Far Side of the Moon

Chang'e 4 Lunar Landing In Detail
Mr. Manley does a good job here. But how is it that we know any of this at all? When we sent Apollo spacecraft to the moon 50 years ago, they were cutoff from communication when they went behind the moon. So how are we getting these pictures? We have sent probes around the moon and they have taken pictures, but they had to come back into view before they could transmit their images. This Chinese probe is on the moon, it isn't coming back into view, ever. Have the Chinese invented a new kind of super-quantum-licious communications technique that allows them to transmit through a thousand miles of rock? No, they sent another satellite, a communications relay, out to Lagrange point 2 which is out beyond the moon.


Queqiao relay satellite enters L2 orbit
Notice that this satellite doesn't just sit at the 'point', the 'point', after all, is unstable. Any slight disturbance from this location will cause the satellite to fall away from the 'point', never to return. Also sitting at the 'point' wouldn't do us any good, as the 'point' is directly opposite the Earth and so is blocked from radio communications by the moon. Instead the satellite goes into a halo orbit where it never actually crosses the point, instead it orbits the 'point'. The James Webb Space Telescope will be using a halo orbit when it eventually gets launched, which is expected in a couple of years.