CE-2 flyby of Toutatis Options

[Paolo]

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

[Paolo]

a few more observations of Chang'e 2 (designated 2010-050A by the COSPAR) in solar orbit were made last saturday by the Catalina Sky Survey
http://www.minorplanetcenter.net/iau/DASO/...DASO_000449.txt
I hope Bill Gray will soon be using them to update its orbit determination and encounter estimates

[TheAnt]

Interesting story thank you for sharing.
Mr Gray seem to be quite the detective and he do use the word 'sleuth' as well. =)

[rlorenz]

I don't suppose they'll rename the spacecraft 'Obelix'....

[Paolo]

I have got a copy of this paper presented at last week's IAF Congress
Low energy trajectory optimization for CE-2’s extended mission after 2012
I will not share the paper, but I can tell you something more about the Toutatis flyby

- first of all: 13 December 2012 is confirmed as the date. no distance nor relative speed or other details are given
- we are told that the Beijing Aerospace Control Center called for proposals on a mission beyond L2 in January 2012.
- there were lots of interesting proposals including one that would flyby Earth and Moon repeatedly, visit the L1 and L2 Lagrangian points, flyby a hundred-meter sized asteroid and finally explore the L4 Sun-Earth point in 2017 (the paper states that CE-2 would have been the first mission to do so. I think one of the two Stereos was first)
- in March 2012 the Toutatis flyby, proposed by the Chinese Academy of Space Technology was selected
- in a non-optimized form, the mission would have cost 107.5 m/s of the remaining 120 m/s delta-v budget
- a 6.2 m/s correction on 15 April "was mainly used to keep the Lissajous trajectory". it was previously reported as the date CE-2 was maneuvered out of the L2 halo orbit
- trajectory optimization was only carried out starting on 16 April. After optimization, an additional 22 m/s delta-v was gained that could be used to ensure a successful flyby
- the first targeting maneuver was carried out on 31 May (32.9 m/s)
- the second targeting maneuver (46.5 m/s) was to be carried out on 24 September

[tolis]

According to JPL's HORIZONS ephemeris service,

(Some of) The vital statistics of Toutatis on the 13th December 2012 are as follows:


Epoch (UT) () Geocentric distance () Apparent Magnitude () Solar Elongation
() (AU) () () (deg)
13/12 00:00 () 0.0466 () 10.73 () 125
13/12 12:00 () 0.0471 () 10.65 () 128
14/12 00:00 () 0.0478 () 10.59 () 132


Toutatis will be east of the sun and so an evening object in the sky. Judging from the magnitude and
solar elongation, I would say that it is well within reach of backyard observers (including myself).

Regards to All,


Tolis.

[Paolo]

I saw it in November 1996 using a small, 114 mm telescope. under dark skies, it was easy to spot and it was amazing to see it clearly glide against the background stars

[Paolo]

today on arXiv: Composition of Near-Earth Asteroid (4179) Toutatis

[tolis]

I saw it in November 1996 using a small, 114 mm telescope. under dark skies, it was easy to spot and it was amazing to see it clearly glide against the background stars

It will be moving quite fast on this occasion too, about 1/3 degree per hour.

[Paolo]

to answer Phil Stooke's question in another thread http://www.unmannedspaceflight.com/index.p...st&p=193809 about the CE-2 end of mission I noted playing with the orbital elements published by Bill Gray that the orbital period of the probe is now 1.044 years that is it will trail behind the Earth by 15 degrees every year. in four years that is in July 2016 it will pass close to the trailing Lagrangian point L5. It will then be back in the vicinity of Earth in 24 years.
I pointed this out to someone in China who worked on orbit design for the Toutatis flyby but he told me that this is a pure coincidence and that it was not done on purpose
BTW I posted this graph of the orbit of CE-2 up to the end of 2016 in a fixed Sun-Earth reference to the NASAspaceflight forum a few weeks ago. L5 is the red dot.

Attached thumbnail(s)

 

[Phil Stooke]

Excellent - thanks for this.

Phil

[Tom Tamlyn]

The link to Bill Gray's August 25 planetary.org article in post # 1 is broken.

