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China to the Moon - Chang'e 1 and 2, Chinese unmanned lunar orbiters
Guest_Zvezdichko_*
post Jan 10 2009, 11:58 AM
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http://news.xinhuanet.com/english/2009-01/...nt_10625458.htm

According to this publication Chang'e will impact the Moon in proper time, but not detail is given, as usual mad.gif
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Geert
post Mar 1 2009, 12:32 PM
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Chang'e has impacted the moon after de-orbit burn

see http://www.chinadaily.com.cn/china/2009-03...ent_7523687.htm

Regards,

Geert
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Phil Stooke
post Mar 1 2009, 03:12 PM
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Another point on the map! This is in Mare Fecunditatis, about 120 km west of the Luna 16 landing site.

Phil


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nprev
post Mar 1 2009, 09:25 PM
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Anybody know why Chang'e was deliberately deorbited @ EOM? I'm just wondering why they'd bother; it wasn't targeted towards a suspected volatile-rich area or anything like that.


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Phil Stooke
post Mar 2 2009, 03:13 AM
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Lunar spacecraft may be removed from orbit so they won't interfere with other missions - a second Chinese orbiter will follow this one and they may need to avoid communications issues - and also, they may be brought down in a controlled manner, if it's possible, to avoid damaging historic sites.

Phil


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nprev
post Mar 2 2009, 04:25 AM
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Thanks, Phil. I sort of thought that was why, but lunar orbit is hardly crowded these days. Concur with the historical site aviodance rationale, of course.


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dvandorn
post Mar 2 2009, 05:13 AM
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Although, I have to wonder -- what are the odds against an unguided impact by Chang'e (or anything else, for that matter) hitting an area of historical importance?

How many of these locations are there? Six Apollo sites, five Surveyor sites, two Lunakhod sites, three Luna sample return sites and two simple Luna lander sites -- a total of 18 sites, over the entire surface area of the Moon. (This assumes you're not going to count impact sites -- many of them unidentified -- of other hardware, from Luna 2 through Chandrayaan's MIP. I find it hard to imagine a tourist viewing platform to observe what appears to be just another crater out of quadrillions, just because it was made by a man-made vehicle. Though I might make an exception for Luna 2.)

I understand that a vehicle in polar orbit does eventually overfly most all of the Moon. But that also means it has the entire surface area of the whole body on which to impact, raising the odds significantly against an unguided impact coming within a hundred km of *any* given spot.

The idea of historic site preservation is a good one, but I just have to wonder what the odds of an inadvertent impact really are... huh.gif

-the other Doug


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centsworth_II
post Mar 2 2009, 06:34 AM
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QUOTE (dvandorn @ Mar 2 2009, 12:13 AM) *
Although, I have to wonder -- what are the odds...

We recently experienced an "improbable" mid orbit collision here at Earth. And the volume of possible lunar orbits is a lot smaller.

Someone at the BAUT forum indicated that Chinese media reported the de-orbit was used as training for future landing missions.
(Link to post below)

http://www.bautforum.com/space-exploration...tml#post1446047

EDIT: link to the Chinese news report from The Planetary Society Blog:
"The planned impact was designed to accumulate experience for landing of China's second lunar probe."
<a href="http://www.chinadaily.com.cn/china/2009-03...ent_7523687.htm" target="_blank">http://www.chinadaily.com.cn/china/2009-03...ent_7523687.htm
</a>
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Guest_Zvezdichko_*
post Mar 2 2009, 08:34 AM
Post #114





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Some people report that the landing was recored by the CCD camera. Do you have any idea whether any pictures will be published, or as usual, nothing will appear?
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Guest_Zvezdichko_*
post Mar 2 2009, 11:25 AM
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I'm asking and I'm answering myself:

http://www.youtube.com/watch?v=Pw15rDMeYko

Take a look of the 29 and 30s second of the clip. Are these images of the impact?
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Phil Stooke
post Mar 2 2009, 11:52 AM
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They may have been taken during the descent, or may be oblique views from another orbit.


Replying to dvandorn's point above - of course the chance of an unintended strike on a historic site is minimal. Communication interference, or learning to track a descent trajectory, are more likely. But there is an agreement to deorbit in a controlled way if possible rather than leaving things to chance.

Phil


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Phil Stooke
post Mar 2 2009, 02:52 PM
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Here's an updated map of the lunar near side with the recent impacts on it. I included Chandrayaan 1 but I don't know its true location - Goswami says 88 south, but does not specify a longitude. It came in along roughly the 15 east meridian, but it might have made it to the far side if it overflew the pole.

Phil

Attached Image


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Geert
post Mar 2 2009, 02:56 PM
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QUOTE (Phil Stooke @ Mar 2 2009, 06:52 PM) *
Communication interference, or learning to track a descent trajectory, are more likely.


Remembering all the problems that mascons gave on earlier lunar landings, tracking a descent trajectory might indeed be worthwhile.

Which immediately leads to another question: given that mascons are very local interferences, it stands to reason that you would like to track the same trajectory that you're lander is supposed to follow, otherwise tracking a descent wouldn't teach you much. So possibly the Chinese lander will land somewhere in the same region as this crash??

And one more item, this position is not far from the Luna 16 position, and those sample-return landingpoints were chosen as only from this longitude you can fly a direct ascent trajectory back to earth without having to do midcourse burns. I don't suppose the Chinese will try a sample-return on their very first landing, but IF they are intending to land somewhere in this vicinity it is at least remarkable that they select a location which allows a direct ascent trajectory..

Regards,

Geert.
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Guest_Zvezdichko_*
post Mar 2 2009, 03:50 PM
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Photo Credit : CCTV/CNSA




Photo Credit : CCTV/CNSA

These are the candidate images that were probably taken during impact.
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djellison
post Mar 2 2009, 04:30 PM
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It's not going to be DURING impact. Just before it, perhaps, but not during.
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