Optimizing the Coordinates of NGLR-1 Using Lunar Laser Ranging Data

Accurately determining the lunar coordinates of newly deployed corner-cube retroreflectors is not only beneficial for improving the predictive accuracy of laser ranging but also enhances the tracking and targeting capabilities of telescopes. This has significant implications for increasing the success rate and observational efficiency of lunar laser ranging. To verify the initial coordinates of the next-generation monolithic large-aperture lunar retroreflector (Next Generation Lunar Retroreflector, NGLR-1) recommended by the International Laser Ranging Service (ILRS), this study processes and analyzes relevant observational data obtained in the first half of 2025 based on a lunar laser ranging observation model independently developed by Yunnan Observatories. The results show that when using the ILRS-recommended coordinates, the two-way O-C residuals between the observed (O) and calculated (C) distances of NGLR-1 reach the order of hundreds of meters in both mean and root-mean-square values, whereas the corresponding results for the Apollo and Luna series retroreflectors remain at the centimeter level. Furthermore, by performing parameter estimation of the NGLR-1 three-dimensional coordinates using the least-squares method and reprocessing the observational data with the optimized coordinates, the mean and root-mean-square residuals are significantly reduced to the centimeter level, comparable to those of other retroreflectors. In addition, this study demonstrates the feasibility of rapidly determining retroreflector coordinates with a limited number of observations, providing a reference for the quick localization, precise laser ranging observations, and related scientific research of NGLR-1.