Trick of memory?

Yesterday evening I felt sure that I had very recently read a piece in the Guardian about the Chinese putting a satellite into orbit on the dark side of the moon, a trick that involved finding a place where the various forces of gravity cancelled out, which in turn involving some equations involving a chap called Legendre. This was a serious matter because, inter alia, if this satellite was to start doing bad things, there was no way we could get at it.

So this morning I try to recover the article. The Guardian website has nothing. The paper copy Guardians of Monday and Tuesday have nothing. Have I been dreaming, on the way getting into a muddle between the three French mathematical gentlemen called Laplace, Lagrange and Legendre? Three gentlemen whom I have recently been looking up.

Further digging turns up reference 1, from where I get to reference 2. So there is a connection between a Chinese satellite (in an L2 halo orbit around point L2 in the snap above), points where gravitational fields cancel out (at least in some sense) and Lagrange, although I am now worrying about how those points move around in time, as the sun, earth and moon move around. And about why the moon doesn't seem to be making any lines of its own in the snap.

So I think I must have seen something, somewhere. But where?

Clearly something with which to while away the long winter evenings.

Reference 1: https://www.planetary.org/blogs/guest-blogs/2018/0519-change-4-relay-satellite.html.

Reference 2: https://en.wikipedia.org/wiki/Halo_orbit.

Reference 3: https://en.wikipedia.org/wiki/Lissajous_orbit. For those with bigger appetites.