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Is a Laser Data Link 1.5 Million Kilometers Feasible?

CmdrTaco posted more than 6 years ago | from the keep-on-truckin dept.

Space 304

An anonymous reader writes "On the Canary Islands last week, a team from Oerlikon Space demonstrated the feasibility of a laser link across a distance of 1.5 million kilometers for the first time ever. In the future, laser links like this one will be able to transmit data across huge distances through the universe far more rapidly and efficiently than is possible using conventional radio links today."

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304 comments

Never saw this coming (5, Interesting)

LiquidCoooled (634315) | more than 6 years ago | (#21268235)

Who would have thought that light could travel such a long distance?

In all seriousness, the problem is not the knowledge a laser can travel that far; its whether you can create precise enough targeting equipment.
A radio signal might be more of a splatter, but at least if you point it "over there" with enough power behind it, it will get there.

As they say their simple hilltop to hilltop test failed because of weather conditions, whats going to happen when they do put 'scopes at the lagrange points?

"Oh sorry, we can't get the data today because its cloudy"

Back onto the radio front, we have Voyager 1 which is 15 billion miles away, proven with radio, that would seem good enough for me.

Re:Never saw this coming (2, Insightful)

WormholeFiend (674934) | more than 6 years ago | (#21268283)

I'm assuming that in space, the problem will not be weather conditions, but "aim"

Re:Never saw this coming (5, Funny)

erroneus (253617) | more than 6 years ago | (#21268331)

I'm not sure the space-technology people will be using "aim." If anything, I'd suspect they'd lean to something OSS like "Pidgin."

Re:Never saw this coming (1)

LiquidCoooled (634315) | more than 6 years ago | (#21268359)

Are the scopes going to be sending the data to themselves or will they be expected to transit it back to earth?

Re:Never saw this coming (1)

PieSquared (867490) | more than 6 years ago | (#21268663)

They'll send data to communications satellites which will use radio to send it back to earth?

Re:Never saw this coming (0)

Anonymous Coward | more than 6 years ago | (#21268861)

which is bloody obvious had the GP thought about it for one fucking millisecond.

Re:Never saw this coming (2, Insightful)

phil reed (626) | more than 6 years ago | (#21268401)

Back onto the radio front, we have Voyager 1 which is 15 billion miles away, proven with radio, that would seem good enough for me.
Yeah, but what's the data rate?

Re:Never saw this coming (1)

mastershake_phd (1050150) | more than 6 years ago | (#21268507)

Back onto the radio front, we have Voyager 1 which is 15 billion miles away, proven with radio, that would seem good enough for me.

Yeah, but what's the data rate?

14.4?

Re:Never saw this coming (1, Funny)

Anonymous Coward | more than 6 years ago | (#21268541)

Yeah, but what's the data rate?
About 299,792,458 m / s.

Re:Never saw this coming (1)

SnoopJeDi (859765) | more than 6 years ago | (#21268881)

I guess the introduction of the Meter as a datatype is one of the features of that new Leopard thing?

Re:Never saw this coming (0)

Anonymous Coward | more than 6 years ago | (#21268651)


Yeah, but what's the data rate?


The data rate is fine. It is the ping times that are a killer.

Re:Never saw this coming (0)

CommunistHamster (949406) | more than 6 years ago | (#21268869)

Voyager 1 has 70kb of memory (or storage, I can never remember which) so the bandwidth of the data link must be less than or equal to that.

Re:Never saw this coming (1)

Neo_piper (798916) | more than 6 years ago | (#21268491)

Not to mention routing air traffic around signal stations.
And speaking of "Splatter" how (I'll put this gently) "nature proof" are those transceivers?

Re:Never saw this coming (5, Funny)

ricosalomar (630386) | more than 6 years ago | (#21268595)

...proven with radio, that would seem good enough for me.

I agree. We should stop all development and research in this area immediately.

Is there anything else that people are working on that you don't see a need to improve? They should have checked with you first, I guess.

This is a very good point... based on that logic.. (2, Insightful)

keirre23hu (638913) | more than 6 years ago | (#21268939)

we have the Gas engine... it works.. lets forget about all this crazy hybird and electric car talk...

While we're at it, Coal Plants do a good job at producing energy and they work too... lets forget about all that fandangled alternate energy source stuff...

