月球激光测距发射的激光为圆环光束，它的测距效果以及获得最多回波光子数的激光发射方式没有得到深入研究，导致月球激光测距的回波光子数、跟踪偏差容许量与理论及计算结果相差两较大。本项目基于标衍射原理，通过理论分析、数值模拟以及实验室测量产生机制相同的小口径激光束等方法，研究月球激光测距发射的圆环激光束传输特性；然后从激光束特性角度入手，探寻计算回波光子数和跟踪偏差容许量更贴近实际的理论，以及兼顾激光发散角与能量损失，进一步提高月球激光测距回波光子数的激光发射方式；最后将研究成果在云南天文台月球激光测距实践中应用，提高月球激光测距回波率。本项目研究可提升我国月球激光测距技术水平，为我国空间基准等重点科研项目及相关科学研究提供技术支持。

The laser transmitted during Lunar Laser Ranging (LLR) is a circular beam. As its ranging effect and the best transmitting method to obtain the maximum number of photons have not been studied thoroughly, the number of echo photons and the tracking deviation tolerance are quite different from the theoretical and calculated results in LLR experiments. Based on the principle of standard diffraction, this project is aimed to study the transmission characteristics of circular laser beams transmitted in LLR by means of theoretical analysis, numerical simulations and laboratory measurements of small-caliber laser beams with the same mechanism. Then, from the view of laser beam characteristics, a more practical theory for calculating the number of echo photons and the tracking deviation tolerance is to be explored, and laser transmitting methods, which takes laser dispersion angle and energy loss into account, is to be studied to further improve echo-photon number in LLR experiments. Finally, the research results will be applied in Yunnan Observatory's LLR practice to raise LLR echo rate. The research of this project can improve domestic LLR technology level and provide technical support for key scientific research projects such as space benchmark and related studies in China.