Author Topic: Chang'e-4 lunar operations  (Read 68782 times)

Online Satori

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Chang'e-4 lunar operations
« on: 12/19/2018 12:42 pm »
This is the thread for the lunar operations of the Chang'e-4 Chinese lunar mission.

For the preparations and launch see https://forum.nasaspaceflight.com/index.php?topic=30377.0

Online luhai167

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Re: Chang'e-4 lunar operations
« Reply #1 on: 12/19/2018 05:53 pm »
Chang'e-4 lander makes contact with Queqiao relay satellite from lunar orbit

https://gbtimes.com/change-4-lander-makes-contact-with-queqiao-relay-satellite-from-lunar-orbit

Original social media post in Chinese here. Looks like CAST has kept the tradition of making 1st social media postings for the mission in first person voice from CE3.

https://mp.weixin.qq.com/s/Fd7xObI8Sc97-oO6_rdFNQ

Offline mcgyver

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Re: Chang'e-4 lunar operations
« Reply #2 on: 12/21/2018 07:30 am »
It appears from radio-amateurs measurement, that Chang'e4 is currently in an orbit which allows it being always in contact with Earth rather than passing behind the Moon.
This is more clever than it sounds: the orbit plane has a fixed orientation, but the "terminator plane" of the Moon rotates around Earth at one turn per month, so there will be no need to turn on the engine to move to dark side, it will be the dark side itself to come under Chang'e4!  ;) 


If right now the orbit is exactly perpendicular to the Earth-Moon line, it will be parallel to it 7 days and 21 days from now (1/4 and 3/4 of a 28 days period rotation, i.e. 90° and 270°), hence 28/12/18 and 11/1/19.


Landing site (Von Kármán crater) is around  47.7° S, 177.9° E, with 0°E facing Earth.
« Last Edit: 12/21/2018 07:43 am by mcgyver »

Offline ZachS09

Re: Chang'e-4 lunar operations
« Reply #3 on: 12/21/2018 04:39 pm »
Remind me if this question needs to be in a different thread:

Has CNSA figured out a name for the Chang'e 4 rover? Or will they name it "Yutu" like the previous rover?
Because the Falcon Heavy Test Flight was successful, it has inspired thousands of people to consider changing the future of space travel.

Offline Phil Stooke

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Re: Chang'e-4 lunar operations
« Reply #4 on: 12/21/2018 04:54 pm »
The name has not been announced yet, but they have candidates.  Follow @AJ_FI on Twitter for updates.

Online Phillip Clark

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Re: Chang'e-4 lunar operations
« Reply #5 on: 12/28/2018 08:19 am »
The Chinese are being very quiet about this lunar mission!

The initial selenocentric orbit was announced at being 100-400 km, presumably "polar" which can be quite a vague term.   I would have thought that the orbit would have been lowered by now, but as far as I am aware there have been no Chinese statements about this.
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Offline mcgyver

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Re: Chang'e-4 lunar operations
« Reply #6 on: 12/28/2018 10:37 am »
The Chinese are being very quiet about this lunar mission!

The initial selenocentric orbit was announced at being 100-400 km, presumably "polar" which can be quite a vague term.   I would have thought that the orbit would have been lowered by now, but as far as I am aware there have been no Chinese statements about this.
Considering tha "failure" of latest rover, I hope they will not wait  until the new rover has safely traveled several hundreds meters before releasing news...




Online Phillip Clark

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Re: Chang'e-4 lunar operations
« Reply #7 on: 12/28/2018 11:33 am »
Considering tha "failure" of latest rover, I hope they will not wait  until the new rover has safely traveled several hundreds meters before releasing news...

The instrumentation on the rover worked for a long time, only the wheels failed because the Chinese underestimated the effects of lunar soil.   And don't forget that the main Chang'E 3 spacecraft is still returning data - the longest-operating unmanned spacecraft on the Moon.
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Offline mcgyver

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Re: Chang'e-4 lunar operations
« Reply #8 on: 12/28/2018 03:25 pm »
Considering tha "failure" of latest rover, I hope they will not wait  until the new rover has safely traveled several hundreds meters before releasing news...

The instrumentation on the rover worked for a long time, only the wheels failed because the Chinese underestimated the effects of lunar soil.   And don't forget that the main Chang'E 3 spacecraft is still returning data - the longest-operating unmanned spacecraft on the Moon.
That's why I used the "quotes"; all instruments worked  fine... but the wheels. So it actually turned from a rover to a... lander after a few days, hence as a rover it failed.


BTW, I never read about root cause of the failure, any link?




