New High Precision Measurements of Apollo Samples: 0.3–5 GHz Complex Refractive Indices

Active and passive radar techniques provide information on the subsurface structure and history of planetary bodies. However, interpretations of radar data are limited by our understanding of the complex dielectric permittivity and magnetic permeability of the surface material. For lunar radar and radiometry missions, wave propagation and absorption are modeled based on measurements of returned Apollo samples. These models typically focus on the dielectric permittivity of the lunar regolith with the assumption that the magnetic permeability is negligible. Using three cavity resonators, we reinvestigate a subset of previously studied lunar soils and report measurements of the complex permittivity and permeability from 0.3 to 5 GHz. We find there is a frequency dependence in both the dielectric and magnetic loss tangents, and that at Ultra High Frequency frequencies, magnetic losses tend to dominate the absorption.