This week NASA announced it has beamed an image of the Mona Lisa to a satellite orbiting the moon. The image treveled almost 240,000 miles from the Next Generation Satellite Laser Ranging (NGSLR) station at NASA's Goddard Space Flight Center to the Lunar Reconnaissance Orbiter orbiting the moon.
The transmission was a test of laser communication with the lunar satellite. The Mona Lisa was piggybacked on laser pulses that are normally sent LOLA's Lunar Orbiter Laser Altimeter (LOLA) to track its position. The successful transmission was verified by sending the image back to Earth using the LRO's radio telemetry system.
"This is the first time anyone has achieved one-way laser communication at planetary distances," said David Smith, LOLA principal investigator at the Massachusetts Institute of Technology (MIT). "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."
Satellites around Earth are normally tracked using radio waves. The LRO is the only non-Earth satellite to be tracked by laser.
"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," said Xiaoli Sun, a LOLA scientist at Goddard.
For the transmission, the Mona Lisa was split into an array of 152 x 200 pixels. The pixels were then converted into a shade of grey, then transmitted by laser pulse at a data rate of around 300 bits per second. The LRO's LOLA instrument reconstructed the image based on the arrival times of the laser pulses from Earth. All of this was accomplished without interfering with the NGSLR's tracking and the LOLA's primary task: mapping the moon's elevation and terrain.