Abstract: Water ice exploration is one of the research hotspots in the field of extraterrestrial object sampling and in-situ resource utilization. Ground penetrating radar and in-situ impedance measurement are typical methods based on dielectric characteristics. The water content can be obtained by data inversion of dielectric properties. Due to the special environmental conditions and states of lunar water ice, the existing methods are difficult to apply into lunar water ice exploration. The dielectric properties measurement system under extremely low temperature vacuum was built, and the standard size sample block for dielectric measurement was prepared by using the special procedure with minimal moisture loss. Obtain the 20 Hz-1 MHz dielectric spectrum of water-simulated lunar regolith mixture with a wide temperature range of 100-250 K and water content of 0-10%, analyze the dependence between the dielectric properties, temperature and frequency of water-simulated lunar regolith mixture, fit the function model between water content and dielectric properties under different temperature and frequency conditions, and explore the sensitivity of water content inversion under different temperature and frequency conditions. Depending on the experimental results, a water content inversion method which based on low-frequency real part dielectric properties is proposed for lunar polar regolith exploration. The feasibility and accuracy of the inversion method are verified by experiments.

Key words: lunar water ice, water content, dielectric properties, dielectric relaxation, sensitivity