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NASA Achieves Laser Communication With Lunar Satellite

Posted by Soulskill on from the and-i-can't-even-shine-my-penlight-at-airplanes dept.

New submitter EngnrFrmrlyKnownAsAC writes "Communicating with lasers has become the hot new thing. While most researchers are seeking faster throughput, NASA set its sights in a different direction: the moon. They recently announced the first successful one-way laser communication 'at planetary distances.' What did they send? An image of the Mona Lisa, of course. 'Precise timing was the key to transmitting the image. Sun and colleagues divided the Mona Lisa image into an array of 152 pixels by 200 pixels. Every pixel was converted into a shade of gray, represented by a number between zero and 4,095. Each pixel was transmitted by a laser pulse, with the pulse being fired in one of 4,096 possible time slots during a brief time window allotted for laser tracking. The complete image was transmitted at a data rate of about 300 bits per second.'"

13 of 99 comments (clear)

  1. 300 bits per second? by SternisheFan · · Score: 3, Interesting

    No budget left over to get FIOS?

    1. Re:300 bits per second? by VortexCortex · · Score: 3, Funny

      Who wants to play tw2002 on my moon server?

      I do. 300 Baud is a nice reading speed...
      But First!...

      He who would negotiateth a handshake of that breadth must answer me these questions three, Ere the ATDT ye see...
      0. What is your FidoNet node address?
      1. What number of in & out dials have you?
      2. What is the land area coverage of an unladen local call?

    2. Re:300 bits per second? by dissy · · Score: 3, Interesting

      Would you like to play a game?

      0. What is your FidoNet node address?
      1:226/201

      1. What number of in & out dials have you?
      7 / 1 (8 chans of a frac pri)

      2. What is the land area coverage of an unladen local call?
      About half of the area code, guessing 100 square miles?

      I never understood why some parts of 614 were local but others were long distance, while at the same time a small part of 740 was local to me yet a different area code.
      I had to route mail to another board across town in 614, where he could reach the other half of 614 locally, just to avoid minutely charges.

      My 8 PRI channels were to my home (well, to my parents home at the time) and mostly for dialin. I rocked Oblivion/X by the time I was on fido. One line floated for scheduled callouts, but none dedicated to that.
      Once I discovered the Internet in '89, first one then later two channels were dedicated to PPP.
      By '92 I was getting less than 5 calls a day to the board, and shortly converted my whole frac PRI to be dedicated Internet, and I pretty much gave up the sysop role for good in exchange for EFnet as things turned out. Even ran an efnet server for a short time back in '95 i think it was.

      While I can say for certain that communications have only changed for the better as far as the Internet goes, there is still a lot I miss from those days, even though I wouldn't want to go back to that for anything.

  2. 300 bits per second? by Ardeaem · · Score: 4, Funny

    My dream of running a BBS on the moon grows ever closer! Who wants to play tw2002 on my moon server?

  3. Overkill on detail? by CodeheadUK · · Score: 4, Funny

    > Every pixel was converted into a shade of gray, represented by a number between zero and 4,095.

    Obviously 50 shades of gray wasn't enough..

  4. 300 bits per second is pretty damn good by The+Living+Fractal · · Score: 4, Insightful

    ...considering how tight this beam was, and that you'd have to be pretty much directly in its path to intercept the transmission.

    --
    I do not respond to cowards. Especially anonymous ones.
  5. Re:This is awesome by K.+S.+Kyosuke · · Score: 4, Insightful

    Each pixel was transmitted by a laser pulse, with the pulse being fired in one of 4,096 possible time slots during a brief time window allotted for laser tracking.

    I have an idea. What if, instead of this encoding, they used twelve time slots for each pixel and, by either sending or not sending a pulse, transmitted a small amount of information with each (non)pulse? Then, they could interpret the slots by repeatedly adding a one or zero and multiplying the whole thing by two. I think I've read about it somewhere...

    --
    Ezekiel 23:20
  6. What about Lenna? by ericcc65 · · Score: 5, Interesting

    The Mona Lisa? Are you serious? Way to break tradition NASA, my heart weeps for Lenna:

    http://www.cs.cmu.edu/~chuck/lennapg/lenna.shtml

  7. Re:This is awesome by AmiMoJo · · Score: 4, Informative

    Because they can't reliably send individual bits. If you RTFA (I know, I know...) it shows that there is a fair bit of error and quite a few lost pixels. Rather than sending bits they send a pulse of a certain length per pixel, and if the edge of that pulse is distorted somehow they just lose some intensity resolution and don't end up with totally corrupted digital data.

    It's kind of analogue. The timing method they use is a bit like PWM with one cycle per pixel, and actually there are far fewer than 4096 shades reliably transmissible, that is just the range they measure.

    --
    const int one = 65536; (Silvermoon, Texture.cs)
    SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
  8. Re:This is awesome by WrecklessSandwich · · Score: 3, Informative

    The timing method they use is a bit like PWM with one cycle per pixel, and actually there are far fewer than 4096 shades reliably transmissible, that is just the range they measure.

    It would actually be PPM (pulse-position modulation).

  9. Fermi Paradox by yanom · · Score: 5, Interesting

    If laser communication overtakes radio for our own space equipment, it might explain the Fermi paradox - we cannot detect alien civilizations because the communicate with lasers (emitting no radio signals at all), making them undetectable to those not in the path of the beam.

    --
    "That's either incredibly asinine or the most brilliant troll I've ever read. Not sure which." -Anonymous Coward
    1. Re:Fermi Paradox by doublebackslash · · Score: 3, Informative

      https://en.wikipedia.org/wiki/Diffraction-limited_system

      It doesn't matter. Laser. Radio. Gama ray.Doesn't matter. At these distance the systems are, no matter how well focused, diffraction limited. Just like we can't build a mircoscope to see infinitely deep into the smal we cannot build a laser com with perfect focus. Diffraction wins. We can cheat a little, but not over these distances.

      We could see laser flashes just as easily as hear radio waves from parabolic dishes.

      --
      md5sum /boot/vmlinuz
      d41d8cd98f00b204e9800998ecf8427e /boot/vmlinuz
  10. And that's why SETI will never find the aliens by Anonymous Coward · · Score: 3, Interesting

    As I've been saying for years SETI doesn't have a hope in h**l finding the aliens because they use the much more efficient point to point message casting as opposed to the broadcasting in every direction used here on earth. Why use the inefficient method sending your message/data/... everywhere when it is really only destined for 1 place.

    I think in 100 years we'll look back and see that the use or radio and the inefficient broadcasting methods was a short segment in our history. It will likely be the same for other developing races.

    I recall a few years back they actually found something that looked like real alien communication. It couldn't be captured again. Of course it coul'n't be found again. We were no longer behind the target of the message beam.