ESTIMATES OF COMMUNICATION SATELLITE SYSTEM DEGRADATION DUE TO RAIN,
RAND CORP SANTA MONICA CALIF
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The performance of a communication satellite link is influenced by the fact that rain not only attenuates the signal but also adds thermal noise to the other sources of sky noise. The influence of sky noise on the choice of communication satellite system parameters has been studied for some time. Some publications have emphasized the contributions of cosmic noise, and noise due to oxygen and water vapor absorption in the atmosphere to sky noise, but neglected the noise due to rain. A few publications have looked specifically at the problem of the sky noise contribution due to rain. Combining all these sources of noise as a function of frequency and elevation angle is the first task this paper will cover. The combined system degradation at 4 kMc due to both rain effects, i.e., attenuation and noise, as a function of cumulative time distribution is calculated it may be a key factor in evaluating the worth of better receivers, e.g., cooled parametric amplifiers, at communication satellite ground terminals in regions of heavy and frequent rainfall. Presenting estimates of these time distributions of degradation of the down link due to rain for various system noise temperatures in the absence of rain is the second task of this paper.