Optical model of the atmosphere for problems of calculating the irradiance of the entrance pupils of optoelectronic systems

Abstract

This paper describes an optical model of the atmosphere that fundamentally differs from the working models used to estimate how the atmosphere affects the operation of optoelectronic devices. The model includes concepts of typical aerosol situations (tropics, mid-latitude summer, etc.) and obtains its input parameters from standard weather reports. Molecular absorption is determined on the basis of the HITRAN spectral-line database; the concept of the transmission function is not used in this case, and accordingly the problem of an unresolved spectrum does not arise in problems of radiation transport in a medium with a complex structure of the absorption spectrum in the IR region. The latter problem is especially acute in determining the contrast of observed objects when the viewing paths have complex geometry. The approach used here is equivalent to line integration with an insignificant loss of accuracy and significant speed-up of the calculation. The model makes it possible to take into account diurnal and seasonal changes of the viewing conditions in the troposphere and especially in its lower layers with the maximum adequacy, both in clear weather and under low unbroken clouds, with and without precipitation.