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Communications Space Science

An Interplanetary Laser Communications System 303

Posted by timothy from the sharks-not-included dept.
caffiend666 writes "A news article at Yahoo states NASA is planning on testing the first laser-based interplanetary communications system on the Mars Telecommunications Orbiter to be launched in 2009. 'Unlike radio frequency signals that wash over the entire Earth, Fitzgerald and his colleagues will be shooting for a much smaller target - the southwestern corner of the United States.' Does this mean we will soon have telescopes outside of our homes soon to pick up high definition TV signals instead of our current 18 inch dishes?"
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An Interplanetary Laser Communications System More

An Interplanetary Laser Communications System

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  • It's eventual use. (Score:5, Funny)

    by teiresias ( 101481 ) on Tuesday November 16, 2004 @12:29AM (#10827251)
    Earth - 'Hey'
    Mars - 'Hey'
    Earth - ...'
    Mars - '...'
    Earth - 'a/s/l?' ;)

  • Time to do the wash (Score:5, Insightful)

    by kfg ( 145172 ) on Tuesday November 16, 2004 @12:30AM (#10827261)
    Does this mean we will soon have telescopes outside of our homes soon to pick up high definition TV signals instead of our current 18 inch dishes?"

    No.

    Because for television broadcast to the general population you want to wash the signal over the whole earth, rather than trying to target each receiver. And if you think your reception sucks when it's raining out now. . .

    KFG
    • A dish is a telescope. Ever see a picture of Aricebo?

      Check it! [naic.edu] Just a big version of what you got on your house.
      • Ever see a picture of Aricebo?

        Yes. I've even taken pictures with radio telescopes, although not of the Aricebo facility. I've got an invisible light laser hanging around the place in some drawer or other too.

        I've never been to Aricebo myself, but my mother has. She took pictures of it, in visible light.

        Just a big version of what you got on your house.

        My house is not so bedecked.

        KFG
    • Because for television broadcast to the general population you want to wash the signal over the whole earth, rather than trying to target each receiver.

      Unless you are something like the license-fee-funded BBC where you want only British television-license-payers to receive your signal and not any Germans, French, or anybody else.

  • Dishes ARE Telescopes! (Score:5, Interesting)

    by CyberBill ( 526285 ) on Tuesday November 16, 2004 @12:31AM (#10827267)
    I always wondered why they would want to use the visible spectrum...

    We *CAN* make Laser-Radio waves! They go through atmosphere and trees and buildings....
    • The L in LASER stands for Light. Perhaps they could use MASERs.
    • One reason is that the higher in frequency you go, the higher potential bandwidth you can use. Also the higher the freq. in the electromagetic spectrum the more particle like the photons become. One of the effects of that is the energy spreads out less over distance. The more the energy spreads out over distance, the less there is to collect at the endpoint (and thus harder to maintain a good signal/noise ratio). Another reason might be that lasers are cheap and easy to produce. If you use a laser you
    • Ever tried to modulate a high energy laser? I do not mean semiconductor toys. Even in space their useable distance can hardly exceed a few million km. I am talking about something real which can be seen a few ae from Earth - CO2, HF or HI eximer or the high end crystals. The only way to modulate them is a combination of two polarization cells which are controlled by electric field. The switching speed for this is rather lame. It is a few kbit at best and you have to fire it in short pulses so that the cel

  • obligatory austin powers misquote (Score:5, Funny)

    by Anubis350 ( 772791 ) on Tuesday November 16, 2004 @12:31AM (#10827270)
    will this be implemented with sharks with frikin lasers on their heads?

  • Very specific uses (Score:5, Interesting)

    by Chairboy ( 88841 ) on Tuesday November 16, 2004 @12:31AM (#10827272) Homepage
    It's unlikely you'd use lasers for wide scale signal distribution. A laser must be aimed, and to provide a signal to a thousand receivers you would need to fire a thousand beams, or have some intricate device that actively retargets thousands of times per second, squirting packets off to each receiver. Moving parts, complicated, no clear advantage.

