Accurate estimates of the propagation impairments that affect link quality and availability and determine signal interference fields are essential for the reliable design of telecommunication systems and the efficient use of the electromagnetic spectrum. Recent announcements by commercial entities of their intent to use Ka-band spectrum to supply satellite services have heightened interest in propagation data and models for these frequencies. This paper provides a brief overview of Ka-band Earth-satellite systems and requirements in relation to the need for specific types of propagation data.

A brief review of hydrometeor scatter interference is given, focusing on recent improvements to International Radio Consultative committee (CCIR) texts on interference between terrestrial and earth stations, and research to effect possible future improvements. The following improvements are suggested: smaller reflectivity factor slope above the 'rain height' coupled with a revised empirical constant in the transmission loss equations; inclusion of melting layer scatter; improved rain height model; improved horizontal structure model for precipitation cells; consideration of correlation between the wanted and unwanted signals; and consideration of a range of terrestrial elevation angles in coordination.>

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.>

At frequencies above 10 GHz, tropospheric propagation effects can significantly alter signal transmission performance. Important phenomena on earth-satellite (slant) paths include attenuation and sky noise increases resulting from atmospheric gases, clouds, and precipitation, depolarization by raindrops and ice crystals, and refractive effects, particularly at low path elevation angles. Various practical aspects of propagation phenomena for satellite broadcasting at frequencies above 10 GHz are reviewed in this paper, with emphasis on the near-term implementation Of services atKu-band.