NASA beams Mona Lisa to Lunar Reconnaissance Orbiter at the moon (w/ video)

Jan 17, 2013 by Nancy Neal-Jones / Elizabeth Zubritsky
To clean up transmission errors introduced by Earth's atmosphere (left), Goddard scientists applied Reed-Solomon error correction (right), which is commonly used in CDs and DVDs. Typical errors include missing pixels (white) and false signals (black). The white stripe indicates a brief period when transmission was paused. Credit: Image courtesy: Xiaoli Sun, NASA Goddard

(Phys.org)—As part of the first demonstration of laser communication with a satellite at the moon, scientists with NASA's Lunar Reconnaissance Orbiter (LRO) beamed an image of the Mona Lisa to the spacecraft from Earth.

The iconic image traveled nearly 240,000 miles in digital form from the Next Generation Satellite Ranging (NGSLR) station at NASA's Goddard Space Flight Center in Greenbelt, Md., to the Lunar Orbiter (LOLA) instrument on the spacecraft. By transmitting the image piggyback on laser pulses that are routinely sent to track LOLA's position, the team achieved simultaneous laser communication and tracking.

"This is the first time anyone has achieved one-way laser communication at planetary distances," says LOLA's principal investigator, David Smith of the Massachusetts Institute of Technology. "In the near future, this type of simple laser communication might serve as a backup for the radio communication that satellites use. In the more distant future, it may allow communication at higher data rates than present radio links can provide."

Typically, satellites that go beyond use for tracking and communication. LRO is the only satellite in orbit around a body other than Earth to be tracked by laser as well.

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NASA Goddard scientists transmitted an image of the Mona Lisa from Earth to the Lunar Reconnaissance Orbiter at the moon by piggybacking on laser pulses that routinely track the spacecraft. Credit: NASA's Goddard Space Flight Center

"Because LRO is already set up to receive laser signals through the LOLA instrument, we had a unique opportunity to demonstrate one-way laser communication with a distant satellite," says Xiaoli Sun, a LOLA scientist at NASA Goddard and lead author of the paper, posted online today, that describes the work.

Precise timing was the key to transmitting the image. Sun and colleagues divided the image into an array of 152 pixels by 200 pixels. Every pixel was converted into a shade of gray, represented by a number between zero and 4,095. Each pixel was transmitted by a laser pulse, with the pulse being fired in one of 4,096 possible time slots during a brief time window allotted for laser tracking. The complete image was transmitted at a data rate of about 300 bits per second.

The laser pulses were received by LRO's LOLA instrument, which reconstructed the image based on the arrival times of the from Earth. This was accomplished without interfering with LOLA's primary task of mapping the moon's elevation and terrain and NGSLR's primary task of tracking LRO.

The success of the laser transmission was verified by returning the image to Earth using the spacecraft's radio telemetry system.

Turbulence in Earth's atmosphere introduced transmission errors even when the sky was clear. To overcome these effects, Sun and colleagues employed Reed-Solomon coding, which is the same type of error-correction code commonly used in CDs and DVDs. The experiments also provided statistics on the signal fluctuations due to Earth's atmosphere.

"This pathfinding achievement sets the stage for the Lunar Laser Communications Demonstration (LLCD), a high data rate laser-communication demonstrations that will be a central feature of NASA's next moon mission, the Lunar Atmosphere and Dust Environment Explorer (LADEE)," says Goddard's Richard Vondrak, the LRO deputy project scientist.

The next step after LLCD is the Laser Communications Relay Demonstration (LCRD), NASA's first long-duration optical communications mission. LCRD will help develop concepts and deliver technologies applicable to near-Earth and deep-space communication.

