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NASA Testing Frickin' Laser Communications

timothy posted about a year ago | from the beam-it-up-scotty dept.

Communications 108

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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http://tech.slashdot.org/ (-1, Offtopic)

Kathryn (3028993) | about a year ago | (#44663969)

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Re:http://tech.slashdot.org/ (-1, Offtopic)

LordKaT (619540) | about a year ago | (#44664005)

Yes, the website a29. is amazing, isn't it? 29 a's, all lined up in a row. My, how far technology has come!

Re: http://tech.slashdot.org/ (-1)

Anonymous Coward | about a year ago | (#44664491)

This is true. But for the sake of time savings, why don't I not look at he site and just send you an envelope of cash? Then I don't have to read all that web copy writing for idiots, by idiots. NO! You may not use that as your new slogan.

Speed, yes. Latency... NO. (3, Funny)

girlintraining (1395911) | about a year ago | (#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.

Re:Speed, yes. Latency... NO. (2)

maxwell demon (590494) | about a year ago | (#44664037)

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.

Re:Speed, yes. Latency... NO. (3, Funny)

peragrin (659227) | about a year ago | (#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).

Re:Speed, yes. Latency... NO. (1)

K. S. Kyosuke (729550) | about a year ago | (#44665273)

Hah. Love the Iron Sky reference!

Re:Speed, yes. Latency... NO. (0)

Anonymous Coward | about a year ago | (#44664231)

AND it only works when the moon isn't blocking the beam. So much for Zynga's lunar business model.

Re:Speed, yes. Latency... NO. (1)

girlintraining (1395911) | about a year ago | (#44664281)

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.

Re:Speed, yes. Latency... NO. (0)

Anonymous Coward | about a year ago | (#44665225)

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.

/. has a threaded discussion system. From the fact your post appeared as a top-level post, not as a reply to some earlier post, I feel confident in stating "No, you were not replying to that post." Don't blame other people for your failure to indicate what you were talking about (by replying to and/or quoting the parent post).

Re:Speed, yes. Latency... NO. (1)

wagnerrp (1305589) | about a year ago | (#44665649)

There was a post earlier I was replying to...

So why didn't you actually reply to that earlier post?

Re:Speed, yes. Latency... NO. (1)

Nutria (679911) | about a year ago | (#44665813)

Must. Not. Snark. About. Girls. Bungling. Technology....

Re: Speed, yes. Latency... NO. (0)

Anonymous Coward | about a year ago | (#44666085)

Let's give her some leeway. She's still in training after all.

Re:Speed, yes. Latency... NO. (0)

Anonymous Coward | about a year ago | (#44666513)

No, you really don't want to do that. It only takes an errant glance (or a single -1) to set girlintraining off on one of her rants.

Re:Speed, yes. Latency... NO. (1)

Shavano (2541114) | about a year ago | (#44664341)

With a direct radio link, you also get the lowest latency physically possible. The laser is to allow more energy efficient transmission.

Re:Speed, yes. Latency... NO. (1)

K. S. Kyosuke (729550) | about a year ago | (#44665265)

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?

Re:Speed, yes. Latency... NO. (2)

mcgrew (92797) | about a year ago | (#44664275)

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.

Re:Speed, yes. Latency... NO. (1)

girlintraining (1395911) | about a year ago | (#44664437)

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 that.

It's fine though for a satellite with a fat buffer and whose data isn't time sensitive, which is what NASA is using it for; My comments were directed towards people who think this could be used for something else. Achem... it could, but it'd be a bad idea.

Re:Speed, yes. Latency... NO. (1)

Nutria (679911) | about a year ago | (#44665831)

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

Where are those people's comments/delusions?

Re:Speed, yes. Latency... NO. (3, Informative)

mikael (484) | about a year ago | (#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.

Re:Speed, yes. Latency... NO. (3, Informative)

girlintraining (1395911) | about a year ago | (#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.

