GRANDTOUR can simulate space asseen from the Voyager and Giotto spacecraft. In addition, GRANDTOUR cangenerate scenes from arbitrary points in space or the Earth, with thespacecraft visible to the observer. The planet, moons, and rings ofinterest (or comet, nucleus, and tail), stars, the sun, and thespacecraft are all accurately drawn with wireframe representations.Hidden line removal is done for the body surfaces. The motions of thebodies themselves are highly accurate, with errors no greater than 500kilometers. The user has considerable control over the time step, field ofview, etc., and many frames per second are typically generated.The program was originally developed at the Jet PropulsionLaboratory by John D. Callahan to assist in the analysis of science and optical navigationdata. In addition, the program was filmed by the BBC as part of a NOVAdocumentary on the Voyager Uranus encounter, and by the Four PointEntertainment Company for a commercially available video on Halley\'sComet. Program conveniently runs from any Windows/DOS.