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Communications Networking Shark Moon NASA Space

NASA Testing Frickin' Laser Communications 108

Posted by timothy
from the beam-it-up-scotty dept.
itwbennett writes "The lunar laser communications demonstration will be part of the agency's Lunar Atmosphere and Dust Environment Explorer (LADEE) mission, which is scheduled to launch on Sept. 6. Here's how the system will work: When the satellite is in orbit around the moon and visible from Earth, one of three ground stations will shoot a laser towards its approximate location. The laser beam from Earth will scan a patch of sky and should illuminate the spacecraft at some point. When that happens, the spacecraft will begin transmitting its own laser towards the ground station and the two will lock on to each other. The technology should allow an upstream data rate, from the Earth to the spacecraft, of around 20Mbps and a much faster downstream rate of 622Mbps. That's roughly six times the speed that's currently possible with radio-based transmission, said Don Cornwell, mission manager for the lunar laser communications demonstration."
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NASA Testing Frickin' Laser Communications

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  • by girlintraining (1395911) on Saturday August 24, 2013 @11:26AM (#44663993)

    The latency will be absolute shit. Useless for most bandwidth-intensive internet applications. Imagine trying to play a game with twice the lag of a dialup modem. Not only that, but one cloud in the sky and it's game over, man.

    Not reliable at all.

    • This is not for communication between two points on earth. This is for communication with the satellite itself. With a direct Laser link, you should get the lowest latency physically possible.

      • by peragrin (659227) on Saturday August 24, 2013 @11:42AM (#44664099)

        Wooooosh.

        Girlintraining wants to play WOW from their secret moon base. Blizzard won't put a server up there for those of us with hidden moon bases.(something to do with Nazi space zeppelins).

      • This is not for communication between two points on earth. This is for communication with the satellite itself. With a direct Laser link, you should get the lowest latency physically possible.

        There was a post earlier I was replying to suggesting this could be used for internet communications.... erm, no. This wasn't about sending back telemetry, etc., from a satellite... that can be lagged to hell and it doesn't matter much.

      • by Shavano (2541114)
        With a direct radio link, you also get the lowest latency physically possible. The laser is to allow more energy efficient transmission.
      • This is not for communication between two points on earth. This is for communication with the satellite itself. With a direct Laser link, you should get the lowest latency physically possible.

        Well, that's the problem. This is, among other things, what NASA will have to use for the space edition of Need for Speed. Now imagine the rover races at a three-second packet roundtrip. Also, a direct laser link is not going to have any lower latency than a direct microwave link. They're sort or equally fast, ja wohl?

    • by mcgrew (92797) *

      The latency will be absolute shit.

      Unless you can get light to go faster than light there's nothing you can do about that. You're not in Kansas playing Quake with someone on the moon, you're controlling robots with a hell of a lot less latency than controlling the Martian robots.

      • Unless you can get light to go faster than light there's nothing you can do about that. You're not in Kansas playing Quake with someone on the moon, you're controlling robots with a hell of a lot less latency than controlling the Martian robots.

        Well, satellites don't care much about latency; They aren't doing much that's time sensitive to begin with. Whether the pictures take 50ms or 50 minutes to beam back doesn't much matter for a surveyor. But others have indicated that this could be used for land-to-land communications (satellite being the bounce) ... but bouncing something out to geosync orbit and then back down is a helluva lot of latency... and for something that can be gobbled up by atmospheric effects... it's just not reliable enough for

        • by Nutria (679911)

          My comments were directed towards people who think this could be used for something else.

          Where are those people's comments/delusions?

    • by mikael (484) on Saturday August 24, 2013 @12:17PM (#44664337)

      Probably the laser will probably in a wavelength of light that clouds don't absorb. There are a few "infra-red windows" that can be used.
      http://www.st-andrews.ac.uk/~bds2/ltsn/ljm/JAVA/SPECTRUM/details.html [st-andrews.ac.uk]

      Then they'll use TCP/IP adapted for space communication - modifying the protocol to handle time lag. That's more or less what it was like using the "Kermit" protocol with a 9600 or 19200 baud modem (~960 characters/second) - we used to "turbo boost" our connections by using large packets (1024 bytes). Even so, five packets could be sent down, in the time it took the other end to calculate the CRC's and send back the acknowledgement.

      It's better than what they have now, so they won't complain.

      • by girlintraining (1395911) on Saturday August 24, 2013 @01:09PM (#44664607)

        Probably the laser will probably in a wavelength of light that clouds don't absorb. There are a few "infra-red windows" that can be used.

        Ah, this link [wikipedia.org] might be a bit more useful in explaining the phenomenon to which you're referring.

        The thing is, these windows are not very big, and there are only two big ones. What's worse, clouds still scatter and mush up the signal... it may not be absorbed, but that doesn't mean it won't go all over the place. It'd be like trying to piss in a hurricane... good luck getting a straight stream into the toilet in wind gusts that'll get you my pretties (and your little dog too).

        It's only useful in dry atmosphere. Fortunately... guess where they put the communications array. :) I'll give you a hint: Not Seattle.

