Atmospheric attenuation is a reduction with distance from the source of the intensity of an acoustic or an electromagnetic signal propagating through the atmosphere caused by interaction of the signal with gaseous constituents of the atmosphere, aerosols, or hydrometeors. Mostly scattering and absorption accounts for attenuation.

The primary causes of atmospheric attenuation are oxygen, which is of course always present, and water. Attenuation due to water is present in humid air and is more pronounced with fog and rain. Another factor that affects attenuation is the angle of elevation of the satellite from the earth station (angle () ). The smaller the angle of elevation, the more of the atmosphere that the signal must travel through. Finally, atmospheric attenuation depends on frequency. In general, the higher the frequency, the greater the effect. The given figure shows typical amount of attenuation as a func- tion of angle of elevation for frequencies in the C band. Of course, the attenua- tion due to fog and rain only occurs when those elements are present in the atmosphere.

Fig: Signal Attenuation Due to Atmospheric Absorption (C Band):