Attenuation statistics in Italy as measured by the SIRIO satellite during its five year lifetime

The results of a campaign of attenuation measurements carried out by means of the Italian satellite SIRIO at the two frequencies 11.6 and 17.8 GHz are presented. The campaign lasted five years (1978- 1982) and yielded almost continuous measurements at the lower frequency (acquired in three Italian stations) and measurements for a considerable fraction of time at the higher one (acquired in two of the three stations). The major aim of these measurements was to acquire long-term statistics to be employed in future earth-space radiolink design. This objective has been fully accomplished, owing to the very long life of the satellite, and the acquired data have been already utilized, properly extrapolated in frequency, for designing the domestic satellite system Italsat planned to start in 1987. Year-to-year and site-to-site variation have been found to be very high. Conversely the ratio between equiprobable values of attenuation at the two frequencies has proved to be very similar in the two stations and rather stable across the attenuation range.