      • by Nutria (679911)

        we used to "turbo boost" our connections by using large packets (1024 bytes).

        Takes me back to the days of ZMODEM, which was significantly faster than TCP/IP and FTP

    • by gmuslera (3436)
      For some games that latency would be a killer. But the US army think that it would be ok for playing Space Invaders.
    • by LordKaT (619540)

      oh god, reading all of the comments ... I love girlintraining. Best troll ever.

      • by Anonymous Coward
        The secret to success is getting modded up no matter how wrong you are. No amount of AC trolling can compete with that.
    • by Khyber (864651)

      "Not only that, but one cloud in the sky and it's game over, man."

      And that shows you know jack shit about wavelengths or even basic modern satellite design.

      Plenty of wavelengths that don't get absorbed or scattered by clouds.

    • Are you sure the latency would be so bad? If light travels approx 300,000km per second, and GEO is approx 35,768km(at it's lowest) - isn't that about 80-90ms of latency?

      I could be *way* off, and admittedly don't know enough in this discipline to be certain...but it seems like very acceptable latency, even for something like VOIP.

      • Correction, I was wrong. Latency at it's least will be 242ms. At it's greatest it should be 50% more. Sound right?

        Showing my work...

        speed = 299,792,458 m/s
        distance = 36,560,000 meters (approx)

        Time in seconds for for round trip at ideal position = 242ms.

      • by Smallpond (221300)

        Did you perhaps miss that it is in Lunar orbit? Try 384,000 km.

        • Yea I saw that from another reply to my post...totally missed the ball there :) I was thinking about GEO.

    • by Anonymous Coward

      Latency is completely irrelevant for the intended purpose. It's clearly mentioned in TFA that link speed and efficiency / beam focus are the critical concerns. I don't think parent understands that NASA's purposes don't always involve simplistic consumerist notions of two-way low latency traffic, such as with computer games.

      Latency will always be constrained by the speed of light. I don't see the point of lamenting the speed of light in a criticism of a new technology, when that ought to be dead obvious.

      Abo

    • *Any* communication with the moon is going to have a latency of at least 1 1/4 seconds, because the moon is 1 1/4 light-seconds away. Are you seriously faulting this method for not being able to exceed the speed of light?

    • by slick7 (1703596)

      Not reliable at all.

      Maybe if they mounted them on sharks, the reliability would increase, just sayin'.

    • The latency will be absolute shit. Useless for most bandwidth-intensive internet applications. Imagine trying to play a game with twice the lag of a dialup modem. Not only that, but one cloud in the sky and it's game over, man.

      Not reliable at all.

      ===
      Its not the latency, but the fact that communication is truly point to point. In a way, far far more secure than radio transmission. And why should laser communications be slower than radio? Both signals travel at the speed of an I/O interrupt.

    • by grcumb (781340)

      The latency will be absolute shit. Useless for most bandwidth-intensive internet applications. Imagine trying to play a game with twice the lag of a dialup modem. Not only that, but one cloud in the sky and it's game over, man.

      Not reliable at all.

      Besides, they haven't even begun development on space sharks, and without space sharks, what good is a frickin' space laser?

    • The latency will be absolute shit. Useless for most bandwidth-intensive internet applications.

      Well, latency has nothing to do with bandwidth. Youtube and Facebook over store and forward? Sure, it's called the Netflix Queue and Email. I'm already looking into supporting the DTN (Delay Tolerant Network -- the interstellar Internet) for an action / strategy video game with user generated content. You know another name for Store and Forward? Co-Location. Yep. Those repeated requests for the same data? They can be served by the nodes that still have them. It's networking with built in caching.

      Imagine trying to play a game with twice the lag of a dialup modem. Not only that, but one cloud in the sky and it's game over, man.

      Not reliable at all.

      U

      • Hmm, botched a link, but you could search it. Here: Delay-Tolerant Networking [wikipedia.org]

        So, let's pretend you're on Mars, and for some retarded reason my browser is saying that wiki link I typed is known not to exist in the Mars archive. Thus, I would include an excerpt (or maybe Interplanetary Slashdot would do this automatically):

        Delay-tolerant networking (DTN) is an approach to computer network architecture that seeks to address the technical issues in heterogeneous networks that may lack continuous network connectivity. Examples of such networks are those operating in mobile or extreme terrestrial environments, or planned networks in space.

  • by Anonymous Coward

    and no shark?!?

  • Awful headline (Score:2, Insightful)

    by Anonymous Coward

    I hate you

  • As if laser communication would be something new...

  • NASA stands up and says, "Ignore the volunteers, put a robot there."

    I remember leaving Olduvai Gorge, the first person to look past the rim of the canyon walls. For a moment, I was alone, and concerned. But I noticed the same crap happened along the rim as it did by the river. So I kept going outward, I noticed a lot more food on the Serengeti. I like it, I think I'll keep moving forward.

