CE-2 flyby of Toutatis |
CE-2 flyby of Toutatis |
Aug 25 2012, 04:27 PM
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#1
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
I thought it was time to split the subject from the Moon forum.
Admins, can you move the relevant messages here? anyway, just out: an interesting blog article by Bill Gray explaining how he recovered the probe and how he computed the orbit yielding the 13 December flyby date Chang'e 2: The Full Story |
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Dec 16 2012, 12:36 PM
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#91
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Member Group: Members Posts: 796 Joined: 27-February 08 From: Heart of Europe Member No.: 4057 |
We can look to the past. CE-2 flyby was in many ways similar to the NEAR flyby around Mathilde.
Here are scientific papers about Mathilde and NEAR. CE-2 engineering cameras are not scientific instruments, but it's better than nothing and images from those cameras can be useful for shape determination, topography (as you said), geology (cratering record, boulders), rudimentary photometry etc. Another thing: Flyby was very close, so it's maybe possible to refine mass measurements of Toutatis and with better shape model, we can better derive its density and models of internal composition as well. -------------------- |
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Dec 16 2012, 01:22 PM
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#92
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
It may also provide a bridge between what we are seeing in radar imaged asteroids vs what we are seeing with from spacecraft flybys.
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Dec 16 2012, 03:24 PM
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#93
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Solar System Cartographer Group: Members Posts: 10182 Joined: 5-April 05 From: Canada Member No.: 227 |
"beside basic shape and topography, what can be extracted from this kind of webcam-like, probably uncalibrated images? not much I suspect."
Basic shape and topography tell us a lot - geological history, surface age from crater counts, redistribution of regolith by downslope processes, existence or not of 'ponds' as on Eros or smooth plains areas on Itokawa, hints of internal structure such as fractures or rubble-pile structure. The literature on small bodies extracts a great deal from images like these. Even without the big scanning camera, the close images from the smaller camera(s) will give us great details for many kinds of analysis. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Dec 16 2012, 04:29 PM
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#94
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Senior Member Group: Members Posts: 2517 Joined: 13-September 05 Member No.: 497 |
what can be extracted from this kind of webcam-like, probably uncalibrated images? What does "webcam-like" mean? A camera is a camera. These images might be a bit blurry, but they're a lot better IMHO than the science camera's on, for example, Deep Space 1. Most use of panchromatic or relatively broadband color imaging is morphologic and has little to do with calibration. As often as not, calibration is more about removing objectionable image signature, not data analysis, and these images look pretty good. I'm impressed, and even more so by the close flyby distance. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Dec 16 2012, 10:15 PM
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#95
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Senior Member Group: Members Posts: 2492 Joined: 15-January 05 From: center Italy Member No.: 150 |
I tried to make a stereogram using the fourth and last (biggest) image in the sequence poster:
Not sure about the result, however... if a parallax does exist, it is very small indeed! PS: I just updated asteroids/comets poster: -------------------- I always think before posting! - Marco -
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Dec 17 2012, 04:40 AM
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#96
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Member Group: Members Posts: 903 Joined: 30-January 05 Member No.: 162 |
Appreciate the stereogram effort very much. I think the compression noise in the images is what's giving me a headache, but underneath the noise, there does seem to be some appropriate depth in the image. For me, the upper right crater like depression seems appropriately bowled out, and the divot at the right end looks gougy enough. Let's hope some better feedstock turns up, or maybe some more massaging of the image can alleviate the compression artifacts.
