A system and method are disclosed for bidirectionally coupling a first satellite communication system to a second satellite communication system, wherein the first and second systems operate with different protocols. In a presently preferred embodiment of this invention the first system uses a spread spectrum (SS), code division multiple access (CDMA) technique wherein the satellites serve as simple `bent pipe` repeaters for relaying communications between a user and a gateway. The second satellite communication system may be any other type of system having at least one characteristic that precludes direct communication between the first and the second systems. In an exemplary embodiment the second system uses a time division multiple access (TDMA) technique, and furthermore enables direct satellite-to-satellite communication links. A ground-based protocol conversion unit (70) is positioned for receiving a communication from a satellite of either the first or the second system, and includes circuitry for converting the transmission into a transmission that is suitable for transmission into the other system.