Seasonal and annual analysis of slant path attenuation over a 12 GHz earth-satellite link in subtropical Africa

With a view to establish a measurement-based profile and prediction model of slant path attenuation due to subtropical rain, rainfall data as well as received signal level (RSL) over a 12 GHz satellite TV Receive Only (TVRO) link were monitored simultaneously over a period of about two years in Durban South Africa (28°87‘S, 30°98‘E). The rain rate (R_0.01) exceeded at 0.01% of time at the location seasonally and over the period of measurement was obtained as 69 mmh^-1. The variation pattern of the received signal in clear air over the period was investigated and its relationship with fluctuations of atmospheric parameters other than rain was established by multiple regression. Event-by-event correlation of the rain rate data with that of the RSL in the time domain was carried out, resulting in a reliable subtropical rain attenuation profile which was used to develop a model for slant path rain attenuation due to subtropical precipitation. The model was validated by comparison with the generalized ITU-R model. The latter was found to slightly overestimate path attenuation at rain rates higher than 30 mm/h. The path attenuation exceedance probability over the link is also presented.