Re:Speed, yes. Latency... NO. (0)

Anonymous Coward | about a year ago | (#44665099)

Those bands, which are not relevant to clouds but are still relevant to an otherwise very wet atmosphere, are huge for communication. There is more than two, including ones that cover some very common communication laser equipment in the near infrared.

Re:Speed, yes. Latency... NO. (0)

Anonymous Coward | about a year ago | (#44665251)

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.

You're a bit thick, eh? We're talking laser comms here, which are nearly monochromatic -- you don't need a "big" window.

Re:Speed, yes. Latency... NO. (1)

Nutria (679911) | about a year ago | (#44665867)

You're a bit thick, eh? We're talking laser comms here, which are nearly monochromatic -- you don't need a "big" window.

Unless you want to simultaneously use multiple frequencies so as to increase throughput even more.

Re: Speed, yes. Latency... NO. (0)

Anonymous Coward | about a year ago | (#44666145)

Yeah, but girlintraining is complaining about windows on the order of an octave wide (e.g. from ~1um to ~2um). Yeah, you need some room for multiple wavelengths, but how bloody many lasers can you afford to shine at one spacecraft? (Keep in mind there's no need for wavelength multiplexing to accomodate different satellites, since we're using quite narrow beam-widths It's limited to the up- and down-link equipment in the satellite.)

Re:Speed, yes. Latency... NO. (1)

girlintraining (1395911) | about a year ago | (#44666761)

Unless you want to simultaneously use multiple frequencies so as to increase throughput even more.

Now now, be nice. He probably still thinks that if we do morse code fast enough, we can transmit the whole internet on 1hz of spectrum. :\ I'd enlighten him about shannon's law, and the relationship between SNR, bandwidth, and how to go about encoding information using phase, amplitude, frequency, etc., but at some point you just have to tell him to stay in school, read a few more books... you get the idea. The worst part is, he probably doesn't realize that lasers don't operate on a single frequency, but in a range. Admittedly, it's a limited range, but there is a spread -- it's not just 'off on off on off on'...

Re:Speed, yes. Latency... NO. (0)

Anonymous Coward | about a year ago | (#44667133)

Except that one of many of those windows is in the tens of THz wide, and tunable lasers can be narrowed to a 100-200 MHz wide spectrum, to the point you are more limited by the amount of information you want to send than the natural width of the laser. That doesn't sound like a restriction a "narrow" communication band really in any meaningful sense for decades to come.

Re:Speed, yes. Latency... NO. (0)

Anonymous Coward | about a year ago | (#44668041)

It is like watching a discussion of the feasibility of a supersonic jet airliner, and you're a person talking down to people because they are "too unenlightened to not acknowledge the speed of light and relativity as an issue." It is not that the speed of light and Shannon's law are not ultimate limits, as they sometimes are a very serious concern, it is that they are so far removed from the scales of the particular situation under discussion. It looks like you are just throwing things out and seeing what sticks, or just have a hammer and are trying to make everything look like a nail instead of actually contributing something relevant.

Re:Speed, yes. Latency... NO. (1)

Nutria (679911) | about a year ago | (#44665849)

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

Re:Speed, yes. Latency... NO. (0)

Anonymous Coward | about a year ago | (#44664355)

That's OK, there's nobody on the probe to play a game. But there will be lots of accumulated data to download.

Re:Speed, yes. Latency... NO. (1)

gmuslera (3436) | about a year ago | (#44664401)

For some games that latency would be a killer. But the US army think that it would be ok for playing Space Invaders.

Re:Speed, yes. Latency... NO. (1)

LordKaT (619540) | about a year ago | (#44664413)

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

Re:Speed, yes. Latency... NO. (1)

Anonymous Coward | about a year ago | (#44664433)

The secret to success is getting modded up no matter how wrong you are. No amount of AC trolling can compete with that.

Re:Speed, yes. Latency... NO. (1)

Khyber (864651) | about a year ago | (#44664511)

"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.

Re:Speed, yes. Latency... NO. (1)

module0000 (882745) | about a year ago | (#44664669)

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.

