision was probably highly inelastic. It seems like the comet is some kind of spongy network of dust with frozen CO2 and H2O mostly in the voids. That by itself sounds like enough to make the comet absorb much of the energy from any impact. And the lander itself looks about farthest from a bouncing ball. So I'd expect that the lander would absorb a lot of energy in any kind of collision.

Still, given the slow nature of the impact (to this earth centric individual) I can imagine that collisions might be more elastic than expected when the accelerations are so small that the depression of the comet's surface might be small enough that the surface returned much of the impact energy to the lander. But as an empirical matter the comet and the lander absorbed enough energy that lander rebound velocity stayed below .5 m/sec.




https://en.wikipedia.org/wiki/Rosetta_(spacecraft)#cite_note-47

 

[Southwind17]

From: https://en.wikipedia.org/wiki/Rosetta_(spacecraft)

The lander, named Philae, approached Churyumov–Gerasimenko at a relative speed of around 1 m/s (3.6 km/h; 2.2 mph) and on contact with the surface, two harpoons were to be fired into the comet to prevent the lander from bouncing off because the comet's escape velocity is only around 0.5 m/s (1.8 km/h; 1.1 mph).
​

It sounds like if the impact had been an elastic collision Philae would rebounded back into space. But the collision was probably highly inelastic. It seems like the comet is some kind of spongy network of dust with frozen CO2 and H2O mostly in the voids. That by itself sounds like enough to make the comet absorb much of the energy from any impact. And the lander itself looks about farthest from a bouncing ball. So I'd expect that the lander would absorb a lot of energy in any kind of collision.

Still, given the slow nature of the impact (to this earth centric individual) I can imagine that collisions might be more elastic than expected when the accelerations are so small that the depression of the comet's surface might be small enough that the surface returned much of the impact energy to the lander. But as an empirical matter the comet and the lander absorbed enough energy that lander rebound velocity stayed below .5 m/sec.

And how far away from the designated landing site did Philae settle?

 

[Gawdzilla Sama]

New forum glitch here and maybe operator error. deleting the post

You ain't alone, brother.

 

[ceptimus]

And how far away from the designated landing site did Philae settle?

About a kilometre they think, but they've yet to locate it using photos from the main Rosetta craft.

The first bounce lasted about two hours and took Philae up to about a kilometre high. 50% faster and it would have exceeded escape velocity and bounced away into space probably forever - certainly for a very long time - though its orbit around the sun might have meant that it would impact the comet again many years later.

 

[marplots]

Has anyone asserted yet that the slight bump delivered to the comet has altered its course, just enough to kill us all sometime in 2025?

If not, I'll just go ahead and make the claim to get it out of the way.

 

[Beelzebuddy]

Has anyone asserted yet that the slight bump delivered to the comet has altered its course, just enough to kill us all sometime in 2025?

If not, I'll just go ahead and make the claim to get it out of the way.

I'm not worried. That's after peak oil, so there will be plenty of out of work, down-on-their-luck ragtag groups of former drilling crews around to tap for our last-second salvation.

 

[Pianoro]

Looks like ESA has spotted Philae's first point of touchdown.

http://blogs.esa.int/rosetta/2014/11/16/philae_spotted_after_first_landing/

The bigger dark spot is dust or disturbed ground from the impact, the brighter small feature is thought to be Philae, at this point bouncing back off the comet. The lander only shows up as a couple of pixels (not much bigger than the two-pixel artifacts in the images).

Finding Philae at this location would have been comparatively easy as it was close to the intended point of touchdown and the surface of the comet is fairly smooth and even there.

Spotting the lander at its current location looks like a difficult task, especially if it is resting in rugged terrain.

 

[Southwind17]

Has anyone asserted yet that the slight bump delivered to the comet has altered its course, just enough to kill us all sometime in 2025?

If not, I'll just go ahead and make the claim to get it out of the way.

80 billion tonnes vs. a washing machine! I would imagine that gravitation pull from other celestial bodies will have a greater diverting effect.

 

[Southwind17]

About a kilometre they think, but they've yet to locate it using photos from the main Rosetta craft.

The first bounce lasted about two hours and took Philae up to about a kilometre high. 50% faster and it would have exceeded escape velocity and bounced away into space probably forever - certainly for a very long time - though its orbit around the sun might have meant that it would impact the comet again many years later.

It's amazing Philae didn't pick up some vertical rotation from the bounce. Darned lucky it succeeded to land at all, at least upright.

 

[Southwind17]

Given that Comet 67P is, what, 4 billion years old and only a small rock by astronomical measures, how come it's still active, and hasn't cooled to a benign rock? Does it get super heated periodically from a close pass of the Sun, for example?

 

[Robin]

Has anyone asserted yet that the slight bump delivered to the comet has altered its course, just enough to kill us all sometime in 2025?

If not, I'll just go ahead and make the claim to get it out of the way.

I think that disappointing thing about the whole mission is the poor quality of the conspiracy theories so far.

That and the stupid promotional video.

 

[Mikemcc]

BBC have just had an excellent Sky At Night episode about the rendezvous and the life of the Lander. One of the best episodes of SofN that I've ever seen. It was so personal with the mission control crew and some of the instrument scientists. Apparently there was a last minute attempt to free and re-orientate the lander. That was successful, but not sufficient to prevent shutdown.

Apparently the hammer drill broke during the attempt to use that, so it looks like the surface under the dust coat is harder than expected, and this may have been a factor in the bounces.