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Chang'e-4 lunar operations
by
Satori
on 19 Dec, 2018 12:42
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#1
by
luhai167
on 19 Dec, 2018 17:53
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#2
by
mcgyver
on 21 Dec, 2018 07:30
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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.
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#3
by
ZachS09
on 21 Dec, 2018 16:39
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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?
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#4
by
Phil Stooke
on 21 Dec, 2018 16:54
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The name has not been announced yet, but they have candidates. Follow @AJ_FI on Twitter for updates.
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#5
by
Phillip Clark
on 28 Dec, 2018 08:19
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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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#6
by
mcgyver
on 28 Dec, 2018 10:37
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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...
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#7
by
Phillip Clark
on 28 Dec, 2018 11:33
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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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#8
by
mcgyver
on 28 Dec, 2018 15:25
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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?
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#9
by
Phillip Clark
on 28 Dec, 2018 16:37
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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.
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#10
by
Blackstar
on 28 Dec, 2018 16:59
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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.
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#11
by
Galactic Penguin SST
on 30 Dec, 2018 03:36
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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.
SourceDoes 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.
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#12
by
Phillip Clark
on 30 Dec, 2018 04:12
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#13
by
Phil Stooke
on 30 Dec, 2018 05:59
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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!
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#14
by
Phillip Clark
on 30 Dec, 2018 10:54
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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?
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#15
by
mcgyver
on 30 Dec, 2018 11:21
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#16
by
JimO
on 30 Dec, 2018 12:39
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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?
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#17
by
Blackstar
on 30 Dec, 2018 13:44
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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.
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#18
by
ugordan
on 30 Dec, 2018 13:49
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Also, autonomous hazard avoidance needs to, well... *see* the terrain below.
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#19
by
Phillip Clark
on 30 Dec, 2018 14:29
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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.
