Author Topic: Chang'e-4 lunar operations (Read 280388 times)

Phillip Clark · « **Reply #40 on:** 01/02/2019 05:25 pm »

I was wondering whether the precession of the orbital nodes around the Moon could be something not taken into account, but for a polar orbit that is about 0.07 deg/day for a 15-100 altitude.

As an aside, I make the rotation of the apsides to be 0.64 deg/day.

tdenk · « **Reply #41 on:** 01/02/2019 05:32 pm »

Less then 2 deg/month, not really enough.
And most time the probe was on a higher orbit.
Two questions:
1) In which direction?
2) What about non polar orbits (e.g. 85deg inclination)?

Phillip Clark · « **Reply #42 on:** 01/02/2019 06:05 pm »

My estimates are:

Inclination 90 deg 85 deg
Nodal Apsides Nodal Apsides
Precession Rotation Precession Rotation
deg/day deg/day deg/day deg/day

Aposelene-Periselene km
400-100 0 0.460 -0.080 0.442
100-100 0 0.598 -0.104 0.576
100-15 0 0.650 -0.113 0.625

The apsides are rotatying in the direction of the satellite's travel.

Skylab · « **Reply #43 on:** 01/02/2019 06:21 pm »

There won't be any live coverage of the landing, I reckon?

Phillip Clark · « **Reply #44 on:** 01/02/2019 06:33 pm »

Quote from: Skylab on 01/02/2019 06:21 pm

There won't be any live coverage of the landing, I reckon?

Currently there are no rumours of such coverage. I am wondering whether to stay awake, "just in case".

Phil Stooke · « **Reply #45 on:** 01/02/2019 06:41 pm »

"According to 'the Sun' article:"

The Sun, the journal of record for all things astronomical, also suggests the landing is near the pole and that the SPA is near the north pole, despite the dark basin interior being clearly visible in the southern hemisphere in their image.

mcgyver · « **Reply #46 on:** 01/02/2019 06:48 pm »

According to Techradar, landing could maybe be covered by CGTN (China Global Television Network), which apparently is not available in some countries, but maybe (any confirmation) it can be watched from alternate sites:

https://america.cgtn.com/livenews
Guys which can access first link can please confirm in 2nd and 3rd whow same contents?

Phillip Clark · « **Reply #47 on:** 01/02/2019 06:54 pm »

In Hastings, UK, I am watching some political waffle on the channel right now: . Digits crossed for the Chang'E 4 coverage.

Steven Pietrobon · « **Reply #48 on:** 01/02/2019 08:51 pm »

Quote from: tdenk on 01/02/2019 04:46 pm

The third assumption of course is that they really land
in the eastern part of the Von-Kármán crater
and did not change the landing zone without notification.

That has happened before. Chang'e 3 was supposed to land in Sinus Iridum, but instead landed east of that location in northern Oceanus Procellarum, south of Montes Recti.

lcs · « **Reply #49 on:** 01/02/2019 09:14 pm »

Quote from: tdenk on 01/02/2019 04:40 pm

The idea is simply that
(1) the orbital plane at LOI was perpendicular (normal vector pointing to Earth) and then
(2) remained fix in space. The Moon rotates below until the trajectory goes over the Von-Kármán crater.
Apparently, one or both of the assumptions were wrong.
Thorsten

@df2mz X-band doppler analysis implied a nearly perpendicular orbital plane as of ~12 hours ago.

https://twitter.com/df2mz

A12 · « **Reply #50 on:** 01/02/2019 09:14 pm »

Visible here in Rome, Italy.

centaurinasa · « **Reply #51 on:** 01/02/2019 09:21 pm »

Geological Characteristics of Von Kármán Crater, Northwestern South Pole-Aitken Basin: Chang’E-4 Landing Site Region
http://www.planetary.brown.edu/pdfs/5294.pdf

Von Kármán Crater: Awaiting A Visitor:
http://lroc.sese.asu.edu/posts/1082

Bob Shaw · « **Reply #52 on:** 01/02/2019 09:37 pm »

Quote from: Phil Stooke on 01/02/2019 06:41 pm

"According to 'the Sun' article:"

The Sun, the journal of record for all things astronomical, also suggests the landing is near the pole and that the SPA is near the north pole, despite the dark basin interior being clearly visible in the southern hemisphere in their image.

