NASA says laser beams reflected between Earth and Moon, could enhance experiments

Dozens of times over last decade, NASA scientists have launched laser beams at a reflector size of a paperback vel about 240,000 miles (385,000 kilometers) away from Earth. US ncy anunced Tuesday, in collaboration with ir French colleagues, that y received signal back for first time, an encouraging result that could enhance laser experiments used to study physics of universe.

reflector NASA scientists aimed for is mounted on  Lunar Reconnaissance Orbiter (LRO), a craft that has been studying Moon from its orbit since 2009. One reason engineers placed reflector on LRO was so it could serve as a pristine target to help test reflecting power of panels left on Moon’s surface about 50 years ago. Scientists have been using reflectors on Moon since Apollo era to learn more about our nearest neighbor.

NASA says it's a fairly straightforward experiment: Aim a beam of light at reflector and clock amount of time it takes for light to come back. Decades of making this one measurement have led to major discoveries.

One of biggest revelations is that Earth and Moon are slowly drifting apart at rate that fingernails grow — 1.5 inches (3.8 centimeters) per year. This widening gap is result of gravitational interactions between two bodies.

“w that we’ve been collecting data for 50 years, we can see trends that we wouldn’t have been able to see orwise,” said Erwan Mazarico, a planetary scientist from NASA’s Goddard Flight Center who coordinated LRO experiment that was described on August 7 in journal Earth, Planets, and .

“Laser-ranging science is a long game,” Mazarico said.

But if scientists are to continue using surface panels far into future, y need to figure out why some of m are returning only a 10th of expected signal.

re are five reflecting panels on Moon. Two were delivered by Apollo 11 and 14 crews in 1969 and 1971, respectively. y are each made of 100 mirrors that scientists call “corner cubes,” as y are corners of a glass cube; benefit of se mirrors is that y can reflect light back to any direction it comes from. Ar panel with 300 corner cubes was dropped off by Apollo 15 astronauts in 1973. Soviet robotic rovers called Lukhod 1 and 2, which landed in 1970 and 1973, carry two additional reflectors, with 14 mirrors each. Collectively, se reflectors comprise last working science experiment from Apollo era.

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What do researchers aim to achieve?

By measuring how long it takes laser light to bounce back — about 2.5 seconds on aver  — researchers can calculate distance between Earth laser stations and Moon reflectors down to less than an inch, or a few millimeters. This is about thickness of an orange peel.

Magnetic measurements of Moon samples returned by Apollo astronauts revealed something one had expected given how small Moon is: our satellite had a magnetic field billions of years ago. Scientists have been trying to figure out what inside Moon could have generated it.

Laser experiments could help reveal if re’s solid material in Moon’s core that would’ve helped power w-extinct magnetic field. But to learn more, scientists first need to kw distance between Earth stations and Moon reflectors to a higher degree of accuracy than current few millimeters.

“ precision of this one measurement has potential to refine our understanding of gravity and evolution of solar system,” said a Goddard planetary scientist who helped design LRO’s reflector.

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