Attenuation of propagation through rain for an earth--Satellite path correlated with predicted values using radar

During the summer of 1974 and spring of 1975, measurements of attenuation of propagation through rain were made at Wallops Island, VA, using 13 and 18 GHz transmitters operating in the uplink mode toward the ATS-6 satellite. Simultaneously, rain reflectivity levels were measured along the earth-satellite path using a high resolution ( beamwidth) -band radar having a scanning antenna. Four raingages and two disdrometers were also located in the vicinity of the transmitters. The radar and disdrometer data were used in a modeling program to predict attentuation levels which were subsequently compared to the directly measured fades over nearly simultaneous time intervals. Predicted attentuation levels were obtained for three drop size distributions; namely, those of Joss et al. for thunderstorm activity, Marshall-Palmer, and the average distribution measured in the vicinity of the transmitter (APL distribution). Comparisons between predicted and measured attenuation levels showed the APL dropsize distribution gave the smallest rms difference of 1.3 dB at 13 and 18 GHz although the rms difference corresponding to Marshall-Palmer was close to this value. Although the sample sizes were relatively small, the good agreement suggests the validity of using radar to model path attenuation to obtain attenuation statistics.