Dielectric Properties of Lunar Subsurface Materials

The dielectric permittivity is one of the most significant properties of lunar material. For the past decades, researchers have assumed or used an indirect density versus depth relation to constrain the subsurface permittivity on the Moon. On 3 January 2019, Chang'E-4 (CE-4) rover-borne lunar penetrating radar (LPR) successfully landed on the Von Kármán crater on the Moon's farside. CE-4 LPR is the first surface radar on the Moon's farside for exploring regolith thickness and geological structure. Numerous parabolic-shaped diffractions (PSD), which indicate subsurface objects, are identified in LPR data. We estimate the permittivity of the first ~50 m at the landing region using these PSDs based on a hyperbolic fitting method. A best-fit permittivity/density versus depth relation is obtained, and this relation could be used at different areas on the Moon.