The application of semiconductor optical radiators to space communication

The recently developed incoherent and “lasing” optical semiconductor radiators have considerable potential for specialized applications in the space environment. The attractive features of these radiators are their small size and weight, high efficiency, narrow beamwidth, and capability of being directly modulated with high-frequency continuous waveforms or short pulses. In this paper, these characteristics are discussed and the communication range capability is determined using a photomultiplier as a receiver. The communication range may be limited by background noise, detector noise, or noise generated by the signal itself. The range equations resulting from these various conditions are presented. Two illustrative examples are given: (1) communication with a transmitter located on the sunlit lunar surface; and (2) communication with a transmitter against the night sky background.