Radiative transfer theory
Radiation propagation in the atmosphere

The atmosphere is one of the most restrictive parasitic sources for optronic systems, due to its scattering of ambient radiation in the visible and near infrared, and its own emission in the far infrared. It is the most important and significant parameter for reducing the contrast of observed objects.

The calculation of these effects is complex, involving all the physical parameters described in the previous paragraphs: transmission, absorption, diffusion, etc. Today, highly advanced and complex calculation programs provide a good average simulation of these effects.

The most important of these are based on the LOWTRAN, MODTRAN and FASCOD codes described at