Laser Communications in Space

Nasa's Jet Propulsion Laboratory will test laser-based space communications on the International Space Station. It arrives on this month's SpaceX orbital cargo run. Once installed outside the station, the Optical Payload for Lasercomm Science (Opals) will transmit high definition video to a telescope in the mountains north of Los Angeles. JPL expects to show that it can maintain a 10-50 megabit per second transfer rate during the minute-and-a-half that the space station cruises over Southern California.

Opals is the latest in a series of Nasa experiments that will ultimately create an interplanetary high-bandwidth extension of the Internet. Bandwidth is one of the biggest limiting factors affecting deep space exploration and a growing issue for orbital operations. Space agencies maintain networks of large dish antennas up to 70 meters in diameter to pick up the faint radio signals arriving from Mars, Saturn, and the edges of the Solar System. The signals are so faint that the space probes only manage to transmit at 200-400 bits per second - slower than a twenty year old modem. Laser signals don't attenuate as much over the millions of kilometers between planets which should allow future space probes to reach 1 megabit per second from Mars. Bandwidth is an issue even for spacecraft like the International Space Station. As more experiments arrive at the station, the demand for downlink capacity grows. A laser-based communications system would give Nasa and its partners the alternative to radio-based data links they need to make the most of their space investment.

What does this mean for amateurs? Faster communications means more data flowing into the space agencies archives. That creates more opportunities for crowdsourced citizen science projects as well as for classroom and independent amateur research. Expanded research on the space station enabled by faster communication creates more opportunities for student experiments. DIY satellite-building is still in its early stages. The KickSat project's amateur satellites-on-a-circuit reach orbit on the same SpaceX launch as Opals. It won't be long before amateur satellite-makers start chafing against bandwidth limits in low-Earth orbit. High-altitude balloonists already run into this situation with their flights into Near Space. They must wait for the balloon's instruments to fall to Earth before they can recover their video and other data. Getting data back from space is even harder with amateur budgets. A future orbital communications system that connects small satellites to laser-based ground-links will let amateur satellite projects do more .

The Opals project itself reflects the trends that make amateur space exploration possible. Early-career engineers and scientists at JPL developed the experiment as part of the laboratory's Phaeton professional development program. Phaeton gives recently-hired JPL staff  a chance to develop small-scale missions to prepare them for the full-scale deep space missions. But small-scale also means small budget. The Opals team pieced the experiment together using commercial hardware - including smartphone technology - rather than space-rated components. In JPL's press release Mission Manager Matt Abrahamson said "We were not as constrained by mass, volume or power on this mission as we were by cost." Modern Moore's Law-driven technology let them get the project done on tight budgets and deadlines that would have been impossible to achieve with space-rated hardware.