Reliability of Components for Communication Satellites

All the necessary components and circuit techniques are available to fabricate a simple communication system using low-orbit satellites. 1 Such a system would use many satellites at an altitude of a few thousand miles and be capable of global communications with a few megacycles baseband. The ground receiver portion of the system could achieve adequate signal-to-noise for very low received power by use of high-gain receiving antennas, low-noise maser receivers and FM modulation with feedback. The satisfactory performance of this type of receiver was demonstrated in the Echo I experiment. 2 In conjunction with such sensitive ground receiver equipment, it is possible to use a satellite repeater putting out only a few watts of power from an isotropic antenna, and hence avoiding the additional complexity of attitude stabilization. The components needed for such a satellite, including the traveling-wave tubes, transistors, diodes and solar cells, are all either available or achievable within the capability of existing technology. Thus a communication satellite system is feasible in principle. Whether or not it is economical and therefore practical, depends upon the life expectancy of the system, and specifically on the life of the satellite itself. It will be assumed here that a satellite life of at least five years is a reasonable target in the design of a practical communication system. By the very nature of the system, repair of the satellite is presently impossible (and if 035