SaVi allows you to simulate the movement of satellite constellations such as Galileo and Globalstar, in two and three dimensions. (3D viewing requires Geomview, also from Sourceforge.)
The SaVi 1.2.8 release makes the fisheye window a Tk canvas, removing the need to compile with X libraries, bringing the fisheye to Cygwin Insight Tcl users, and making the SaVi binary 20% smaller.
SaVi 1.2.8 also allows fisheye views to be saved as postscript, adds a rosette constellation generator, corrects plane phasing in @atcontact, Celestri, Galileo and GS2 scripts, adds a slider for realtime coverage width adjustment, improves TLE-handling code, adds -fake-geomview flag to test features for Geomview without running Geomview, adds -map-view-height <no. of pixels> flag to scale coverage map arbitrarily, and indicates map coordinates clicked directly in coverage panel.