18.7 GHz tropospheric scintillation and simultaneous rain attenuation measured at Spino d'Adda and Darmstadt with Italsat

We present experimental results on the relationship between rain attenuation and simultaneous scintillation, obtained with measurements of attenuation time series at 18.7 GHz, collected in two slant paths to Italsat (13.2 degrees E): at Spino d'Adda (Italy, a 37.7 degrees slant path, times series of 50 samples/s and 1 sample/s) and Darmstadt (Germany, a 32.7 degrees slant path, 1 sample/s). We have found that the average rain attenuation A (dB) and the average standard deviation sigma(m) (dB) in 1-min intervals (calculated from the 1 sample/s time series), of the scintillation standard deviation sigma (dB), are linked by a power law sigma(m) = C(3a)A(5/12), or by the more refined model sigma(m) = C(3b)A(5/12x0.9), that can be due to an effective thin layer of turbulence aloft. The constants C-3a,C-3b can be estimated by applying the ITU-R formula for scintillation predictions. For conservative design, a best fit model of the conditional standard deviation of sigma is also provided, as a function of A, as sigma(s) = C(s)A(d) (dB), where C-s and d are constants.