Synchronous communication relay satellites for manned space flight in earth orbit.

Results are presented from a feasibilitystudy and laboratory demonstration "which describe a system for using synchronous-altitude satellites as communication and tracking relays for manned spacecraft in earth -orbit. This system can provide "worldwide, continuous coverage. With proper tracking of the Doppler shifts, two-way simultaneous voice and data communication can be received with adequate margins. Range and range rate can be measured "with sufficiently high precision to give position information comparable with that obtainable with tracking ships and aircraft. Maximum use Is made of existing equipment to provide compatibility with the Apollo unified S-band communication system.