RECOMMENDATION ITU-R P.1621 - Propagation data required for the design of Earth-space systems operating ... 1 Atmospheric considerations 2 Absorption 3 Scattering 3.1 Rayleigh scattering 3.2 Mie scattering 3.3 Wavelength independent scattering 4 Refraction 4.1 Formula for the effective atmospheric refractive index 4.2 Apparent change in elevation angle 5 Turbulence 5.1 Measures of turbulence