I found the post at:

http://www.planetary.org/blogs/guest-blogs...full-story.html

[Paolo]

just tweeted by @asrivkin at the AGU meeting

In asteroid news, China's Chang'E 2 will fly by the asteroid Toutatis in a few weeks. My (USA) source tells me it'll get 2 images

which to me confirms the difficulty of imaging Toutatis with a push-broom camera instead of a proper 2-dimensional CCD

[Phil Stooke]

Check out this e-poster from the current AGU meeting:

http://fallmeeting.agu.org/2012/eposters/eposter/p31a-1873/

This is about radar imaging of Toutatis. Even if we only get a couple of reasonably well resolved images of Toutatis, it will be a big help in interpreting the radar images which contain complex ambiguities. There is a detailed shape model, but such models are also not without problems. Plus of course, there will be some information (we would hope) about albedo variations etc. which the radar does not give.

Phil

[Paolo]

I saw it. It's a pity that 2 pics will not be enough to reveal the complex spin of Toutatis

[Phil Stooke]

No, but radar does that very well.

Phil

[Paolo]

speaking of which, the first radar image of the 2012 flyby
http://echo.jpl.nasa.gov/asteroids/Toutati...2_planning.html

[Paolo]

from this post to the mpml asteroids and comets group http://tech.groups.yahoo.com/group/mpml/message/27635 the two pics will be taken one on the inbound leg, the other on the outbound leg. my Chinese sources say the targeted distance will be 1000 km.
I guess what this means is that CE2 will aim at the point in space where Toutatis is supposed to be and wait for it to cross the field of view of its push-broom camera at the correct angular rate. then it will be reoriented to take a second picture with the same technique on the outbound leg

[machi]

So we can expect images with resolution ~100 m/pix at best. This isn't much for such small body like Toutatis (~2.5 km diameter), but still it can be very interesting.
~25 image elements per diameter is enough for major units, like albedo regions or big craters and it's sufficient for Emily's size comparison poster.

[Explorer1]

So the images will be the equivalent of what Deep Space 1 did, assuming they pull them off?

[machi]

Deep Space took images of Braille with resolution around 180 m/pix. Braille is two times smaller than Toutatis. So with some luck, we can expect images four times better than those of asteroid Braille (4× more pixels across diameter of asteroid).
This is what we can expect, if everything goes well and image will be taken close to 1000 km flyby distance.

Attached image(s)

 

[Paolo]

anyway, as the camera has two linear CCDs, a forward looking and a rearward looking one I would rather expect two couples of pictures instead of two pictures

[Phil Stooke]

Machi, that is Steins, not Braille.

And Paolo - doesn't that suggest the forward camera will take one and the rearward camera will take one? Otherwise you seem to be suggesting the spacecraft reorient itself during each sequence.

And there's another new image here:

http://echo.jpl.nasa.gov/asteroids/Toutati...2_planning.html



Phil

[machi]

Machi, that is Steins, not Braille.

Yes, I know.
That is image of Steins from Rosetta used for demonstration as Toutatis may appear from CE-2.
I thought that I wrote this clearly, if not my apologies, it was lost in translation.
In fact this image was uploaded with name "Steins_as_Toutatis_from_Change2", but evidently forum system still uses some kind of thumbnail with different name even for small images.

[Paolo]

And Paolo - doesn't that suggest the forward camera will take one and the rearward camera will take one?

the camera has two parallel CCDs, one looking 8 degrees forward of the nadir (when in lunar orbit), the other 17.2 degrees to the rear. To me the most logical sequence would be one where Toutatis crosses the field of view of the first CCD almost perpendicular to it and then about one minute later (the exact timing depends on the encounter geometry, which is not known) that of the second sometime on the inbound leg. Around closest approach the probe is reoriented so that Toutatis crosses again both fields of views in the outbound leg. this gives two pairs of images.
If no reorienting is done, you get only one pair of images a few tens of seconds apart

[Paolo]

third radar picture http://echo.jpl.nasa.gov/asteroids/Toutati...32Hz.s439.b.gif
it's amazing how the quality and resolution of these images has increased since 1992

[machi]

According to this page, flyby distance will be around 300 km.
If it's true, then images from CE-2 will much better than in my simulated image (maybe 4× better).

[tasp]

I'm not thinking of any other 'rocks' imaged with ground based radar getting a nice visible light camera flyby. (It is REALLY early for me though, and no coffee yet) (we need a 'sleepy' emoticon)

Anyone recall any others?

