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Re:China prepares mission to land spacecraft on moon's far side by gardaani on Friday December 07, 2018 @07:44AM (#18627156)
The lander plans to transmit data to Earth using a relay satellite orbiting at the Earth-Moon L2 halo orbit: http://www.planetary.org/blogs/guest-blogs/2018/0519-change-...

The relay satellite included two micro-satellites for the moon, only one of them survived: http://www.planetary.org/blogs/guest-blogs/2018/20180615-que...

Re:China prepares mission to land spacecraft on moon's far side by Isamu on Friday December 07, 2018 @12:49PM (#18629801)
That Earth-Moon L2 halo orbit is cool, I didn't even know that was a thing.

[edit] I mean I was aware of Lagrange points, but not the practicality of the halo orbit. This is a nice explanation:

http://hyperphysics.phy-astr.gsu.edu/hbase/Mechanics/lagpt.h...

Re:China prepares mission to land spacecraft on moon's far side by Florin_Andrei on Friday December 07, 2018 @01:41PM (#18630278)
Yeah, it instantly makes sense if you calculate the force at the Lagrange point and notice the vector points back at the exact L point when you're in the vicinity - and then you go, hmmm, looks like it might be possible to orbit that thing.
Re:China prepares mission to land spacecraft on moon's far side by enos on Friday December 07, 2018 @02:54PM (#18630980)
Will L2 congestion become a problem once JWST and a few more missions join this craft? Will we have to manage that orbit like we do with geostationary?
Re:China prepares mission to land spacecraft on moon's far side by acranox on Friday December 07, 2018 @01:15PM (#18630049)
Re:China prepares mission to land spacecraft on moon's far side by Isamu on Friday December 07, 2018 @01:24PM (#18630121)
An interesting point from that page:

>A full n-body dynamical system such as the Solar System does not contain these periodic orbits, but does contain quasi-periodic (i.e. bounded but not precisely repeating) orbits following Lissajous-curve trajectories. These quasi-periodic Lissajous orbits are what most of Lagrangian-point space missions have used until now. Although they are not perfectly stable, a modest effort of station keeping keeps a spacecraft in a desired Lissajous orbit for a long time.

Re:China prepares mission to land spacecraft on moon's far side by daveslash on Friday December 07, 2018 @05:50PM (#18632435)
https://en.wikipedia.org/wiki/Halo_orbit "Halo orbits can be thought of as resulting from an interaction between the gravitational pull of the two planetary bodies and the Coriolis and centrifugal accelerations on a spacecraft."