System engineers are currently planning satellite communications links in the 20/30 GHz bands and frequency reuse through orthogonal polarizations. This thesis examines the system level constraints imposed by medium effects at these high frequencies of which the most serious is rain induced attenuation and depolarization. The effect of crosstalk between orthogonal channels is calculated in terms of a degradation of the carrier to noise ratio. This concept is combined with the results of rain propagation modeling to define a rain induced effective attenuation which incorporates the effects of depolarization and attenuation. Methods for computing the effective attenuation and link outage times caused by rain are outlined which are applicable to any earth to space millimeter wave communication link. The Millimeter Wave Communications Experiment is used as an illustrative example of these methods. / Master of Science