While were at it.. smoke signals work too.. no need for complicated technology like telephone and email...

okay.. now that my sarcasm limit has been reached... because something works is not a good reason for ignoring technology that can potentially supercede it...

Re:Never saw this coming (5, Interesting)

vertinox (846076) | more than 6 years ago | (#21268661)

As they say their simple hilltop to hilltop test failed because of weather conditions, whats going to happen when they do put 'scopes at the lagrange points?

Huh? The logical thing do to would be have the laser communicators in orbit, and the communication from ground to the laser satellites would be via the conventional means. If its cloudy in your town, then the satellite can talk to another town which isn't cloudy and you can use fiber to talk the rest of the way.

Lagrange points (4, Interesting)

camperdave (969942) | more than 6 years ago | (#21268805)

whats going to happen when they do put 'scopes at the lagrange points?

I've been thinking about the Earth/Sun Lagrange points lately. I think they might be an excellent location to test an Earth/Mars transit vehicle. ESL5 is far enough away to be out of Earth's magnetosphere, so it will experience the raw radiation environment. It would be able to remain in position for long periods of time. The only hitch I can see is it may not be easy to get to/from. I can't seem to find any data. If we put a test platform with a "lifeboat" craft there, how quickly could the craft get back here. Is it days away? weeks away? Anybody know?

Re:Never saw this coming (1)

moderatorrater (1095745) | more than 6 years ago | (#21268893)

There's also the little matter of, well, matter. Dust clouds, intervening meteors, etc, that would degrade the quality of the signal. The problem with radio isn't that it's not reliable, it's that it's bandwidth is lower and it can't be aimed as precisely. With the proper optical equipment, we could shoot a laser from Alpha Centauri that hit the earth and nothing but the earth. Doing the same with a radio wave would be difficult at best.

However, as you said, radio's doing just fine for us right now. I imagine radio being the old reliable, the copper wire to laser's fibre optic, as it were.

Mis-aiming (1)

TWX (665546) | more than 6 years ago | (#21268905)

Just be careful to keep the aim right, you don't want to end up blowing up your power station and taking out a few blocks of your city...

My dick is 1.5 million kilometers long (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#21268237)

Thats right. I'm huge.

A bit exaggerated? (2, Interesting)

Greg01851 (720452) | more than 6 years ago | (#21268281)

"laser links like this one will be able to transmit data across huge distances through the universe" I think they mean "through the solar system"... laser wouldn't be very efficient "through the universe"... I think we may have other means of communication by the time we need to think about distances that vast.

One important warning (5, Funny)

Anonymous Coward | more than 6 years ago | (#21268299)

Do not look into laser with remaining eye.

Just wait... (-1, Redundant)

Anonymous Coward | more than 6 years ago | (#21268311)

...until they mount them in the heads of FREAKING sharks!

Interesting to use this with radio telescopes (3, Insightful)

DamonHD (794830) | more than 6 years ago | (#21268313)

Hi,

It seems to me that this would be especially useful to reduce the amount of induced radio noise when communicating with L1 (etc) radio telescopes or other instruments potentially sensitive to the normal radio frequencies used for communication, eg keep the comms out-of-band of what is being measured as far as possible.

Rgds

Damon

Question about lasers (1)

schnikies79 (788746) | more than 6 years ago | (#21268335)

Do lasers follow the inverse square law? I'm guessing it doesn't since it's focused.

Either way, correct alignment seems pretty tough.

Re:Question about lasers (3, Informative)

rcw-home (122017) | more than 6 years ago | (#21268445)

Do lasers follow the inverse square law? I'm guessing it doesn't since it's focused.

Yes they do, since that focus is never perfect. A cheapie laser pointer will show a 1/8" dot at 30 feet and a 1/4" smudge at 60 feet.

Re:Question about lasers (0)

jnewmano (462029) | more than 6 years ago | (#21268619)

Unfortunately your example is not the inverse square law. It would be more along the lines of 1/8" at 30 feet and 1/2" at 60 feet. Your example is showing the effects of a lens, which would explain the nice linear relationship with distance.....

It doesn't sound like you know much about optics or lasers....

