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From a comment by Jim Chiang for Checkout 1: gtorbsim is a simple interface to the pointing mode options that are calculated in the GPS class of the astro. As far as I can tell, the comments in astro/GPS.h are the only documentation of these various pointing modes.
7 April - Here are the results so far of my examination of gtobssim. (Stephens)
8 April - Added a page reviewing the ObsSim.py GUI. (Stephens)