Linked Questions

3 votes
3 answers
400 views

Could the Lunar Lagrange Points work for space telescopes?

Every orbit in space has its pros and cons. Low Earth Orbit has accessibility but frequent eclipses whereas a Solar Lagrange Point is clear and stable but distant. In the case of the Lunar Lagrange ...
6 votes
1 answer
463 views

Why put DSCOVR in a Lissajous orbit? Wouldn't a halo orbit completely avoid the Sun exclusion zone?

Halo orbits are a sub-class of Lissajous orbits. See this answer for (much) more on that. DSCOVR's orbit will put it in it's Sun Exclusion Zone in about 2020 where the communications line of sight ...
17 votes
4 answers
4k views

Are some Halo Orbits actually Stable? (stable orbits about unstable Lagrange points)

update: some more sources; the broken site spacecraftforall.com/a-new-orbit used to have an interactive simulation, here's an old screen shot: Hat tip to @NgPh for finding this Space College page ...
8 votes
1 answer
278 views

Where can I find access to information provided by CNSA and Chinese scientists and reputable science authors?

The lack of finality to the current answer to Was Queqiao in a halo or Lissajous orbit? Why do sources disagree? is due in part to the difficulty of finding good, clear, reliable scientific sources ...
0 votes
0 answers
103 views

Is a 2:1 "figure-eight" Lissajous orbit possible in the Circular Restricted Three Body Problem?

Was Queqiao in a halo or Lissajous orbit? Why do sources disagree? says Proper halo orbits have the same period for their in-plane oscillations and out of plane oscillations, so they are closed ...
4 votes
2 answers
272 views

How can one know that Chang'e-4 was in "locked to the Queqiao" from this SDR spectrogram?

Deep space SDR enthusiast and amateur radio operator Edgar Kaiser @df2mz's 28-Dec-2018 tweet says: Chang'e 4 in lunar orbit last night on 8479.77 MHz. The spacecraft seems to be locked to the ...
2 votes
1 answer
550 views

What radio frequency does China use to communicate with the Chang'e-4 satellite?

I would assume this probably isn't publically disclosed information, but it doesn't hurt to ask. I am an amateur ham radio enthusiast and I want to listen in on the data.
4 votes
2 answers
487 views

Transmission time per day for Chang'e 4?

Congratulations for the sucessfull landing on the back side of the Moon. There is continuous line of site available for radio connection from the lander to the Queqiao relay satellite at the Earth-...
5 votes
1 answer
986 views

Why is Queqiao's dish antenna so big? (Chang'e-4 relay satellite) Largest ever on/near the Moon?

Source: Chinese language blogpost The NASA Spaceflight article Queqiao relay satellite launched ahead of Chang’e-4 lunar mission describes the communications relay satellite that will be used to ...
11 votes
1 answer
3k views

What is the difference between halo orbits and Lissajous orbits?

The Wikipedia articles for halo orbit and Lissajous orbit leave me wondering how these two orbits are different from an orbital mechanical point of view. Could they be discussed together here, so I ...
11 votes
4 answers
2k views

Are large halo orbits around L₁'s and L₂'s preferred over small orbits for reasons other than geometry?

There have been many examples of the placement of satellites in orbits around Lagrange points, most have been sun-earth and earth-moon $L_1$ and $L_2$ due to their proximity to earth. In each case ...
19 votes
1 answer
3k views

What is the purpose of the satellite that China is putting in lunar orbit?

I was just reading an article about the satellite that China is putting in Lunar orbit as phase one for their exploration of the far side of the Moon. Is this satellite just to be used as a signal ...