Atmospheric Scattering

Scattering is the redirection of EMR by particles suspended in the atmosphere or by large molecules of atmospheric gases. Scattering not only reduces the image contrast but also changes the spectral signature of ground objects as seen by the sensor. The amount of scattering depends upon the size of the particles, their abundance, the wavelength of radiation, depth of the atmosphere through which the energy is traveling and the concentration of the particles. The concentration of particulate matter varies both in time and over season. Thus the effects of scattering will be uneven spatially and will vary from time to time.

Theoretically scattering can be divided into three categories depending upon the wavelength of radiation being scattered and the size of the particles causing the scattering. The three different types of scattering from particles of different sizes are summarized below:

Scattering process

Wavelength

Approximate dependence particle size

Kinds of particles

Selective

• Rayleigh

X -4

< 1 |m

Air molecules

• Mie

Xo to X-4

0.1 to 10 |m

Smoke, haze

• Non-selective

Xo

> 10 | m

Dust, fog, clouds

0 0

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