    Lasers for interplanetary communication is another thing. It's one sender to one receiver, and then you can go radio for inside planetary systems. Eg, you could set up a Mars Relay Station that takes low power local radio transmissions and beams the info back to Earth via laser, and vice versa. You get the advantage of cheap, small radio technology plus the range and bandwidth of laser.

    • Re:Very specific uses (Score:5, Interesting)

      by Naikrovek ( 667 ) <jjohnson@p[ ]com ['sg.' in gap]> on Tuesday November 16, 2004 @01:24AM (#10827510)
      when i was a kid (early 80s) my dad set up a thing kinda like that. he used a focusable flashlight, hooked it up to an amplifier, and pointed at a sensor he had in the window of our detached garage.

      whenever he'd go out there to work, he'd turn on a microphone in the house, and turn the reciever in the garage on. he originally built it when cordless phones were a high-priced luxury, and didn't want to wire a phone just for the garage, but he still wanted to hear the phone ring from in there. later he used it to listen to the TV while he worked outside.

      he used a cadmium-sulfide cell on the recieving end. those change resistance according to light. conveniently, they ignore the signal bias (ambient light) and only respond to changes in light intensity. the amplifier inside the house changed the amount of current to the flashlight, and thus the brightness. that variable-intensity light got sent to the CdS cell and the variation in light was reproduced into sound. it sounded surprisingly clear. i don't remember a muffled sound at all.

      you could update the design by using polarized light going in two directions. horizontal polarization for transmission, vertical for reception, or simply seperate them a little. our seperated garage had a window adjacent to our home, and light shined into the garage would bounce off the glass and back into the house. if we tried to do two-way then we would have had some signals bouncing off windows in weird ways, and probably some weird sound->light->sound->light feedback loop.

      wonder what that would have sounded like...

      anyway the setup worked great, and my dad used it until the day he died. good designs last.

      I recently tried it again with a laser pointer, but it seems that they have voltage regulators in them that smooth out the variations far too much.

      • Re:Very specific uses (Score:3, Informative)

        by tylernt ( 581794 )
        Forgive me if I am skeptical. A flashlight bulb has a very slow response time; feed it a low-frequency square wave, you get a sine(ish) wave. Feed it a high-frequency square wave and you get a steady light. I have a hard time beleiving that a flashlight bulb could transmit a 10,000Hz audio signal -- those light bulbs in your house? They run on A/C, but they stay bright enough in between cycles that you don't see the 50 or 60Hz flicker.

        Not that I would doubt a 3 digit UID, who also lives next door to the Be

        • across the street (Score:2, Insightful)

          by Loualbano2 ( 98133 )
          Actually, he lives across the street from The Beast.

          664 and 668 live next door.

          ft

        • Yes, it will work (Score:3, Informative)

          by wowbagger ( 69688 )
          Yes, it will work - I've done it myself.

          You don't need much modulation of the light beam - just a percent or so will be enough to detect, and you won't see a percent modulation with your eye (unless you have a reference to compare against).

          Yes, you aren't going to be pushing 20Hz-20kHz across this - between the thermal mass of the filament and the slow response of the CdS cell you're going to be lucky to get 3kHz, but that is good enough for voice.

        • Re:Very specific uses (Score:4, Interesting)

          by Naikrovek ( 667 ) <jjohnson@p[ ]com ['sg.' in gap]> on Tuesday November 16, 2004 @07:43AM (#10828785)
          try it. the response time of whatever bulb he was using was good enough to provide clear sound. being a person of scientific reasoning i was skeptical too. i clearly remember it not sounding muffled at all. i honestly don't know why.

          try it yourself. the sound is clearer than you'd think.

      • Re:Very specific uses (Score:2, Informative)

        by jerde ( 23294 )
        no way... how fast can an incandescent filament change brightness? Could you get audio frequencies as high as a few thousand Hertz?

        I've seen kits to modulate lasers with audio (and even video) -- they specifically use a laser module with the proper (lack of) regulation so that it works cleanly. Similar circuits are used with simple IR LEDs for those "wireless" headphones that are line-of-sight.

