"Hello, World" – Video beamed from ISS using laser-based communications
By David Szondy
June 8, 2014
While the International Space Station (ISS) may be mankind’s outpost for the conquest of space, it still leaves a lot to be desired when it comes to a decent YouTube connection. That’s because, for all its sophistication, the station’s communications system is still based on 1960s radio technology and has all the bandwidth of a soda straw. This changed on Thursday as NASA took a step into the video age with the test of its Optical Payload for Lasercomm Science (OPALS) demonstrator, which used a laser to beam a video to Earth in seconds instead of the usual minutes.
Developed by NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, OPALS is designed to test the effectiveness of lasers as a higher-bandwidth substitute for radio waves. It was delivered to the ISS on April 20 by an unmanned Dragon space freighter and is currently undergoing a 90-day test. The system has 10 to 1,000 times greater capacity for data transmission than radio links.
For the test, OPALS transmitted the “Hello, World” video from the ISS to a ground station on Earth. In some ways, it was more difficult than the Lunar test undertaken by the LADEE lunar probe last year. The station orbits Earth at an altitude of about 260 mi (418 km) at 17,500 mph (28,000 km/h). The result is that the target is sliding across the laser’s field of view much faster than it did for the lunar test.
"It’s like trying to use a laser to point to an area that's the diameter of a human hair from 20-to-30 feet away while moving at half-a-foot per second," says Bogdan Oaida, the OPALS systems engineer at JPL. "It’s all about the pointing."
The OPALS system sought out and locked onto a laser beacon from the Optical Communications Telescope Laboratory ground station at the Table Mountain Observatory in Wrightwood, California. It then transmitted its own 2.5-watt, 1,550-nanometer laser and modulated it to send the video at a peak rate of 50 megabits per second. According to NASA, OPALS transmitted the video in 3.5 seconds instead of the 10 minutes that conventional radio would have required.
"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. "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."
The video below includes the first OPALS video message.