Global predictions of slant path attenuation on earth-space links at EHF

Experience gained using the Italian Space Agency (ASI) satellite, ITALSAT F l, has shown that there is a need to account for attenuation caused by clou d and gases in the atmosphere when transmission frequencies above similar t o 30 GHz are employed. This paper describes a method that has been develope d to predict attenuation caused by rain, cloud and gas. By using this metho d, attenuation levels to the closest of five geostationary satellites have been predicted for a link frequency of 39.6 GHz and maps showing global pre dictions of slant path attenuation that would be exceeded for 10, 5, 2 and 1 per cent of the time are presented. Comparisons between attenuation predi ctions and measurements collected from beacons carried on the ITALSAT Fl & ACTS satellites are made to establish the validity of the predictions. Copy right (C) 1999 John Wiley & Sons, Ltd and (C) Crown Copyright 1999.