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Beginning in the late 1960's Voyager spacecraft will be launched to Venus and Mars. These spacecraft may contain both orbiting and landing modules. One of the first questions which arises in such a system is whether to transmit the data originating in the lander directly back to earth or to relay through the orbiter. This paper discusses the theoretical, operational and environmental aspects of the problem and concludes that a relay link is definitely required for Venus and would be advantageous for Mars. A 100-mc carrier frequency for the relay link is recommended, and the results of comparisons of promising modulation and multiplexing techniques are presented.