1. A satellite simulator adapted for use with a plurality of satellite ground stations, said satellite simulator comprising: a distributed messaging system for providing communications among a plurality of separate modules comprising said simulator, said distributed messaging system configured for providing communication between said modules installed on both a single host and multiple host computers; an application specific telemetry output module configurable for data transmission to any one of a plurality of satellite ground station data acquisition systems; an application specific command input module configurable for receiving data from any one of a plurality of satellite ground station data transmission systems; and, whereby said satellite simulator can simulate different satellites and satellite constellations for exercising different ones of said plurality of satellite ground stations.