Weather Loss

Weather loss in satellite communications is the attenuation of Earth–satellite signals caused by hydrometeors in the atmosphere, including rain, hail, ice, fog, cloud, and snow. As the signal propagates through the atmosphere, these condensed water particles absorb and scatter electromagnetic energy. The magnitude of the loss depends on operating frequency, particle size and concentration, dielectric properties of the hydrometeors, and the effective path length through the atmosphere (which is influenced by elevation).

Rain produces the dominant contribution to weather loss because raindrop sizes are often comparable to microwave wavelengths. Attenuation due to rain is generally negligible below about 7 GHz, becomes noticeable above roughly 10 GHz, and is a major design consideration above about 15 GHz, particularly for Ku-band and Ka-band systems. Weather loss increases rapidly at low elevations, where the slant path through precipitation is longest.

Weather-induced attenuation leads to increased link margins, adaptive coding and modulation, uplink power control, or site diversity being required to maintain link availability.