Re:Question about lasers (5, Insightful)

Anonymous Coward | more than 6 years ago | (#21268757)

It doesn't sound like you know much about mathematics. Please check the relation between the diameter of the laser spot and the power/area ratio, then rethink what the inverse square law actually says.

Re:Question about lasers (1, Insightful)

Anonymous Coward | more than 6 years ago | (#21268495)

laser are not focussed they are coherent... sheesh.

Re:Question about lasers (2, Interesting)

kevmatic (1133523) | more than 6 years ago | (#21268557)

Lasers diffuse over a distance, just like normal light bulbs, albeit a much smaller rate.
So, the farther away you go, the bigger the "dot" the beam casts is. The inverse square law applies. If it didn't, overall power would have been added as the beam travels (the dot would be bigger, but the same brightness). This is a law of physics.

I'd imagine you'd kinda have to aim carefully, but by the time it could 1.5 billion miles the beam would be, at least, hundreds of miles across. Which means you better have a sensitive photo detector, just as you would need sensitive antennae with radio waves.

But having to aim is the point (PUN), really. Concentrating the beam reduces the energy needed to get it there, because the energy is spread out over a smaller area.

Laser moon and back = a few feet in diameter spot (1)

davidwr (791652) | more than 6 years ago | (#21268723)

I don't recall the details bit I seem to recall astronauts putting a target on the moon's surface back in the '60s or '70s. The laser was a few feet or less in diameter when it returned to earth.

Laser moon and back feet, more like *miles* (5, Interesting)

Overzeetop (214511) | more than 6 years ago | (#21268907)

Correct, they did put corner cubes on the moon (aka retroreflectors, or three mirrored surfaces all at 90 degree angles to one another).

However, the beam size from a collimated laser is a couple miles across at the moon. Typically, receiving a signal back takes a large telescope which counts single-digit photon returns from a Nd:YAG q-switched laser. It's been almost 2 decades since I worked with the stuff (you might search for Satellite Laser Ranging, Goddard Optical Research Facility and MOBLAS or TLRS) and the units that ranged on the moon cubes were at Mt. Haleakala in Hawaii.

It was neat stuff, but I remember one of the PIs saying the spot on the moon was the size of Georgetown (a section of Washington DC), though I can't remember exactly now. The outgoing laser was about 4" in diameter.

Re:Question about lasers (2, Informative)

hansraj (458504) | more than 6 years ago | (#21268725)

I could be wrong so someone knowing better please correct me.

The inverse square law is applicable only for point sources that are radiating in every direction. The inverse square of distance d arises in the formula that you are interested in the surface of a ball centered at the source with radius d. The surface area is proportional to the square of distance so intensity in some part of the surface relates to the inverse.

Now lasers are not omnidirectional so the inverse square law is not applicable.

Aiming will be a major problem (1, Redundant)

Constantine XVI (880691) | more than 6 years ago | (#21268369)

One of the biggest problems we'll run into with this is aiming the beam between the sender/reciever. 1.5Mil Kilometers is already enough of a distance, but we also have to keep in mind the fact that both ends will likely be in constant motion.

Re:Aiming will be a major problem (2, Informative)

onion2k (203094) | more than 6 years ago | (#21268675)

When the Apollo mission landed on the Moon they left behind a retroreflector that NASA used (still use?) to bounce a laser back and forth to measure the distance from the Earth very accurately. That's 385,000 km. If they were doing that in the late 1960s I don't see any reason why 1.5m km should be that tricky today.

Hard to aim == Hard to intercept (1)

ebolaZaireRules (987875) | more than 6 years ago | (#21268933)

Perhaps - but on the other hand, its not like it will be easy to eavesdrop on. (almost) no divergence... you know that the only person listening is the person to who its directed.

I guess you could get _some_ info from diffraction (eg - metal powder), but at a much reduced intensity - and a resulting weaker signal.

Re:Aiming will be a major problem (1)

Stonent1 (594886) | more than 6 years ago | (#21269031)

If you think about this like a lever. A change in yaw of 1mm on the sender side could shift the end point many kilometers.

The horror... (0, Redundant)

SlipperHat (1185737) | more than 6 years ago | (#21268381)

Space sharks with frikkin' laser beams! They use lasers not to kill, but to coordinate with other space sharks.

