Angles-of Arrival Fluctuation at 20 GHz on Earth-Space Path

Abstract

The angles-of-arrival (AOA) of beacon signals transmitted from Japan's geostationary satellites, CS and CS-2b, were continuously measured with both an interferometer method and an auto-tracking error method. The beacon signals were circularly polarized waves at 19.45 GHz and were received at an elevation angle of about 48 degrees. The cumulative distribution of standard deviations of AOA is derived. Seasonal and diurnal variations of the distribution are also derived. From the statistical point of view, the fluctuation of AOA increased in the daytime and decreased in the evening and in the early morning. The fluctuation decreased also in winter. AOA standard deviations of up to 6 milli-degrees were observed in May and October 1982, and AOA peak deviations from average AOA of up to 30 milli-degrees were observed in May and July 1982. It is found that the fluctuations of AOA in both elevation and traverse directions are nearly the same. This suggests that the fluctuation of AOA is isotropic on a propagation path with a sufficiently large elevation angle.