From: utzoo!decvax!cca!REM@MIT-MC@sri-unix
Newsgroups: net.space
Title: 
Article-I.D.: sri-unix.1691
Posted: Wed Jun  9 15:52:41 1982
Received: Thu Jun 10 02:44:34 1982

From: Robert Elton Maas 
Note, the libration points are only points in the Earth-Moon frame of
reference. In the Earth-Sun or Earth-Stars etc. frames, they aren't
points, rather they're orbits around the Earth with a period of one
month, the same as the moon (one synodic month if you're in the
Earth-Sun system, or one siderial month if you're in the Earth-Stars
system, I think, but that's irrelevant to this general point I'm making).

In the Earth-Moon frame, L4 and L5 are points of minimal energy, i.e.
potential wells. Thus you can either sit at the bottom of the well
not moving (in that frame) or move in an orbit inside the well but
around the bottom rather than exactly at it. I believe this first
approximation assumes the orbit of the Moon around the Earth is circular
and no other bodies purturb the potential well. Does somebody on this
list have a more complete analysis that includes the non-circular motion
of the Moon around the Earth (actually around the center of gravity of
the Earth-Moon system) and purturbations from Sun, Venus, Mars, Jupiter etc.?