"far more rapidly" (4, Funny)

InvisblePinkUnicorn (1126837) | more than 6 years ago | (#21268407)

Because lasers travel at least 42 times as fast as radio waves!

Re:"far more rapidly" (2, Insightful)

Abcd1234 (188840) | more than 6 years ago | (#21268533)

Well, while I thought the same thing you did at first, I suspect they mean that the actual data rate will be higher due to lower noise on the channel and/or other factors.

Re:"far more rapidly" (1)

Kjella (173770) | more than 6 years ago | (#21268539)

Yeah, I was also thinking WTF at that summary. Radio waves and laser light are both electromagnetic waves and travel at the same speed, so this will do nothing for say the responsiveness of say controlling a drone on Mars. It may improve bandwidth so we can transfer more data, but I'd say we're doing pretty good in that department already, I'm not sure what a HDTV feed from Mars would give us.

Re:"far more rapidly" (1)

j0nb0y (107699) | more than 6 years ago | (#21268727)

Oh c'mon. You don't want to watch the Mars Bowl in low def, do you? With technological advances like these, soon we'll be able to watch all intergalactic sporting events in Hi Def!

Referring to Bandwidth? (1)

dunc78 (583090) | more than 6 years ago | (#21268545)

I was curious about the same comment, but they must just be referring to the higher bandwidth available at optical frequencies compared to radio frequencies. In other words, the latency would be the same, but once the first bit hits, you will get the next million bits "more rapidly" and the next trillion bits "far more rapidly."

Re:"far more rapidly" (2, Funny)

huckamania (533052) | more than 6 years ago | (#21268553)

I'm guessing that the laser packs the 1s and 0s better then the radio waves. Or maybe they leave out the 0s.

Re:"far more rapidly" (1)

dylan_- (1661) | more than 6 years ago | (#21268781)

Yes, that's how the data is sent more rapidly. It's a little known fact that the UHF waves from 802.11g wireless points travel about 5 times the speed of those from 802.11b points.

Re:"far more rapidly" (1)

Sockatume (732728) | more than 6 years ago | (#21268859)

We'll just get the European Parliment to increase the speed of light. It's such a silly limit, anyway.

Targeting that is going to be a bitch. (1)

y86 (111726) | more than 6 years ago | (#21268441)

Great idea, now try to do the math on all of the floating bodies and the effect of the gravity from neighboring quasars and other space phenomena.

I could see it working but the receiver would have to be huge. It's hard enough to hit someone with a gun at a mile using a laser sight (windage which would be comparable to space effect on the laser light).

Maybe a single shot of data, but maintaining that connection would be very difficult IMHO.

It's still a cool idea.

Re:Targeting that is going to be a bitch. (5, Funny)

meringuoid (568297) | more than 6 years ago | (#21268559)

now try to do the math on all of the floating bodies and the effect of the gravity from neighboring quasars and other space phenomena.

If an object 1.5 million kilometres away has a neighbouring quasar, you have bigger worries than communication.

Re:Targeting that is going to be a bitch. (1)

DirtySouthAfrican (984664) | more than 6 years ago | (#21269009)

And if we were able to measure the effects due to quasars, (gravitational radiation?) that would be a scientific breakthrough in itself.

Re:Targeting that is going to be a bitch. (4, Interesting)

kebes (861706) | more than 6 years ago | (#21268773)

Great idea, now try to do the math on all of the floating bodies and the effect of the gravity from neighboring quasars and other space phenomena.
For the mentioned application (communicating inside the solar system to the Lagrange points, for instance), gravitational effects will not be a big deal. The light deflection that the Earth or the moon will cause are negligible. The real challenge in targeting, I would imagine, will be accounting for relative motion between the two ends of the link.

Maybe a single shot of data, but maintaining that connection would be very difficult IMHO.
I expect just the opposite to be true. Once a link has been established, I imagine maintaining it wouldn't be that hard. Why? Probably the optics on both ends will measure the positioning of the incoming laser on their detector. They can then send information to each other about alignment (e.g. "you're drifting to the left...") so that they can actively compensate (the time lag [google.com] between them will be ~5 seconds, or ~10 seconds roundtrip).