        With those solid state devices, i'd expect pretty "instant" response in brightness output. That's really neat th
        • try it yourself. i don't know how but the incandescent light changed brightness fast enough - the sound was surprisingly clear. some light bulbs would work better than others, i'd imagine. my dad was a big fan of those big 6V lanterns, the ones that take the big brick 6V batteries.

  • That's going to make for... (Score:4, Funny)

    by Brad1138 ( 590148 ) <brad1138@yahoo.com> on Tuesday November 16, 2004 @12:32AM (#10827275)
    Some serious lag in UT2004
    • from the article
      For scientists eager to download bandwidth-intensive imagery and other data collected by planetary orbiters, probes and landers, the laser communications would offer a dramatic breakthrough in the amounts of information spacecraft can reliably transmit back to Earth.
      itd be faster tdio signal.....
      not sure, doesnt give nums, but it might be faster than 56k....

  • 4.3 Gigabytes (Score:5, Interesting)

    by morcheeba ( 260908 ) * on Tuesday November 16, 2004 @12:33AM (#10827283) Journal
    a little math...

    344 million km / (0.3 million km/sec) = 1147 seconds travel time
    1147 seconds * 30 megabits/sec peak rate = 4.3 Gigabytes in transit at any instant.
    • Almost like mercury delay memory. :)
    • so for pluto,

      5913 km / 0.3 km/s = 19710 s
      19710s * 30mbit/s = 591.3 TB in transit. How about a raid of laser planet storage devices? And then give them full boxen and make a beowulf....sorry I had to add that last bit.
      • You may laugh, but I knew a guy who was convinced that the future of mass storage was networks. The idea was exactly that - instead of putting stuff on a hard drive, send it to a computer across the network. That computer would just bounce the data back when it got it. When you needed info, you would just wait for the data to come back, then grab it.

        The magic of all of this is you are using in-flight packets as storage!

        OK, no, I don't get it, either.
    • I have often thought about the possibilities of storing data by constantly keeping in transit over the internet... if you want to store something, send it in segments as a ping packet... if you send it far enough away, or over a slow enough link, that's a good few seconds you don't need to store it on your local computer.. now do that to several million locations, and have a fat enough pipe out to the rest of the world, and you could be onto something.
    • a little math...
      344 million km / (0.3 million km/sec) = 1147 seconds travel time
      1147 seconds * 30 megabits/sec peak rate = 4.3 Gigabytes in transit at any instant.

      Eeeeyup, that's called the bandwidth delay product and shows how much could be in the pipeline at any given time. This is what the TCP "window" value is for, and since most TCP implementations max out with a TCP window size around 64 kB, this means that TCP is very poor for space communications. Even TCP links over geosynchronous satellites

      • Re:4.3 Gigabytes (Score:3, Informative)

        by Muad'Dave ( 255648 )

        There is an RFC [faqs.org] that addresses this, and support for it seems fairly well deployed (Linux kernel 2.4 had it but it was disabled, kernel 2.6 used a 2**7=128 scaling factor). The new option allows 1 GByte windows. Even with this RFC in place, you'd only get a 25% utilization between Earth and Mars (Send a GB, wait for 3GB's worth of send time).

        I became aware of it having been recently bitten by a window scaling bug in a router between my PC and where I work. I found the RFC quite interesting.

  • Radio is Light! *gasp* (Score:4, Informative)

    by Dancin_Santa ( 265275 ) <DancinSanta@gmail.com> on Tuesday November 16, 2004 @12:35AM (#10827293) Journal
    Radio, or electromagnetic radiation, is a fancy name for a special spectrum of invisible light. Yes, Virginia, your radio is replaying music broadcast over light!

    Also, a laser is a special form of coherent light. It just means that all the wavelengths in the beam of light are the same wavelength. It also means that the beam of light doesn't disperse very much unlike incoherent light (which no one can make heads or tails of what it is trying to say).

    Since the radio requires a specific band to tune in to, it makes sense that the broadcasting station not waste time generating unnecessary wavelengths and focus on only those wavelengths that correspond to our chosen band. This restricts us to AM (amplitude modulation) bands only, but since we're trying to get data signals and not Martian stereo there is no big loss.

    So why deal with visible light lasers when it could be invisible and work just as well?

