By Albert A. Whalen, NASA/Goddard Space Flight Center
The present communication satellites used for international and domestic traffic employ low-powered transponders. This characteristics is compatible with the mission of interconnecting a few earth stations in a high density traffic mode. From the total system viewpoint when there are a small number of earth stations, it is economical to spend more on the earth station and minimize the cost of the satellite segment.
However, if the number of earth stations is large, it is far more economical to reduce the size and cost of the earth terminal and increase the power (and cost) of the spacecraft. The total systems cost is lowered by the reduced cost of the total ground segment.
Communications experiments with the Applications Technology Satellite-VI and the Communications Technology Satellite, both high-powered spacecraft, broadcasted to low-cost earth stations. These experiments demonstrated that low-cost, good performance earth stations are a reality.