Systems Tool Kit (STK) is a 3D modeling software for complex systems, including ground vehicles, satellites, unmanned aerial vehicles, and more. The program was initially created to monitor satellites in orbit but is now used by aerospace and defense communities around the globe. In addition to modeling behavior and movement patterns, STK also analyzes communication systems and sensors. All of these operations and behaviors are reported within the context of mission objectives for the vehicles being modeled. AGI has made their software free to the public with special download license to protect their source code.
For more information about STK and to try it out for yourself, visit http://www.agi.com/home