[Paolo]

Itokawa had been imaged by radar before Hayabusa arrived

[machi]

I'm not thinking of any other 'rocks' imaged with ground based radar getting a nice visible light camera flyby...
Anyone recall any others?

Not exactly "rock", but also comet Hartley 2 was imaged by radar.
Here is article about "Radar observations of asteroid 25143 Itokawa".

[Phil Stooke]

Comparing the Itokawa radar images and shape model with the spacecraft images shows the limitations of using low resolution radar data. The basic size and elongation are well established but the two-lobe shape is not seen. For Hartley-2 two lobes are also resolved but not much more. But for Toutatis we have high resolution radar data and a detailed shape model, and nothing with that kind of radar data has been visited by a spacecraft. So this will be a very interesting encounter.

Phil

[JimOberg]

Technical info is great. Hsieh hsieh.

Big picture question: has anybody received any word about the health of the spacecraft in the past two months?

We're only days from the encounter. Is the absence of any news from China something to worry about?

[Explorer1]

The absence of news is business as usual over there. Has there even been an official announcement of this flyby yet from CNSA in Beijing?

[JimOberg]

The absence of news is business as usual over there.

I beg to differ. When things have been going well, China has released a stream of information, even ahead of actual events. They have been far more open then the Soviets were in Space Race days. I remember and can compare/contrast.

This silence is unusual.

[Explorer1]

Yes, I've read Don Mitchell's page on the old Soviet missions to the Moon and Venus, and the lengths he had to go to. I'm not sure if he posts on here, but I;m sure has has good insights too.
I'm just saying we should not get our hopes for a real crisp and immediate release like we've become used to from NASA or even ESA. I'd even be happy with a Halley's nucleus type blur.

[Paolo]

there was a long article on the development of CE-2 on a Chinese site recently
http://zh.cnr.cn/2100zhfw/zhhz/201211/t201...511342196.shtml and http://zh.cnr.cn/2100zhfw/zhhz/201211/t201...1342196_1.shtml
at a certain point it is stated (my adaptation of a google translation):

According to the latest news, Chang E 2 successfully completed further extend the test a second halfway correction, the whole control process satellite subsystems work properly, in good condition. Until October 9, Chang'e II satellite in orbit flight 736 days, has 2.61 million kilometers from Earth. Follow-up will be used to track and test our new two deep space monitoring stations and to carry out the technical test.

[JimOberg]

there was a long article on the development of CE-2 on a Chinese site recently

Thanks, Paolo, that's encouraging.

I also found this more recent URL but I can't get my translators to work:
http://news.e23.cn/content/2012-12-10/2012C1000084.html

[Paolo]

another long article in Chinese linked today on the 9ifly forum
http://y234.cn/?p=6128

[JimOberg]

another long article in Chinese linked today [url="http://bbs.9ifly.cn/thread-9843-109-1.html"]on the 9ifly forum [

I see a picture of chang'e-2 but can't get translator to work. Any help?

[stevesliva]

^ Google Translate
... seems to be a blogger asking similar questions. It appears based on english articles, so you get what we already know translated to chinese and then google-translated back. Wouldn't assume that will do anything but subtract information.

[elakdawalla]

Google translate worked for me. There's no new information in here -- in fact it links to Bill Gray's guest blog on planetary.org and to MPML. It provides background on Toutatis and on NEOs. Mostly it asks why the national space agency isn't ballyhooing this more, and then answers the question by explaining that Chang'E 2's ability to get good data on the encounter is limited, concluding that while any data will be interesting, the significance of this is more as an engineering test of the Chinese ability to make the encounter succeed, providing "valuable experience." Seems like a very nice explainer -- hopefully the author will get some traffic from Chinese readers

[JimOberg]

Google translate worked for me.

thanks. i agree that the technology demonstration of the SEL2 dwell, and the departure to the toutatis intercept point, are awesome new levels of space navigation capabilities. it would be nice to get images but your own blog put that in perspective.

i'm working to get my own media clients to appreciate the accomplishment and not to set artificially high success criteria.

would clementine have faced the same problem with asteroid imaging, or was its survey camera of a different design?

[mcaplinger]

would clementine have faced the same problem with asteroid imaging, or was its survey camera of a different design?

The Clementine cameras were all framing cameras with filter wheels, so no.

