Lunar Laser Ranging Retroreflectors: Velocity Aberration and Diffraction Pattern

The Lunar Laser Ranging (LLR) retroreflector arrays have been on the Moon for one-half century. During that time the laser range accuracy has improved by a factor of 100. Consequently, the science results have also improved by orders of magnitude. New retroreflectors are scheduled to go to the Moon on Commercial Lander Payload Services missions and the Lunar Geophysical Network mission. The new retroreflectors are single 10 cm corner cube retroreflectors that will not spread the laser pulse during reflection like the existing arrays do. Due to the orbital and Earth rotational speeds, there is a velocity aberration of 0.7" to 1.5". Larger corner cubes require attention to ensure that the spread of possible velocity aberration displacements be optimally contained within the diffraction pattern. The diffraction pattern can be changed by making one of the rear dihedral angles slightly different from 90º. Improvements in the equipment at the LLR stations and improvements in the data analysis software are also desirable. Future possibilities are described.

月球激光测距（Lunar Laser Ranging, LLR）后向反射器阵列已部署于月球长达半个世纪。在此期间，激光测距精度提升了100倍，相关科学研究成果也随之提升了数个数量级。新型后向反射器将通过商业着陆器有效载荷服务任务与月球地球物理网络任务部署至月球。该新型反射器为单个10厘米角锥后向反射器（corner cube retroreflectors），其不会像现有阵列那样在反射过程中扩散激光脉冲。受月球轨道运动与地球自转速度的影响，存在0.7角秒至1.5角秒的速度像差。尺寸更大的角锥反射器需要进行针对性优化，以确保可能的速度像差位移可被最优地限制在衍射图样范围内。通过将其中一个后部二面角调整为略微偏离90度，即可改变衍射图样。此外，月球激光测距站的设备升级与数据分析软件优化同样极具必要性。本文还对未来的研究可能性进行了阐述。