| Lunar illumination is one of the most important factors in the study of lunar surface evolution,which influences the temperature distribution of the lunar surface.It is one of the most important factors in determining the location of the lunar base as well as the main energy source of human lunar activities in the future.Solar radiation is one of the important factors that affect the space weathering of the lunar surface,and the lunar regolith particles will change in the microstructure in the long-term space weathering,forming the unique nature of lunar regolith.The solar radiation is a significant factor of the interpretation of thermal emission spectra based on remote sensing and the research of lunar thermal evolution model.Therefore,it is of great significance to build an illumination model to study the illumination characteristics of the whole Moon and typical landforms.At present,the study of lunar illumination characteristics mainly focuses on the lunar poles,which lacking of the research on the illumination characteristics of mid-low latitudes and the whole Moon.The study on lunar thermal evolution is also lack of illumination information reference.Building a high-resolution and the whole Moon illumination rate database is one of the urgent problems to be solved in lunar science research.In view of the lack of research on the characteristics of lunar illumination,the main work of this paper is as follows:1.The geometric illumination model is built without considering the terrain as an ideal situation.The calculation results show that elevation of the Sun annularly declines from the direct point to the poloidal at a certain illumination moment,the north and south poles are completely illuminated at certain moments.In a long time range,the lunar illumination rate is between 50% and 58%,the illumination rate of near-side is slightly higher than that of the far-side,and theillumination rate in the high latitudes is higher than that in the middle and low latitudes,the maximum of illumination rate exists near the latitude of 88.5° and the variation period of illumination rate is about19 years.2.Based on the existing two-pole illumination model,the illumination model suitable for the whole Moon is established.Illumination database is created for one year using LOLA data.The results show that the polar regions are the areas with the largest variation in illumination rate.The maximum illumination rate is 91.69% in one year,and there exist permanent shadow regions.The mares in the near-side are the regions with better illumination conditions in the mid-low latitude,while the high-lying ridge at the polar regions have good illumination conditions.3.The illumination characteristics of the polar regions and the mid-low latitudes of the Moon are studied with improved model under the full consideration of the precession period.The results show that:(1)there is no permanent illumination regions in the poles of the Moon and exist the permanent shadow regions,the illumination distribution of the polar regions in half of the precession period is given for the first time.In one precession period,the areas of permanent shadow regions in the north and south poles are 7215km2 and 1683km2,respectively;the maximum of the illumination rates are 91.46% and 90.98%,respectively,and the longest continuous shadow durations are 4.2 days and 5.0 days,respectively,and the longest continuous illumination durations are 231.0 days and 203.9 days,repectively.Compared to the previous research results,the maximum illumination rate in the north pole has increased by 1.41% and the area of permanent shadows in the south pole has increased by 854 km2.(2)Taking the Aristarchus plateau as an example,the illumination characteristics of the mid-low latitudes are studied in detail and the changes of illumination rate of the typical geomorphological points are analyzed.The illumination conditions of the Tycho crater,the Orientale basin,the Marius Hills,the Mare Imbrium and the Mare Moscoviense are briefly described,and suggestions are given for the selection of the study area of landing sites and lunar evolution.In this paper,the illumination distribution at high spatial resolution is given for the first time.This can not only serve as the basisfor the future lunar landing site selection,scientific goal setting and engineering design,but also provide reference for the research of lunar thermal evolution in the future. |
