Updates Rosetta Mission News

[boogabooga]

How much do we know about comet surfaces ahead of time?

This whole harpoon thing seems a bit risky. What are the odds that the surface is hard as a rock (or inches of ice) and the harpoon bounces right off? Or the opposite, the surface is covered in feet of icy loose dust and the harpoon can't grab a hold on anything solid?

It would seem to me that the Hayabusa method of just maneuvering down to the surface would seem better, at least when all of your reaction wheels are working.

---------- Post added Nov 12th, 2014 at 01:33 AM ---------- Previous post was Nov 11th, 2014 at 06:52 PM ----------

Live coverage has started!

 

[Urwumpe]

How much do we know about comet surfaces ahead of time?

Not that much, but the Deep Impact mission gave us some clues. We do know that the average density of the comet must be around 400 kg/m³, which is an average value for snow on Earth. So, the surface will likely be something like a porous snow/dust mixture.

This whole harpoon thing seems a bit risky. What are the odds that the surface is hard as a rock (or inches of ice) and the harpoon bounces right off? Or the opposite, the surface is covered in feet of icy loose dust and the harpoon can't grab a hold on anything solid?

The harpoons won't bounce off, unless you are firing at something harder than old ice. In latest ground tests, the harpoons even destroyed the wooden box that enclosed the snow/dust mixture they used for testing.

The biggest danger is that the spacecraft simply lands on one of the large boulders on the comet. The chance is low, but existing.

But as long as just a single harpoon manages to make contact successfully, the landing will be successful. Even if it lands on its side, it might at least perform limited science

It would seem to me that the Hayabusa method of just maneuvering down to the surface would seem better, at least when all of your reaction wheels are working.

A comet is no asteroid. The density of the comet is 4 times lower than the found lowest density of Itokawa, it is far more erratically formed, venting dust and gas... the Hayabusa method is also not suitable for the science that should get performed.

The primary goal of the mission is to have two observation points on the comet while it approaches the sun and develops its coma. One in low Orbit around the comet, another on the surface of the comet, both should ideally survive until March 2015.

 

[Cosmic Penguin]

Despite problems with Philae's cold thrusters, the decision was given to release it for landing in a few hours!

 

[Urwumpe]

The other live stream:

https://xkcd.com/1446/

 

[Cosmic Penguin]

Philae should have separated from Rosetta and sails alone by now...we will know in 15 minutes.

 

[Cosmic Penguin]

And she's off!

 

[Cosmic Penguin]

After 10 additional minutes of suspense ESA has re-gained communication with Philae and Rosetta after Rosetta went out of contact as the spacecraft did the post-separation burn to put it away from the comet. :thumbup:

5 hours from touch-down....

 

[fort]

It seems there is a problem with the Philae anti rebound system

 

[Urwumpe]

It seems there is a problem with the Philae anti rebound system

Yes, the Active Descent System is not reacting, but that's just for assisting the other two systems doing their job.

It won't be like Philae will slam into a the comet and bounce away into space. Its more like a slow motion impact on snow, when all goes like expected. The lander will have ground contact with the comet for multiple seconds, before slowly bouncing away (at slightly less speed than the impact speed ... of 89 cm per second)

The first pictures seem to arrive in Cologne right now.

 

[fort]

1m / s ... I was thinking about this this morning. It is still fast enough ?

 

[ISProgram]

Considering the gravity of the comet, yeah. Exceeds escape velocity, in fact.

 

[Urwumpe]

1m / s ... I was thinking about this this morning. It is still fast enough ?

Its damn fast for a celestial body with an escape velocity of 1 m/s.

 

[fort]

No. I wanted to say: it's fast is'n it ?

 

[Astro SG Wise]

watch NASA TV at 8 CST

 

[SolarLiner]

Alternatively you can watch ESA's stream on Livestram: http://new.livestream.com/esa/cometlanding
French speaking people can watch the stream from La Cité de l'Espace: http://youtu.be/K8kTISUIfL8

 

[Artlav]

So, where are the pictures that should have been received by now?
The farewell shot?

 

[Unstung]

I guess this is a decent excuse to not bother getting any sleep... Philae, you ruin my beauty sleep worrying about you.

From what I read, the failure of the cold-gas system reduced chances for success from 75% to 50%.

---------- Post added at 07:18 AM ---------- Previous post was at 07:09 AM ----------

Unprocessed Philae farewell image!

 

[SolarLiner]

From what I read, the failure of the cold-gas system reduced chances for success from 75% to 50%.

Cold gas system was designed for the previous comet, with a much lower mass. From what I've heard on the stream those are not that much of a big deal.

 

[Unstung]

Cold gas system was designed for the previous comet, with a much lower mass. From what I've heard on the stream those are not that much of a big deal.

Comparing the shapes of resolved comets, 67P is the most interesting but also looks the most hazardous. Philae's landing legs were upgraded for the more massive comet, IIRC. Knowing the cold gas isn't that necessary is comforting.

Also, Philae from OSIRIS!
http://i.imgur.com/2ORKTEh.png (original)

(HD)

Unstretched Philae image:

 

[Astro SG Wise]

Here goes nothing!

Philae: Gotcha!
Comet: Aww man! After 10 years, I thought you would have given up!