月基观测地球辐射平衡探索性研究

Understanding the balance between solar radiation and earth's outgoing radiation at top of atmosphere （TOA） is critical to the climate change study. Although the data from a single existing radiation measurement equipment are of sufficient precision, the uncertainty of TOA net flux derived from the space observation system is still unsatisfactory due to the the limitation of low earth orbit satellite in field of view, viewing angle, longevity and stability. The Moon is a stable and longstanding platform. Proposing a sensor on the moon will bring about overlaps in time and space between existing sensors and moon-borne one. Thus, the latter is capable to be the calibration reference of different sensors as well as the complementary to existing system. In this program, the simulative and analytical method is supposed to help understand the relationship between moon-borne observed parameters and earth radiation balance parameters, and to study some key scientific issues of lunar observatory construction. The main research content includes: Research on the variation of the lunar surface radiation and lunar surface temperature of different positions, research on the earth's reflectance variation on the moon direction, research on the senstivity of lunar surface radiation and lunar surface temperature to earth's reflectance, instrument parameter design and observotary location.

理解大气上界太阳辐射和地球辐射支出之间的平衡对于研究地球气候变化至关重要。虽然目前单个仪器测辐射测量数据已经十分精确，但是由于低轨卫星视角视野受限，且不是长期稳定的观测平台，因此卫星观测数据反演获得大气上界净辐射通量的不确定性还比较大。月球是一个长期稳定的平台，如果在月球上进行观测，可以在时空上与已有传感器形成重叠，既可以作为不同传感器之间校正的参考，也可以成为现有观测系统的重要补充。本项目拟通过模拟和分析的手段，获取月基观测参数与地球辐射平衡参数的相关关系及规律性认识，研究月基观测站建设的一些关键科学问题。主要研究内容包括：研究不同位置月面辐射与月面温度的变化规律、研究地球在月球方向上反射率的变化规律、研究月面辐射和月面温度对地球反射率变化的敏感性以及月基观测地球辐射平衡仪器参数设计与观测站位置选择。

本项目主要进行了以下创新性研究：（1）建立了精确的月基对地观测几何模型，对光行差和光时效应进行了校正。（2）对月表接收到的地球发射辐射进行了研究，发现月面接收到的地球反射辐射受地相角（0-1之间）进行周期变化；不同月面位置接收地球辐射的入射角不同，总体看来月面中心附近接收能量较多，而离中心越远，接收能量越少；月表温度主要由太阳辐射控制，地球反射辐射影响较小，很难从月面温度中获取关于全球表面的细节信息。（3）形成月基观测地球辐射平衡的整体思路，明晰了月基观测地球辐射平衡的科学问题，形成了详细可行的观测整体方案，初步设计了相关传感器参数，并给出了后续研究的主要方向和难点。本研究部分内容被嫦娥后续计划科学论证所采纳。