GrandTour can simulate space as seen from the Voyager and Giotto spacecraft. In addition, GrandTour can generate scenes from arbitrary points in space or the Earth, with the spacecraft visible to the observer. The planet, moons, and rings of interest (or comet, nucleus, and tail), stars, the sun, and the spacecraft are all accurately drawn with wire frame representations. Hidden line removal is done for the body surfaces. The motions of the bodies themselves are highly accurate, with errors no greater than 500 kilometers. The user has considerable control over the time step, field of view, etc., and many frames per second are typically generated. The program was originally developed at the Jet Propulsion Laboratory by John D. Callahan to assist in the analysis of science and optical navigation data. In addition, the program was filmed by the BBC as part of a NOVA documentary on the Voyager Uranus encounter, and by the Four Point Entertainment Company for a commercially available video on Halley's Comet. Program conveniently runs from any Windows/DOS.