is a satellite visualization software that lets you create, run, examine, and modify satellite orbits in two and three dimensions. Simulations of Iridium, Teledesic, Globalstar, GPS, and other satellite constellations are included. SaVi requires Tcl and Tk on a Unix system. SaVi works well with the 3D renderer Geomview. Geomview is optional, though recommended for its 3D rendering capabilities.