    • Re:Radio is Light! *gasp* (Score:5, Informative)

      by uberdave ( 526529 ) on Tuesday November 16, 2004 @12:51AM (#10827371) Homepage
      All light is electromagnetic radiation, but not all electromagnetic radiation is light. Light is the small, visible portion of the elecromagnetic spectrum. So, Virginia's radio is *not* replaying music broadcast over light.

    • Also, a laser is a special form of coherent light. It just means that all the wavelengths in the beam of light are the same wavelength. It also means that the beam of light doesn't disperse very much unlike incoherent light (which no one can make heads or tails of what it is trying to say).

      Well, Laser light generally have the following five properties:

      1. Monochromatic - All the photons have the same colour.
      2. Coherent - All the photons are in phase
      3. Polarised - All the photons "travel in the same plane". (We

  • If we are just now experimenting with this..... (Score:4, Insightful)

    by Conspiracy_Of_Doves ( 236787 ) on Tuesday November 16, 2004 @12:36AM (#10827298)
    Does that mean that something like this might be in widespread use in advanced alien civilizations, and SETI has no chance of ever finding anything?

    • Re:If we are just now experimenting with this..... (Score:5, Informative)

      by TheDayOfMe ( 808363 ) on Tuesday November 16, 2004 @12:48AM (#10827360)
      That is why some are looking for lasers [harvard.edu]
    • Actually, we should be hoping that this is in widespread use with alien civilizations. This directed radiation leaks a lot less out of the solar system then relatively unfocused radio waves do. It has been speculated that we may not find advanced civilizations precisely because of reasons like this. There is no good reason to be just blasting radiation all over the place if you don't need to.
    • the reason SETI has no chance of finding anything is there aren't any aliens!

    • Keep in mind that SETI is looking back in time as it looks out into the universe. The Earth lies at the centre of a shell of radio transmissions that is currently about 60 light years in radius (for signals worth picking up). Those transmissions aren't coming back. They won't pop out of existence if we all move to laser based communications. An alien SETI program 70 light years away will have to wait another 10 years before discovering that life here uses radio.

      The upshot is that laser SETI should be run i

    • Isn't it a bit of a rash assumption that extra-terrestrial intelligence has technology anything like our own (regardless of how advanced or not it may be)?

      For that matter, isn't there also an assumption regarding the size of intelligent extra terrestrial beings? Seriously - they could be the size of mice, have correspondingly small means of transport and communication and thus be a lot harder for us to find.

  • Probably not telescopes (Score:4, Insightful)

    by reality-bytes ( 119275 ) on Tuesday November 16, 2004 @12:36AM (#10827301) Homepage
    "... Does this mean we will soon have telescopes outside of our homes soon to pick up high definition TV signals instead of our current 18 inch dishes?"


    Its unlikely because Optical Telescopes rely on somewhat precise pieces of equipment such as lenses which are not known for their 'year-round' hardiness.

    Speaking from experience, line-of-sight laser communications systems can be a right-royal pain to keep maintained when they are within meters.

    I don't know for sure, but I would image that initial targetting of your telescope would be a very tricky operation (and you know that sat dishes are hard enough). And then, once installed, the fixings would need to be exceptionally heavy-duty to hold the telescope on target during gales etc.
  • AFAIK the higher frequency electromagnetic radiation you use, the more susceptable the signal is to physical interference (although the energy "particles" dissipate less so that it can have a more reliable signal over further distances.) I somehow doubt we would ever see HDTV coming in via telescope, unless of course you can find a cure for bad weather.

    I only recently started taking chemistry courses though, somebody correct me if I am wrong.

    • Then how to you explain that both radio waves (low frequency) and x-rays/gamma rays (high frequency) can pass through most solids but visible light cannot?

      Maybe the high energy of high frequency waves can just ram them through most things?

  • Typical (Score:5, Insightful)

    by Anonymous Coward on Tuesday November 16, 2004 @12:37AM (#10827307)

    Here's a story about an ambitious plan to build a laser-based interplanetary communications network and the only thing the story submitter is concerned with is how this will influence his TV reception.