Re:Speed, yes. Latency... NO. (2)

module0000 (882745) | about a year ago | (#44664761)

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.

Re:Speed, yes. Latency... NO. (1)

K. S. Kyosuke (729550) | about a year ago | (#44665317)

The Moon is ten times farther away.

Re:Speed, yes. Latency... NO. (1)

module0000 (882745) | about a year ago | (#44665337)

Doh, that's what I get for barely reading the summary! I was thinking about satellites in GEO.

Re:Speed, yes. Latency... NO. (1)

Smallpond (221300) | about a year ago | (#44665349)

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

Re:Speed, yes. Latency... NO. (1)

module0000 (882745) | about a year ago | (#44665355)

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

Re:Speed, yes. Latency... NO. (1)

Anonymous Coward | about a year ago | (#44664793)

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.

About the cloud issue:

The laser on NASA’s upcoming LADEE mission will communicate directly with Earth using a different approach that is less susceptible to atmospheric interference. It encodes information AM-style by tweaking the amplitudes rather than the frequency of a light wave’s peaks.

And:

LADEE carries NASA’s first dedicated laser communications system. With a bandwidth of 622 megabits per second, more than six times what is possible with radio from the distance of the Moon, the system can broadcast high-definition television-quality video. But even though its AM optical system is good at penetrating Earth’s turbulent atmosphere, it will still need a backup radio link for cloudy days when the laser is blocked. To minimize this problem, LADEE’s primary ground station is in a largely cloudless desert in New Mexico, with alternative sites in two other sunny spots: California and the Canary Islands.

Nature | News - Lasers boost space communications [nature.com]

Re:Speed, yes. Latency... NO. (1)

radarskiy (2874255) | about a year ago | (#44665431)

*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?

Re:Speed, yes. Latency... NO. (0)

Anonymous Coward | about a year ago | (#44665809)

Apparently was too excited about that Star Trek news yesterday....

Re:Speed, yes. Latency... NO. (1)

slick7 (1703596) | about a year ago | (#44666569)

Not reliable at all.

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

Re:Speed, yes. Latency... NO. (1)

lsatenstein (949458) | about a year ago | (#44666575)

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.

Re:Speed, yes. Latency... NO. (0)

Anonymous Coward | about a year ago | (#44666981)

no not really. The latency will improve over traditional sattiles which is what it will replace.

Lasers travel faster than radio waves.

Re:Speed, yes. Latency... NO. (1)

grcumb (781340) | about a year ago | (#44667537)

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?

Re:Speed, yes. Latency... NO. (1)

VortexCortex (1117377) | about a year ago | (#44668063)

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.

Uh, yeah, and? Playing and developing network applications and games for such networks is old hat to us BBS sysops... You've just been spoiled by the Internet; It's quaint, really.

Latency has nothing to do with reliability. Bonus, if the connection is down it doesn't matter since the system is called Delay Tolerant Networking. Soon as it comes back up again the data is beamed to the nearby nodes, and next time you check it's there even if the remote connection isn't. Look at it the other way: The Green Mechanoid Army has set the siege plans in motion sometime last night, and even though the link is broken right now, the relay is providing their cached deployment strategy and when you join the game you can see they're taking the bait and call on your alliance with the Warlock Empire of Earth to flank them. Sure, gameplay is slower, but that's fine for some games, (see: BBS Door Games -- Protip: Tradewars was rated 10th best game of all time by PC World...) Not every game has to be played the same time-frame. It's a different experience to check in, see what happened, and make your moves then be done with that game for the day. See? It's not a ton of grinding for grinding's sake, and lets you get on with your life (or local multiplayer deathmatch) -- We can all just get along: The highest rated Cat Videos of Earth can be beamed up to Mars or the Moon on schedule while that video that everyone linked in their earth-bound emails of the Rover with Bunny Ears only has to get sent down once through the network.