Instead, I imagine the initial linkup might be the limiting step. The system might require an initially higher-power signal (that is broad so that targeting tolerances are lower) to initialize the link, then active feedback could allow the two ends to narrow the beams for lower-energy high-speed data transfer. Maybe the initial phase will use conventional radio signals (or radar) to establish the locations (and relative movement) of the two endpoints of the link. With that information, the two ends can then aim the laser fairly accurately.

I could see it working but the receiver would have to be huge. It's hard enough to hit someone with a gun at a mile using a laser sight (windage which would be comparable to space effect on the laser light).
Luckily there is no wind in space, and the motion of objects is measurable and fairly predictable. Obviously over those distances any amount of error or jitter translates to a huge positioning error, but laser-steering systems can also be made quite accurate (not to mention that a laser doesn't have to be perfectly collimated, you can easily tune the aperture so that the beam is 500 m wide at the target... as long as the laser is strong enough, the receiver will still easily be able to measure the signal).

Not exclusive concepts (2, Insightful)

mdmkolbe (944892) | more than 6 years ago | (#21268467)

Can't you also make a laser out of radio waves? I know they have microwave "lasers" called masers, so do "rasers" exist?

Re:Not exclusive concepts (0)

Anonymous Coward | more than 6 years ago | (#21268695)

only in japan?

Re:Not exclusive concepts (0)

Anonymous Coward | more than 6 years ago | (#21268749)

yup.. I think they are produced by Motorola...

Re:Not exclusive concepts (2, Funny)

Radon360 (951529) | more than 6 years ago | (#21268779)

so do "rasers" exist

Well, Motorola developed something that sounded like this, but from what I understand, they often have to be packaged in an enclosure that's some gaudy shade of pink, occasionally emit short, audible clips of annoying boy-band songs, and they're only useful for conveying gossip between young teenage girls.

(sorry, couldn't resist.)

Speed (1)

rossdee (243626) | more than 6 years ago | (#21268475)

Laser beam has more bandwidgth than radio, but it still travels at the same speed (c).

And the distance mentioned (1.5 million kilometres) doesn't seem very useful. thats too far for the moon, but not far enough for Mars - theres nothing out there to talk to.

Re:Speed (1)

necro81 (917438) | more than 6 years ago | (#21268643)

The last paragraph of the press release [oerlikon.com] explains. The distance chosen was about the distance to the L1 and L2 Lagrangian Points [wikipedia.org] around the Earth. These are candidate locations for the next generation James Webb Space Telescope [nasa.gov] (also at wikipedia [wikipedia.org]). For that application, high data bandwidth is extremely useful.

Very likely, if something like this were incorporated into the Webb design, it would be augmented with traditional radio for tracking, telemetry, and as a backup to the laser link for bulk data transfer.

Re:Speed (1)

luke2063 (1137533) | more than 6 years ago | (#21268699)

There might not be anything there now, but thats the distance to some locations that we could put some stuff and it be useful
From the article -

The distance of 1.5 million kilometres that was simulated on the Canary Islands is equivalent to the distance between the Earth and Lagrange points L1 and L2. These mark specific positions in space at which it is particularly advantageous to place space telescopes. Equipped with laser terminals, telescopes such as these will in future be able to transmit far greater quantities of observation data to Earth than is possible by radio today.

lagrangian points (1)

j1m+5n0w (749199) | more than 6 years ago | (#21268811)

In the article, they say that the distance was chosen because it is the distance between the earth and either of the L1 or L2 lagrangian points [wikipedia.org]. SOHO [esa.int] currently sits at L1 and talks to earth with a 200 kbit/s radio, so this isn't exactly a hypothetical scenario. (An interesting question in that case, though, might be whether we can reliably receive a laser signal against the sun's background radiation.)

100 metres (0)

Anonymous Coward | more than 6 years ago | (#21268525)

We recently had a laser link installed between two buildings here. 100 metres was the distance between them. The recent foggy mornings rendered them useless.

1.5 million kilometres? Good luck!

