NASA shoots the Moon

By Phil Plait | September 29, 2010 11:30 am

Clearly defeated in their attempt to destroy the galaxy with a laser, NASA sets its sights somewhat closer and tries to destroy the Moon:

Moon_laser

Cooooool. Actually, while that is a laser, it’s a bit too low power to do any damage to our friendly Moon. But it does have enough to help NASA track satellites! It’s part of the Goddard Space Flight Center’s Laser Ranging Facility in Maryland. We know the speed of light very accurately, so if you ping a satellite with a laser beam you can time the pulses and very accurately determine the satellite’s position.

In this case, two beams were being used to track the position of NASA’s Lunar Reconnaissance Orbiter, one of my favorite space missions of all time (to see why, check out this gallery of images I posted recently).

I used to work at Goddard, and I remember going to this facility once because it was a dark site from which I could try to spot a comet that happened to be passing us at the time. The laser was being used, and it was positively awe-inspiring and quite surreal to see it streaking up into the sky. And yes, they have to keep a careful eye out for airplanes and such flying past. While that beam isn’t enough to melt a satellite, it’s certainly enough to fry a pilot’s eyes!

Which is why you don’t want sharks equipped with these things. Really, that’s just asking for trouble.

Image credit: NASA

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Comments (32)

Links to this Post

  1. Preparen, apunten… luz… « Pablo Della Paolera | September 29, 2010
  2. Moon Town by Steve Ogden - Real Life VBL | September 29, 2010
  1. chris.j.

    when chairface chippendale was appointed the director of the goddard center, i knew there’d be trouble…

  2. Ed H.

    So is it safe to assume that the “second beam” is a second beam up, *NOT* the return? I would imagine that, laser or not, the return beam would be too wide/weak to appear on film.

  3. Vandalous

    Why does this sound somewhat familiar? Oh wait, you helped us with it a few years ago: http://www.badastronomy.com/bad/movies/powers.html

    Hehe!

  4. phil

    Would a beam like this be visible at all from lunar orbit?

  5. Charles

    @Ed H. 2.

    Yes, not only is the return signal extremely diffuse, but there is not a reflector on the other side pointed *directly* back towards the Goddard Space Center. Think about how exact that reflector would have to be positioned to reflect back from the moon! The return signal is not a “beam” but it is detectable by very sensitive receptors.

  6. I was there for Int Observe the moon night. Truly an amazing sight. The two beams are the older and newer systems – they don’t generally turn them both on but it makes for an amazing sight! Older system is at 10Hz, newer is pulsed at 28Hz. The older/slower one reminds me of the beam shot toward the mountain from the Rocket Car in Buckaroo Banzai Across the 8th Dimension because of the observable flicker :)

    Follow me on Twitter @VAXHeadroom
    Emory

  7. mike burkhart

    I thought NASA fired a laser at the moon durring the Apollo missions ? Well maybe a few more shots won’t mater.

  8. DrFlimmer

    Clearly defeated in their attempt to destroy the galaxy with a laser, NASA sets its sights somewhat closer and tries to destroy the Moon:

    Hmm… but that was ESO’s VLT that shot the galactic center and not NASA….. just a little nitpick 😉

  9. Finally, now if we can just get some fricken’ sharks with some fricken’ laser beams on their heads we’ll be all set

  10. Kevin

    Heck, anyone can fire a laser at the reflectors up there.

    They did it on The Big Bang Theory last year. :)

  11. Chris

    Are they sure they aren’t going to blow up the moon? 😛

  12. Nemesis

    I think the Moon is doing the shooting- two lasers: a preemptive one towards the observatory and one at Dick Cheney.

  13. Dave Scruggs

    Ok, I’m a bit confused. (Not hard to do any more, I have teenage children.) The lasers are visible on what looks like a clear night. They shouldn’t be visible at all with no smoke or dust or whatever to reflect off of. So what’s going on here?

  14. “We know the speed of light very accurately . . . .”

    Since 1975, we know the speed of light exactly, because it became a defined constant rather than a measured value. The speed of light is now defined as 299,792,458 meters per second with no uncertainty. Some time before that the second was defined as “9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom”, and now the meter is derived from those two constants.

  15. Charles:

    Yes, not only is the return signal extremely diffuse, but there is not a reflector on the other side pointed *directly* back towards the Goddard Space Center. Think about how exact that reflector would have to be positioned to reflect back from the moon!

    Actually, the reflectors left by the Apollo astronauts do just that — reflect directly back at the sender.

    http://www.lpi.usra.edu/lunar/missions/apollo/apollo_11/experiments/lrr/

    And I hope that no one at Goddard left a dirty sock nearby. :-)

  16. HvP

    Dave Scruggs,

    That’s generally true for red lasers. There are usually enough particulates just generally floating in the air to cause some scattering of any laser except that our eyes aren’t sensitive enough to see it at the low levels that they use. However, you might notice that these lasers are green in color. Shorter wavelengths are more easily scattered by our atmosphere, as you can see by the blue color of the sky on a clear day.

