Coexistence of Celestial and Terrestrial Communications

Artificial satellite repeaters will revolutionize radio communication by permitting the use of microwaves over long paths. There will also be a continuing and mounting need for terrestrial applications of microwave services over relatively short distances. Achieving coexistence between these long- and shortdistance systems will conserve and enhance the utilization of the microwave spectrum. Extensions of prior interference coordination techniques, such as use of three-dimensional antenna directivity, can cause the desired signal to override interfering signals and thus permit most satellite communication systems to share frequencies with most terrestrial microwave communication systems. Even though satellite communication may not need such a large fraction of the microwave spectrum for some years, focusing prompt attention on the needs and probable problems of frequency sharing can help guide its evolution around subsequent difficulties.