    This, my friends, is why the human race is doomed. Here on slashdot, where we care more about science than most people, all some people can think about is how a new technological advancement can facilitate the transmission of market-research-constructed-SitComs or advertisements for the latest yuppie gizmo to their home.

    • Jeez Loise (Score:2, Interesting)

      by Sai Babu ( 827212 )
      Why use LASER?

      With a laser, The beamwidth is small allowing a greater energy density. See geometry [gsu.edu].
      One drawback that may come to mind aiming. This is easy to get around if you have an active target, say a LASER signal from the Earth.
      The information carying capacity of a radio (or LASER) signal =
      POWER * BANDWIDTH. Power = energy * time.
      With a narrow beamwidth you've increased the power*bandwidth. Think of a rectangle. Bandwidth is the length, power the height. The area in the rectangle is available for

  • submitter was being a smartass, but they're right (Score:4, Informative)

    by ArbitraryConstant ( 763964 ) on Tuesday November 16, 2004 @12:37AM (#10827309) Homepage
    One of the limitations for geosynchronous satelites is that their proximity to each other is limited due to the unavoidable spread of the signal. Shorter wavelength means a tighter signal, which means more satelites.

    Of course... cloud cover is a problem, but there are ways around that (like those robot blimps that loiter in a given area above the clouds).

  • That's really cool, but....why? (Score:3, Insightful)

    by Zen Punk ( 785385 ) <cdavidbonner@gma i l . c om> on Tuesday November 16, 2004 @12:40AM (#10827323) Journal
    Perhaps I need to read TFA more closely, but I am left wondering what the advantages of using lasers for interplanetary communications would have over our traditional RF or microwave systems. After all, it's all EM radiation, so it's speed of light, and the lasers they're using apparently can't reach through clouds, so what are the reasons why you would want to use lasers instead of radio antennas?
    • From another "Fancy Article" on the mission:

      That leap in capacity is due to the different wavelengths of light carrying the data. The laser will use infrared light with a wavelength of 1.06 microns, which is thousands of times shorter than radio waves. Since all light travels at the same speed through space, shorter wavelengths carry more information in the same time.

    • Re:That's really cool, but....why? (Score:5, Interesting)

      by jfengel ( 409917 ) on Tuesday November 16, 2004 @01:11AM (#10827467) Homepage Journal
      The advantage is that lasers are collimated, which means that the light doesn't spread out in a cone. Since you're concentrating the energy on a few hundred square miles rather than a few million square miles, you can broadcast with a lot less power. You can also make much more reliable communications, which means your bandwidth is higher.

      In theory you can do this with any wavelength of light; if you do it with microwaves it's called a maser rather than a laser. Higher frequencies mean more bits, which is a good reason to choose light over microwaves, but the light is absorbed by clouds. I'm not sure about microwave frequencies, and I'm not sure if anybody's ever built a laser-type thing for radio frequencies (raser? I find people joking about it on the Internet but it doesn't seem unreasonable to me).

      Eventually you might want a relay system: Mars to earth-orbiting satellite via laser, which then amplifies it and relays it to the earth on a frequency which cuts through coulds better, or just saves it up for a time when it can get through. But the first step is to see if you can get light accurately aimed at the Earth.
      • Huh? Lasing has nothing to do with collimation! Most lasers aren't collimated! You can collimate any EM source (like a light bulb!) - a collimated beam is a beam with a fixed width down the direction of propagation. Perhaps you were confusing coherence with collimation?
    • The real reason is the directed signal takes less energy than a broadcast. This pans out to faster data rates since they can use higher frequencies.

    • Re:That's really cool, but....why? (Score:5, Informative)

      by Phil Karn ( 14620 ) <`ten.q9ak' `ta' `nrak'> on Tuesday November 16, 2004 @01:59AM (#10827650) Homepage
      To a first order, frequency/wavelength is irrelevant. All electromagnetic radiation follows an inverse square propagation law that's independent of frequency.

      But it does matter in practice.