Online Phillip Clark

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Re: Chang'e-4 lunar operations
« Reply #9 on: 12/28/2018 04:37 pm »
Considering tha "failure" of latest rover, I hope they will not wait  until the new rover has safely traveled several hundreds meters before releasing news...
The instrumentation on the rover worked for a long time, only the wheels failed because the Chinese underestimated the effects of lunar soil.   And don't forget that the main Chang'E 3 spacecraft is still returning data - the longest-operating unmanned spacecraft on the Moon.
That's why I used the "quotes"; all instruments worked  fine... but the wheels. So it actually turned from a rover to a... lander after a few days, hence as a rover it failed.
BTW, I never read about root cause of the failure, any link?

I am sure that it was given in the Chang'E 3 thread in the Chinese section: something to do with the soil being more adhesive than expected and "clogging" the wheels I think.
I've always been crazy but it's kept me from going insane - WJ.

Offline Blackstar

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Re: Chang'e-4 lunar operations
« Reply #10 on: 12/28/2018 04:59 pm »
I heard that it was that something (a rock?) cut a key wire on the underside of the rover. I originally got that from a coworker who had met with a Chinese official years ago. He heard that even before it became public, and I think it was later publicly confirmed. But we'd have to go digging around here for better confirmation.

Offline Galactic Penguin SST

Re: Chang'e-4 lunar operations
« Reply #11 on: 12/30/2018 03:36 am »
After days of silence it was finally announced that Chang'e 4 made the orbit lower burn (from 100 km circular to 15 x 100 km) a few hours ago at 00:55 UTC.

Source

Does anyone "in the field" (as we speak - especially if you have contact with the European institutions with instruments on board) knows the planned landing date? I have seen January 2nd and 3rd mentioned in various places and I am sure official updates will be sparse until after the lander is on lunar surface.
Chinese spaceflight is a cosmic riddle wrapped in a galactic mystery inside an orbital enigma... - (not) Winston Churchill

Online Phillip Clark

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Re: Chang'e-4 lunar operations
« Reply #12 on: 12/30/2018 04:12 am »
News at last!

http://www.xinhuanet.com/english/2018-12/30/c_137708555.htm

I am wondering if there's an intermediate orbit - say 100 km circular - or whether they did a periselene burn in the 100-400 km orbit to reduce it to 15-100 km.
I've always been crazy but it's kept me from going insane - WJ.

Offline Phil Stooke

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Re: Chang'e-4 lunar operations
« Reply #13 on: 12/30/2018 05:59 am »
If anyone uses LRO's Quickmap, it shows the sun rising over Von Karman right about now.  Landing would be several days later but we are getting there!

« Last Edit: 12/30/2018 06:41 am by Phil Stooke »

Online Phillip Clark

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Re: Chang'e-4 lunar operations
« Reply #14 on: 12/30/2018 10:54 am »
Just a thought: on Chang'E 3 the 15-100 km orbit was reached just about 96 hours before the landing.

So that suggests a Chang'E 4 landing very early on Thursday morning, UK time?
I've always been crazy but it's kept me from going insane - WJ.

Offline mcgyver

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Re: Chang'e-4 lunar operations
« Reply #15 on: 12/30/2018 11:21 am »

Offline JimO

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Re: Chang'e-4 lunar operations
« Reply #16 on: 12/30/2018 12:39 pm »
If anyone uses LRO's Quickmap, it shows the sun rising over Von Karman right about now.  Landing would be several days later but we are getting there!

Apollo needed to land with early morning shadows to guide the pilot. Why would a robot landing need sunlight?

Offline Blackstar

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Re: Chang'e-4 lunar operations
« Reply #17 on: 12/30/2018 01:44 pm »
If anyone uses LRO's Quickmap, it shows the sun rising over Von Karman right about now.  Landing would be several days later but we are getting there!

Apollo needed to land with early morning shadows to guide the pilot. Why would a robot landing need sunlight?

Power, for starters. You want to land when you can immediately get power from the solar panels. Land in the dark and you have to work on batteries. At the recent Lunar Exploration Analysis Group meeting in Maryland several people talked about potential American lunar landers. I remember at least one of them assuming a landing 46 hours after local dawn.

Online ugordan

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Re: Chang'e-4 lunar operations
« Reply #18 on: 12/30/2018 01:49 pm »
Also, autonomous hazard avoidance needs to, well... *see* the terrain below.

Online Phillip Clark

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Re: Chang'e-4 lunar operations
« Reply #19 on: 12/30/2018 02:29 pm »
Apollo needed to land with early morning shadows to guide the pilot. Why would a robot landing need sunlight?

If you think back to the  Luna sample return missions, those had two lunar landing periods each year: the one for February-July launches had landings during local daylight and called for launches back to Earth when the lunar elongation from the Sun was ~90 deg: the other one from August-January had landings on the Moon during local darkness and launches back to Earth with an elongation of ~270 deg: see my JBIS/Space Chronicle paper in issue 1 for 2004.

Of course the sample-return missions only spend around 24 hours on the Moon so solar batteries were not needed for operations during local nighttime.
I've always been crazy but it's kept me from going insane - WJ.

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