Beam Wander Along Uplink Paths

In this chapter we use weak and moderate-to-strong irradiance fluctuation theories to present further analysis of the behavior of a collimated beam along an uplink path to space, taking into account whether movement of the short-term wandering beam is being tracked or not. In particular, following the analysis in Chapter 3, we develop expressions for the on-axis and off-axis scintillation index of an uplink Gaussian-beam wave that involves an “apparent” pointing error that must be accounted for in the scintillation index when the beam is not tracked (e.g., tilt-corrected, centroid tracked, etc.). In addition to the scintillation models, we also introduce probability density functions (PDFs) for the uplink irradiance in the presence of beam wander, both without tracking the beam and tracking the beam through a tilt-correction to offset beam wander.