Help - Search - Members - Calendar
Full Version: Chang'e-4 farside landing mission
Unmanned Spaceflight.com > Earth & Moon > Lunar Exploration > Chang'e program
Pages: 1, 2, 3, 4, 5, 6, 7
HSchirmer
QUOTE (stevesliva @ Jan 11 2019, 06:48 PM) *
Amazing how fractal the cratering is. Well, amazing when I realize I have no idea of vertical height when looking straight down.

I've heard from family who flew over the Atlantic, Pacific and Gulf of Mexico that ocean waves are fractal.
You can't tell vertical height by looking down, waves at 10-feet up look just like waves at 100-feet up, which look just like waves at 1,000-feet up. That's why, when you're on a parachute, you don't look down; you look at the horizon to judge altitude, and you don't release the parachute harness until your feet hit the water.

- Interesting whether the fractal dimensions of cratering might constrain the atmospheric properties of moons and planets?

Curious- are there any papers on "fractal dimensions of lunar craters" addressing the range of sizes?
neo56
Thanks Phil. The resolution of images on the quickmap was enough to locate the landing site.
Here is a montage I did to help locate it.



And my guess on the orientation of Chang'E 4 based on the shadows and position of craters:
Click to view attachment
wildespace
QUOTE (neo56 @ Jan 11 2019, 08:42 PM) *
Phil, where did you download this picture? I'm on the QuickMap LROC website but the resolution is not as good as your picture.

For everybody's convenience, here's a high-quality NAC strip of the area:

http://wms.lroc.asu.edu/lroc/view_lroc/LRO....0/M134022629LE

The landing site is slightly below the centre of the image strip.

200% scale crop:

Click to view attachment
Phil Stooke
I know several of us were looking for the landing location in images like these before we saw the panorama. I looked at this place among many others, but I thought the hazard avoidance system would divert the lander away from a place like that which is surrounded by craters. There are nice smooth spots close by, to the west or northeast. But it's all about the scale of the hazard avoidance, I suppose. We did get a nice level area between the craters.

Phil
Phil Stooke
While waiting for news of any activity on the 12th, here is a comparison of horizon features between the panorama and an LRO wide angle (heavily processed) image.

The central peak is visible, but Ba Jie crater is not. More than half of the horizon is the rim of Von Karman. The small hill about 10 km north of the lander, which might make a good target for the traverse, is probably visible as a low ridge labelled X here.

Phil

Click to view attachment

EDIT: My crater 'C' might be the one higher up on the rim of the main crater, with ridge D adjacent to it.
wildespace
QUOTE (Phil Stooke @ Jan 12 2019, 06:25 PM) *
I know several of us were looking for the landing location in images like these before we saw the panorama. I looked at this place among many others, but I thought the hazard avoidance system would divert the lander away from a place like that which is surrounded by craters. There are nice smooth spots close by, to the west or northeast. But it's all about the scale of the hazard avoidance, I suppose. We did get a nice level area between the craters.

Phil

The landing footage shows the craft pausing briefly when over that location, seemingly detecting an even space between those craters, and "making the decision" to land there. Simple and effective, just like what Chinese would do.

https://www.youtube.com/watch?v=JJi_YEubKCY&t=1m54s
wildespace
"The space probe is moving south across the Mn"

Excellent video processing and analysis here. https://www.youtube.com/watch?v=unEbg_dt3DM
Huguet
Panoramas from chang'e-3 and chang'e-4. I expected the number and pattern of the impact craters to be more diferent beetween the two landing sites, it apears to have double of small craters (less than 1 meter) on the darkside.
Thorsten Denk
I think we have to be careful with generalizing
"lunar farside" = "heavily cratered" = "this landing spot".

The first "=" is generally true,
but the specific Chng'-4 landing site
is a lava flooded crater and hence
should rather have properties of (near side) Mare areas.
Untypical for far side in general.

The difference in craters should be more indicative
to age than to "near" vs "far" side.

