Apparent temperatures of smooth and rough terrain

Abstract

The apparent temperatures of smooth and rough terrain surfaces are calculated for frequencies between 1 and 75 kMc, for angles of incidence between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5\deg</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">80\deg</tex> , and for observation altitudes between 2 km and 32 km. The attenuation and thermal radiation caused by the atmosphere are accounted for by an experimental model atmosphere, and the surface emissivities are based on measured complex dielectric constants (for the smooth surfaces) and measured radar return (for the rough surfaces). It is found that perpendicular polarization provides the greatest temperature contrast between rough and smooth surfaces, and that the contrast decreases as the altitude of observation increases; at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f=75</tex> kMc (approximately the resonant frequency of the oxygen molecule), there is likely to be little, if any, contrast between rough and smooth surfaces.