Study On Measurement Method Of Water-ice Dielectric Properties Of Lunar Soil For In Situ Penetration

With the rising of lunar water ice exploration,how to use the in-situ method to detect water ice and its occurrence state is a hot spot for future exploration of extraterrestrial bodies.Based on the comprehensive analysis of the dielectric properties of lunar soil,the current status of lunar soil water ice detection,the case of in-situ detection and the measurement method of dielectric properties,a method of measuring the dielectric properties of lunar soil water ice mixture was proposed to characterize the water-ice properties of lunar soil mixture.This paper focuses on two parts: the basic dielectric properties of lunar soil water-ice mixed media and their influence rules,and the dielectric properties method for in-situ contact detection.These studies lay a foundation for further design of sensors,realization of in situ measurement and inversion of water ice content.The self/mutual impedance probe method has been the first choice for the exploration of extraterrestrial bodies due to its great advantage of being suitable for in-situ measurement.In this paper,based on the analysis of in-situ measurement cases at home and abroad,in order to o btain the most suitable sensors for in-situ detection,the basic dielectric properties of the waterice mixture of simulated lunar soil were obtained by studying the standard dielectric property measurement method and its influence law.In this paper,the effects of deep and low temperature on the dielectric properties of water and ice mixture in simulated lunar soil were studied.After comprehensive comparison of various laboratory configurations,this paper completed the design and manufacturing of measuring fixture with protective electrode based on parallel plate method.The established deep and low temperature measurement system was used to measure the dielectric characteristics of the mixture samples,and the sample database of "water ice content-measurement frequency-temperature" was obtained,which provided the design basis and verification reference for further sensor designDue to the great advantage of being suitable for in-situ measurement,self/mutual impedance probe has become the preferred measurement method for the detection of extraterrestrial bodies.After analyzing the origin and development of impedance measurement theory,this paper further explains the impedance theory from the point of view of in-situ measurement,and studies the relationship between the real part of impedance,capacitance and dielectric coefficient.The analytical model of capacitance based on element integration method and the modified model of capacitance based on numerical simulation lay a theoretical foundation for the design and engineering application of capacitance sensing element.In view of the actual environment of in-situ measurement,this paper proposes three electrode induction element configurations for the measurement of dielectric characteristics.COMSOL finite element simulation software is used to analyze and compare the evaluation indexes under each configuration in detail.Finally,the linear cone configuration probe is selected as the suitable scheme for in-situ measurement.The detailed design of the scheme was carried out,and the mechanism and implementation of the sensor were explained,the structural parameters were optimized,and the development of the principle prototype was completed.The environment of the verification test is set up,and the measuring circuit is designed based on the principle of impedance measurement.The water ice samples of simulated lunar soil with different water ice contents were tested and verified.The experimental results were compared with the experimental resu lts of simulating the dielectric properties of the lunar soil water-ice mixture,and the analytical model of capacitance and its modified model were verified through the experiments.The preliminary design of the in-situ measurement method was realized.