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CE-2 flyby of Toutatis
ElkGroveDan
post Nov 22 2013, 03:11 PM
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QUOTE (Explorer1 @ Nov 21 2013, 12:19 PM) *

Be careful, you can't believe everything you read on the internet.


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elakdawalla
post Nov 22 2013, 03:51 PM
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QUOTE (Paolo @ Nov 21 2013, 10:22 PM) *
one of the papers at this year's IAC had a closest distance of 1,564 +/- 10 m. from the center of mass, I think

That's pretty amazing considering the long axis is 4.5 km.

QUOTE (ElkGroveDan @ Nov 22 2013, 07:11 AM) *
Be careful, you can't believe everything you read on the internet.

rolleyes.gif


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Paolo
post Nov 22 2013, 05:31 PM
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I checked the paper "Relative Distance Estimation Between the Asteroid 4179 and Chang'E II Based On Spaceborne Opitcal Images" and it states:

QUOTE
the distance of the relative motion curve from the centroid of Toutatis to Chang’e II, i.e., their actual fly-by distance, is calculated.


so they are indeed not determining the distance from the surface. and later they conclude

QUOTE
the actual fly-by distance is 1564 m±~10 m.


note also that the paper by Huang et al referenced by the Icarus paper is this one: http://tech.scichina.com:8082/sciE/CN/abst...act511202.shtml
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Paolo
post Nov 22 2013, 05:33 PM
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by the way, Huang et al. (page 600) state, google translated:

QUOTE
Flying over the nearest point from the target time: 770 ± 120 m;
Distance from the geometric center of the overflight time: 1.32 km ± 120 m;
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elakdawalla
post Nov 22 2013, 06:36 PM
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Thanks very much for digging those up! I will add those details into my blog post.


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Paolo
post Dec 12 2013, 05:47 PM
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another (open access, this time) paper on the scientific results of the flyby
The Ginger-shaped Asteroid 4179 Toutatis: New Observations from a Successful Flyby of Chang'e-2
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Dysgraphyk
post Dec 13 2013, 04:58 PM
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according to this paper

QUOTE
Chang'e-2 implemented the flyby on 13 December 2012 at 8:29:58.7 UTC at a closest distance of 770 ± 120 (3σ) meters from Toutatis' surface at a high relative velocity of 10.73 km s−1,


quite a close shave... blink.gif


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Paolo
post Dec 13 2013, 05:04 PM
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QUOTE (Dysgraphyk @ Dec 13 2013, 05:58 PM) *
quite a close shave... blink.gif


it still surprises me that they seem to have done it entirely without optical navigation. they just knew the exact orbit of the asteroid thanks to radar tracking and that of the probe thanks to ranging and they managed to pull out the closest flyby ever with these data
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ElkGroveDan
post Dec 14 2013, 12:58 AM
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QUOTE (Paolo @ Dec 13 2013, 09:04 AM) *
....they just knew the exact orbit of the asteroid thanks to radar tracking and that of the probe thanks to ranging and they managed to pull out the closest flyby ever ....

There probably was some serendipity involved.


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Paolo
post Dec 14 2013, 08:41 AM
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actually, they had a trajectory correction (and a sizeable one, 3.3 m/s) the day before the flyby, so I guess they were aiming for a very close encounter on purpose
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Paolo
post Apr 10 2014, 05:28 PM
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a paper on the future orbit of CE-2, due for publication in the Chinese Science Bulletin: The Earth co-orbital motion and recapture of the Chang'e-2 spacecraft
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Paolo
post May 29 2014, 08:07 AM
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this interesting paper on the imaging strategy of CE-2 at Toutatis (which was also discussed on UMSF) has been published in Chinese Astronomy and Astrophysics: A Research on the Imaging Strategy and Imaging Simulation of Toutatis in the Chang’e-2 Flyby Mission.
the English version is unfortunately behind the paywall (but I have tried to contact the author to have a copy), while the Chinese version is available here.
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Paolo
post Oct 25 2014, 06:34 AM
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this was just published online in Advances in Space Research (and, incredibly for Elsevier, seems to be in open access): Navigation of Chang’E-2 asteroid exploration mission and the minimum distance estimation during its fly-by of Toutatis
from a first, quick look, lots of interesting infos not published elsewhere:
- a detailed timeline of the corrections maneuvers leading to the flyby
- the targeted flyby distance was approx. 30 km but CE-2 ended being much closer (less than 2 km) to Toutatis
- distant images of the Earth and Moon were taken after departure, on 31 July and 1 August 2012. apparently, these were taken to test the camera (the CMOS monitoring camera used during the flyby, I suspect). it would be nice to see these images...
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