![]() ![]() We have learned some fascinating things about the moon because of this clever device, such as:ġ) The moon is moving away from Earth at a rate of 3.8 cm per year.Ģ) The force of gravity is extremely stable, having changed less than 1 part per billion since the experiments began. The reflectors are located at specific points on the moons surface so measurements can be taken at various points in the lunar cycle. Because the mirrors are ‘ corner-cube reflectors’, they redirect the pulse and send it straight back to where it came from. Large LRAs were placed on the Moon by the Apollo astronauts and the Russian lunar landers and have been used for lunar laser ranging from Earth over the past 50 years 2-4. So, how does this work? A laser pulse shoots out of a telescope (here on earth) and hits this array. Small laser retro-reflector arrays (LRA) have been used for laser ranging to Earth-orbiting satellites from ground stations. The Soviets also have a set of mirrors parked onboard the Lunokhud 2 moon rover (which landed in 1973) in the Sea of Serenity. In addition to the mirror array left at the Sea of Tranquility by Apollo 11, similar arrays were also left at Fra Mauro (Apollo 14) and Hadley Rille (Apollo 15). We are also able to check Einstein’s theory of gravity (better known as general relativity). This is a wonderful way to learn about the moon’s orbit and to test theories of gravity.” Explains University of Maryland physics professor, Carroll Alley. “Using these mirrors, we are able to ‘ping’ the moon with laser pulses and measure the Earth-moon distance very precisely. The orbiter has been observing the moon since 2009, and its reflector is a smaller version of reflector panels placed on the lunar surface during the Apollo 11, 14 and 15 landings on the. The Lunar Laser Ranging Retroreflector Array is a 2-foot wide panel with 100 mirrors pointing at Earth. As a graduate student at Princeton University in the late 1950s, he had written a paper titled A Proposed Lunar Package: A Corner Reflector on the Moon, envisioning a durable, lightweight. To this day, 43 years later, it is the only Apollo science experiment still running. So, one day, when there are tourists on the moon looking at that footprint, or at the first flag planted on the moon, will they notice something 100 feet away that was also left behind? The Lunar Laser Ranging Retroreflector Array was left on the surface of the moon during Buzz Aldrin’s and Neil Armstrong’s final moonwalk. The use of lasers with pulse-lengths of less than 1 nsec is expected to give an accuracy of 2 to 3 cm in the next few years. This corresponds to 15 cm in the one-way distance. There are few moments and pictures from the moon missions that live on in the public eye Neil Armstrong’s footprint, the US flag being planted on the moon, the lunar rover, “That’s one small step for man, on giant leap for mankind” – these are moments, pictures, videos, and sayings that will live on forever. The lunar ranging measurements now being made at the McDonald Observatory have an accuracy of 1 nsec in round-trip travel time. The Lunar Laser Ranging Experiment from the Apollo 11 mission.
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