INTERMEDIATE SCALE LUNAR ROUGHNESS

A model surface consisting of parallel troughs has been examined in order to assess the importance of roughness in accounting for the properties of lunar thermal radiation. Insolation, emission from the surface, reabsorption of emitted radiation, and conduction are all considered. Brightness temperatures both in the midinfrared and microwave region are computed for eclipse and lunation conditions, not only as a function of lunar phase, lattitude, longitude, and direction of observation, but also for a variety of trough dimensions. All those features of the observed thermal radiation which cannot be accounted for on the basis of a plane homogeneous model are listed and the extent to which they can be accounted for by the proposed model is considered. In particular, a model for which the width and height of the raised portions are both equal to a quarter of the trough interval gives good agreement with the directional effects observed for lunar daytime radiation in the 10-14 μ wavelength band. In addition a number of other anomalies, including some already accounted for in the literature by other causes, receive more or less good explanations on the basis of roughness. © 1970.