Space communications with Earth have now entered a new and exciting era – laser communications. The LADEE (Lunar Atmosphere and Dust Environment Explorer) had a very sucessful 30 day mission. Her primary task was the following: 1) Determine the global density, composition, and time variability of the lunar exosphere before all us earthlings take over and disturb it. 2) Determine if diffuse emission seen and sketched by Apollo were actually sodium glow or dust. AND 3) Document the dust impactor enviroment to aid in the design/engineering of future robotic missions as well as a lunar outpost.
But LADEE has one more objective. Actually it was her first objective. LADEE was carrying the LLCD (Lunar Laser Communications Demonstration), an optical communications system. (above) Prior to completing her 100 day lunar orbit and collection of data, she first conducted a successful test on October 18, 2013 – a test where using a laser, she transmitted & receive data as pulses of light. A communications method that can provide 5 times the data that radio frequency communication offers and carries the information much the same as fiber optic cable would (think FIOS, then remove the cable) to three Earth sites previously selected and configured. (One was an ESA site as they graciously took part in this experiment. ALSO they set a record. This test set a downlink record of 622 megabits per second (Mbps) from spacecraft to ground, and an "error-free data upload rate of 20 Mbps" from ground station to spacecraft. This was all in advance of LCRD (Laser Communications Relay Demonstration) due to launch in 2017.
The LCRD seeks to build upon the success and show that not only would this communication be successful for a mission, but also to continuously offer capabilities at one billion bits per second using a satellite in geosynchronous orbit. This sort of data communications offers not only replacement of previous radio comms but data collected on a science mission by robotic spacecraft.
Case & Point; at missions end, the LADEE’s LLCD equipment was turned back on and used to transfer scientific data collected during the 100 day mission. Although the spacecraft contained a radio system, the entire stored data was able to download in 5 minutes whereas with the radio system it would take several days.
So now NASA is able to confidently state that they see NOTHING that would prevent the operational use of this new technology (well, new for space) in the future.
TESTING INCLUDED error-free communications both during broad daylight, even when the moon was within 3 degrees of the Sun (as seen from the Earth) as well as when the Moon was low on the horizon, less than 4 degrees which had the added benefit of demonstrating that wind and atmospheric turbulence did not have a significant impact. Best of all and not anticipated, LLCD was able to communicate through thin clouds, a definite bonus!
Just a quick review of the difference between the two forms of communication so that you can grasp why this is soooo fantastic!
RADIO WAVES travel through space but can be reflected, refracted, or diffracted. Basically waves go out in a V shape from the point of origin. They bounce off in other directions when they hit things which could varying from clouds in space to asteroids, anything that gets in its way. Now the collection side is a smaller v and so it will miss the outer portions of the radio communications that have bled outward.
LASER WAVES are faster and travel at the speed of light. Certainly we need that level of communications as NASA takes its show on the road farther and farther out in the solar system. While previously anticipated were various negatives such as: beam dispersion, atmospheric absorption, space weather or pollution in our atmosphere or clouds (etc) in space. The LCRD however did so well that we find we CAN communicate through light cloud cover and CAN communicate with the Sun in close proximity. It just may be easier in space then in all the tests on earth!
Now, am I overlooking the obvious, the data LADEE sent regarding her main mission? Actually, I am not. NASA has a lot of data to go over, but thanks to LLCD they were able to start days sooner, let’s give them time to run the data down!
In the meantime, we now can add AFAL communication to our list! (As Fast As Light)
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