基于嫦娥微波亮温数据和理论模型的月表浅层石块丰度反演研究

Knowledge of the rock abundance in the lunar subsurface is significantly important for the understanding of overturns, formation and regression of the lunar craters. A new chance to obtain the global quantitative rock abundance of the Moon is now provided by the huge brightness temperature (TB) data observed by the microwave radiometers onboard the Chang'E mission. However, there are significant differences between Chang’E-1 and Chang’E-2 datasets, and the thermal anomalies in the data still need explanations. Besides, a better TB model including the rock effect should be founded to improve our initial model. These three issues should be solved before the inversion of rock abundance. This project focus on three aspects: (1) we plan to improve the physical models of the lunar surface based on the Apollo in-situ data and Diviner infrared radiometer data, and then estimate the dependence of physical temperature and emissivity on rocks to improve the initial rock TB model, which will also be used to interpret the thermal anomalies in the Chang'E microwave data. (2) The data recalibration will be carried out between Chang'E-1 and Chang'E-2 datasets from two aspects: theoretical model and the radiometry mechanism. (3) After that, we can obtain the inversion result of lunar rock abundance with a suitable method, based on the calibrated microwave data and the established TB model. This result could be applied to analyze the overturns, formation and regression of the lunar craters.

月表浅层纵向的石块丰度对于研究月表撞击坑的成坑机理与后期退化、月表浅层土壤的翻耕次数都有重要指导意义。嫦娥探月工程微波辐射计观测的全月亮温数据，为研究全月表浅层的纵向石块丰度定量反演提供了新机遇。但是，嫦娥一号和二号两套亮温数据存在较大差异；亮温图中存在未解释的热异常点即温度明显高于或低于周边区域的亮温；月表微波亮温模型的改进工作仍然迫切。针对这三个问题，本项目拟开展以下研究：（1）基于Apollo地区就位观测热流数据和Diviner红外辐射计观测数据，完善现有的月表物理参数模型，通过重新评估石块对月表浅层物理温度和发射率的影响，改进亮温模型，进而对全月微波亮温图中的热异常进行解译。（2）从辐射计探测机理和理论亮温模型两个方面对嫦娥一号和二号两套数据的绝对亮温进行校正。（3）采用一定的反演方法对月表浅层的石块含量分布进行估计；将反演的石块丰度用来分析月表浅层的地质演化过程。

嫦娥探月工程微波辐射计观测的全月亮温数据，为研究全月表浅层的纵向石块丰度定量反演提供了新机遇。为此，本项目已开展以下三方面的研究：1）在原有的混合层物理参数的基础上，改进了原有的混合介电常数模型和热传导模型；改进的包含石块影响的月表微波亮温模型不仅能够与嫦娥二号观测的亮温匹配，还能够匹配月球勘探者号携带的Diviner红外辐射计观测数据。此外，结合改进型的亮温模型对月球永久阴影区嫦娥二号微波辐射计数据异常季节变化也做了相应的解释。2）基于改进的亮温模型，结合辐射计的两点定标方程和辐射计的探测机理，推导出最终的定标亮温由冷空与观测天线的传输系数之比和月壤的介电损耗两个参数来确定。结合嫦娥四个通道的亮温，通过使模拟亮温与标定的亮温差异最小估算出合理的传输系数，并且给出13个低纬度地区的整点纬度的传输系数。3）在前两项工作的基础上已完成对月球典型撞击坑的石块丰度反演。结果表明：次表层的石块丰度大于或等于月表的岩石丰度。