That said, slewing a pushbroom imager is not that big a deal; see http://mars.jpl.nasa.gov/mgs/msss/camera/i..._98_phobos_rel/ Of course I don't know how CE2's attitude control system works.

[Phil Stooke]

http://echo.jpl.nasa.gov/asteroids/Toutati...2_planning.html


New images appearing on this site now - one other difference between radar and CE2 images, worth remembering - the visible images will have MUCH better signal to noise - radar images are speckly and show very little detail near the terminator (except bits of it which are tilted towards the radar, like a crater rim) - in fact it's sometimes hard to see where the radar terminator is. So the new images really will be complementary in many ways.

Phil

[machi]

Very interesting images. Here is image pair from 9. December in more "visible" look:

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[Phil Stooke]

15 years ago I made a map of Toutatis, using an experimental image interpretation method. It was never published because of a dispute about the validity of the concept I had devised. This is the map, in case anybody is interested. Apart from the concept I used to convert the geometry of radar images to the equivalent of visible images for mapping (that's where the dispute came in) I also tended to push my interpretation of craters too far in those days. Every little hollow became a crater in my map. Now I would be more cautious in my interpretation. (Note - rotation is about the long axis - and because of ambiguity in the images, this might be a mirror image of the real surface)

Phil

[Paolo]

anybody knows whether ESA is providing tracking support to CE-2?
otherwise, has anybody tried computing the windows of visibility for the Chinese Deep Space Network stations? just to know when we can expect to have some news of the flyby

[Greenish]

The images at http://echo.jpl.nasa.gov/asteroids/Toutati...2_planning.html get better every day. Will be really interesting to see how the delay-doppler representations compare to the visible light ones.

I just noticed the following on that page: "Scheduling update: due to an equipment failure, radar observations of Toutatis at Arecibo were cancelled." Not sure when this appeared... Can anyone explain what the potential impact could be on the observing campaign? Not that I'm complaining, the Goldstone quick results are great and impressive on their own.

[Phil Stooke]

I don't see anything in the online chinese press yet.

Phil

[Paolo]

I have seen a release (in Chinese) on the site of the Chinese Academy of Sciences.
I don't have a link at hand, but it really didn't say anything new.

[machi]

I read on multiple Chinese pages, that they planned ~12 images of Toutatis.
But source is unknown, respectively it's some astronomer in Beijing.

EDIT:
Here is info from Chinese Academy of Sciences.

[Paolo]

be sure to check this!
http://www.youtube.com/watch?v=waH9zfEbNJs

[Phil Stooke]

The radar video is great - first time I have seen something like this, and it does a fantastic job of resolving the front-to-back ambiguity. In a still image you can often see two lobes appearing to intersect, but you can't tell which is in front and which behind.

Phil

[machi]

The video is great, but Toutatis looks somewhat distorted.
On every image all sides are doubled, so it looks like two overlaid images of Toutatis:

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[Phil Stooke]

That's because of the bizarre geometry of radar images. Imagine looking out over a range of hills with peaks at varying distances. Now imagine they are semi-transparent so you can see hills behind other hills. At the radar limb in these images, that is what we are seeing. The geometry is totally different from visible images. But with many images the ambiguities can be resolved - which is what this is all about, and why the Chinese images will be really useful. We have never had both high resolution radar and (reasonable resolution) visible imaging for any object before.

Phil

[tedstryk]

Assuming it is better than the 2002 NY40 images, this could be significant.

[yaohua2000]

Video: http://news.cntv.cn/china/20121215/100850.shtml

Relative speed at 10.73 km/s
Closest flyby at 3.2 km altitude

Sequence (local time):
• Dec13 15:25 Return solar panels to 180 degrees
• Dec13 15:30 Switch to inertial attitude control
• Dec13 15:45 Switch to star orientation 10
• Dec13 15:48 Switch to star orientation 2
• Dec13 16:20 Solar panel monitoring camera power up
• Dec13 16:30 Closest flyby
• Dec13 16:45 Solar panel monitoring camera power down

Attached image: captured at 93–240 km distance between 16:30:09–16:30:24, maximum resolution 10 meters/pixel

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[Cosmic Penguin]

Just in from the Chinese news TV reports an hour ago: the fly-by was a success! The closest fly-by was at 08:30:09 UTC on December 13 at an altitude of just 3.2 km and at a relative velocity of 10.73 km/s. Quite a few photos were snapped by the CCD camera - including this series of photos taken 93 - 240 km away from Toutatis:





Chinese news report about the fly-by (may translate it later if I have time): http://news.cntv.cn/china/20121215/100850.shtml

P.S. My first post here! (my interest in planetary exploration started in grade 1 after seeing photos from the twin Voyagers)

[tedstryk]

Woah! That is better than I was expecting. Welcome to the interplanetary club, China!

