Propagation, Noise, and General Systems Considerations in Earth-Space Communications

As man's ability to escape the attraction of the earth's gravitational field increases, the science of earth-space communications becomes more and more important. In this paper, an attempt is made to analyze the relevant propagation, noise and general system aspects of earth-space systems and to predict the operating frequencies for maximum range. The earth's atmosphere is shown to be nearly transparent to the transmission of radio frequencies (RF) between 80 and 15,000 megacycles. The various sources of noise both internal and external to the earth-space communications system are investigated and a spectrum of system sensitivity is plotted. Maximum available transmitter power and practical antenna parameters are predicted for the 1965-1970 era. All of these factors are then combined and weighted according to the "beacon" or "radar" equations, and the optimum operating frequencies for maximum range one-way and two-way earth-space communications systems are shown to lie in the microwave region of the spectrum.