Nowadays we have better than ANSI graphics, but we can also do some wicked client side prediction: Think of that progress bar that seems to slow down logarithmically... In game time can go like that, picking back up as new data arrives, but I won't bore you with details... Responsiveness is a luxury of a local planetary network, but store and forward does work. High bandwidth is key for spotty connections with high latency. Fidonet, for all it's drama, actually delivered my pre-Internet email just fine...

In a decade or so there will be bored people on Mars.... That's a problem we have the technology to fix in a big way. The massive amount of bandwidth of Laser Communication is actually a much needed addition to the DTN.

TL;DR: This has all happened before, and it will all happen again. Don't be a lamer, newb.

Re:Speed, yes. Latency... NO. (1)

VortexCortex (1117377) | about a year ago | (#44668101)

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.

freaking lasers (1)

Anonymous Coward | about a year ago | (#44664023)

and no shark?!?

Re:freaking lasers (5, Funny)

Shark (78448) | about a year ago | (#44664327)

Nah, I'm here. The laser hadn't locked in yet. Do you know how hard it is to aim your head at something in frickin' space?! Gimme a break, jeez...

Re:freaking lasers (2)

Concerned Onlooker (473481) | about a year ago | (#44667455)

Glad to see you came out of the tornado OK.

Awful headline (2, Insightful)

Anonymous Coward | about a year ago | (#44664043)

I hate you

Speed of light v. Comcast (0)

Anonymous Coward | about a year ago | (#44664061)

The moon gets locked in as monopoly territory and those speeds will drop.

Re:Speed of light v. Comcast (0)

Anonymous Coward | about a year ago | (#44664075)

Yeah, but the price goes up by an order of magnatude after the trial period ends.

Re:Speed of light v. Comcast (0)

Anonymous Coward | about a year ago | (#44664477)

Attitude + Magma = Comcast's magnatude?

Not so impressed (1)

Morpf (2683099) | about a year ago | (#44664133)

As if laser communication would be something new...

Re:Not so impressed (1)

mcgrew (92797) | about a year ago | (#44664279)

Apparently newer than reading the summary.

I See the Reason, ROBOTs on the Moon 24/7 (1)

LifesABeach (234436) | about a year ago | (#44664159)

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.

Re:I See the Reason, ROBOTs on the Moon 24/7 (1)

gmuslera (3436) | about a year ago | (#44664417)

That would be nicer than putting (spoiler alert) the clones of Sam Bell [imdb.com] there.

A long time coming (3, Informative)

mbone (558574) | about a year ago | (#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.

Re:A long time coming (1)

mikael (484) | about a year ago | (#44664359)

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.

Re: A long time coming (1)

Anonymous Coward | about a year ago | (#44664811)

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 difficult to maintain altitude(even floaters go from very high, near 60,000 feet or more, in the day, to almost touching the ocean at night). Either way the ballons will move latterally with wind patterns so the link wouldn't last long either. Even modern tracking systems(of which I've built one) depend on GPS data and couldn't maintain accuracy for such a small beamwidth as a laser to go that far.

Re:A long time coming (3, Interesting)

Shavano (2541114) | about a year ago | (#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.

Re:A long time coming (1)

Immerman (2627577) | about a year ago | (#44664685)

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 and streams them to Earth for analysis, in which case more bandwidth translates to either greater temporal resolution or longer "filming" periods.

As for lasers to Earth, it depends on the laser. UV penetrates clouds pretty well, and ducks aren't enough of an obstacle to interfere with any decent error-correcting transmission encoding.

Re:A long time coming (4, Informative)

mbone (558574) | about a year ago | (#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.

Re:A long time coming (1)

Immerman (2627577) | about a year ago | (#44665007)

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.