    Then I realized how NASA is oriented; they are alone, and concerned. Only it's every day, and it never changes.
  • A long time coming (Score:4, Informative)

    by mbone (558574) on Saturday August 24, 2013 @11:53AM (#44664179)

    One of the weaknesses of the NASA science / PI driven culture is that engineering tests like this can take a very long time to fly, as they do not directly provide science and have no scientific community demanding them. Laser communications was proposed for testing on the space station (as a down-link site) in the 1980's, has made it close to getting into space several times, but every previous attempt to fly it was eventually canceled to save money. Now, finally, it will be tested (or, in NASA speak, achieve a TRL of 8).

    As it is, numerous deep space missions are data limited, such as the Mars Reconnaissance Orbiter, which could take more pictures, if it could get the data back. Laser comms is badly needed, let's hope the LADEE test goes well and it can finally get deployed.

    • by mikael (484)

      Couldn't amateurs try this? If they can get a digital camera up to 120,000 feet using Helium balloons, they could get a platform that maintains it's altitude without the balloon bursting and then downloading images by laser. That would be good practice.

      • by Anonymous Coward

        Actually, maintaining altitude with a weather balling is a notoriously hard feat. Super pressure Ballons are typically used(that reach a a limit of expansion without bursting and can maintain internal pressure therefor attitude) but they're out of the range of most hobby ballon groups, and can vary in altitude with weather patterns. Another option is a ballast/gas release system, similar to the Sprirt of Knoxville university group that attempted a transatlantic 'floater' but even then it's expensive and dif

    • by Shavano (2541114) on Saturday August 24, 2013 @12:42PM (#44664459)

      What's proposed here makes more sense as a technology demonstration than a practical solution. Lasers from Earth to space (and reverse) are unreliable because of clouds and ducks that radio goes right through. But lasers from space to space are excellent. You get more reliable comunications with a relay in Earth orbit to downconvert the laser signal to a microwave frequency. Also because there's no need to get high-res video streaming from the moon for this kind of science experiment.

      • by Immerman (2627577)

        On the one hand yes, from the article it sounds like is just the first space mission that was able to squeeze an experimental laser communication system into it's budget. At least they don't mention any specific benefit for this satellite to have the extra bandwidth. Then again the article doesn't mention much of anything about the satellites primary mission beyond the name - Lunar Dust and Atmosphere Environment Explorer. Perhaps it takes rapid-fire broad-spectrum "photographs" across the Moon's rim an

        • by mbone (558574) on Saturday August 24, 2013 @01:37PM (#44664805)

          I have talked with the people doing the laser comm experiment on LADEE - it is just a technology demo, and is not needed for the LADEE mission primary science goals at all. (That is the difference between a science mission, such as LADEE, and a technology demonstration mission, such as Deep Space 1, where the science is secondary and can depend on the successful working of the new gizmo.)

          If it works on LADEE, then someone can propose doing it on a real mission (i.e., one that would depend on it), just as the ion engines from Deep Space 1 are now powering DAWN.

          • by Immerman (2627577)

            Thanks for the insider info.

            I certainly assumed that an experimental system wouldn't be *required* for the primary mission if it could be avoided, but ideally if it works as intended it would enable the probe to exceed it's mission parameters, in this case presumably by collecting more data than otherwise possible.

  • My moon satellites will all use FiOS to communicate with Earth.
  • Using lasers for communications is not new. HAM Radio [arrl.org] geeks have been experimenting [southgatearc.org] with it for some time. The big problems seem to be maintaining the alignment of the laser, and atmospheric attenuation of the signal. That aside, the bandwidth of visible light signals will be awesome, compared to longer wavelengths.

  • by koan (80826)

    Why is it asymmetric? Gravity?

    *wink*

    • by EnsilZah (575600)

      I believe it has to do with the increased efficiency of spherical sharks operating in microgravity and near-vacuum.

    • by mbone (558574)

      Behrooz Amoozad gets part of it - the rest is that space communications always tends to be asymmetric, because commands going up almost always require much less bandwidth than data going down. Automatic satellites, after all, may generate high-def video but they do not watch it.

  • What happens on a cloudy day ?
  • Has NASA settled the question? I guess so. Upload rates are ALWAYS a fraction of download rates.
    • Since upload vs download is a matter of perspective that's not true. The fact that your home connection has a different download speed than upload speed is due to differences in hardware and requirements. Cheap home modems can not transmit at the same speed as expensive cable/adsl switch points can.
      Besides most people only need limited upload at home. Download speed is far more important to most.
  • The Earth terminal does not have to be on the ground. That resolves the cloud/atmospheric adsorption problem.

    A satellite can be in any convenient orbit near earth to send/receive communication and then relay data to/from an earth station. The last hop can be radio or laser, whatever is most appropriate.

    NASA currently has a set of eight satellites in orbit that do exactly this for radio signals, called TDRS [wikipedia.org]. This program has been operational since 1983, and NASA is now working on the third generation of s

  • And make it 9.99 a month and put everyone else out of business. Pretty please.
  • Wasn't the faulty "laser communications" device the plot motive used in the movie "Dark Star"?

    "TALBY Before we get too far away, and our signals start to fade, I just wanted to tell you... you were my favorite."

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