Project Echo: System Calculations

M a n y factors, such as power o u t p u t , frequency, a n t e n n a gain, freespace path loss, receiver noise temperature, and method of modulation, influence the performance of a satellite communication system such as the Project Echo experiment. In addition to those mentioned, which are also common to point-to-point microwave systems, three other factors m u s t be considered in the design of satellite communication systems. All three are functions of satellite position in the region of m u t u a l visibility. T h e y are: (a) variations in free-space path loss, (b) variations in sky noise temperature, (c) loss in the earth's atmosphere. In this paper these system parameters are used to predict the performance of the voice circuits that constitute the Echo communications experiment. T h e performance is discussed for the case of normal propagation conditions, and does not take into account attenuation due to rainfall or multipath fading. These are statistical occurrences, and are beyond the scope of this paper.