Re:A long time coming (0)

Anonymous Coward | about a year ago | (#44664733)

Yes, the real application for this will clearly be a laser link to an extraplanetary satellite/probe from a satellite or station in Earth orbit. For added reliability, have a handful of EORLs (earth-orbiting relay laser satellites, note that I hereby trademark the acronym!). No need to shoot lasers through earth's atmosphere -- and in a few more years, we won't have to do microwave downlinks either, since we can just leave the data in one of Google's orbiting server farms. :-)

Re:A long time coming (0)

Anonymous Coward | about a year ago | (#44665821)

because of clouds and ducks that radio goes right through

Because the sharks with lasers eat the ducks?

Cool, (0)

Anonymous Coward | about a year ago | (#44664197)

but it's still sub-space communications...

Laser communications huh? (0)

Anonymous Coward | about a year ago | (#44664233)

I first saw a laser used to send a voice transmission in like 1969 or so so exactly what is new about this?

Re:Laser communications huh? (1)

Shavano (2541114) | about a year ago | (#44664465)

Long distance in space.

Re:Laser communications huh? (1)

Immerman (2627577) | about a year ago | (#44664689)

Careful, the roaming charges are killer.

Interference? (0)

Anonymous Coward | about a year ago | (#44664251)

Fix it for actual transmissions further away in space, that way you don't need to think about refraction in the atmosphere.

all the better to psy on you my lil dearies (0)

Anonymous Coward | about a year ago | (#44664301)

yes yes what can be done with this .......

Huh? (0)

Anonymous Coward | about a year ago | (#44664353)

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."

The Terra satellite was doing 150 Mbp/s downlink in the late 1990's. Mr Cornwell needs to check his math, and find out what the current technology is.

Re:Huh? (5, Insightful)

mbone (558574) | about a year ago | (#44664891)

A modest suggestion - whenever you feel like someone has made a basic math error in their own field, or doesn't know basic facts about the technology in their own field, and they are a high-level professional in that field, say, a mission manager talking to the press, and you are not, you should consider the possibility that you might be the one who is mistaken.

Re:Huh? (1)

yusing (216625) | about a year ago | (#44666593)

But this is the Internet. You don't have to know anything about a subject, or even understand what someone's saying to remit some dopey argument because there's nothing worth watching on TV.

But this is Slashdot. So thanks for making the modest suggestion, even though that never seems to penetrate the cloud cover.

Re:Huh? (1)

swillden (191260) | about a year ago | (#44666679)

A modest suggestion - whenever you feel like someone has made a basic math error in their own field, or doesn't know basic facts about the technology in their own field, and they are a high-level professional in that field, say, a mission manager talking to the press, and you are not, you should consider the possibility that you might be the one who is mistaken.

OTOH, the Terra press kit [nasa.gov] distributed by NASA includes the following statement:

The science data recorded onboard will be transmitted via Kuband at 150 Megabits per second.

Re:Huh? (0)

Anonymous Coward | about a year ago | (#44667443)

Original AC misunderstood what comparison was being made. The "six times faster" is not six times faster than radio communication in any given situation (consider how fast experimental WiFi can go...), but six times faster than if radio communication was used on the same probe, at the same distance with the same power budget. Terra would be in a whole different class of satellites in a different situation.

Re: Huh? (0)

Anonymous Coward | about a year ago | (#44664907)

The Terra satellite was in orbit around the Earth, not the Moon.

Bandwidth drops when distance increases (see "free-space path loss" and "channel capacity"). As a result, Terra's bandwidth to Earth would have been significantly lower if it had been in orbit around the Moon, much farther from Earth.

Re:Huh? (3, Informative)

Anonymous Coward | about a year ago | (#44664939)

The Terra satellite was also almost 5 tons in mass with 2.5 kW of power to work with in low Earth orbit. LADEE is a twentieth of the mass, with a tenth of the power budget, and in lunar orbit. The situations are different, and it is like you are complaining a 1000+ HP car is trivial because cargo ships do that all the time.

Pffft (1)

fahrbot-bot (874524) | about a year ago | (#44664395)

My moon satellites will all use FiOS to communicate with Earth.

Re:Pffft (2)

rrohbeck (944847) | about a year ago | (#44664861)

But wouldn't the cable get all tangled up?

