I'll See You On The Far Side Of The Moon
It was just announced that China has successfully put a probe on the moon. The Chinese mission, called Chang'e-4 has successfully achieved the first "soft" landing of a craft on the far side of the moon, and has deployed a robotic rover. Chang'e, named for the Chinese moon goddess, has sent back pictures thanks to a communication relay satellite, Queqiao, which was previously launched into a halo orbit back in May.
The communications system being used is actually quite fascinating. The far side of the Moon is pretty much the only place in the solar system where you can't directly talk with Earth, ever, because it's always facing directly away and blocked by the Moon itself. The Moon turns too slowly to have a geostationary (actually LUNAstationary) orbit, so you can't just park a satellite overhead, and a constellation of comsats for one mission is too difficult and expensive. So the Chinese looked to Harrison Schmitt's suggestion and put a single comsat in a lazy orbit around the Lagrange-2 point. Schmitt, the last man on the Moon and the only actual scientist to go there, lobbied vehemently to have Apollo 17 land on the far side, and the audacious L2 proposal was considered very bold. But it is working perfectly!
I read in a job the other time that the moon is artificial I do not know that there is a certain point, it is that I have decided to investigate a lot about it. Soon write about the matter.
Is it Sun-Earth L2 or Earth-Moon L2?
Each couple of bodies has its own L2 point. When i first read about chinese mission I thought they where using Earth-Moon L2, which is suspended just above the far side. A satellite can draw an "halo orbit" around it. But your picture shows Sun-Earth L2, which sunds more suitable for communicationes (since the moon is not in between) but also more difficult to achieve (since it is much further).
You are right! My mistake...I will fix this, thanks for correcting me. Looks like I need to do some research and educate myself better on the subject. Sorry for taking so long to get back, I was under the weather for a while there and wasn't keeping up with my Steemit comments.
Thanks for the clarification!
Lagrange points are fascinating, I am thinking on writing a post on them (but I would have to study a bit first). They have very interesting uses in terraformation projects. For example, a giant umbrella located at Sun-Venus L1 could help to cool down the planet to make it habitable. Another example: a huge superconducting magnet at Sun-Mars L1 could be used to scatter the solar wind particles reducing the intensity of radiation at the surface, while a lens at L1 or a mirror at L2 could be used to increase the amount of light that reaches the planet, and then its temperature.