Wikipedia's Lissajous orbit says that sources disagree on the nature of Queqiao relay satellite's orbit; if it was in a proper halo orbit or just a Lissajous orbit.

Proper halo orbits have the same period for their in-plane oscillations and out of plane oscillations, so they are closed orbits with roughy circular motion in the rotating frame, whereas Lissajous orbits are those where the two periods are unequal. They could be closed with a period ratio that is a rational number or be open, non-repeating orbits. Either way they will have "etch-a-sketch" or "squiggly" Lissajous-like motion.

Question: Was Queqiao in a halo or Lissajous orbit? Why do sources disagree? Considering that Queqiao's radio signals were regularly monitored by amateur radio astronomers and its doppler shift well documented, it should be relatively easy for those skilled in the art to determine its trajectory with great precision. From an orbital-mechanical perspective don't understand why this couldn't be nailed down.

Related and may provide helpful information to finding an answer:

Amateur radio astronomers regularly listening to Queqiao from this answer and tweet:



Was Queqiao in a halo or Lissajous orbit?

It is hard to say which, or even yes or no, because there are so many kinds of Lagrange point orbits possible that can be maintained with a little help from propulsive station keeping, and a specific, definitive answer would require either plenty of orbital tracking data or more information from the spacecraft's owners.

Why do sources disagree?

What appears to be the issue is that several conflicting definitions of a "halo" orbit is in use, in order of increasing strictness:

  1. Halo orbits are orbits around L-points.
  2. Halo orbits are Lissajous with an equal in-plane and out-of-plane oscillation period. (also exists in a variation where halo orbits are not counted as a subset).
  3. Halo orbits are planar Lissajous orbits.

The spacenews source linked by Wikipedia is reporting on press releases using (1), while itself defines halo orbits as (3), and Wikipedia uses (2).

And thus the confusion is complete.

Since the press releases at the base of it all use the widest possible definition, it's, not actually possible to use them to determine whether the orbit satisfies (2) or (3).

Actual spacecraft can't manage to stay for long in perfect but unstable halo orbits. They will eventually degrade back to some close Lissajous orbit.

  • $\begingroup$ Thanks for the answer to the second part; "Why do sources disagree?" But to the first part "Was Queqiao in a halo or Lissajous orbit?" possible answers include "halo", "Lissajous", "both", "neither", "yes", "no", "it depends", "impossible to answer" and I'm sure others. Is it possible to address it in some definitive way? $\endgroup$ – uhoh Oct 3 '20 at 2:03
  • $\begingroup$ @uhoh Not from the sources I have available. $\endgroup$ – SE - stop firing the good guys Oct 3 '20 at 6:19
  • $\begingroup$ slightly related: 1) the answer to Are some Halo Orbits actually Stable? seems to be yes, and refers to this longer answer, but of course that's CR3BP halo orbits, and invoking the word "spacecraft" invokes solar system reality at which point "stable" looses a singular definition. 2) I don't know what a "planar Lissajous orbit" even is, so I'll have to read up on that. and... $\endgroup$ – uhoh Oct 3 '20 at 23:59
  • $\begingroup$ 3) Any further thoughts on Is a 2:1 “figure-eight” Lissajous orbit possible in the Circular Restricted Three Body Problem? $\endgroup$ – uhoh Oct 3 '20 at 23:59
  • $\begingroup$ Since the bounty was in "grace period" mode and I wanted to award it, I've added a preamble based on what you've expressed in comments. Feel free to roll back or edit further, but I think that this addition will be helpful to future readers who arrive at this page with an interest in finding out. $\endgroup$ – uhoh Oct 9 '20 at 1:33

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