Early ranging Results to the Next Generation Lunar Reflectometer in Mare Crisium

EARLY RANGING RESULTS TO THE NEXT GENERATION LUNAR RETROREFLECTOR D. G. Currie.1, D. Baden1, D. D. Wellnitz1, C. S. Wu1, G. O. Delle Monache2, B. B. Behr1, J. G. Williams3, D. H. Boggs3, W. Kleyman1, L. Wise1, R. C. Carter1, N. Russo,1 , S. Dell’Agnello2, C. C. Davis, P. S. Russ1, L. Putnam and M. Peckerar1. 1University of Maryland, College Park, MD, USA [email protected] 2INFN/LNF, Frascati, Latium, Italy Giovanni.DelleMona[email protected]nfn.it NASA Jet Prolusion Laboratory, Pasadena, CA USA Introduction: On the 3rd and the 4th of March 2025, the Lunar Laser Ranging Observatories (LLROs) in Grasse, France and Wettzell, Germany and later the APOLLO LLRO obtained hundreds of successful range measurements to our Next Generation Lunar Reflector (NGLR-1) on the Moon in Mare Crisium. The launch was performed by SpaceX’s Falcon9 rocket at 1:11 am on the 15th of January from the Kennedy Space Center. NGLR-1 was carried to the Moon by Firefly Aerospace’s Blue Ghost lander. The Blue Ghost successfully deployed NGLR-1 on the Moon on the 2nd of March at which time the LLROs began Lunar Laser Ranging (LLR) operations to search for laser returns from NGLR-1 on the Moon. Figure 1 NGLR-1 as delivered to Firefly Aerospace for mounting on the Blue Ghost lander. The objective of the NGLR-1 project, and of the later deployments of NGLR-2 and NGLR-3, is to greatly improve the precision (the standard deviation of the magnitude of the residuals) and accuracy of the LLR measurements. The analysis of preliminary data obtained during the first month of operation indicate the ranging precision and the relative local accuracy objectives have been achieved. These objectives and analysis of the early results obtained during the initial test phase [1] will be discussed. The improved precision in LLR provided by the NGLR-1 provides two effective advantages with respect to ranging to the retroreflector arrays. The uncertainty of the average magnitudes of the residuals in a Normal Point Interval (NPI) depends upon the square root of the precision. This means that NGLR-1 will improve the precision of the magnitude of the average of the returns in an NPI to a factor up to four with respect to the precision for the same number of returns from the Apollo 15 retroreflector array. The second advantage is the reduction of the impact of the noise from the sun-lit Moon and/or the sun-lit Earth’s atmosphere. This advantage depends linearly on the dispersion, so the ranging to the NGLR-1 can improve the detectability of returns by a factor up to17 with respect to the detectability for the Apollo 15 array. In order to determine the accuracy of science results that may be expected due to the improved precision, simulations of a 6-year mission addressing the expected improvement in the accuracy of the scientific results were performed with Jim Williams of JPL [2]. This analysis indicates that the scientific results, beginning when all three NGLRs are deployed, may be expected to provide an order of magnitude improvement in the accuracy of the various scientific results as compared to the current scientific accuracy that has been obtained using the Apollo Retroreflector Arrays (ARAs) and the Lunokhod retroreflector arrays. The analysis using the latter has already discovered the liquid core of the Moon, obtained the best estimate of any possible deviations of the Weak Equivalence Principle, provided the best evaluation of the temporal and spatial changes in Big G, and provided many of the best tests of General Relativity. A brief review of the operational issues and design history of NGLR-1 [3,4] will be compared to our Apollo 11 Retroreflector Array. NGLR-2 is being prepared for deployment near the south pole during the Artemis III mission. A candidate configuration for the deployment is indicated in figure 2. Figure 2 Thermal model of NGLR-2 in our SOOTO [] simulation suite of programs. This is the configuration for the Artemis III mission covering the various candidate landing sites. The current results of the preliminary analysis and background material on our NGLR project may be found on our draft site at https://www.physics.umd.edu/nglr/. This is the start of a new era in lunar physics, astrophysics, and the study of General Relativity. References: [1] The Objectives NGLR-1 Project https://www.physics.umd.edu/nglr/ [2] Williams J. G. Boggs D. H. Currie D. G. (2022) Next-generation laser ranging at lunar geophysical network and commercial lander payload service sites The Planetary Science Journal 3 (6), 136-150 [2] Currie D. G. Dell’Agnello S. Delle Monache G. O. (2013) A lunar laser ranging retroreflector array for the 21st century Acta Astronautica 68 (7-8), 667-680. [4] A general description of the NGLR Project https://www.physics.umd.edu/nglr/ [5] Description of the SOOTO Suite of Simulation programs https://www.physics.umd.edu/nglr/ Acknowledgements: We are pleased to acknowledge the contributions of the APOLLO LLRO at Apache Point, NM, USA, the MeO LLRO in Grasse, France, the Wettzell LLRO in Wettzell, Germany and the Matera LLRO in Matera, Italy that are the source of the ranging data, the NASA/LSSO and NASA LSI programs that supported the development of the NGLR, and NASA/MSFC that supported the fabrication of NGLR-1 and Firefly Aerospace, whose lander carried NGLR-1 to the Moon and the NGLR team for the analysis of this data.