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Rosetta - Post Separation Ops at Comet 67P C-G, November 14, 2014 -
Explorer1
post Nov 14 2014, 05:17 AM
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I think I heard it mentioned during the press conference today, (I can't find it now), about Rosetta itself possibly landing eventually, similar to what NEAR did at the end of the main mission at Eros? Since it's not like there's anywhere else to go with the remaining delta-v left by the end of 2015, and sunlight levels and activity starting to drop after perihelion, and the low gravity makes the difference between orbiting and 'landing' trivial. The whole thing would weigh a kilo or two, right?
Obviously there's a few more pressing concerns right now, but it's something to eventually think about.
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Gerald
post Nov 14 2014, 10:39 AM
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At some point Rosetta will run out of propellant for orbit corrections.

The mass of Rosetta at regular EOM should be 2900 kg - 660 kg - 1060 kg - 100 kg = 1080 kg.
(Start weight - propellant - oxidizer - mass of Philae, from here)
The surface gravity of the nucleus at 2 km distance from the center of mass should be
g = GM/r² = (6.672e-11 Nm²/kg² * 1e13 kg) / (2000 m)² = 1.668e-4 N/kg.
The weight of 1080 kg is F = m a = 1080 kg * 1.668e-4 N/kg = 0.18 N.
0.18 N is the force of a mass of 18.37 grams in 9.80665 m/s² gravity.
The actual weight of Rosetta would be a little less due to inertial forces by the rotation of the nucleus.

To be more precise: The centripetal force for a radius of 2000 m and a rotation period of 12.7 h = 45,720 s is m r 4 pi² / T² = 1080 kg * 2000 m * pi² / (45,720 s)² = 0.0102 N.

So we are at 0.18 N - 0.01 N = 0.17 N for Rosetta's EOM weight, corresponding to the weight of a little more than 17 grams on Earth.

That's a model estimate, and may differ, depending on the actual landing coordinates.
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MahFL
post Nov 14 2014, 11:35 AM
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They have already stated they want to follow the comet during 2016, as it enters the dormant state. They would need a mission extension for that.
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neo56
post Nov 15 2014, 11:01 AM
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NavCam mosaic taken on 6 November 2014, with Agilkia landing site on top of the top lobe:


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tolis
post Nov 15 2014, 11:25 AM
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QUOTE (Explorer1 @ Nov 14 2014, 05:17 AM) *
Since it's not like there's anywhere else to go with the remaining delta-v left by the end of 2015, and sunlight levels and activity starting to drop after perihelion


Actually, it will go somewhere, after a fashion.

67P will approach Jupiter to within 0.4 AU in Nov 2018.

Whether Rosetta will be able to do anything about it, out of power and out of fuel, is another matter.

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astroman
post Nov 16 2014, 10:07 PM
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"rejoined" (forgot password) for this epic event- hopefully it will spawn a co-op esa-nasa cometary exploration program - especially good time being alive for following an historic and species first...


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SpaceScout
post Nov 17 2014, 04:08 PM
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Deutschlandfunk says the comet's surface remind of corals... Interesting comparison smile.gif but might lead to some misunderstanding...


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katodomo
post Nov 17 2014, 05:48 PM
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"Coral reefs under the sea" is what Paolo Ferri supposedly said in a radio interview for HR-Info - which is where Deutschlandfunk took it from, among others. Interview isn't available online (yet?), so can't check it for certain.

Considering quite a lot of people aren't even aware corals are alive i think the extent of misunderstandings will be limited wink.gif
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fredk
post Nov 19 2014, 06:52 PM
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QUOTE (Explorer1 @ Nov 14 2014, 05:17 AM) *
I think I heard it mentioned during the press conference today, (I can't find it now), about Rosetta itself possibly landing eventually, similar to what NEAR did at the end of the main mission at Eros?

From this New Scientist story:
QUOTE
Rosetta itself could one day join Philae on comet 67P. The orbiter will run out of fuel at the end of 2016, and ESA must decide whether to put it into hibernation, or put it down on the surface.

A large flat area on the dark side of the comet was not an option for Philae, but it will be well illuminated by 2016. Rosetta could crash-land there, taking extreme close-up pictures of the comet and sniff its atmosphere on the way down. "If we are called to do something like this I would be pleased," says Accomazzo. "If you ask me personally, I wouldn't do anything else."
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Y Bar Ranch
post Nov 19 2014, 09:38 PM
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QUOTE (fredk @ Nov 19 2014, 01:52 PM) *

Obviously it'd take a lot of precise planning, but if in the end game it was possible to drift down, and then blip the thrusters for the next-to-the-last-time to clean off the overlaying dust from the icy underside...
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neo56
post Nov 20 2014, 09:19 PM
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NavCam mosaic of 17 November:


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Phil Stooke
post Nov 24 2014, 03:14 PM
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The long wait for an OSIRIS color image may be over:

https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/22395

The AGU abstracts are online and full of good stuff, and a very small number of them contain images, including this one.

Phil



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ugordan
post Nov 24 2014, 05:48 PM
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The color mottling in that image is very interesting (other than obvious color fringes caused by rotation between frames), I wonder if that's real or an instrument artifact.


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neo56
post Nov 24 2014, 05:52 PM
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Many talks will be given to present the results from the instruments of Rosetta.


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Malmer
post Nov 24 2014, 06:38 PM
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Made a new animation of navcams draped over my shapemodel. This time with the november 17 navcam quad.

My shapemodel is becoming better with each iteration. The match between features in the images and the shape of the model is surprisingly good if I may say so myself smile.gif

http://mattias.malmer.nu/2014/11/navcam-november-17/
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