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NASA scientists routinely use lasers to track the position of the Lunar Reconnaissance Orbiter's
laser altimeter as it orbits the moon.
Recently, however,
they also tried something a little...different
In addition to tracking the instrument, they used the laser to send a picture
of the famous Mona Lisa in the first demonstration of laser communication
with a satellite at the moon
To do this, the LRO team used the existing laser tracking signal
sent by the Next Generation Satellite Laser Ranging Station
at NASA's Goddard Space Flight Center.
The image was divided into pixels, which were then sent to the spacecraft one at a time
by re-timing the regular tracking pulses.
By delaying the tracking pulses by specific amounts, LRO scientists
could use the difference between the expected arrival time and the actual arrival time
to indicate the brightness of an individual pixel.
Once the image was sent, scientists corrected for transmission errors
caused by the Earth's atmosphere using common techniques used in CDs and DVDs.
They also studied signal fluctuations due to Earth's atmosphere.
The final image was verified when it was returned to Earth using LRO's radio
telemetry system.
This test and the data obtained from it
sets the stage for future 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.
So, while lasers are currently being used to track NASA satellites,
in the future they may also be used to communicate with them,
sending not only data, but perhaps images that one day wil be as famous as...
the Mona Lisa.