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CE-2 flyby of Toutatis
Paolo
post Aug 25 2012, 04:27 PM
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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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I'm one of the most durable and fervent advocates of space exploration, but my take is that we could do it robotically at far less cost and far greater quantity and quality of results.

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Paolo
post Aug 27 2012, 10:02 AM
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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


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James Van Allen
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TheAnt
post Sep 1 2012, 10:03 PM
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Interesting story thank you for sharing.
Mr Gray seem to be quite the detective and he do use the word 'sleuth' as well. =)
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rlorenz
post Sep 1 2012, 10:19 PM
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I don't suppose they'll rename the spacecraft 'Obelix'....
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Paolo
post Oct 7 2012, 08:37 AM
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I have got a copy of this paper presented at last week's IAF Congress
Low energy trajectory optimization for CE-2s 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


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tolis
post Oct 10 2012, 01:45 PM
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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.
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Paolo
post Oct 10 2012, 03:15 PM
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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


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Paolo
post Oct 11 2012, 07:00 AM
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today on arXiv: Composition of Near-Earth Asteroid (4179) Toutatis



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James Van Allen
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tolis
post Oct 12 2012, 10:22 AM
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QUOTE (Paolo @ Oct 10 2012, 04:15 PM) *
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.
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Paolo
post Oct 28 2012, 08:43 AM
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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)
Attached Image
 


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Phil Stooke
post Oct 28 2012, 01:38 PM
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Excellent - thanks for this.

Phil



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Tom Tamlyn
post Oct 28 2012, 03:49 PM
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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
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Paolo
post Dec 5 2012, 06:29 PM
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just tweeted by @asrivkin at the AGU meeting

QUOTE
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


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I'm one of the most durable and fervent advocates of space exploration, but my take is that we could do it robotically at far less cost and far greater quantity and quality of results.

James Van Allen
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Phil Stooke
post Dec 5 2012, 07:10 PM
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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



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Paolo
post Dec 5 2012, 07:20 PM
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I saw it. It's a pity that 2 pics will not be enough to reveal the complex spin of Toutatis


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I'm one of the most durable and fervent advocates of space exploration, but my take is that we could do it robotically at far less cost and far greater quantity and quality of results.

James Van Allen
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