Thorsten
Steve G
Chang'e 3 landed on lunar maria, Chang'e 4 on lunar highlands, which is a big difference especially in age, so I'd expect more craters in a highland area. Of course, that depends on the age of the basin in Von Karman.
Phil Stooke
Von Karman is filled with basalt lava flows, probably not very different in age than typical mare basalts on the Earth-facing side of the Moon. Von Karman is in the highlands but its floor is not highland, in other words. But these things are deceptive. Because highland surfaces are older they have a thicker regolith, and it affects the survival of small craters during impact-generated siesmic shaking. Sometimes highland surfaces can look smoother and younger just because their craters are more softened by shaking. A slope helps that process, so the rolling topography of highland areas is ideal for erasing craters in this way.

Here is an example from Flamsteed, the almost completely buried crater in which Surveyor 1 landed in 1966. Mare basalt at the top, low relief highland surface at the bottom. The image is about 800 m wide, 1.9 south, 43.0 west. More craters in a given area on the mare, but the highlands are older. At this scale they just don't preserve craters. Larger craters are not erased this way so at broad scales the basic rule 'older = more craters' is true.

Phil

Click to view attachment
kenny
Lovely little color video of Yutu-2 driving away from the Chang'e-4 lander and executing the 180 degree turn ...

Yutu-2 driving away from lander
Hungry4info
China's Chang'e-4 probe conducts first bio test on moon as first plant grows
https://news.cgtn.com/news/3d3d414f7949444d...54/share_p.html

Edit: From this Global Times article.
QUOTE
Chinese media state that the experiment contains six species: cotton, rapeseed, potato, arabidopsis, fruit fly and yeast, with Xinhua reporting that no signs of growth have been found among the species other than cotton.
GoneToPlaid
[quote name='Phil Stooke' post='243419' date='Jan 13 2019, 09:51 PM']Von Karman is filled with basalt lava flows, probably not very different in age than typical mare basalts on the Earth-facing side of the Moon. Von Karman is in the highlands but its floor is not highland, in other words...

Phil

Very true. In fact, where Chang'e-4 landed is approximately -6km relative to the moon's mean radius. Definitely not highlands, and instead is lowlands within the huge Von Karman crater floor.
Phil Stooke
I have been following the discussion here:

http://www.9ifly.cn/thread-5819-70-1.html

(in translation) which seems to be saying that a power failure has ended the biological experiment. Does anyone have any other information?

Phil
Explorer1
This (English) article says they were powered down for sunset (i.e. the experiment would not go past lunar night).
https://news.cgtn.com/news/3d3d414f7949444d...54/share_p.html

QUOTE
Now it is night on the Moon and the temperature has dropped to nearly 180-degree centigrade below freezing. All the equipment has powered down, and the remaining seeds and animals will be gradually decomposed down to organic fundamentals.
Phil Stooke
OK, that's good. I had thought it was supposed to work through the lunar night with warmth and artificial light, though I know it piped in natural light during daylight. It does seem like a useful next step would be to allow longer operation on a future mission. Maybe that is more suited to polar missions, which we know are in the plan.

Phil
wildespace
What the landing site will look in early morning. High incidence angle (86.68 degrees) view from M178833263LC

Click to view attachment
Phil Stooke
Click to view attachment

I saw this picture tweeted on the 11th or 12th and then couldn't find it again to save it. Now I found it on this site (near the bottom):

http://py.qianlong.com/2019/0116/3064840.shtml


It is from the last position on the first lunar day, looking back on the tracks from that day's drive. Does anyone have a better version of it?

Phil
kenny
According to the Google image-matching search function, that is the only version of that image on the internet at the moment.
Google's best guess for the subject of that image is a River Clyde steamer ! smile.gif
Huguet
Yutu 2 will have a hard time avoiding all that craters, he will need to be making adjustments at almost every meter.

