CE-2 flyby of Toutatis Options

[machi]

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.

[tedstryk]

It may also provide a bridge between what we are seeing in radar imaged asteroids vs what we are seeing with from spacecraft flybys.

[Phil Stooke]

"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

[mcaplinger]

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.

[dilo]

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:

[tasp]

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.

[Paolo]

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

[JimOberg]

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?

[JimOberg]

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.

[JimOberg]

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.

[ElkGroveDan]

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?

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[ngunn]

Venice?

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[Phil Stooke]

"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

[JimOberg]

"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.

[Paolo]

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)