Testing for the military (0)

Anonymous Coward | about a year ago | (#44664419)

They want reliable communications that can't be jammed. NASA wants high-bandwidth deep space comms.

See also : (0)

Anonymous Coward | about a year ago | (#44664523)

http://www.esa.int/Our_Activities/Telecommunications_Integrated_Applications/Alphasat/Optical_Communication

Launched last July 25th on Ariane 5.

Questionable Utility (1)

ATestR (1060586) | about a year ago | (#44664853)

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.

Huh... (2)

koan (80826) | about a year ago | (#44664917)

Why is it asymmetric? Gravity?

*wink*

Re:Huh... (1)

Behrooz Amoozad (2831361) | about a year ago | (#44665111)

Nope, It's just because they can build a very huge receiver on the ground that can receive signal with much less error and that allows them to have less FEC and bla bla bla that makes this huge difference.

Re:Huh... (1)

EnsilZah (575600) | about a year ago | (#44665207)

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

Re:Huh... (1)

mbone (558574) | about a year ago | (#44667767)

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.

OH OH o:O (1)

Nov8tr (2007392) | about a year ago | (#44665027)

OMG!! It's Sharknado with frikin' laser!! RUN!!

Weather Forecast (1)

Kuruk (631552) | about a year ago | (#44665129)

What happens on a cloudy day ?

Re:Weather Forecast (1)

Smallpond (221300) | about a year ago | (#44665419)

Did you know you can still get a sunburn on a cloudy day? Why do you think that is?

Re:Weather Forecast (1)

Nutria (679911) | about a year ago | (#44665925)

Ultraviolet Magic Pixie Rays.

unsolved problem (1)

Zecheus (1072058) | about a year ago | (#44665539)

Has NASA settled the question? I guess so. Upload rates are ALWAYS a fraction of download rates.

Re:unsolved problem (0)

Anonymous Coward | about a year ago | (#44666953)

Has NASA settled the question? I guess so. Upload rates are ALWAYS a fraction of download rates.

I'm not from NASA, but I'll try to settle the question. It's not a conspiracy, it's just that you want your space vehicle to send down as much data as it can but there is no need to send a lot of data back to it.

You want to get as much science data (pictures, video, data, etc.) from your space vehicle to the ground as you can, but there isn't a lot of data that needs to be sent up to the space vehicle. Most science missions collect tons of bytes of data and it takes far fewer bytes to control them (i.e. tell them where to point their camera, when to collect images, and when to turn on the transmitter to send data back to Earth, etc.). You also want to ensure that the space vehicle reliably receives the instructions you send it and the slower the data rate the more reliably you can receive it.

Think of your space vehicle as a video site like hulu. You want to watch as many streaming videos on your PC as you can so you care about having high download speed, but it doesn't take high upload speed to watch your videos. You don't upload video to hulu so your upload speed doesn't matter. If you are a hulu watcher and you pay more for a higher speed connection then you would want to put as much money into your download speed as you can and save on upload speed. A science space vehicle isn't a web site - you don't ever upload video or lots of data to it. Space missions do pay more for higher data rates so they size their communications equipment for what it takes to get the mission done. Lots of data down means you need high downlink rates. Not too much data up means you don't need very high uplink rates. Higher data rates equal higher cost, and in this era of limited budgets for space science nobody can afford to do any more than the bare minimum necessary to get the job done or their mission gets cancelled before they ever launch.

That's why for missions that collect science data the download rates are ALWAYS much higher than the upload rates.

Space to space communication (1)

Required Snark (1702878) | about a year ago | (#44665799)

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 satellites.

Hopefully this works better than his speed cameras (0)

Anonymous Coward | about a year ago | (#44666215)

Because it is demonstrated again and again the Optotraffics' lidar based speed cams SUCK!

Now put it in a sat and give me one for home. (1)

Ralph Ostrander (2846785) | about a year ago | (#44667189)

And make it 9.99 a month and put everyone else out of business. Pretty please.
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