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Dec 17 2012, 09:39 AM
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#97
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
Even without the big scanning camera, the close images from the smaller camera(s) will give us great details for many kinds of analysis. thanks everyone. as I said, I didn't mean to belittle the achievement, I was merely trying to get an idea of what could be extracted (beside ooohs and wows) from images by a camera not meant for science. according to JPL experts it may even be possible to get some info on the mass of Toutatis from tracking data. http://www.skyandtelescope.com/news/home/T...-183673171.html |
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Dec 17 2012, 01:57 PM
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#98
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Junior Member Group: Members Posts: 43 Joined: 11-March 10 From: Houston, Texas, USA Member No.: 5259 |
Can that be right? Navigationally I'd have thought getting that close was impossible without some kind of autonomous or at least very fast-turn optical navigation. Impressive if true. My thinking exactly. I don't know any interplanetary nav team in the solar system who would AIM at such a fly-by with a required error of +/- 2 km. Is it possible that the aim point was much farther out and this is just an accidental close pass? |
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Dec 17 2012, 02:05 PM
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#99
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Junior Member Group: Members Posts: 43 Joined: 11-March 10 From: Houston, Texas, USA Member No.: 5259 |
as for another extended mission, I think even merely tracking the probe as long as possible, without firing the engine anymore would provide useful experience for future missions beyond the Moon Tracking to determine the exact course change from the close fly-by will give superb data on asteroid mass. With images that show volume, you get real density data. Accidental or not, the very close fly-by itself is a major scientific experiment. |
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Dec 17 2012, 02:09 PM
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#100
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Junior Member Group: Members Posts: 43 Joined: 11-March 10 From: Houston, Texas, USA Member No.: 5259 |
On a policy issue note, we must realize that China kept this encounter secret -- even the date -- with the intent, arguably, to cover up any failure. Not revealing it until almost 48 hours after fly-by is a very discouraging retreat to 'Space Race' soviet-style secrecy. Glory and kudos to the spacecraft operators, for sure -- and more to come. Shame on the government information managers.
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Dec 17 2012, 02:12 PM
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#101
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Senior Member Group: Admin Posts: 4763 Joined: 15-March 05 From: Glendale, AZ Member No.: 197 |
PS: I just updated asteroids/comets poster: Thanks dilo that demonstrates nicely how the size fits in the gap between Itokowa and Eros. It's interesting that the surface features as someone pointed out above, appear to be transitional; somewhat like Itokowa, but with hints of characteristics of larger bodies. Now if we could come up with a popular-press unit of measure. Too big to measure in "battleships" like Itokowa, not big enough to measure in "manhattans" like Eros. Can someone think of a well known, elongated island 2.5 to 3 miles long? -------------------- If Occam had heard my theory, things would be very different now.
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Dec 17 2012, 03:28 PM
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#102
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
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Dec 17 2012, 03:31 PM
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#103
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Solar System Cartographer Group: Members Posts: 10182 Joined: 5-April 05 From: Canada Member No.: 227 |
"China kept this encounter secret -- even the date -- with the intent, arguably, to cover up any failure. "
Jim, post #5 at the start of this thread suggests to me that China did not keep anything secret. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Dec 17 2012, 04:09 PM
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#104
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Junior Member Group: Members Posts: 43 Joined: 11-March 10 From: Houston, Texas, USA Member No.: 5259 |
"China kept this encounter secret -- even the date -- with the intent, arguably, to cover up any failure. " Jim, post #5 at the start of this thread suggests to me that China did not keep anything secret. Phil Good point, and I'd seen that paper -- so was puzzled by total lack of run-up and real-time coverage of the encounter. To modify my complaint: despite disclosure to the space science community of the planned intercept date [a fact independently discovered and published by foreign astronomers], there was no Chinese media attention to the progress of the mission for months leading up to, and days AFTER, the encounter. I'm still dismayed by that behavior. And to discourage it happening again, I urge those who share my dismay to pass it on to their Chinese contacts. It really was out of character of recent Chinese public information release policies, which have been satisfyingly candid and open, even about future plans and actions. We had gotten accustomed to an open publicity policy. Seeing this one exception to it startled me. |
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Dec 17 2012, 06:21 PM
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#105
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
Is it possible that the aim point was much farther out and this is just an accidental close pass? apparently, they aimed a point 15 km from the asteroid (its center of mass, I think). ephemeris uncertainties of the two objects probably summed (in the worse possible direction) to yield 3.2 km (I don't know whether this is measured relative to the surface or center of mass. in the former case, it would translate in a miss distance from the center of mass of some 5 to 6 km) |
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