We're lucky they didn't call it the west pole...

tdenk · « **Reply #53 on:** 01/02/2019 09:42 pm »

Final orbit of Cháng'é-4 begins more or less NOW!

zubenelgenubi · « **Reply #54 on:** 01/02/2019 10:18 pm »

Quote from: Taxidermista on 01/02/2019 10:02 pm

And this is the proud that China feels about its own space program. Unbelievable...

Welcome to the NSF forum!

IMO: The Chinese Communist Party (CCP) is more concerned about the negative connotations of a failure than the spontaneous enthusiasm garnered by live coverage of success.

Compare to the media coverage in the Soviet Union vs. USA during the "classic space race." (my term for the Sputnik to Apollo lunar landing era.)

And I would differentiate between the policies of the rulers and the opinions and feelings of the ruled. Unfortunately, we outside the PRC don't receive very much direct, expressed-in-English exposure to the second. And, that's because of the first!

Even though the CCP is not very communist anymore, they are still of a totalitarian mind-set.
***

Back to following the gleanings of our NSF contributors--a sincere thank you for your efforts (and findings and informed opinions)!

Josh_from_Canada · « **Reply #55 on:** 01/02/2019 10:35 pm »

It should be landing within the next hour.

Phil Stooke · « **Reply #56 on:** 01/02/2019 10:36 pm »

Steven Pietrobon:

"That has happened before. Chang'e 3 was supposed to land in Sinus Iridum, but instead landed east of that location in northern Oceanus Procellarum, south of Montes Recti."

Not really. The "Sinus Iridum landing area" extended well outside Sinus Iridum itself, as defined by the area covered by high resolution (low orbit) imaging from Chang'e 2. The landing was targeted for the eastern end of the area so that any delay would allow a landing a few orbits later, still within the landing area. If you aim for a site in the middle of Sinus iridum a delay may push you outside the landing area, in rough terrain in the Jura Mountains, the rim of the 'bay'.

Phillip Clark · « **Reply #57 on:** 01/02/2019 10:37 pm »

Quote from: Josh_from_Canada on 01/02/2019 10:35 pm

It should be landing within the next hour.

I think it will be closer to 01:00 UT, in 80 minutes or so.

Chris Bergin · « **Reply #58 on:** 01/02/2019 10:44 pm »

Reminder to all, a lot of people have this thread on notification, so no useless posts. Small trim.

frank808 · « **Reply #59 on:** 01/02/2019 10:49 pm »

Quote from: zubenelgenubi on 01/02/2019 10:18 pm

Quote from: Taxidermista on 01/02/2019 10:02 pm
And this is the proud that China feels about its own space program. Unbelievable...

Welcome to the NSF forum!

IMO: The Chinese Communist Party (CCP) is more concerned about the negative connotations of a failure than the spontaneous enthusiasm garnered by live coverage of success.

Compare to the media coverage in the Soviet Union vs. USA during the "classic space race." (my term for the Sputnik to Apollo lunar landing era.)

And I would differentiate between the policies of the rulers and the opinions and feelings of the ruled. Unfortunately, we outside the PRC don't receive very much direct, expressed-in-English exposure to the second. And, that's because of the first!

Even though the CCP is not very communist anymore, they are still of a totalitarian mind-set.
***

Back to following the gleanings of our NSF contributors--a sincere thank you for your efforts (and findings and informed opinions)!

Probably due to the recent trade war and US reaction toward "Made in China 2025", Chinese government is trying to playing down any that could be considered attempt to catch up US, albeit in this field US is at least half century and billions miles ahead. Before that, we did see live media coverage over Chang'e -3 landing and maiden flight of its new rocket.