Space

NASA Launched Laser Beams at the Moon – For the First Time, They Received a Signal Back

Lunar Reconnaissance Orbiter Artist Concept

Artist’s rendering of NASA’s Lunar Reconnaissance Orbiter. Credit: NASA’s Goddard Space Flight Center

Dozens of times over the last decade NASA scientists have launched laser beams at a reflector the size of a paperback novel about 240,000 miles (385,000 kilometers) away from Earth. They announced today, in collaboration with their French colleagues, that they received signal back for the first time, an encouraging result that could enhance laser experiments used to study the physics of the universe.

The reflector NASA scientists aimed for is mounted on the Lunar Reconnaissance Orbiter (LRO), a spacecraft that has been studying the Moon from its orbit since 2009. One reason engineers placed the reflector on LRO was so it could serve as a pristine target to help test the reflecting power of panels left on the Moon’s surface about 50 years ago. These older reflectors are returning a weak signal, which is making it harder to use them for science.

Scientists have been using reflectors on the Moon since the Apollo era to learn more about our nearest neighbor. It’s a fairly straightforward experiment: Aim a beam of light at the reflector and clock the amount of time it takes for the light to come back. Decades of making this one measurement has led to major discoveries.

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

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

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

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

A close-up photograph of the laser reflecting panel deployed by Apollo 14 astronauts on the Moon in 1971. Credit: NASA

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

Some experts suspect that dust may have settled on these reflectors over time, possibly after getting kicked up by micrometeorite impacts to the Moon’s surface. As a result, the dust could be blocking light from reaching the mirrors and also insulating the mirrors and causing them to overheat and become less efficient. Scientists hoped to use LRO’s reflector to determine if that’s true. They figured that if they found a discrepancy in the light returned from LRO’s reflector versus the surface ones, they could use computer models to test whether dust, or something else, is responsible. Whatever the cause, scientists could then account for it in their data analysis.

Despite their first successful laser-ranging experiments, Mazarico and his team haven’t settled the dust question just yet. The researchers are refining their technique so they can collect more measurements.

The Art of Sending a Photon Beam to the Moon … and Getting it Back

In the meantime, scientists continue to rely on the surface reflectors to learn new things, despite the weaker signal.

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

Besides the Earth-Moon drift, such measurements over a long period of time and across several reflectors have revealed that the Moon has a fluid core. Scientists can tell by monitoring the slightest wobbles as the Moon rotates. But they want to know whether there’s a solid core inside of that fluid, said Vishnu Viswanathan, a NASA Goddard scientist who studies the internal structure of the Moon.

“Knowing about the Moon’s interior has bigger implications that involve the evolution of the Moon and explaining the timing of its magnetic field and how it died out,” Viswanathan said.

This photograph shows the laser-ranging facility at the Goddard Geophysical and Astronomical Observatory in Greenbelt, Md. The facility helps NASA keep track of orbiting satellites. Both beams shown, coming from two different lasers, are pointed at NASA’s Lunar Reconnaissance Orbiter, which is orbiting the Moon. Here, scientists are using the visible, green wavelength of light. The laser facility at the Université Côte d’Azur in Grasse, France, developed a new technique that uses infrared light, which is invisible to the human eye, to beam laser light to the Moon. Credit: NASA

Magnetic measurements of Moon samples returned by Apollo astronauts revealed something no one had expected given how small the Moon is: our satellite had a magnetic field billions of years ago. Scientists have been trying to figure out what inside the Moon could have generated it.

Laser experiments could help reveal if there’s solid material in the Moon’s core that would’ve helped power the now-extinct magnetic field. But to learn more, scientists first need to know the distance between Earth stations and the Moon reflectors to a higher degree of accuracy than the current few millimeters. “The precision of this one measurement has the potential to refine our understanding of gravity and the evolution of the solar system,” said Xiaoli Sun, a Goddard planetary scientist who helped design LRO’s reflector.

Getting more photons to the Moon and back and better accounting for ones that are lost because of dust, for instance, are a couple of ways to help improve precision. But it’s a herculean task.

Consider the surface panels. Scientists must first pinpoint the precise location of each one, which is constantly changing with the Moon’s orbit. Then, the laser photons must travel twice through Earth’s thick atmosphere, which tends to scatter them.

Astronaut Edwin E. Aldrin Jr., lunar module pilot, deploys two components of the Early Apollo Scientific Experiments Package on the surface of the Moon during the Apollo 11 extravehicular activity in 1969. A seismic experiment is in his left hand, and in his right is a laser-reflecting panel. Astronaut Neil A. Armstrong, mission commander, took this photograph. Credit: NASA’s Johnson Space Flight Center

Thus, what begins as a light beam that’s about 10 feet, or a few meters, wide on the ground can spread out to more than 1 mile, or 2 kilometers, by the time it reaches the Moon’s surface, and much wider when it bounces back. That translates to a one-in-25-million chance that a photon launched from Earth will reach the Apollo 11 reflector. For the few photons that manage to reach the Moon, there’s an even lower chance, one in 250 million, that they will make it back, according to some estimates.

