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Rosetta - Early Orbital Operations at Comet 67P C-G, August 6, 2014 - November 13, 2014
MarsInMyLifetime
post Sep 13 2014, 05:09 PM
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Yes, it's fascinating to look at each part of landscape from its own "local level" as it were. The closest terrain appears scoured to me, suggesting that some venting occurs laterally, perhaps out from underneath rocky layers. Considering the eons of activity on this world, I'm actually surprised there is not much more buildup or selective puddling of boulders on the surface. Do they get ejected regularly, or is it a case of actually very low populations of boulders that are too heavy to leave the gravity well?


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vikingmars
post Sep 13 2014, 06:57 PM
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QUOTE (polaris @ Sep 12 2014, 07:42 PM) *
Impressionnant, Olivier ! La présentation pour La Villette avance ?

Thanks Polaris, Thanks Neo smile.gif
Oui, ca avance bien mais Gilles doit faire un point très vite avec l'ESA, car la mission est gérée un peu aussi au "jour le jour". Le noyau est extremement cabossé à l'échelle du mètre de ce nous avons compris et meme sur les sites retenus l'atterrissage sera dangereux. En plus, ils n'ont aucune idée dans quoi va se ficher les grappins pour que la sonde s'aggrippe au noyau... En bref, c'est "chaud", plein de surprises et on est suspendus aux décisions. Du coup, je suis en retard sur ma presentation et Gilles aussi ! Je vous tiendrai au courant...
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PaulM
post Sep 14 2014, 07:41 AM
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QUOTE (vikingmars @ Sep 13 2014, 06:57 PM) *
Thanks Polaris, Thanks Neo smile.gif
Oui, ca avance bien mais Gilles doit faire un point très vite avec l'ESA, car la mission est gérée un peu aussi au "jour le jour". Le noyau est extremement cabossé à l'échelle du mètre de ce nous avons compris et meme sur les sites retenus l'atterrissage sera dangereux. En plus, ils n'ont aucune idée dans quoi va se ficher les grappins pour que la sonde s'aggrippe au noyau... En bref, c'est "chaud", plein de surprises et on est suspendus aux décisions. Du coup, je suis en retard sur ma presentation et Gilles aussi ! Je vous tiendrai au courant...

Thanks Polaris , Thanks Neo wink.gif
Yes, AC is progressing well but Gilles must make a point quickly with ESA, because the mission is managed a little as the " day to day " . The core is extremely dented across the meter that we understand and even to the selected sites will be dangerous landing . In addition , they have no idea what will file grapples for the probe aggrippe kernel ... In short , it is " hot" , full of surprises and is suspended from the decisions. So, I 'm late on my presentation and Gilles too! I 'll keep you posted ...
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Hungry4info
post Sep 15 2014, 08:17 AM
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In about an hour, the landing site will be announced.
http://www.esa.int/Our_Activities/Space_Sc...on_announcement

Edit:
Site J is the Primary site.
Site C is the secondary site.

If I understood right, they think they see some hints of activity from near the site, which they believe is associated with some of the cyllindrical pits we're seeing.


Edit2: new images of primary landing site.
http://www.esa.int/spaceinimages/Images/20...ry_landing_site
http://www.esa.int/spaceinimages/Images/20...g_site_close-up

And backup site.
http://www.esa.int/spaceinimages/Images/20...up_landing_site
Attached thumbnail(s)
Attached Image
 


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Malmer
post Sep 15 2014, 10:28 AM
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Interesting that the landingsite 3D view looks like it is made using a digital elevation model with a picture draped over it.

The signal to noice ratio is just fabulous with the osiris camera!
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MahFL
post Sep 15 2014, 10:31 AM
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How accurately can they target the lander ? I know it just floats down due to the comets gravity.
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MarsInMyLifetime
post Sep 15 2014, 12:46 PM
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QUOTE (MahFL @ Sep 15 2014, 04:31 AM) *
How accurately can they target the lander ? I know it just floats down due to the comets gravity.

From http://www.esa.int/Our_Activities/Space_Sc...setta_s_lander:
"The descent to the comet is passive and it is only possible to predict that the landing point will place within a ‘landing ellipse’ typically a few hundred metres in size."

This is actually a quite good dispersion zone for this method of placement. Let's hope everything goes well with the release process and the calculations!


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Gerald
post Sep 15 2014, 01:08 PM
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I don't think, that they really know the accuracy of the landing (at the moment). Roughly 1 square kilometer.

The actual landing position is highly sensitive to the velocity vector (amount and pointing) after separation of the lander. They first accelerate the orbiter roughly towards the nucleus onto a hyperbolic orbit, then separate Philae from Rosetta, and return to an elliptical orbit for Rosetta. Separation after accelaration towards the nucleus reduces the descent time, and the sensitivity of the trajectory regarding the field of gravity of the comet, and regarding the initial velocity vector after separation.
Neither the result of the first burn nor the momentum provided to Philae by the separation are known precisely.
There is some sensitivity to the mass of the nucleus. This mass cannot be determined exactly, since the orbit of Rosetta is influenced by the gravity as well as by gas emanated from the nucleus; this orbit is used to determine the mass and field of gravity of 67P/C-G.
There is some more subtle dependency of Philaes's trajectory from the detailed field of gravity of the nucleus.

Overview of the operations for landing (cropped screenshot of today's press conference) :
Attached Image


This is the area they are considering for site J to estimate the risk induced by slope (another screenshot):
Attached Image
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Ron Hobbs
post Sep 15 2014, 01:51 PM
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... and the winner is ...

http://www.esa.int/Our_Activities/Space_Sc...osetta_s_lander
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fredk
post Sep 15 2014, 03:06 PM
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QUOTE (Malmer @ Sep 15 2014, 11:28 AM) *
Interesting that the landingsite 3D view looks like it is made using a digital elevation model with a picture draped over it.

The caption says they used two images to make the anaglyph.
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Gerald
post Sep 15 2014, 03:43 PM
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First, I thought, they would provide a complete recorded version of the press conference immediately after the conference. Seems not. So here some of the slides:
Attached Image


Edit: Quite some more background info about the selection process last week-end is described in this CNES article (in French).
Two things I didn't see elsewhere thus far have been, that Philae is expected to set on site J with 0.95 m/s, and site C won't be suitable for Consert.
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SpaceScout
post Sep 15 2014, 05:15 PM
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here is the replay of today's landing site announcement:

http://www.esa.int/spaceinvideos/Videos/20...te_announcement



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Malmer
post Sep 15 2014, 05:27 PM
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I made a detailed 3D model of the landingarea:

http://mattias.malmer.nu/wp-content/upload...07C90EBCBD8.mov

You can play with the 3d model if you like. (3D print?) Here is the obj file:

http://classic.syndicate.se/image/space/Landingsitemodel.zip
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SpaceListener
post Sep 16 2014, 02:32 AM
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Up to now, I still haven't see on what axis the comet rotates. This is an important matter for simplifying the landing operation and the illumination factor. By the way, Click for an interesting NASA report.
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JohnVV
post Sep 16 2014, 04:27 AM
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for the rotation see the thread that was split off this one
i have posted many images with the X axis as the axis of rotation
http://www.unmannedspaceflight.com/index.p...st&p=212592

http://www.unmannedspaceflight.com/index.p...st&p=212594
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