"From the images sent back from Chang'e 4, we can see the area surrounding the probe is dotted with craters of different sizes, and it's very difficult for the rover to drive in the region," explained Sun Zezhou, chief designer of the Chang'e 4 probe, according to Xinhua.

"We'll try to find the relatively safe areas and make a reasonable plan for the route of the rover based on the images taken by it," Sun said, adding, "we haven't found any insurmountable obstacle in the region."
John Moore
Looks like the top-left (squiggly) tracks are those where it stopped at the crater south (classic image, well-published at this stage), the rover did a 180 deg there (and more), and from the current image,
we're still looking back southwards as the Rover travelled north after two wheel-abouts (the Lander would be to the left - some several metres away).

Have a simulated image put together of the possible track, but it would have been poor to post.

The stopped-off position of the Rover is well within the lunar night-time -175 deg C temperatures now; waiting for further activation round the 28/29 Jan 2019. Fingers crossed.
Phil Stooke
This must be the first journal publication to come out of Chang'e 4 operations.... the DOI or title will lead you to the journal website, from which the paper, in English, can be downloaded free by anyone.

Phil

Di, K. C., Liu, Z. Q., Liu, B., Wan, W. H., Peng, M., Wang, Y. X., Gou, S., Yue, Z. Y., Xin, X., Jia, M. N. and Niu, S. L., 2019. Chang'e 4 lander localization based on multi-source data. Journal of Remote Sensing, v. 23, no. 1, pp. 177-184. DOI: 10.11834/jrs.2019015.


EDIT - here is the direct link to the journal site - I should have given it in the first place. Open in Chrome to translate.

http://www.jors.cn/jrs/ch/reader/view_abst...23-1-dikaichang
Explorer1
Looks like the lander and rover have woken up (judging from in the know social media accounts)! First science data release February 1st, apparently.
tolis
One might wonder what is the contribution of the Earth, as a reflector of solar radiation, to lunar surface temperatures during the night
given that it has (i) 4x4 = 16 times more surface area, and (ii) a higher albedo than the Moon.

Anyone care to take up this exercise?
ngunn
QUOTE (tolis @ Feb 1 2019, 11:42 AM) *
One might wonder what is the contribution of the Earth, as a reflector of solar radiation, to lunar surface temperatures


An interesting question (though maybe not for a farside mission thread). To the reflected solar you would need to add the Earth's own thermal IR
tolis
QUOTE (ngunn @ Feb 1 2019, 12:12 PM) *
An interesting question (though maybe not for a farside mission thread). To the reflected solar you would need to add the Earth's own thermal IR


Perhaps it is relevant to farside surface conditions insofar as the absence of the Earth in the sky would result in a lower nighttime temperature compared to the nearside (everything else being equal of course).
ngunn
OK I've done some very crude calculations based on black bodies and a nominal night surface temperature of 100K and I'm getting answers on the order of 0.1K.
tolis
QUOTE (tolis @ Feb 1 2019, 12:20 PM) *
Perhaps it is relevant to farside surface conditions insofar as the absence of the Earth in the sky would result in a lower nighttime temperature compared to the nearside (everything else being equal of course).


I'd say that is ~100x less than anything that would contribute to the nighttime temperature in a significant way.

Thanks.
Station
Here goes a new image taken from Yutu2. Apparently rover took it after driving few meters bit forward to NW.

tolis
The tip of that vertically-erected antenna is sitting some 7m above the surface (say 5m for the antenna, 2m for the lander deck). Would that constitute the tallest
articifial structure on the Moon at the moment?
Phil Stooke
Yes, I think it would be the highest structure.

The picture is newly released, and might be newly transmitted, but it was taken before sunset on the previous lunar day (based on the direction of the shadow). I have not seen any pictures or evidence of driving on this second lunar day.

Phil
Steve G
What spectacular scenery! Will the cameras on the lander have survived the lunar night? I believe that on Chang'e 3 the colour cameras were not protected and did not function afterwards.
Station
Newly released image (from first "sol") taken by Yutu2 shortly after deployment onto lunar surface.



