Analysis of a sateffite communication channel: optical scintifiations and fade statistics

Estimates of the fractional fade time, expected number of fades, and mean duration of fade time associated with a transmitted Gaussian-beam wave are developed for uplink laser satellite-communication channels and compared with similar results based on a spherical wave model. Weak fluctuation theory using the lognormal model is applicable for zenith angles less than 600. Because spot size and off-axis scintillations are significant in the Gaussian-beam wave model but not for the spherical wave model, pointing errors become an important consideration in a reliable laser communication link. Off-axis scintillations increase even more rapidly for large diameter beams and can in some cases lead to a scintillation saturation for pointing errors greater than 1 jrad off the optical beam axis.