NASA sends Mona Lisa into space by LASER
NASA has fired a greyscale image of the Mona Lisa to its Lunar Reconnaissance Orbiter, as part of an experiment using optics instead of radio for deep-space communications. Any space-watcher knows the frustration at the delays imposed by skinny radio channels in anything involving a deep-space mission. NASA is intensely …
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Re: But...
To counter-troll, no it isn't. The converse would be true, a device transmitting radio through the stimulation and spontaneous emission of excited electrons in a gain medium would, in a particular form of pedantry, also be a laser (as is a maser, in this view), but a device employing a laser not in the radio region of the spectrum is not radio communication.
Unless you think for instance that radio waves are the same thing as gamma rays, in which case I invite you to put a strong gamma source to your ear and see how that works for you.
Re: But...
Depends who you ask. Wikipedia (yes, I know) for example defines Radio as "...the wireless transmission of signals through free space by electromagnetic radiation..." - which would include lasers - but then adds "...of a frequency significantly below that of visible light, in the radio frequency range, from about 30 kHz to 300 GHz." - which takes lasers out of the context.
And just to confuse things further, here's another extract from Wikipedia: "The prefix radio- in the sense of wireless transmission, was first recorded in the word radioconductor, a description provided by the French physicist Édouard Branly in 1897. It is based on the verb to radiate (in Latin "radius" means "spoke of a wheel, beam of light, ray")."
Personally, I think laser transmission is a radio transmission under the technical definitions. Under the *popular* definition (i.e., to people who listen(ed) to radios), it isn't. <sigh>
Re: But...
I hardly think referring to the "radio spectrum" is "popular". It's rather pointless to use a definition of radio which covers any wavelength... we could similarly refer to radiowaves and gamma rays as 'light' which is technicallyt true but rather unhelpful.
Re: But...
Referring to radio and gamma as "light" is certainly both technically true and rather unhelpful; what's normally done is to refer to them all as electromagnetic radiation and to use "light" to refer to the visible range. So you have the roughly defined long-wavelength radio / radio / microwave / IR / visible / UV / X ray / gamma ray / hard gamma ray / instant cancer parts of the spectrum. "Radio" then does have a clear definition, but with fuzzy borders that overlap "microwave". You certainly would never have anyone referring to gamma rays as radio, but you might hear someone referring to both as "light", as ambiguous as that is.
@Neoc
Language evolves :) I'm mainly talking from common usage within physics; this isn't my field but I did courses on optics (as part of both physics and astrophysics), on laser physics and on quantum mechanics in general. It's fairly easy, and interesting, to find counter-examples that make just as much sense -- particularly historically -- but acknowledging that defeats the point of trolling and counter-trolling :)
Fibre to the planet
BT is interested but doesn't expect to be able to offer the full 300bps to all its fibre customers without more subsidy
More detail on the error budget?
"Reed-Solomon coding was used to overcome interference caused by atmospheric turbulence."
Of the total errors, what proportion were caused by atmospheric turbulence? I'm wondering how well this method would perform if the laser communication was through the 'vacuum' of space over the entire path. Also, I assume that modifying a ranging laser is not the most effective way to give high speed data transmission.
In the future, I can imagine a high orbit laser being used for the 'space' part of the link with a broadband radio downlink to earth. The narrow beam spread of a laser would give much better energy density on the target but would make steering and pointing more difficult.
Re: More detail on the error budget?
"The narrow beam spread of a laser would give much better energy density on the target but would make steering and pointing more difficult."
It's a subject JPL have given much thought to.
I think the phrase "nanorad pointing" will give some idea of their work.
You're right a lot of the errors are likely to be in the last 100km or so as all that air turbulence leads to the beam "wobbling" about. Adaptive optics or serious post reception processing are probably involved.
Oh I see
I though this was about the Mona Lisa mooning NASA.
How long before we etch her head on the moons surface. When will this madness end?
** oh, just read article, seems no etching of moon
But it's not
Except that laser is optical and radio is wavelength > IR. if you'd said "MASER is radio communication" you'd be correct
Gravitons
No atmospheric distortion.
Only minor earthquake damage.
I predict a new Meme
After 'Rick Rolling' are we going to get
La Gioconda Giffing.
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Seagulls
All this is fine of course, until something inadvertently flies through the laser beam...
But...
... shouldn't have been a picture of a frickin' shark?
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