Chang'e-4 farside landing mission Options

[Phil Stooke]

Woohoo! (to coin a phrase). Check this out:

https://www.hou.usra.edu/meetings/planetdat...19/pdf/7030.pdf

An abstract for the Planetary Data meeting with a map of Yutu 2's path and other information.

Phil

[Phil Stooke]

Meeting abstracts are here:

https://www.hou.usra.edu/meetings/planetdat...ram.htm#sess101

Phil

[Phil Stooke]

This is the map from the abstract (hopefully considered 'fair use' for educational purposes). It is an excellent illustration of how the rover is driven, not with a 'joystick' controller and live (slow-frame) TV like the Lunokhods, but by mapping a safe route from end-of-drive images like the various Mars rovers. Sites are labelled, so I will be updating the route map soon.

Phil

[John Moore]

Below, an attempt to match the doughnut track positions to Phil's map. But don't take them as literal, as with most tracks, they all look the same, so open to correction (it all has to do with viewing/estimating the angles between each doughnut track - some approach angles under 90 degrees, others over 90, not to mention the paths taken, where some are straight-like, some curvable).

John

Attached thumbnail(s)

 

[Phil Stooke]

That looks good, John.

Several new images were tweeted by Andrew Jones.

https://twitter.com/AJ_FI/status/1143769296973291521


Here I have reprojected them to make it easier for me to compare with a map, but so far I don't have good matches to locations for them. They suggest that the rover moved a bit to the west and then turned south during day 6 (so a map revision is needed), but I don't know enough to draw the route yet.

The article linked by Andrew says (according to Google Translate) that there were control problems during day 6 caused - apparently - by a single bit flip error on a chip. The Mars rovers have seen these occasionally and recovered. They are caused by cosmic ray strikes. Yutu 2 has been recovered successfully.



EDIT: I replaced the middle image with a different version. The orientation is changed, but please bear in mind that these Hazcam images have a wider field of view than I show here.

[John Moore]

When I first saw the left-most image, Phil, I immediately thought 'Oh, that doesn't look good - some kind of surface-gripping struggle going on there.' But then thought that perhaps the rover was just doing more than one pivot on its axis as it planned its next route.

Btw, the doughnut images are probably wrong, as while the date they appear publicly are always out by several earth days to weeks, the actual lunar day date that they were taken is tricky to pin down (of course, CLEP, has that data).

John

[charborob]

Two images of the lunar surface on the CNSA page.

[Phil Stooke]

Andrew Jones tweets two new images:

https://twitter.com/AJ_FI/status/1148511189216956416

They can be fitted together to make a mini-panorama:



(here with some contrast enhancement).

And that can be roughly reprojected to give a more map-like view:



The lighting is around noon, so the rover may have travelled further since they were taken. No details on the distance travelled yet.

Phil

[Phil Stooke]

That last view with the 6th night location shown.

Phil

[Phil Stooke]

A new paper on topo mapping of the landing site:

http://www.pmrslab.cn/publications/publica...3-1383-2019.pdf

Here is a very small panorama from it (I have cleaned up some glare in it):



and a circular version for mapping:



These are from the end of lunar day 1.

Phil

[Phil Stooke]

This 'rover driving diary':

https://mp.weixin.qq.com/s/ULbPx6V957kW9CtR_cTU5g"" target="_blank">https://mp.weixin.qq.com/s/ULbPx6V957kW9CtR_cTU5g</a>


has some new images in it from day 7. Andrew Jones had tweeted some of them. The impression I have is that the rover did not move very far after its lunch break in day 7, so the estimate in my last map was overly optimistic. The drive was 25 m in day 7.

Here is a reprojected version of a mini-panorama from the link:



It is similar to the one I posted above but shows a little more progress, and the rover shadow at left shows it is taken with afternoon lighting.

There are also two sun-struck images, which can be fitted together like this:




The view is to the northwest (showing the central peak) near sunset, presumably on day 7.

Phil

[Phil Stooke]

Daniel Estevez has an analysis of the Longjiang 2 impact expected on 31 July:

https://destevez.net/2019/07/dslwp-b-mission-end-prediction/

It will crash near 15.5 north, 157.5 east, SE of Mare Moscoviense and about 300 km north of the Lunar Orbiter 1 impact site.

Phil

[John Moore]

Looks like somewhere northeast of Van Gent T.

John

[charborob]

Two images on the CNSA webpage, presumably taken on lunar day 8: http://www.cnsa.gov.cn/n6759533/c6807005/content.html

[Paolo]

meanwhile, DSLWP-B has crashed on the moon, as expected
https://twitter.com/cgbassa/status/1156575266153648128

There is a new crater on the Moon... We are already 5 minutes past the moment DSLWP-B would've appeared from behind the Moon if it had not crashed. The fact that we are no longer receiving signals means it has impacted the lunar surface. RIP DSLWP-B.