Clear-air transmission impairments at low path elevation angles

At very low path elevation angles, propagation effects on Earth-space paths, including impairments caused by clear-air refractive phenomena, can be quite severe. Partly due to scarcity of measured data, low-angle refractive multipath fading is not as well modeled as the scintillation (forward-scattering) mechanism. In particular, the importance of surface reflections to fading is not well characterized. Low-angle fading behavior is analyzed to surmise preliminarily the likely physical character of this effect.