NASA developed a laser communication system, which they tested for the first time in 2013 when they communicated with their Lunar Atmosphere and Dust Environment Explorer (or LADEE) probe, orbiting the moon. The the laser communications system demonstrated record-breaking speeds for data transfer. Now, Guan Yang, an optical physicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland has developed a new system based on that technology. Yang’s system will not only provide those same extremely fast data transfer speeds, it will also be able to provide highly precise distance and speed measurements, all without taking up a lot of space.
Yang’s new creation is called the Space Optical Communication and Navigation System. It’s not made from any exotic materials or custom parts. It’s constructed with commercially available components. In recent laboratory testing Yang’s system demonstrated that it could make distance measurements down to the micrometer level and that it could transfer data at 622 megabits-per-second (Mbps).
”Combined with the large communication bandwidth,” Yang says, “high-precision ranging over an optical communication network will bring about significant advances in navigation and communications, to say nothing of science gathering, notably in the area of geodesy.” Geodesy, by the way, is the study of the varying size and shape of the Earth or large parts or aspects of it, like the movement of its tectonic plates or changes in its gravitational field. Yang goes on to explain that his new system’s small size, “… will enable use on CubeSats.” CubeSats are a new satellite format that is about the size of a shoebox.
You can probably guess that using a laser for transmitting data is better than using radio waves, but you may not know exactly why. There are two main reasons. Because the frequency of a laser beam is much higher than that of a radio wave, you can pack much more data into it. Also laser beams are highly focused, whereas radio waves radiate out in all directions. So essentially, in a laser communication system or a lasercom all of the energy you’re using is going exactly where you point it, instead of spreading out everywhere the way a radio wave does. The New Horizons probe is still using its radio transmitter to send the images it took of Pluto and Charon back to Earth, and it will be through 2016. Remember dial-up modems? New Horizons is transmitting data at that rate. To look at it another way, when NASA did its lasercom test with LADEE, it took just four minutes to download the data that would have taken several days if NASA was only using LADEE's onboard radio system.
Yang’s system achieves it’s remarkable precision by incorporating a Doppler frequency combined with a highly specialized computing algorithm, called the Fast Fourier Transform. "If you can measure that precisely,” Yang explains, “you can easily use it for navigation.” Yang’s vision for his system is that it could be used on a fleet of CubeSats flying in formation, making simultaneous, multi-point observations or as a navigational guide to carry for autonomous rendezvous and docking between space vehicles.