Relative Importance of Reflected and Emitted Flux Density in 3-14-μm Range

Using the LOWTRAN 3 Midlatitude Summer Model which includes atmospheric effects, the reflected and emitted radiant flux densities from theoretical lambertian targets were calculated. The following conclusions were obtained. At 3.5 μm, q (ratio of radiant flux density emitted by a natural target to the radiant flux density reflected from it) is much less than one, except at high temperatures and emissivities. At 4 μm, q is of the order of magnitude equal to one for most targets. At 4.6 μm, q is much larger than one at high temperatures and emissivities. Previously acquired field spectroradiometric data on soils in the 3.6-5.4 μm were found to agree closely with theoretical calculations of reflected and emitted radiant flux densities.