      Background noise. The electromagnetic background noise level varies enormously with frequency. Here optical communications is actually at a big disadvantage compared with microwave, mainly because stars are brightest in the visible and near infrared. (Fortunately, it's fairly easy to exclude stars from interplanetary links with narrow-field telescopes.) The microwave range between 1 and 10 GHz is pretty quiet, which is why it's so heavily used for satellite and deep space communications. Below that range you start to run into sources of noise other than thermal radiation, such as lightning and radiation from charged particles trapped in magnetic fields.

      Bandwidth. Optical frequencies have much more room for broadband signals, but in practice microwave bandwidth is plentiful for deep space communications. Those links tend to be signal-to-noise ratio limited, not bandwidth limited.

      Antenna gain. Although the inverse square law applies equally at all wavelengths, antennas are not equally effective at all wavelengths. A receiving antenna's performance depends primarily on its aperture, the area with which it collects radiation, and that's independent of wavelength. But a transmitting antenna is different. The beamwidth of an antenna depends on its diameter in wavelengths, so a given antenna will transmit a narrower, tighter beam at shorter wavelengths, so more of it will land on the receiving antenna (assuming it's pointed accurately). So if you use a given pair of antennas on a given point-to-point link and vary just the wavength, the end-to-end power transfer efficiency will improve with shorter wavelengths at a rate of 6 dB per octave.

      Atmospheric absorption. Space is an empty vacuum, but the attenuation of the earth's atmosphere is a complex function of frequency. Below about 30 MHz, the ionosphere acts like a mirror; that's how "shortwave" broadcasts get worldwide coverage. There's a broad window from about 30 MHz up to about 10 GHz. Above that frequency, water vapor becomes increasingly important. There's a sharp absorption line at 60 GHz due to oxygen absorption, and above there it becomes increasingly opaque up until the infrared. There's another broad opening in the infrared and visible range, followed by more absorption bands in the ultraviolet (due, among other things, to the ozone layer).

      This leaves two places for interplanetary communication links: the microwave range between 1-10 GHz, and the optical range. The advantage in going optical lies entirely in the increased transmitter antenna gain that would allow much more of the limited spacecraft transmitter power to be directed to the receiving antenna on or near earth.

  • Women (Score:5, Funny)

    by 3770 ( 560838 ) on Tuesday November 16, 2004 @12:44AM (#10827335) Homepage
    I'd be happy if I could communicate with women. Why don't they work on that first?
    • Much like poverty and homelessness this talking with women can not be solved by technology... we've tried (www.americansingles.com, www.playboy.com, www.harmony.com) but to no avail... men who are beta-men will always be beta-men... just learn to live with it.... ...and accept YOUR ALPHA MALE SUPERIORS!

      Damn it man, be an asshole for once... treat the girl like a whore and she willlll respond.

      Don't be nice until you've gotten laid... then slam the door and move on...

      It's a numbers game... tell her this:

      "

  • The obvious thing to say is... (Score:5, Funny)

    by hunterx11 ( 778171 ) <hunterx11.gmail@com> on Tuesday November 16, 2004 @12:46AM (#10827347) Homepage Journal
    Suck on this, inverse-square law!
  • Just aim your telescope at Mars and hope someone miscalculates the reply message coordinates.

    BZAP!

  • It's a pretty cool idea. And I really like the way (Score:4, Interesting)

    by multiplexo ( 27356 ) on Tuesday November 16, 2004 @12:57AM (#10827408) Journal
    they're getting more use out of the big scope at Palomar. Both Palomar and Lick, which until the 1980s housed the largest telescopes in the world (200 inch and 120 inch respectively) have been impacted by light pollution from encroaching urban areas and air pollution. But here's a way to use these scopes for something that can't be affected much by either. Cool!

  • Well, OK (Score:5, Informative)

    by Anonymous Coward on Tuesday November 16, 2004 @01:05AM (#10827438)
    Hams object, not because it's a good and valid method of delivering bits, but because it interferes with emergency communications.

    There's lots of ways to get good Internet feeds to folks; just look at what Robert X. Cringely has done with 802.11b. Look in the archives of his columns at www.pbs.org and see there are untapped alternatives.

