Design And Preliminary Experiment Of Electric Field Sensors For Martian Atmosphere

Mars is a red planet which is most similar to Earth in our solar system.In recent years the Mars exploration has become one of the hottest topics in planetary science.The surface environments of Mars have a huge difference,with a thin atmosphere,strong cosmic radiation,high ionization levels and frequent dust storms,to Earth.Large-scale and frequent dust phenomena(e.g.dust devil and dust storms)on Mars lead to the global atmospheric electrical phenomena and atmosphere electric fields on Mars.The unique atmospheric composition,gas pressure and ionizations of Mars raise present challenges for the design and calibration of Mars Atmospheric Electric Field sensor.The measurement of the Martian atmospheric electric field is of great scientific significance.As the Martian atmospheric electric field is propitious the formation of some Martian oxidative materials.Modelling analysis suggests that the Martian electric field enhances some ultraviolet(UV)photochemical reactions in the Martian atmosphere.Dust storm electric fields lead to dark discharges,glow discharges and even lightning(no reported observations),which are possible cause of the production of strong oxidizing materials on the Martian surface peroxide,ozone,chlorate and hydrogen chloride,and methane in the atmosphere.Therefore,the understanding of the mechanism of the generation and evolution of the electric field of the Martian atmosphere is of great scientific significance for the origin of the oxidative nature of the Martian surface environment,the interaction between the atmosphere and surface materials,and the exploration of biological information on the surface.Since there are still no successful in situ measurements of the Martian atmospheric electric field,the development of instruments for the Martian atmospheric electric field and the related research on its measurement methods are groundbreaking.This work develops and calibrates a Mars atmospheric electric field measurement system aim to in-situ electric field measurement on Martian surface,and conducts a series of experiments to simulate dust storm electric field measurements.(1)According to comparative analysis based on Martian environment,a suitable measurement method should first be developed for Martian atmospheric electric field measurement.Mars has a harsh,and even unknown environment.Considering that the payload needs to be shock resistant,low weight/volume,low energy consumption and able to work in harsh environment,conventional space atmosphere electric field measurement methods such as conductor surface binding method,dual-probe method and particle drift method are not suitable for Mars exploration.The single-probe method was finally selected by comparison for the dust storm electric field measurement.(2)Mars atmospheric electric field measurement sensor is then designed and developed.In this paper,a copper hollow sphere was selected as the probe for electric field measurement,and a signal acquisition system is used to collect,convert and transmit the recorded signal to analogue and digital data.An upper computer software is written to display and store images of the collected signals in real time.(3)Mars atmospheric electric field measurement sensor was calibrated on the ground using the single-probe method.According to the detection principle of the atmospheric electric field meter,the coupling resistance and capacitance between the measuring-probe and the Martian atmosphere environment are simulated by using the equivalent resistance and capacitance as same as that of the electric field meter in the actual detection process in space,Therefore,the instrument can be calibrated.(4)Ground-based dust storm was simulated for the electric field measurement.In order to investigate the influencing factors of the atmospheric electric field during dust storms and to verify the performance of this system,dust storm simulation experiments were designed.The voltage signals of the atmospheric electric field in the simulated dust storm were detected using the atmospheric electric field meter developed in this work,and also compared with the recorded signals of a commercial digital multimeter.Based on the self-made measure system of Martian atmospheric electric field and simulated dust storm experiment,the results showed that the intensity of the atmospheric electric field of a dust storm dependent on many factors such as wind speed,dust particle type,dust storm particle size,etc.With the fast sampling aped of 256 kHz,the Martian Atmosphere Electric Field Meter reaches has the advantage of high sensitivity and fast sampling speed.The development of this system provides the hardware and methodological basis for the measurement of the electric field of the Martian atmosphere in future.