Next year, when NASA chooses a new Discovery-class planetary mission for a scheduled launch in 2021, the agency also hopes to introduce a new and potentially revolutionary technology: laser communications. Proposers who include that capability in their mission design will get an additional $30 million to develop the technology.
Optical communications, as it’s called, will boost data transmission rates—and hence the amount of information returned by planetary spacecraft—by orders of magnitude. “We have not been bringing most of the science data back,” says Donald Cornwell, who managed a laser communication experiment that ran on NASA’s LADEE (Lunar Atmosphere and Dust Environment Explorer) spacecraft in 2013. “Something on the order of 90 percent of it is left there.”
During that test, LADEE achieved download speeds exceeding 620 megabits per second in brief bursts—easily fast enough to stream HDTV. Downloads from Mars are currently hundreds to thousands of times slower. Upload speeds to LADEE from a station in New Mexico were also fast for a planetary mission, reaching 20 megabits per second.
If high transmission speeds were the norm, movies from space could become a reality. Before that happens, however, spacecraft laser communication needs to overcome key limitations. The focused data beam used in optical communications requires precise receivers on the ground, and the beam is so narrow that clouds can easily scatter it—which means receivers need to be in relatively dry, cloudless locations like New Mexico.
Investigators dealt with these issues during the first phase of testing last year for an experimental laser system on the space station called OPALS (Optical Payload for Lasercomm Science). Over the course of 18 test transmissions, researchers experienced problems sending to a ground station in Oberpfaffenhofen, Germany, where mountains made for cloudy conditions. Transmissions to a station in dry California were far more successful, according to Matthew Abrahamson, OPALS project manager.
The next step for OPALS is to counter atmospheric interference with the same kind of adaptive optics used in large telescopes. In tests to be conducted this year, the ground station will flex its receiver to account for the distortion.
Beyond that, NASA plans to test laser communications with a Space Systems/Loral commercial satellite to be launched into geostationary orbit no earlier than 2017. Over the course of two years, NASA hopes to transmit and receive information at speeds of up to 1.24 gigabits per second.