A multi-frequency radar sounder for lava tubes detection on the Moon: Design, performance assessment and simulations

Lunar lava tubes have attracted special interest as they would be suitable shelters for future human outposts onthe Moon. Recent experimental results from optical images and gravitational anomalies have brought strongevidence of their existence, but such investigative means have very limited potential for global mapping of lavatubes. In this paper, we investigate the design requirement and feasibility of a radar sounder system specificallyconceived for detecting subsurface Moon lava tubes from orbit. This is done by conducting a complete perfor-mance assessment and by simulating the electromagnetic signatures of lava tubes using a coherent 3D simulator.The results show that radar sounding of lava tubes is feasible with good performance margins in terms of signal-to-noise and signal-to-clutter ratio, and that a dual-frequency radar sounder would be able to detect the majorityof lunar lava tubes based on their potential dimension with some limitations for very small lava tubes havingwidth smaller than 250 m. The electromagnetic simulations show that lava tubes display an unique signaturecharacterized by a signal phase inversion on the roof echo. The analysis is provided for different acquisitiongeometries with respect to the position of the sounded lava tube. This analysis confirms that orbiting multi-frequency radar sounder can detect and map in a reliable and unambiguous way the majority of Moon lava tubes.