Calculations of the effect of roughness on microwave emissivity with application to the Moon and Venus

Abstract

Microwave emissivities have been calculated for a variety of rough surfaces assumed to reflect and emit according to geometric optics. Both the surface dielectric constant and the function defining the distribution of slopes are varied in the calculations. The results are applied to existing passive microwave observations of the moon and Venus. For the moon, the presence of an acceptable roughness can reconcile the dielectric constant calculated from polarimetric data at λ21 cm with the dielectric constant obtained from the λ68‐cm radar data (ε ≃ 2.7). For Venus, the surface parameters obtained from an analysis of the λ12.5‐cm radar results are used to calculate the polarization visibility function. The calculated curve deviates significantly from the curve observed at λ10.6 cm. Because the inclusion of the indicated roughness does not produce a good fit, it is believed that the answer may be found in atmospheric absorption and thermal emission, as suggested by J. E. Hansen and S. Matsushima and by J. V. Evans.