Lunar Exosphere Density Inversion And Its Spatial-Temporal Variation Analysis Based On LADEE Data

Experiencing decades of efforts, lunar exploration has accumulated a large number of data which is obtained through remote sensing detection methods. The successful implementation during the period of Apollo provides a direct measurement of the samples and precious data for further understanding the moon. The sensor that brought to the moon surface by Apollo astronauts detect low atmospheric pressure and detect He and Ar atoms. In 1985, Na and K were found. In the solar system, Na and K element are not very rich, but easy to detect relatively, because they can scatter light effectively. They are not the major component of the moon’s atmosphere, but they are the good "tracer" elements of those may exist but hard to detect gas. Therefore, the study of the lunar Na and K can provides new ideas for the future detection and research of the lunar exosphere. And the origin and disappearance process of the lunar exosphere is of great significance to the study of the moon.As there are no specialized probe satellites that explore the lunar exosphere in the past, and the abundance of exosphere detected by Apollo is limited, the exosphere density may not be able to achieve the accurate calculation. In this paper, using radiation data of UVS aboard on the LADEE satellite which dedicated to study exosphere and dust of the moon to inverse Na and K density directly, and using the abundance of Ar, He and Ne data detected by NMS that also carrying on the LADEE satellite to study the Spatial-Temporal variation analysis of lunar exosphere.This paper selects Chanberlain model which has been applied to the moon to inverse the Na and K density of lunar exosphere. Generally the model of lunar exosphere analysis is based on Chanberlain model, especially the symmetrical distribution of gas around the world. The calculation of column density and vertical intensity profile is based on maxwell’s velocity distribution equation. The advantage of this method is that it considered the gravity changes with height. Considering the source process of the moon’s atmosphere is very complex, this paper expounded the process of Na source in detail, and introduced the using conditions of Chanberlain model. We obtained the density value of Na and K by Chanberlain method near the equator. By comparing atmospheric density of Na and K value near the equator with the traditional experience, we got the conclusion:the results of Chanberlain model is very close to experience values. Then we got the Spatial-Temporal variation of Na and K density using the model from November 2013 to April 2013.The abundance distribution of Ar, He and Ne component of the lunar atmosphere shows the rule of the peaks and troughs cycles which influenced by temperature and strong diurnal variation. In the latitude distribution, the abundance increased along with the increase of north latitude, and the abundance of north latitude is higher than the south latitude. In the longitude distribution, the abundance appears similar to the distribution of sinusoidal variation characteristics. What is worth noting is the abundance changing with longitude appears abnormal when science task start and end in November 2013 and April 2014. The reason may be the observation time of these two months is so less that the calculation of the results from the average has no representative.