    To understand why we're concerned, go switch your hi-fi to AM, tune to a vacant spot between stations, and turn up the volume about half way. Then, try to have a phone conversation over a bad cellular connection with your ear six inches from the speakers, and you will still have an easier time communicating than hams will when we experience the 16 db over S9 interference already demonstrated by BPL.

    I will make a small wager with you, shaka999. If you live within North America, I'll wager your state's or province's emergency plan counts on hams. So does your county's emergency plan, and your city's.

    You see, hams _practice_ at getting data through emergency conditions. We do it at our expense, with equipment we buy, build and maintain ourselves, without government funds.

    There's even a subsection of every national ham organization dedicated to emergency services. Yeah, I belong to one, and was out in the last ice storm, two months ago, delivering nurses to the local hospital because the roads were otherwise impassible, and the locals had already overloaded the cellular network to the point where a fast busy tone or "All Circuits Busy" signal was as likely as dial tone.

    BPL threatens the entire ability to function on the frequencies needed the most for long-range communications, the HF bands. If this interfered with TV (VHF and UHF), well, everyone would kvetch, but instead the power companies have designed these systems to use HF (aka shortwave) frequencies.

    Long range radio relies on HF, because it takes those lower frequencies to effectively bounce off the inner layer(s) of the ionosphere. Higher frequencies (VHF, UHF, SHF, microwave) just zip right through the F, F1 & F2 layers, so we can't do bank shots to get a signal from Earthquakestan to Resourceland to let them know how many units of Type A to send.

    Satellite? Well, gee, that presumes the ground stations survived that quake/tornado/hurricane/typhoon, that the power didn't fail, and the phone lines to the earth station still work. Oh, yeah, and IF there's a free satellite channel for us, which NASA's problems have not made any easier.

    Now, America's three-quarters of a million hams are not alone here, as you make it seem. The NTIA (National Telecommunications and Information Administration), who you'd expect to be gung-ho over more bandwidth to previously underserved areas, and also FEMA (Federal Emergency Management Agency), have gone on record to object. They document that BPL was a complete disaster, interference-wise, when tried in Japan. The Austrian trials are on hold because the power companies there were not able to rein in the interference.

    But, it's Politics with a Capital P; who is beholden to whom, and who bought whom.

    Now, you might say, 'well, if there's a disater, the power's down, right'? Not necessarily. BPL can cause interference for miles and miles, but if a hospital needs to call for blood, what's the power company supposed to do, shut down the entire grid?

    Besides, remember that hams buy their own gear to practice and learn with. If we can't use HF, well, no one will buy new HF gear, no one will learn the tricks of HF (which is _very_ different than the skills needed for the garden-variety, talk-around-town two meter and 70 cm band users), and no one will bother to keep the automated packet netowrks in service, the digital backbones of the ham world which move the vast majority of message traffic.

    Sometimes, _nothing_ but Morse ("the original digital") will get through, but with BPL jamming the HF spectrum, morse will become a dead letter.

    I mean, man, you can put a bra on Michael Powell, and yuk it up all you want (see URL) but, damnit, these changes will *kill* people.
    http://www.wweek.com/story.php?story=4858
    • Someone needs to mod the parent up more! This is something everyone's overlooking here. The Amateur Radio service in America is screwed if this becomes reality and the ARRL [arrl.org] needs your help. Get your ham license today!
    • There's even a subsection of every national ham organization dedicated to emergency services. Yeah, I belong to one, and was out in the last ice storm, two months ago, delivering nurses to the local hospital because the roads were otherwise impassible

      Hmm... If you guys are transporting nurses over the radio I'm in the wrong business :)

  • Hmm... (Score:2, Funny)

    by flamechocobo ( 792168 )
    *walking along street* Hmm hmm hmm hmm hmm (humming a tune)... Wha? *looks up* AUUGGGHHHH!!! MY EEEEEEYEEEEESSSSS!!!

  • The benefits of lasers (Score:4, Funny)

    by Fussen ( 753791 ) on Tuesday November 16, 2004 @01:08AM (#10827456)
    When you add lasers to anything, the net benefit is multiplied by %5555. Interstella 5555 is a prime example.

    Ninjas also benefit from lasers ovbiously.

