We discuss some results of investigations of outgoing thermal radiation of the "atmosphere – underlying surface system" in the 3–5 and 10–13 μm wavelength ranges, carried out based on the theory of linear systems. We also made more detailed analysis of the contribution coming from the process of scattering into the formation of upwelling thermal fluxes and its effect on the pulse response of the atmospheric optical channels of formation and transfer of IR images in addition to the results published earlier.
Special attention is paid to the slant paths of observation of the Earth's surface under the conditions of aerosol turbidity of tropospheric and stratospheric layers of the cloudless atmosphere. The result of numerical experiments simulating satellite observations of two types of the temperature-inhomogeneous underlying surface are presented as an example.