Site diversity is a technique to limit the effect of rain fade

Rain fade

Rain fade refers primarily to the absorption of a microwave radio frequency signal by atmospheric rain, snow or ice, and losses are especially prevalent at frequencies above 11 GHz. It also refers to the degradation of a signal caused by the electromagnetic interference of the leading edge of a...

 in satellite communications, mainly in the Ka band

Ka band

The Ka band covers the frequencies of 26.5–40 GHz. The Ka band is part of the K band of the microwave band of the electromagnetic spectrum. This symbol refers to "K-above" — in other words, the band directly above the K-band...

. The downlink transmissions of satellites cover very large areas, that will have different weather. The site diversity technique consists of linking two or more ground stations receiving the same signal: this way, if the signal is heavily attenuated in one area, another ground stations can compensate it. These intense rain areas, for example supercell

Supercell

A supercell is a thunderstorm that is characterized by the presence of a mesocyclone: a deep, continuously-rotating updraft. For this reason, these storms are sometimes referred to as rotating thunderstorms...

s, often have a horizontal length of no more than a few kilometres: putting the ground stations at a sufficient distance the possibility of rain fade in the downlink signal will be reduced.

The configuration works when the attenuation is not great at the two stations simultaneously. This is usually a valid assumption. Site diversity systems have been known to minimize disruption of service by major satellite carriers.