Receiving a message. Image: NASA/JPL
The four-month prime mission of the International Space Station-based OPALS experiment is over, with the results providing one of the strongest proofs-of-concept yet for space-based laser communication. The mission, which isn't the last for OPALS, was to explore the feasibility of sending data through the atmosphere and back using satellite relays, with optics instead of radio signals.So: a wireless global internet, of sorts.The setup's data recipient for the experiment was a ground beacon based at the NASA JPL Table Mountain Observatory in California. The observatory/beacon fired four simultaneous beams at the ISS to establish and maintain a link, with the individual lasers acting to correct for atmospheric distortions."Four lasers from the ground station travel through the sky toward the space station," explained OPALS mission manager Matthew Abrahamson in a statement. "Under clear, dark background conditions, it's very easy for the payload to acquire the ground beacon. Daylight conditions have proven more challenging, but we are working on increasing capabilities during the day as well."Communicating with satellites via radio waves is fine for passing messages and commands and plenty of other things, but for dense streams of data of the sort shouldered by the terrestrial internet, it's not all that great. (Having experienced the horrors of rural satellite internet firsthand, I can attest that it's downright shit.)For its prime mission, OPALS relayed a short video message ("hello, world"), a transmission that would take around 10 minutes with available technology. With lasers, however, the researchers were able to send a copy every 3.5 seconds. The first video transmitted via OPALS was of the 1969 Apollo 11 moon landing, a task that would take some 12 hours via radio waves, but just seconds using optics.The technology is still a ways from perfection. Light is still light, which means being reflected and deflected in the usual ways. "We're finding that differing weather patterns and geometry variations are proving to be challenging," Abrahamson said. "We've had a half dozen or so pass attempts with varying levels of success, and we are looking to continue these collaborations in the future."
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