| In lunar space,the Moon is a microwave radiation source,and the radiation characteristics of its shallow surface material are directly related to the igneous activity in the deep interior of the Moon.Ming’antu radio heliograph can measure the microwave thermal radiation of the moon.If the observation is calibrated by the cosmic radio source or the sun during the observation period,the absolute calibration of the instrument can be achieved by further utilizing the low-resolution data in the history of lunar microwave radiation measurements,combined with numerical simulation and ground-based experimental measurements.The microwave radiometer carried by Chang’E series satellites has been used to measure the lunar microwave radiation for a long time.A lot of scientific achievements have been obtained in the research of microwave radiometer data.The calibrated radio heliograph lunar microwave detection data and satellite microwave radiometer data are further synergistically analyzed to obtain high-quality and high-resolution microwave thermal radiation data from the front of the moon and even the whole moon,analyze the temperature distribution characteristics of certain depth below the lunar surface,study the characteristics of lunar soil microwave thermal radiation,and solve the key scientific problems of lunar igneous activity and thermal evolution.It is of great scientific significance to further promote the study of lunar igneous activity and thermal evolution history in China.Based on the brightness temperature data of Chang’E-1 and Chang’E-2 microwave radiometers,correlation analysis and regression analysis are carried out from the angles of orbit-raising and orbit-lowering,and corresponding linear fitting formulas are established to fit the data.On this basis,the brightness temperature data are fused and corrected to improve the time resolution of the brightness temperature data.Based on the fused brightness temperature data,a linear fitting model of daytime brightness temperature variation,a linear fitting model of daytime brightness temperature variation with latitude,and a three-dimensional model of daytime brightness temperature variation are established by time angle correction to realize the production of brightness temperature maps at any frequency at any time of the whole month.Based on the radiation transfer model,this paper uses optical reflectance data,thermal radiation data and DEM data to calculate the parameters of the lunar surface,such as absorption coefficient,lunar soil thickness and lunar surface temperature profile model,to simulate the brightness temperature of the lunar surface at any time.The research also establishes a mixed pixel decomposition model,which uses the measured and simulated brightness temperature data of the lunar surface,and simulates the small-scale brightness temperature of the lunar surface with radiation transfer equation.The brightness temperature of each component in the original mixed pixel is separated from the measured brightness temperature data,and the spatial resolution of the brightness temperature data of the microwave radiometer is enhanced-Finally,on the basis of resolution enhancement,the reference of space coordinates including lunar solid coordinate system,lunar geographic coordinate system and instantaneous coordinate system is constructed.The reference frame of lunar space is established,which corresponds to the one-to-one relationship between the lunar surface and the lunar projection plane at observation time.The instantaneous points or pixels on the lunar surface are projected to the two-dimensional instantaneous projection plane quickly,conveniently and strictly.The brightness temperature distribution of the lunar surface within the field of view of ground-based observation at observation time is simulated,and the geometric study of ground-based lunar observation is realized. |
