January 17, 2013
NASA Sends Mona Lisa To The Moon
[ Watch the Video: Mona Lisa on the Moon ]
Michael Harper for redOrbit.com — Your Universe Online
NASA routinely uses lasers to track the position of their Lunar Reconnaissance Orbiter (LRO) as it floats around the moon. Recently, these scientists decided to show off what else they could do with these lasers by using them to communicate with the LRO. To demonstrate this new functionality, the scientists chose a famous work of art to beam to the LRO– the Mona Lisa. After some tweaking and reconstruction, a clear image of the Mona Lisa arrived at the LRO and was shot back to the scientists waiting at Goddard Space Flight Center. NASA now claims in the same way CDs made records and cassette tapes obsolete, they plan to use the beams of light to revolutionize the way we communicate to the heavens. In order to receive these signals, the LRO uses an instrument called the Lunar Orbiter Laser Altimeter, or LOLA.
"This is the first time anyone has achieved one-way laser communication at planetary distances," said David Smith, LOLA´s principal investigator in a statement.
"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."
The image of Mona Lisa travelled nearly 240,000 miles in a series of light bursts, piggybacking on the laser beams used to track the LRO´s position. Unlike other planetary satellites, the LRO can be tracked using lasers instead of radio waves.
With this functionality built-in, the scientists at Goddard felt the LRO was a prime target for testing simultaneous laser communication and tracking.
"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," explained Xioali Sun, a LOLA scientist at Goddard. Sun is also the lead author of a paper describing this experiment, which was published today.
As one might expect, beaming an image of the Mona Lisa, pixel-by-pixel, via laser required quite a bit of precise timing. First, Sun and team broke apart the image into a grid of 152 pixels by 200 pixels. These pixels were then converted to different shades of gray and assigned a number from zero to 4,095. Each of these pixels were then fired by laser and captured in a brief time window when the laser could transmit both communication and tracking. All told, the laser transmitted the image at a speed near 300 bits per second.
LOLA´s first attempt to construct the image resulted in a grainy and slightly incomplete picture. Turbulence in the Earth´s air and a slight pause in the transmission caused some of these glitches and errors. To rectify this, Sun and crew used some error collection coding NASA claims is commonly used in CDs and DVDs to repair the image. Once this code was employed, the image came out clearer than it had been, though still in shades of gray.
“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)," said Richard Vondrak, Goddard´s deputy project scientist.
Up next, Goddard´s team plans to launch the Laser Communications Relay Demonstration (LCRD) mission, NASA´s first long-duration job to test optical communications and build upon what they´ve already proved with LRO and the Mona Lisa.