CE-2 flyby of Toutatis Options

[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: 1178

 

[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