If those odds seem daunting, reaching LRO’s reflector is even more challenging. For one, it is a 10th the size of the smaller Apollo 11 and 14 panels, with only 12 corner cube mirrors. It’s also attached to a fast-moving target the size of a compact car that’s 70 times farther away from us than Miami is from Seattle. Weather at the laser station impacts the light signal, too, as does the alignment of the Sun, Moon and Earth.

That’s why despite several attempts over the last decade NASA Goddard scientists had been unable to reach LRO’s reflector until their collaboration with French researchers.

Their success thus far is based on using advanced technology developed by the Géoazur team at the Université Côte d’Azur for a laser station in Grasse, France, that can pulse an infrared wavelength of light at LRO. One benefit of using infrared light is that it penetrates Earth’s atmosphere better than the visible green wavelength of light that scientists have traditionally used.

But even with infrared light, the Grasse telescope received only about 200 photons back out of tens of thousands of pulses cast at LRO during a few dates in 2018 and 2019, Mazarico and his team report in their paper.

It may not seem like much, but even a few photons over time could help answer the surface reflector dust question. A successful laser beam return also shows the promise of using infrared laser for precise monitoring of Earth’s and Moon’s orbits, and of using many small reflectors — perhaps installed on NASA’s commercial lunar landers — to do so. This is why some scientists would like to see new and improved reflectors sent to more regions of the Moon, which NASA is planning to do. Others are calling for getting more facilities around the globe equipped with infrared lasers that can pulse to the Moon from different angles, which can further improve the precision of distance measurements. New approaches to laser ranging such as these can ensure that the legacy of these fundamental studies will continue, scientists say.

Reference: “First two-way laser ranging to a lunar orbiter: infrared observations from the Grasse station to LRO’s retro-reflector array” by Erwan Mazarico, Xiaoli Sun, Jean-Marie Torre, Clément Courde, Julien Chabé, Mourad Aimar, Hervé Mariey, Nicolas Maurice, Michael K. Barker, Dandan Mao, Daniel R. Cremons, Sébastien Bouquillon, Teddy Carlucci, Vishnu Viswanathan, Frank G. Lemoine, Adrien Bourgoin, Pierre Exertier, Gregory A. Neumann, Maria T. Zuber and David E. Smith, 6 August 2020, Earth, Planets and Space.
DOI: 10.1186/s40623-020-01243-w

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  • This story is misleading. NASA had announced the transmission and receipt of the largest amount of data ever reflected of off one of the lunar mirrors back in the early 2000s (around 2007-2009). The story read the data received was without any data loss. Stop relying on Google news exclusively for your scientific research!

  • This headline is terrible. Launch a laser? They've been bouncing lasers off of reflectors since they PUT THEM THERE. Do better

  • There was an episode of the sitcom 'The Big Bang theory' about that a few years ago. They went to the roof ans sent a laser beam to the moon. The same procedure.

  • Fell for the clickbait, but ended up reading the entire article because of the interesting information. I couldn't find an author name, but whoever wrote this did a really good job. It was an easy read, which can be hard to find with science articles.

  • If you read an understand the Holy Bible then you will ALWAYS see why Lucifer has many names and why he became the serpant, the great dragon, Satan and the devil. The 🌙 and the 🌞 is not outside of what Christ created. The imagery of these Satanist is very deceiving to those who lack biblical understanding. No man has NEVER been on the moon but yet they expect you to believe it. This is why many people are like their father the devil because he was a LIAR and the father of it. When we believe these LIARS then many become like him. We always have to look back to the garden incident and see why we must put on the armor of Christ because the serpant knows the bible better than many and he will stop at nothing to keep you away from THE FATHER in HEAVEN. He uses many people to beguile you and they also have hate in them like Cain had for Abel.

    • What part of the Bible says that man has never been to the moon and why does it conflict with your religion?

      • Pff. The only proper religion is the one founded by Jesus Christ himself - Catholicism. If you are not Catholic you are only following a lesser religion.

        • Jesus did did not create Catholicism. It was created well after his death. If your not Jewish you are following the lesser religion.

        • I know people that believe everything in the Bible and not smart enough to know that technically it's possible to go to the moon. I've heard ignorance is bliss but the Bible isn't the first. if god told you to revient the holy book told you would be told you are insane. I personally wouldn't let my son go to a catholic church most of the full grown men are fag's fact. there's a untold story that the 69 Apollo mission was met by 7 body's with wings each as tall as a 1 story building. I don't understand why no-one has been back to the moon but morons look for the American flag it's visible through a large telescope.