Phil Stooke
http://www.9ifly.cn/forum.php?mod=viewthre...ra=&page=89

This link is to the 9ifly forum, where a user has posted a map of Von Karman showing names "approved by the IAU" (the IAU planetary nomenclature site at USGS does not show it but they may not have updated yet, perhaps due to shutdown issues).

Three craters around the landing site take names from the 'summer triangle' of bright stars, Vega, Altair, Deneb but using their Chinese names. The landing site is Statio Tianhe, where Tianhe means Milky Way. The names refer to the story of the Weaver and the Cowherd, lovers separated by the Milky Way and allowed to meet by crossing on a bridge formed of magpies, the same story from which the relay satellite gets its name. Finally the central peak is named Mons Tai after Taishan, a mountain in China.

Phil
volcanopele
LROC got an oblique image of the landing site last week:

http://lroc.sese.asu.edu/posts/1090
Phil Stooke
Spectacular, but I would hope a vertical view was obtained on a later orbit!

Phil
Phil Stooke
Well, a few orbits later but still the same day, a less oblique view:

http://lroc.sese.asu.edu/posts/1091


Lander and rover both visible, just. A vertical view on the next day is probably still to be released. Here is a modified view of the landing site:

Click to view attachment
Station
It's a pity there is no information about second lunar day on the surface. I wonder if the mission is in any trouble and therefore chinese officials don't want to give any further details about the encountered problems...
Phil Stooke
We have information about the first few (Earth) days of the second lunar day as shown on the map. Since then there has been a big holiday period coinciding with New Year in China, and many government offices etc. will have been closed. We might learn more this week. But no reason to expect a problem at this point. Also, a COSPAR meeting coming up where news may be released.

Phil

Paolo
welcome to Statio Tianhe

https://www.iau.org/news/pressreleases/detail/iau1901/
Olympusmonsuk
Vertical LRO view of Chang'e 4 landing site-Statio Tianhe

http://lroc.sese.asu.edu/posts/1092
Station
Hi,

Any further information about CH-4 mission status? Some chinese forum? This continuing lack of info is very disturbing. I wonder if something went wrong and chinese mission's directors don't want to publish it online untill resolution is found...
Paolo
QUOTE (Station @ Feb 20 2019, 08:58 AM) *
Any further information about CH-4 mission status?


there was a very nice full moon this night, which means that it's night on the farside and CE4 and Yutu are sleeping peacefully

Station
I know CH4 and Yutu2 are resting now but I meant SOL-2 which already passed and there is no single photo from this day. (btw. we had plenty of photos, movie clips etc from first SOL so I wonder what's the cause of current situation.).
Thorsten Denk
I've seen one new picture that seems to be from the second month. Maybe.

It's from this tweet linking to this site.

Thorsten

Phil Stooke
This chinese forum page:

http://www.9ifly.cn/thread-5819-98-1.html

includes a route map for the first 2 lunar days. I assume it is based on real data and will update my map shortly. Any further information would be much appreciated.

Phil
Phil Stooke
https://www.weibo.com/5386897742/HjniODYsW?...nd1551722722531

New images in a post on Weibo. Open in Chrome to get a translation. One is from a 'hazard camera' (to use MER/MSL terminology) or ICC (Insight) type of camera, mounted low and very wide angle. It looks northwest with the central peak on the horizon. The rover is only about 7 m further from the last night resting place. The second image is a closeup of the rock in front of the rover taken by the camera in the infrared spectrometer instrument. It shows the IR target on the rock.
John Moore
So, if during the first lunar day the Rover travelled some 44.185 metres, travelled some 75.815 metres during the second day, the third lunar day involved some travelling by the Rover of ~ 7 metres in all to the rock.

John
This is a "lo-fi" version of our main content. To view the full version with more information, formatting and images, please click here.
Invision Power Board © 2001-2020 Invision Power Services, Inc.