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baudrunner
1 / 5 (2) Jan 17, 2013
Eventually, this will lead to quantum communication - teleportation of information using photon entanglement. Undelayed live communication from Jupiter? Yes, someday. Baby steps, then leaps and bounds.
Telekinetic
1 / 5 (1) Jan 17, 2013
"Tesla was the first to attempt to communicate with neighboring worlds using radio waves. In the February 9, 1901, issue of Collier's Weekly, he published his "Talking with the Planets," in which he claimed he had detected an artificial signal from Mars, or possibly Venus, using high-voltage equipment he had set up at Colorado Springs, Colorado. He also predicted that interplanetary communication would "become the dominating idea of the century that has just begun." He went on, "with an expenditure not exceeding two thousand horsepower, signals can be transmitted to a planet such as Mars with as much exactness and certitude as we now send messages by wire from New York to Philadelphia." The local newspaper expressed its delight at Tesla's breakthrough: "If there be people on Mars, they certainly showed most excellent taste in choosing Colorado Springs as the particular point ... with which to open communication."

Notice the year is 1901. There is nothing new under the sun.
yyz
5 / 5 (1) Jan 17, 2013
"In the February 9, 1901, issue of Collier's Weekly, he published his "Talking with the Planets," in which he claimed he had detected an artificial signal from Mars, or possibly Venus..."

In the 1901 Collier article, written as a popular exposition for the lay public, Tesla only discusses (in a rather vague and ponderous manner) his belief that he may have seen indications of ET transmissions ("The feeling is constantly growing on me that I had been the first to hear the greeting of one planet to another.")

http://earlyradio...talk.htm

As is aptly noted with this transcript:

"...his ideas here about long-distance transmissions were pretty vague, and seem to have been based on theories about electrical conduction and induction, and not radio, which uses electro-magnetic radiation" and "...in spite of his promise to "soon convert the disbelievers", most of what he talks about here was never clearly explained or ever demonstrated to actually work."
tigger
not rated yet Jan 18, 2013
Reed Solomon coding is brilliant, I remember studying it at uni... drilling a small hole in a CD, about a mm wide and no problems!
alfie_null
not rated yet Jan 18, 2013
To overcome these effects, Sun and colleagues employed Reed-Solomon coding, which is the same type of error-correction code commonly used in CDs and DVDs.

It's worth noting Reed Solomon codes were originally used for deep space communication well before CDs and DVDs existed.

Regarding CD robustness, I've heard that players will replay a previous sector if a given sector is unreadable. Works OK for music but probably fatal for data. Reed Solomon error correction will recover small numbers of bad bits (depending on the polynomial), but probably not the gross loss caused by a hole being drilled.
antialias_physorg
1 / 5 (1) Jan 18, 2013
It's interesting that they use reed solomon for this.
It's a good correction scheme for noise where the chance of having one bit 'flipped' by noise is independent of any of the other bits in the stream.

However there are other noise types (e.g. block noise - like something you get during a sudden burst of solar radiation) where reed solomon is not be the optimal choice.

Unfortunately using the Mona Lisa doesn't really give a good impression of how well the thing works. A difference image to the original would have been preferrable.
Telekinetic
1 / 5 (1) Jan 18, 2013
"As is aptly noted with this transcript: "...his ideas here about long-distance transmissions were pretty vague, and seem to have been based on theories about electrical conduction and induction, and not radio, which uses electro-magnetic radiation" and "...in spite of his promise to "soon convert the disbelievers", most of what he talks about here was never clearly explained or ever demonstrated to actually work." -yyz

My tendency is to believe the inventor of alternating current and other major inventions in use today over skeptics who have contributed nothing at all but their gleeful disbelief. Tesla's major benefactors, J.P. Morgan and Westinghouse, pulled their support when he proposed free energy for all. Who knows where the world would be today if he had maintained his financing.
It looks like solar electric generation is now a given and financing is robust. Not long ago, the skeptics cawed about solar's inefficiency. Were you one of them, yyz?
ab3a
not rated yet Jan 18, 2013
Reed Solomon coding? I wonder why they used it. LRC and Turbo codes are more commonplace for deep space communications.

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