    • Where does it say that Lucifer lied unfortunately that was the creators favorite he was upset for what he had done to him he is compelled Lucifer that is to serve what man has been given a choice Lucifer knows no evil that is man spitting created and given by the Creator himself

    • I’ve never seen a flat earther’s comment until now. The Bible has undergone many changes over the years, especially during religious reformations. I’m not sure that is one hundred percent accurate, while I am religious, I also think it’s possible to land on the moon. If physics allows us to fly planes in the air, then why not fly rockets through space?

    • I agree with you for the most part, but I believe you got trapped by your own claim, "is very deceiving to those who lack biblical understanding". You said, "The 🌙 and the 🌞 is not outside of what Christ created". The Most High, Our Heavenly Father created the moon and the sun, and you said "armor of Christ". We must put on the full armor of God. Nowhere in Biblical scripture does anyone speak of a holy trinity, if it does I ask you let me know the exact chapter and verse please. The holy trinity is a lie and concept used by the Adversary, Satan, the serpent, found in all Pagan religions including Catholicism and the Vatican, Greek mythology,ancient Egyptians, Altruism which I believe is Vikint mytholgy, ancient Samaritans, and on and on it goes. None shall come before our Father in Heaven, The Most High, The one with dominion over all things. It is through our LORD Jesus Christ only that we can be with our Father in Heaven. There are many lords/principalities. My intention is not to attack you but help a fellow brother in Christ. God bless.

  • Well hello just read your article yes those reflectors have been there since Apollo they've been reflecting ever since it's not new they've done this for decades at Cal jam 2 in the seventies at the Rock concert they shot a green laser at the Moon during the concert we watched it they have tons of data

      • According to NASA dust does...lmbo . Ridiculous. But it will definitely settle in a Hollywood basement.

          • Great info and well written except for the crap click bait title.

            Odd how many nutters complain about an article they clearly didn't read. Sure, keep your weird religious or learning disabilities in the open for all to see, but at least read the dang article so you don't look so obviously insane.

      • Any object with mass has gravity. So yes, dust settles on the moon just like it does on earth, albeit more slowly

  • Obviously 'SciTechDaily' is a phony site. The headline alone is filled with inaccuracies. Reflectors have been in place since 1969 and the 'first' time they reflected the beam was then. Crap site with crap information.

    • Reflectors? Lmbo...I cant help cut laugh at you programmed indoctintated souls. We live under a firmament and they darn well know this. You are fooled by CGI. And why do you have 33 in your username?

        • Oh... Try this indoctrinated one. A Hollywood studio was very popular back then....wow. You guys surely try. CGI is very popular now...If you can't tell it computer graphics there is no helping you folks. Programming runs deep. Repeat the lie enough in movies and TV and even the news and becomes truth.

          • Jeffrey, you seem to be the indoctrinated one. You believe Hollywood actually exists? What a laugh! They have you fooled! And I see you are spouting nonsense about magical "studios" and devices called "computers" and "TV". These things are all made up fairy tales. Wake up! Praise the Lord, hallelujah!

    • Please at least read the article before complaining about it. The title is misleading or click bait, but it is clearly explained by the end of the second paragraph.

  • Disappointed in this headline at the very minimum, still going through the story. The Apollo astronauts left retro reflectors on the lunar surface and there's literally been bottom basement science tv shows that have gone to laser stations and done reflective tests with NASA.

    • Hopefully by the time you "worked" your way through it you had discovered that, yeah, they mention that. Oh, and there's a nice shot of Buzz Aldrin carrying one of the reflectors.

      I don't get the logic of commenting before you finished reading it, but, judging by the comments here that's definitely "a thing."

  • So what you're telling me is that the Big bang theory TV show lied to me when they inferred that this had already happened before? Lol. Still, very interesting. But I'm sure. The moon deniers will figure out how to argue this lol

  • This is not click bait. Had the headline read " NASA pointed Lazer beams at the moon, you won't believe what happened".... THAT would be click bait. I'm tired of people using that term wrong, especially when its self explanatory.

    • What do you want to call it then? A lie? The title says they got a signal back for the first time when, in fact, they've been getting signals back for decades.

      • This is a click bait title because it is an exaggeration and a lie. Click bait does not have to use specific phrases or words to be click bait, it just has to draw attention from a misleading title which this is. The author might not have meant it to be click bait and is just not aware that we have been bouncing lasers off the moon for years.

    • Way I read it is that is is the best they have received because some only send about 10 percent back figuring it is dust kicked up on them

      • People visited moon in 1969, 1971, and deployed reflectors on the surface.
        And in 2020 technological advanced era, scientists still trying to figure out from orbit why the surface reflectors are poorly reflecting. Confused!!!

By
NASA's Goddard Space Flight Center

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