Laser transmission of data likely won't replace radio waves on Earth, but for deep-space communication it could be key.
This week, courtesy of NASA, we saw a first in the world of communications: a high-definition video beamed to Earth from 260 miles above the planet—using lasers. This feat in video transfer comes courtesy of the Optical Payload for Lasercomm Science (OPALS) payload, a technology demonstration from NASA’s Jet Propulsion Laboratory currently on board the International Space Station.
OPALS is a proof-of-concept mission that’s testing a new way of transmitting data through space. Rather than using traditional radio waves, OPALS is looking to a future where spacecraft and astronauts will communicate using high bandwidth lasers.
Radio waves and lasers are on opposite ends of the electromagnetic spectrum, at least in terms of communication. Radio waves are longer and can’t transmit as much data in one go, but they are fairly simple to receive, traveling in all directions from their point of origin to be received by large Earth-bound dishes. Lasers, conversely, are much shorter. They can carry significantly more data in one transmission but they’re harder to receive. Like a laser pointer, laser communications require precision aiming. The beam must hit a receiver at exactly the right spot to transmit its large amount of data.
The capability to receive this highly focused data is what OPALS is demonstrating. During last week’s demonstration, the OPALS instrument first locked onto a laser beacon emitted by the Optical Communications Telescope Laboratory ground station at the Table Mountain Observatory in Wrightwood, California. It then began to modulate the ground-based beam with its own laser, transmitting the "Hello World!" video message.
The entire transmission lasted 148 seconds and reached a maximum data transmission rate of 50 megabits per second. It took OPALS 3.5 seconds to transmit each video copy. Using traditional radio waves, the same transfer would have taken more than 10 minutes.
This OPALS transmission represents the culmination of “decades of research by JPL's laser communication group and nearly five years of work by the core OPALS team in the design, integration, and rest of our laser experiment,” said Rob Witoff, the ISS and Launch Systems Engineer on the OPALS team.
"It's incredible to see this magnificent beam of light arriving from our tiny payload on the space station," said Matt Abrahamson, OPALS mission manager at JPL in Pasadena, California. "We look forward to experimenting with OPALS over the coming months in hopes that our findings will lead to optical communications capabilities for future deep space exploration missions.”
OPALS isn’t demonstrating laser communications for the fun of it. This technology will ultimately improve communication rates with spacecraft and possibly astronauts beyond low-Earth orbit. “With this successful demonstration now behind us, we will continue to operate OPALS to mature our understanding of free space laser communication through the Earth's atmosphere and we're very excited about the understanding we're generating for future spacebound explorers,” said Witoff.
Maybe the first crew that lands on Mars will be able to live-stream the event (with the seven minute light-time delay, of course) in high definition video for everyone in the world to watch in near-real time.