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

We present experimental results on the r elationship between rain attenuation and simultaneous scintillation, obtained with measurements of attenuation time s eries at 18.7 GHz, collected in two slant paths to Italsat ( 13.2 E): at Spino d'Adda (Italy, a 37.7 slant path, times series of 50 s amples/s and 1 s ample/s) and Darmstadt (Germany, a 32.7 slant path, 1 s ample/s). We have found that the average rain attenuation A (dB) and the average standard deviation sm (dB) in 1-min i ntervals ( calculated from t he 1 s ample/s time series), of the scintillation standard deviation s (dB), are linked by a power law sm=C3a x A^(5/12), or by the more refined model sm=C3b x A^(5/(12 x 0.9)), that can be due to an effective thin layer of turbulence aloft. The constants C3a , 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 s is also provided, as a function of A, as ss=Cs x A^d (dB), where Cs and d are constants.