DSN dishes are incredibly sensitive — able to detect, for instance, the weak signals from Voyager at the edge of the solar system. “When the signal arrives, it’s far less than even a billionth of a billionth of a watt,” says the DSN’s project manager, Alaudin Bhanji of the Jet Propulsion Laboratory in Pasadena, Calif. “And that’s 20 billion times lower than the power required for a digital wristwatch.”
The trouble is the data transfer rates are slow in radio communication. Downloading a 1.5-gigabyte video from Curiosity via radio DSN can take up to six hours. Imagine the frustration of trying to Skype with future colonists on Mars at this rate.
That’s where a new technology — optical communication, embedding data in laser beams rather than radio waves — comes in. As a test of this tech, NASA’s latest moon explorer, LADEE, was equipped with a “lunar laser” system that can communicate nearly 20,000 times faster than Curiosity’s DSN-based transmitter. With this successful proof of concept, the agency plans to launch another fast-talking system in 2017 to figure out the limits and logistics of lasers in a low-stakes environment.
NASA intends for such high-speed systems to be standard issue on spacecraft starting in 2025, provided the federal wallet can support their data-hungry habits; they’d be able to download that 1.5-GB video two to 10 times faster.