Rosetta - Early Orbital Operations at Comet 67P C-G, August 6, 2014 - November 13, 2014 |
Rosetta - Early Orbital Operations at Comet 67P C-G, August 6, 2014 - November 13, 2014 |
Sep 13 2014, 05:09 PM
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#286
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Member Group: Members Posts: 148 Joined: 9-August 11 From: Mason, TX Member No.: 6108 |
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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Don |
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Sep 13 2014, 06:57 PM
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#287
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Senior Member Group: Members Posts: 1073 Joined: 19-February 05 From: Close to Meudon Observatory in France Member No.: 172 |
Impressionnant, Olivier ! La présentation pour La Villette avance ? Thanks Polaris, Thanks Neo 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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Sep 14 2014, 07:41 AM
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#288
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Member Group: Members Posts: 206 Joined: 15-August 07 From: Shrewsbury, Shropshire Member No.: 3233 |
Thanks Polaris, Thanks Neo 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 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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Sep 15 2014, 08:17 AM
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#289
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Senior Member Group: Members Posts: 1413 Joined: 26-July 08 Member No.: 4270 |
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 -------------------- -- Hungry4info (Sirius_Alpha)
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Sep 15 2014, 10:28 AM
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#290
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Member Group: Members Posts: 241 Joined: 22-August 05 From: Stockholm Sweden Member No.: 468 |
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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Sep 15 2014, 10:31 AM
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#291
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Forum Contributor Group: Members Posts: 1372 Joined: 8-February 04 From: North East Florida, USA. Member No.: 11 |
How accurately can they target the lander ? I know it just floats down due to the comets gravity.
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Sep 15 2014, 12:46 PM
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#292
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Member Group: Members Posts: 148 Joined: 9-August 11 From: Mason, TX Member No.: 6108 |
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! -------------------- --
Don |
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Sep 15 2014, 01:08 PM
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#293
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
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) : This is the area they are considering for site J to estimate the risk induced by slope (another screenshot): |
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Sep 15 2014, 01:51 PM
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#294
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Member Group: Members Posts: 204 Joined: 14-April 06 From: Seattle, WA Member No.: 745 |
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Sep 15 2014, 03:06 PM
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#295
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Senior Member Group: Members Posts: 4245 Joined: 17-January 05 Member No.: 152 |
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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Sep 15 2014, 03:43 PM
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#296
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
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:
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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Sep 15 2014, 05:15 PM
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#297
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Junior Member Group: Members Posts: 31 Joined: 3-August 14 From: Germany Member No.: 7229 |
here is the replay of today's landing site announcement:
http://www.esa.int/spaceinvideos/Videos/20...te_announcement -------------------- space scout
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Sep 15 2014, 05:27 PM
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#298
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Member Group: Members Posts: 241 Joined: 22-August 05 From: Stockholm Sweden Member No.: 468 |
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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Sep 16 2014, 02:32 AM
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#299
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Member Group: Members Posts: 279 Joined: 19-August 07 Member No.: 3299 |
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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Sep 16 2014, 04:27 AM
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#300
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Member Group: Members Posts: 890 Joined: 18-November 08 Member No.: 4489 |
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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