Atmospheric effects on propagation at millimeter wavelengths

In order to meet future earth-to-space communication needs, new regions of the electromagnetic spectrum must be utilized. This article discusses the feasibility of using the millimeter-wave region. It is shown, for example, that for clear-sky conditions the effects of the atmosphere on propagation at frequencies of 15 and 35 GHz are very small. However, the attenuation increases significantly under conditions of heavy cloud cover and precipitation. On the basis of these results it is evident that atmospheric attenuation is sufficiently low in selected regions of the millimeter-wavelength spectrum to permit wideband earth-to-space communications with moderate reliability. For high reliability the high attenuation due to heavy rainfall must be overcome either by the use of space diversity techniques or by locating the ground terminal in a dry climate.