  • Safety Question (Score:2, Interesting)

    by Anonymous Coward
    Could someone more knowledgeable about lasers than me explain if this type of laser communication is safe? The article says it will be a 5W laser transmitting from 2.3 AU with a target area of several million square miles. That sounds like the signal would be very weak when it reaches Earth, but I don't know how strong a laser has to be to damage the retina. So, if this plan is implemented, would it be safe for people in the target range to look at Mars with a backyard telescope?
    • Safety??? What kind of a geek are you anyway?

      Also, the calculations are simple, once you realize that a 5W laser will put out fewer photons than a 100W light bulb. Now spread them out over "several million square miles" and stop worrying!

  • ...no more listening in for the evil nations (TM) ;-)
  • At least it'll have frickin' laser beams.

  • Problems with laser (Score:3, Informative)

    by smu johnson ( 309071 ) on Tuesday November 16, 2004 @03:05AM (#10827847)
    Laser has at least two major problems that I can think of.

    1. Lasers are pretty damn inneficient. At least compared to radio equipment that can be very efficient. When you're in the 2 percent range you're happy.

    2. Lasers are very high frequency. This is bad. Higher frequencies are absorbed MUCH more readily and are blocked by interfering objects. They also lose power faster through general attenuation through free space much faster than lower frequencies.

    And if you think the laser will make a small dot we can see, you're wrong. The laser light will probably cover half the other planet (this works out to look like attenuation)

    Basically, I dont see the reason to use lasers over long distances when lower freq RF works a lot better.

  • Why I'm a strong advocate of oxygen rationing.. (Score:4, Funny)

    by The Dodger ( 10689 ) on Tuesday November 16, 2004 @03:08AM (#10827855) Homepage
    Does this mean we will soon have telescopes outside of our homes soon to pick up high definition TV signals instead of our current 18 inch dishes?


    No.


    You fucking moron.

    D.

  • It really doesn't make any sense... we can normally aim something precisely by getting optical feedback from the target about the position we are currenly pointed at compared to where we really want to be.

    But several astronomical units away, things get kinda hairy because you won't receive even the slightest bit of feedback on whether you are actually closer to your target or if you overshot it completely for up to minutes later... Even the smallest hair of a fraction of a degree off and the beam wouldn'

    • This sort of thing is made significantly easier if there's a continually running transmitter on mars pointed at the entire earth because you can just look at the received signal strength and optimize on that.

      Of course, how you get it pointed at the earth is an excercise left for the chicken and egg.

  • Wouldn't doppler shifts due to the scale of interplanetary motion cause the wavelength of a laser beam to change its color? If so, you will need more than a telescope with just a simple receiver of, like say 650nm, to be able to pick up communications accurately. You would need a broadband receiver.

    I would sure hate to see another failed mars mission due to a missed conversion between nanometers and angstroms.
  • .....to get in contact with submarines,for example. [laseroptronix.se]

    In practice, it may work for Satellite - to satellite comms, but weather problems would impede its continous use in wide tracts of the earth.
  • Who cares? It all still travels at the same speed.

  • What the? (Score:3, Funny)

    by EmagGeek ( 574360 ) on Tuesday November 16, 2004 @06:04AM (#10828398) Journal
    "Does this mean we will soon have telescopes outside of our homes soon to pick up high definition TV signals instead of our current 18 inch dishes?"

    What kind of asinine question is this? I love it when someone makes themself look like a fucking moron trying to ask some insightful question in their article submission in a thinly veiled attempt at having their submission accepted.

    Of course we aren't going to soon use optics for TV distribution. It makes no sense. If a TV station were going to go out of their way to build a transmitter just to serve the house at 123 Any Street, that would be one thing, but TV stations want, and are required by law, to serve as many people as possible. Also, how does it make sense to use this hypothetical optical wide distribution scheme in an atmosphere that is detrimental to the transmission method? You think your dish TV gets bad in thunderstorms? Just wait until the fog rolls in on your laser receiver.

    Sheesh, the really sad thing is that freakin' timothy couldn't be bothered to exercise an iota of critical thinking skills on this one... fucking christ...

    Let the modding down begin...

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