Communication Techniques for Space Exploration

This article was first given in a symposium at the California Institute of Technology on ``Realities of Space Exploration,´´ showing as graphically as possible that space communication is practical, that the extrapolation of the state of the art is straight-forward, and that the real limitations are those of: 1) external noise, 2) handling an extreme volume of data, 3) certain relativistic effects (more distant future), 4) time, and 5) economics and money. These limitations, at present, indicate frequencies between 500 and 5000 mc, automatic data handling, an awareness that communications outside the solar system is presently impossible, an appreciation that time scales of many years are expected in development and flight times, and a surprising conclusion that space exploration will probably pay for itself.