Lunar Radar Sounding for Ice Deposits and Subsurface Void Detection: Preliminary System Design and Performance Analysis

Shallow lunar subsurface characterization is a key requirement for future exploration activities, particularly for in situ resource utilization and the identification of protected environments for human and robotic operations. This work presents the preliminary design and performance assessment of an orbital very high frequency (VHF) radar sounder tailored to the detection of subsurface water ice deposits and lava tubes at depths relevant to exploration. The analysis combines physically based modeling of acquisition geometry, electromagnetic properties, and surface roughness with quantitative evaluation of signal-to-noise and signal-to-clutter ratios. Results indicate that surface clutter constitutes the primary limitation for subsurface detectability in orbital sounding, thereby driving both instrument design and mission geometry. Quantitative performance bounds are derived for penetration depth and spatial resolution, providing guidance for identifying regions where subsurface access may be achieved with reduced operational risk. One-dimensional electromagnetic simulations further demonstrate the advantages of operating in the VHF regime. While lower-frequency systems retain sensitivity to some subsurface interfaces, their limited vertical resolution prevents reliable separation of closely spaced structures, such as the roof and floor of lava tubes. In contrast, the proposed VHF sounder enables clear separation of multiple subsurface interfaces, allowing geometric characterization of cavities and improved discrimination of ice-bearing layers. These results establish the feasibility and relevance of a VHF orbital radar sounder as a dedicated tool for shallow lunar subsurface investigations in support of future exploration missions.