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We present and discuss two main results concerning the relationship between phase delay due to rain and rain attenuation, useful in calculations concerning high precision tracking of satellites and deep-space spacecrafts using interferometry techniques. We have found these two results with the Synthetic Storm Technique [SST] applied to a large data bank of rain rate time series collected at three sites in Italy. The first result concerns a formula that provides the extra signal phase delay tau (picoseconds) due to rain as a function of rain attenuation A (dB), frequency f (GHz) and slant path elevation angle thetas (degrees), given by tau = (860.4 4.82 thetas)f-1.71A0.73, for 20deg les thetas les 44deg, and by tau = 648.3 f1.71 A0.73,for 44deg les thetas les 90deg. The formula allows estimating the phase delay due to rain attenuation, with overall average (normalized) error -3%, standard deviation 11.1%, rootmean square 11.5 % for 20deg slant paths. The second result concerns a method to predict phase delay from the probability distribution of rain rate (SST probability model), very useful when only the probability distribution of rain rate is known.