Worst month statistics of attenuation and XPD on Earth-space path

Using the attenuation and cross-polarization discrimination (XPD) statistics measured in the CS (20/30 GHz) and BSE (12/14 GHz) centimeter wave propagation experiments performed for over four and three years, the worst month statistics of attenuation and those of XPD on earth-space path at 11.7 and 19.5 GHz are derived. The probability relation between the annual and worst month statistics is approximated by a power-law relation, and the constants for the relation are derived by a least squares procedure. It is found that the relation is independent of both frequency and polarization. The cumulative probability ratios of the worst month to annual statistics at the same attenuation or XPD values are derived as a function of annual cumulative probability. The ratios are well described by the Brussaard model of the worst month statistics. Attenuation ratio and XPD difference among the annual and worst month statistics are also derived and compared with the predicted results.