© GGOSLLR – Lunar Laser Ranging
Lunar Laser Ranging applies the same principle as SLR but measures the distance between Earth-based observatories and retroreflectors placed on the Moon by the Apollo and Lunokhod missions. Because of the much greater distance, the returning light signals are extremely weak, making LLR one of the most challenging measurement techniques in geodesy. The long-term LLR data record, spanning more than five decades, provides valuable insights into the dynamics of the Earth–Moon system, such as the Moon’s recession and variations in Earth’s rotation. LLR also serves as an important tool for testing theories of gravitation and improving the celestial and terrestrial reference frames.
