Radiometer measurements of atmospheric attenuation at 19 and 37 GHz along Sun-Earth paths

The measurements of attenuation described in the paper refer to data recorded over a 3-year period at a frequency of 19 GHz, and over a 1-year period at 37 GHz. The relevance of these data to Earth-space communication links is discussed. Statistics showing the percentage of observation time for which the attenuation exceeds various values are given for each year for various ranges of elevation angle. At 19 GHz, the values of attenuation obtained from the extreme annual distributions differ by a factor of about two at a given percentage of time. Also, the percentage of time for which the attenuation at 19 GHz exceeded 10 dB for the `worst¿ month is an order of magnitude larger than the corresponding value for the 3-year period. Statistics derived from data obtained during periods of common observation at 19 and 37 GHz are compared for various ranges of elevation angle. Histograms showing the number of fades as a function of the duration of the fade are presented for both frequencies for fades greater than 5 and 10 dB, and a comparison of the instantaneous values of attenuation at 19 and 37 GHz at fade maxima has been made.