Water particles floating in space? (1)

n3tcat (664243) | more than 6 years ago | (#21268591)

The transmission unit was modified in such a way that the conditions on the 144-kilometre stretch between the islands exactly reflected those that would prevail on a 1.5 million kilometre link through space. This was achieved primarily by reducing the emission aperture of the laser to a diameter of less than half a millimetre in order to weaken the light signal. I have a hard time believing that a measly 144km stretch on a planet WITH ATMOSPHERE is able to exactly replicate the conditions of a 1.5 million km stretch of space. I mean let's look at the ozone. I'm not a scientist and I only hold a GED, but doesn't that thing block cosmic rays and radiation and shit? What would that do to a laser? And let's assume for a moment that they are just shooting from ship to ship. What about atmosphere? Would the laser require less intensity to be shot such a long distance due to the lack of interference from an atmosphere? And if so, wouldn't little things like the quality of technology have a greater impact on the quality of laser stream? I dunno. I see way too many holes in this to see any plausible correlation to 1.5km of space.

Ozone Layer (1)

Radon360 (951529) | more than 6 years ago | (#21268913)

The ozone layer of the upper atmosphere really only filters out wavelengths of light that are less than 320nm or so (ultraviolet and higher spectrum). Most LASERS typically operate using wavelengths in the visible spectrum of light or infrared range.

This is why (1)

ch-chuck (9622) | more than 6 years ago | (#21268597)

This is why project like SETI are bound to fail - the quaint 20th century notion of using diffuse 'broadcasting' of uncompressed, redundant intelligence (anything distinguishable from noise) using undirected RF energy in all directions is something the aliens abandoned millenniums ago, for more efficient point-to-point methods like this.

It's pretty damn cold up there (2, Interesting)

Anonymous Coward | more than 6 years ago | (#21268607)

What the article doesn't mention is the poor crew that were huddled behind the massive metal crate up by the NOT (Nordic Optical Telescope) on these tiny little white plastic chairs (which had to be weighted down by rocks when they got up). I was up there at the WHT/NOT the other week and happened to pass by their setup, the only potential hint at what they were doing being one of those little yellow hazard signs that simply said 'Laser' on it. Glad they got what they wanted - the weather was pretty terrible for several days, you were basically sitting in cloud.

Huge distances through the universe? (2, Informative)

JohnnyDanger (680986) | more than 6 years ago | (#21268611)

For a sense of scale:

1.5 million kilometers = 1.6 x 10^-7 light year.

Distance to galactic center = 26,000 light years
Distance to nearest (Andromeda) galaxy = 2.5 million light years

"Faster than radio" probably refers to increased bandwidth, because light-speed is light-speed.

Re:Huge distances through the universe? (1)

plasmacutter (901737) | more than 6 years ago | (#21268659)

for years they said man would never fly
the wright brothers proved thousands of years of scientists wrong

then they said you couldn't break the sound barrier
enter the x1

I'm waiting for warp drive, but given how sporadic and far between these sudden leaps in transportation technology are i'm not holding my breath waiting for that vacation to the proxima system.

Line of sight and percise issues? (1)

FadedTimes (581715) | more than 6 years ago | (#21268617)

Would there not be major line of sight issues and percision issues. My crude understanding of radio waves is that you can send a signal across a wide area and it seems to me a laser would have to be more exact to get the data because of the shorter wave length. I see a shorter wave length as a disadvantage; especially over longer distances.

Great! (1)

zeromorph (1009305) | more than 6 years ago | (#21268631)

I hereby welcome you, Oerlikonians. But could anybody tell me where this Oerlikon space is and how Oerlikonians look like?

But seriously:
Now we only need to get something or someone that far away that it actually makes sense to drop radio waves for laser beams.

Faster? (1)

DTemp (1086779) | more than 6 years ago | (#21268637)

Farther... sure, because it's a focused beam.

But faster? Don't radio waves and laser beams both hit the same speed limit (the speed of light)? Radio waves are photons too.

Coming soon... (2, Funny)

SlipperHat (1185737) | more than 6 years ago | (#21268639)

The ability to encrypt nefarious messages in a death-ray across long distances.

Some popular messages include:

- "If you are reading this message, you are probably toast"
- "PWNED!!!"
- "(Scorpio) Avoid reading under strong light"
- "Knock, knock"
- "Is this the James Bond? Oh sorry, my mistake."
- "Can you hear me now?"
- "Special Delivery!"
- "Ceiling Cat sez hi!"

why didn't they use the lunar retro-reflector? (2, Informative)

jfb2252 (1172123) | more than 6 years ago | (#21268667)

It seems strange that they didn't aim for the retro-reflector placed by one of the Apollo missions which has been used for 30+ years for laser ranging experiments. It's location is well known. That would give them a real 800,000 km beam path, roughly half of what they claimed.