[machi]

Fantastic and great news!
Now we have another country in "discovery" class! Congratulations!
BTW, very nice surprise. Images are much better than expected.

[Explorer1]

Very fast release! I'm glad to have been wrong in my earlier speculation. I wonder how real/fake the color is.

[elakdawalla]

I wonder, were these images taken with the webcam-style cameras they used to monitor deployments and rocket firings?

[Phil Stooke]

3.2 km? Amazing, just amazing. Solar panel monitoring camera power up... I guess it was that one. Does this mean there's more to come from the main camera?

Phil

[mcaplinger]

3.2 km? Amazing, just amazing.

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.

[elakdawalla]

I'm trying to figure out what the scale of the image is, with the endgame, of course, being the addition of this body to my asteroids-visited-by-spacecraft montage. A major question for an elongated body is: are we seeing its maximum dimension, or is it foreshortened?

From this JPL page, the radar-derived dimensions of Toutatis:
"The asteroid's maximum extents along the principal axes are (1.92, 2.29, 4.60) +/- 0.10 km. "

Measuring on the photo, I get that the long axis here (which may not be the full length, if it's not broadside-on) is 792 pix
The short axis here should be somewhere in between the 1.92 and 2.29 axes, and it's 312 pix

That ratio is about 0.4, which is almost identical to 1.92/4.60

Which would mean that (assuming the JPL numbers are correct) we really are looking at it pretty close to broadside-on, with the plane of the sky being close to the plane of the minimum and maximum principal axes.

Somebody please check my work!!

[machi]

My measurements are: long axis ~800 pix, short axis ~330 pix and ratio 0.4125.

[Phil Stooke]

I can confirm that this view shows the long dimension, probably no more than a little bit foreshortened. I think it's pretty much being viewed along its shortest axis, so we are seeing the long and intermediate axes.

Phil

[Phil Stooke]

Bringing out a bit more detail in the brighter areas:



(Thanks, Chinese space agency, for these great pictures)

Phil

[machi]

Attempted comparison with Goldstone radar imagery.

Attached thumbnail(s)

 

[ElkGroveDan]

Is there any doubt that we are looking at two distinctly separate objects in contact?

[Phil Stooke]

If this is an approach sequence, there may be a departure sequence as well.

Phil

[elakdawalla]

Beginning to look at the image and try some early (read: arm-waving) interpretation. Some things I notice: there are boulders that remind me of Itokawa. But they're sparse; it's substantially smoother than Itokawa. So I'd interpret that to mean it is mostly covered in a regolith. I also see circular depressions of a wide variety of sizes, the sort of thing one would tend to interpret as impact craters. Some have sharper edges than others. Of course, you have to be cautious; smaller ones especially might be collapse pits. I'm intrigued by the apparent roughness of the larger end. Again, though, I need to be careful; its apparent roughness could be due to lighting geometry. It's a pretty low-phase-angle image. Overall, it seems faceted. A slope map of this thing would be fascinating.

[yaohua2000]

More info: 20 Kbps at 7 million km, 90% data has been received so far.

This is a television screenshot of a close-up image at 5 m/pixel, captured at 08:30:05, 47 km away. (Hope to have raw image soon)

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[tedstryk]

Thanks for posting that! I think you mean 5 m/pixel.

[Phil Stooke]

Shape model and slope map here:

http://echo.jpl.nasa.gov/asteroids/4179_Toutatis/hires.pdf

Phil

[Paolo]

wow! China releases the first pics and I happen to be sleeping?!? btw it's good to be proven wrong about the number of them!
Kudos to the Chinese!

EDIT: gotta love this! in the west we tend to compare asteroids to potatoes. someone on the 9ifly forum is comparing it... to a ginger root!

