Wired‘s Klint Finley describes the advent of a new high-speed communications system that would let people on Earth connect to computers on the Moon at a very high speed.
Traditionally, NASA has used radio frequencies to communicate with spaceships, satellites, and rovers, but that’s rather slow. Plus, the further a contraption gets from earth, the more power–and the bigger the dish–it needs to send a signal. That’s why NASA’s most distant probe, Voyager 1, requires a 70-meter antenna to be heard. Optical connections are much faster, but they’ve been limited by things like varying lighting conditions, cloudy skies, and atmospheric interference.
So, in order to quickly send signals across the approximately 250,000 miles between earth and NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) observatory, Stevens and his team built a completely new optical communication system, with new transmitters as well as receivers, drawing on techniques used in past projects. “People in the space business have long known that laser communications has a lot of potential benefits including higher data rates and smaller space terminals,” Stevens says. “NASA has been pursuing parts of the technology for several decades.”
On the transmission side, the team used four telescopes to beam information coded as pulses of infrared light into space. Each of the four signals travels separately, and though each will encounter interference, this four-pronged approach improves the odds that at least one signal will make it to the receiver.
When a signal arrives, it’s focused into an optical fiber similar to what’s used in high-speed internet connections such as Google Fiber. Then it’s amplified and is converted into electrical pulses that carry the data transmission. Less than one billionth of a watt will be received of the original 40-watt signal, but that’s still about 10 times the signal strength required for error-free communication.
The satellite had its own transmitter, which was able to send the data signal back to earth at an even faster speed: 622 megabits per second. That’s faster than most home internet connections, though not quite as speedy as the one-gigabit speeds you get with something like Google Fiber.