Re:why didn't they use the lunar retro-reflector? (1)

cnettel (836611) | more than 6 years ago | (#21268871)

It would also give the complete atmosphere, twice, along the way. I could see how data modulation schemes and optics that would handle 1.5E6 m in space could still have problems with that.

Re:why didn't they use the lunar retro-reflector? (1)

Overzeetop (214511) | more than 6 years ago | (#21268967)

Funny, I didnt RTFA, but presumed that they did just that and showed a 3-6dB link margin. Oh well, so much for real science.

Greatest Idea Ever... (-1, Redundant)

Anonymous Coward | more than 6 years ago | (#21268711)

This has given me my greatest idea ever!

Imagine a wireless mesh network of laser data links... mounted on sharks!

Man oh man.. (1)

moogied (1175879) | more than 6 years ago | (#21268719)

I think the real question is whether or not LOS for 1.5km can be maintained on a constant basis..

Press release accuracy and Bible units (0)

Anonymous Coward | more than 6 years ago | (#21268747)

I love this quote "The transmission unit was modified in such a way that the conditions on the 144-kilometre stretch between the islands exactly reflected those that would prevail on a 1.5 million kilometre link through space." And in a related story, a vast region of the Atlantic disappears from satellite view. Also, are we now quoting transmission speed in Bible units?

Space lasers? Robot machine guns? (0)

Anonymous Coward | more than 6 years ago | (#21268817)

Does anyone recall the story from a couple weeks ago about an autonomous Oerlikon machine gun killing 6 people at a demonstration in South Africa? I imagine these lasers will be lower power than to burn through objects, but perhaps it's a matter of time before high-powered space lasers come about (think 80s: Star Wars, Reagan-esqe). I hope they put more testing into these lasers than with their machine guns.

P.S. I currently work for Oerlikon Systems, (not Oerlikon Space (formerly Contraves Airspace)). Never thought I'd see this company get Slashdotted!

Will be useful (0)

Anonymous Coward | more than 6 years ago | (#21268827)

if the hot space aliens don't want you and your porn dvds were left on earth.

a better test would have (2, Interesting)

advocate_one (662832) | more than 6 years ago | (#21268915)

bounced the signal off the reflector that Neil Armstrong left at the Apollo 11 landing site. Round trip could have come pretty close to 768,800 kilometers... bouncing it back up and down again would have made the link as near as damn it = 1,500,000 kilometers

InterSatellite Communications (2, Informative)

d-Orb (551682) | more than 6 years ago | (#21268919)

I remember this being done with Earth Observation satellites. The EO satellite beams data using an optical link to a satellite that is in geostationary orbit. This satellite then beams the information down through a microwave link. This frees the EO satellite (that producue huge amounts of data) of the need of high-power consuming RF transceivers, reduces the need for ground stations, and is seriously cool. This was done in 2001 between SPOT 4 and Artemis (Press release [esa.int]). Note that SPOT sits in an orbit around 800km, and Artemis is geostationary... They then did the same with an aircraft (see here [esa.int]).

So it is really quite useful. When you consider the amount of data the sensors on board ENVISAT (or even MODIS) produce, this is an important tool.

SETI (1)

JustNiz (692889) | more than 6 years ago | (#21268937)

This is just more proof of what we already know: that the tighter the beam the more efficient it becomes for point-to-point comms in terms of energy usage and overall loss/noise.

Its also something to think about with respect to SETI. I mean the universe could be swarming with life forms communcating over great distances, and it would make more sense than not that they use tight beams to do this. In which case SETI won't ever pick anything up because nearly all the energy from their comms is only going each other.

If we start shining huge lasers into space (4, Funny)

caluml (551744) | more than 6 years ago | (#21269029)

If we start shining huge lasers into space, we're going to end up accidentally blinding aliens. Which might be good (if they're chest-explody types), or bad (if they're hot sex-starved space-babes). Your call.
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