[Paolo]

I wonder, were these images taken with the webcam-style cameras they used to monitor deployments and rocket firings?

is this schema is to be believed http://english.cri.cn/mmsource/images/2012...8e4073c048f.jpg they were indeed all taken using the webcams (CMOS and not CCD cameras)

• Dec13 15:25 Return solar panels to 180 degrees

from 9ifly forum, this seems to mean that the solar panel that the webcam was designed to monitor was rotated out of the camera fov

[Doc]

Outstanding Chinese performance. Thanks for posting the images so quickly! Really took my breath away

[t_oner]

Here is a 3D PDF of the shape model. (It is heavily optimized to be under the 1MB attachment limit.)

Attached File(s)

 Toutatis.pdf ( 416.97K ) Number of downloads: 1190

 

[machi]

Here is Chinese TV show dedicated to Toutatis flyby and ChangE program.
I recommend you last few minutes (from ~55:00), where you can see some shots from planned ChangE-3 mission.

As I understand from these pictures, they tried some imaging around closest flyby distance (~3.2 km) by different camera, so maybe we can expect even better images in future.

Attached thumbnail(s)

 

[Drkskywxlt]

Congrats to the Chinese! There's some depressions that obviously look like craters there, but not as many as I'd expect and they seem "muted". Would this suggest a low-density "rubble pile" composition?

[Stefan]

If this is an approach sequence, there may be a departure sequence as well.

Phil

I wonder if this "approach sequence" is in fact a single image shown at different sizes.

[machi]

Yes, all images are almost equal (apart from size), but this is exactly what one can expect, when spacecraft is flying in this kind of trajectory (fast and extremely close flyby). From a greater distance, it looks more like a fall.

[tolis]

Amazing stuff!

Apart from the sheer speed of the flyby, I would imagine that Toutatis' extremely long rotation period
(~24hr) would contribute to it appearing the same - apart from a change of scale - in all images.

Also interesting is the relative absence of craters and the presence of boulders. In this sense, Toutatis seems to
be intermediate between larger asteroids (eg Eros) where you have both craters and boulders and Itokawa
where craters are virtually absent.

[Paolo]

this is what a Chang'e 2 CMOS webcam looks like. and some treat from earlier in the mission

Attached thumbnail(s)

 

[Phil Stooke]

Comparison of the new image with the radar shape from the paper I linked to above. I think the new image is tilted a bit, with the top end tilted perhaps 20 degrees toward the camera.

Phil

[Paolo]

Chinese sources such as this http://www.stdaily.com/stdaily/content/201...tent_552959.htm acknowledge that the CMOS monitoring webcam has been used. the 200 g, 1024 x 1024 pixel camera apparently shot 5 pictures every second for more than 100 seconds around closest approach. The camera has a 7.2 degree fov.
I wonder whether any science camera picture was finally taken or not. from the timeline on the left of this picture http://i.dailymail.co.uk/i/pix/2012/12/15/...269_634x422.jpg which yaohua2000 translated here http://www.unmannedspaceflight.com/index.p...st&p=195772 I think it was not even powered on.
Chinese sources also report that a domestic telescopic observation and orbit determination effort was carried out on Toutatis. This was not strictly needed for such a well known object, but was still an useful exercise for an encounter with a more obscure object.

[machi]

I have somewhat different informations about ChangE-2 cameras.
According to this abstract, CE-2 has four monitoring cameras (+ fifth camera - scientific stereo camera). Three cameras are designed to provide engineering monitoring of spacecraft (solar panel, engine, antenna) and one camera is used for moon imaging.
Moon imaging camera weights 502 g and has CMOS chip 1280×1024. Engineering cameras weights 352 g.

[Cosmic Penguin]

Apparently the main camera was not powered on (nor it seems the other instruments on the spacecraft either), due to these reasons:

1. The data transfer from the main CCD camera would be very bad at such a long distance from Earth

2. The double linear-phase CCD camera has such a small FOV that it would not be able to take photos at such a relative speed during the fly-by

I might need to dig around the 1 hour special report on the Chinese news TV channel yesterday to look for other interesting facts on the fly-by.....

Oh and forget about another mission by CE-2, it has less than 10 m/s of delta-v capacity left....

[Paolo]

I don't want to belittle the CE-2 achievement, but I have a question for the scientific data minded: beside basic shape and topography, what can be extracted from this kind of webcam-like, probably uncalibrated images? not much I suspect.

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

[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.