    Apparently, there are high power consumer grade hand-held lasers that can be seen by the naked eye under the right conditions.

  17. Ross

    If you want to experience an actual death ray, you need only go to the Vdara hotel pool in Las Vegas:
    http://abcnews.go.com/Travel/las-vegas-hotel-pool-sunlight-swimming-tourists/story?id=11739234

  18. One Eyed Jack

    Don’t be such a Nancy.

    Friggin lasers on friggin sharks are friggin cool.

  19. Chris

    Dave,
    I work with 10 W green lasers and there are enough dust particles floating around that it makes the laser really easy see. I’m not sure what power they have but even a 1W beam would be powerful enough to see on a dark night.

  20. WJM

    The frickin’ sharks are only dangerous when the frickin’ laser beams are on their frickin’ heads.

  21. Nekura

    It’s a good thing the Apollo astronauts thought to installed those laser deflection stations on the moon when they were there.

  22. Mary

    I love my green laser for pointing out constellations at public star parties, helping others locate specific objects, using instead of a finder scope on my telescopes….
    Mine is a 5 milliwatt. That is the highest I will use. From the information I have, our natural blink reflex will protect one’s eyes if by some accident or stupidity it is pointed at someone. Higher than 5mW poses increased danger of potentially permanent damage, and for me, is not worth the risk. The 5mW does not work in a highly light plolluted area, but does work in areas that are not completely dark. Bigger and brighter, in this case, is not needed when 5mW works adequately for small groups under most conditions . They are not to be used at star parties where someone is astro imaging nor near airports as planes are necessarily at low altitudes. In the U.S. it is not permitted to sell lasers for pointing applications over 5 mW. I think the U.K. is limited to 1mW. Canada, as far as I can find, has no specifc restrictions. I actually wish there were as there have been some cases of idiots pointing green lasers at aircraft. If there are too many foolish uses, these lasers could be banned and that would a shame. They are something to be used with consideration and caution. Green lasers are not toys.
    See
    http://www.laserpointersafety.com/index.html
    for great information on green lasers. The section on ‘Effects on Pilots’ and the ‘this photo’ it links to is particularly interesting.
    I paid a ridiculous high amount for my first one. Now, they can be purchased for ridiculously low amounts. Unfortunatley, some eBay advertisements advertise them as toys—such as showing how the high powered ones might light a match. There are also some high powered ones for sale from other countries that do not meet North American stasndards.
    They are useful educational tools with the potential to be misused.

  23. Gonçalo Aguiar

    When I first saw this picture I thought that the first laser was being reflected back from the moon! How silly am I!? 😀

  24. ma

    woww this is great following this blog now, love astronomy 😀

  25. Lisha Sterling

    Hey, do they have one of these things at UC Berkeley, too? I remember seeing something that looked just like this green laser coming up on the hill, it looked like somewhere near the Lawrence Lab, at Berkeley when I was a student there in the late 90’s.

  26. Mapnut

    As with the Milky way photo, I don’t see how those beams can actually be aimed at the moon. How high up does the part of the beam go that we can actually see? Surely the photo isn’t showing the actual beam just before it contacts the moon, 240,000 miles away. If the beams we see are only visible, say, 100 miles up, then they must cross each other and continue in different directions, going nowhere near the moon. Is it a doctored photo? Or did they temporarily aim the lasers so it would look like they’re hitting the moon?

  27. Andy Beaton

    Yeah, sure, go ahead and laugh. I checked the moon last night and half of it had been COMPLETELY BLOWN AWAY!

  28. “Shooting the moon” more than 60 years ago (before the laser was invented) was rather easy, so I’ve heard :)

    But seriously, this picture is too cool. I’ll take their word for it that it isn’t doctored. As already stated, however, they’ve been shooting lasers at the moon on a regular basis since we first put the reflectors there about 1970.

  29. carl lafonge

    @Mapnut. From the angle that the picture was taken the laser appears to reach all the way to the moon. As you move away from the source, it becomes more faint and the fact that the laser stops short of the moon is obvious. It really does look like this. In person you would be able to see the pulsing. In this picture it looks like a beam.

    The green laser light is visible as long as there is something for it to bounce off of. In this case it’s molecules in the atmosphere (Rayleigh/Raman backscatter ). Above 100 km or so there isn’t anything for the laser to bounce off of until it hits the moon (or the LRO).

  30. Professor Mayhem

    TAKE THAT, MOON!

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