The GEOSTAR Satellite System, now in development, will provide accurate positioning and two-way message capability for subscribers equipped with compact, inexpensive transceivers.The full GEOSTAR Satellite System is scheduled for operation by 1987.The GEOSTAR Satellite System, now in development, will provide accurate positioning and two-way message capability for subscribers equipped with compact, inexpensive tranceivers. Positions are displayed at the transceiver and, if desired, at a central dispatch facility. Messages, in the form of short telegrams, can be exchanged in both directions between any two subscribers or between a subscriber and a central dispatch facility. All positioning and message services are provided by a redundant set of computers at the GEOSTAR ground station. Three GEOSTAR satellites relay signals between the GEOSTAR ground station and user transceivers anywhere in the continental United States. Calculated position accuracy for transceivers carried by pedestrians or mounted in cars, trucks, trailers, railroad cars or boats is better than S meters. Message capacity is over 10,000 messages per second. For automobiles, GEOSTAR radio units can be mounted under a deck lid with a two-inch rod antenna projecting through a seal. The driver's display is connected to it by a single cable. System design has been reviewed and verified in a study by RCA Astro Electronics, a satellite manufacturer. A ground-based emulation of the system has been built and is currently in operation. The full GEOSTAR Satellite System is scheduled for operation by 1987.