SOME FACTORS AFFECTING ELECTROMAGNETIC DETECTION OF LUNAR SUBSURFACE WATER

Determination of the presence or absence of lunar subsurface water appears possible, from a satellite in orbit around the moon or from lunar surface measurements, by the use of inductive electromagnetic techniques. A number of plane-layered models of the moon have been analyzed to obtain values of reflection coefficient, surface impedance, apparent dielectric constant, and apparent conductivity, computed for a normally incident plane wave at frequencies in the range 104 to 108 Hz. The variation of these quantities with frequency is markedly dependent on the presence or absence of subsurface water (in either liquid or “permafrost” form); that is, a fraction of one percent of water, for a wide range of materials that might exist on the moon, yields characteristic signals. The detection depth for the water-bearing layer (if it exists) ranges from tens of meters to at least one kilometer, depending on the characteristics of the layers; results for representative models are displayed. For certain lunar models an equipment resolution of at least as good as ±1 dB is required. Copyright 1969 by the Institute of Electrical and Electronics Engineers, Inc.