What is Lagrange points and halo orbit?
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Lagrange points are the locations in space where the combined gravitational pull of two large masses roughly balance each other. Any small mass placed at that location will remains at constant distances relative to the large masses. There are five such points in Sun-Earth system and they are denoted as L1, L2, L3, L4 and L5.
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A halo orbit is a periodic three-dimensional orbit near the L1, L2 or L3
No gravity doesn’t balance at the Lagrange points. This should be immediately obvious by looking at L2 and L3. From these locations both bodies pull in the same direction. A tug of war can’t be balanced when both contenders are pulling the same direction. Gravity doesn’t even balance at the L1. See http://hopsblog-hop.blogspot.com/2016/11/lamentable-lagrange-articles.html