Radiowave propagation phenomena that affect the performance of satellite communication systems are concisely discussed to introduce some topics in propagation research related to satellite systems design and to illustrate related problems and uncertainties. The focus is on tropospheric effects. A summary of relevant propagation impairments is supplied, and general classes of impairments, the physical cause of each, and the major importance of each for satellite systems are given. Some impairments in the table are critically important for certain systems applications. For example attenuation due to rainfall can be substantial for significant percentages of the time on 30/20 GHz propagation paths and will be the dominant path impairment for most Ka-band systems. Appropriate literature sources are referenced for the additional details that will be required for many applications. >