For someone getting his PhD in Applied Mathematics/Celestial Mechanics at the time of the first lunar landings, coming back to Halo Orbits after decades was a reall "eye-opener"! Yes, we had heard of Ljapunov stability and the fact that Henri Poincaré had forseen various "celestial mechanics wonders", but our computers at the time of Apollo were adequate for integrating Hill type orbits, but not for large scale numerical experiments with halo trajectories! While reading, your article unleached a myriad of ideas in my brain, connecting the special case of fast "swing-by-orbits" and the generalized case of flying between Libration points. Thanks!

Your love for interdisciplinary thinking connects us even further than Celestial Mechanics - astrobiology is another subject that shows we live at just the right time. Well, having passed 70...

Best regards

Bruno Stanek