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


Vicomt

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The latest article on the BBC has some nice information for those of you who are interested. http://www.bbc.co.uk/news/science-environment-27315877

Interestingly, it gives burn times (not accurately) and Delta-V changes, showing just how pathetic Ion drives really are, 8 hours for a 300m/s burn.

It's going to be fun to see exactly what happens as a comet approaches the sun, hopefully surprises are in store.

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You're confusing Rosetta with Dawn I believe - Rosetta doesn't use an ion drive. It's got a normal thruster.

300 m/s over 8 hours calculates to about 1 cm/s2 acceleration. An ion thruster is something like 1 mm/s2 or less. Spaceflight is not very fast :P

Anyway, greatly looking forward to Rosetta. My estimates put the current apparent diameter of the comet viewed from Rosetta to be comparable to the apparent diameter of Ceres as viewed from Earth, so alas, it'll be a while before we get good images.

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Yeah, I don't know too much about the actual specs for the drives, the only thing I could find with a quick google said they were 24x10N thrust, but didn't specify what type of thruster.

Does either Rosetta or Philae have video/still cameras?

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Yeah, I don't know too much about the actual specs for the drives, the only thing I could find with a quick google said they were 24x10N thrust, but didn't specify what type of thruster.

Does either Rosetta or Philae have video/still cameras?

Rosetta has a camera. However, for the reason NovaSiloko said, it can't provide any useful pictures right now. The camera is called OSIRIS(Optical, Spectoscopic and Infrared Remote Imaging System).

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Has anyone been using NASA's eyes to track Rosetta? Shifting time forward, it seemed to 'collide' with the comet in May, even though the actual rendezvous isn't expected to happen until sometime in August?

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well, here they talk about the probe, giving it fuel and oxydizer - so it's using bipropellant hypergolics for it's 24 engines (which are most likely the probe's RCS system - could be used for both attitude and propulsion) - of course, not all 24 fire at the same time :P

it has 1670 kg of fuel + oxidizer on board. (i guess they went with the higher ISP a bipropellant gives them over monopropellant, for the mission delta-v requirements)

http://www.esa.int/Our_Activities/Space_Science/Rosetta/The_Rosetta_orbiter

afterwards, Astrium designed the spacecraft bus - so they might be using technologies they know about - they used MMH and N2O4 on Ariane 5 EPS pressure fed upperstage.

(the space shuttle OMS used roughly the same fuels - it had 316 ISP - so we're surely with very near values - Ariane 5 EPS engine had a ISP of 324 - max ISP for MMH/N2O4 is 336)

Edited by sgt_flyer
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  • 2 months later...

Three weeks from today until orbital insertion completes. Every single day that passes from now on will significantly improve the pictures they can take. Just imagine the scientists who designed this more than 10 years ago, they must be going to work every day with huge grins of anticipation on their faces... all that waiting is finally bearing fruit.

Just compare the actual images of the double nucleus with the predictions shown in the BBC article in early May. And those images are already five days old again! It just shows that nothing can replace an actual visit :P

Edited by Streetwind
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Blog post from ESA about public access to Rosetta images and data: http://blogs.esa.int/rosetta/2014/07/16/access-to-rosetta-data/

All data gathered by all instruments of both the probe and the lander is subject to a 6-month exclusivity period, during which only the team of scientists that designed the specific experiment in question has access. This is normal for space science missions, especially for pioneering missions like Rosetta. However, the scientists involved may elect to waive the proprietary period on a case-by-case basis. For example, the images from July 11th were spontaneously released to the public because the OSIRIS team decided to allow it.

There will probably be another release later today, including both pictures and video.

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Six months, that surprising.

Not really

I don't think NASA does that?

Yes, they do

Do any of the other space agency do this?

Yes, they do

But don't worry. They will release an image or two quite quickly anyway. They always do. They are more hyped on that than we are and they want to share their excitement too. They just try to balance that with their scientific needs.

Anyway, greatly looking forward to Rosetta. My estimates put the current apparent diameter of the comet viewed from Rosetta to be comparable to the apparent diameter of Ceres as viewed from Earth, so alas, it'll be a while before we get good images.

That's why they arrive so early. To track the whole process as it unfolds. That's why IMHO it's the most exciting mission to unfold in 2014.

Edited by Sky_walker
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Six months, that surprising. I don't think NASA does that?

Do any of the other space agency do this?

Yes they do. As mentioned, this is an international standard procedure.

Just ask NASA to see what Hubble photographed yesterday - at best you'll get a smile and a headshake. :P

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Has anyone been using NASA's eyes to track Rosetta? Shifting time forward, it seemed to 'collide' with the comet in May, even though the actual rendezvous isn't expected to happen until sometime in August?

It has to match speed with it and then move toward it.

No you don't want a too close intercept, high chance you have dust around it.

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Yeah, it will come to a full (relative) stop 100km out, then assess the comet in detail (especially gravity). If everything checks out, Rosetta will move in as close as 10km and stay orbiting at that distance for the rest of the mission. Philae will be decoupled later to land on the comet surface.

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Yea, they first need to study the space around comet to make sure that safe approach is possible. Then, once on a low orbit, they need to find a landing spot, and with a comet in that shape - it won't be easy:

20140715_p11363_bae74240d30cd3861f46d3d4dbd367d620140711-67P-Rosetta-assemblage-1000_f840.jpg

(spin period is ~12 hours - so not too bad)

Edited by Sky_walker
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ESA released a video of the comet showing more details - it's much easier now to see how exactly does it rotate:

http://blogs.esa.int/rosetta/2014/07/17/the-dual-personality-of-comet-67pc-g/

Ros_67PCG_14July_mov.gif

Looks like it does have a poles, though I would say that these are the weirdest poles I ever seen - even weirder than these on KSP Moho.

Edited by Sky_walker
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