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Space Station Laser Beams Video Message to Earth

Space lasers have already shown they can beam HD videos from the Earth to the moon and back again. A new NASA demonstration brings the technology a bit closer to home by using a laser communications system to send a "Hello, world!" message from the International Space Station to Earth in approximately 3.5 seconds.

Laser communication could send data for space missions up to 100 times faster than traditional radio-frequency communications—a huge advantage for sending and receiving image and video data taken by spacecraft or robotic rovers exploring distant worlds. In the latest case, NASA tested the laser communication concept with the Optical Payload for Lasercomm Science (OPALS) installed on the ISS.

"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," said Matt Abrahamson, OPALS mission manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, in a press release.

OPALS uses a 2.5-Watt, 1550-nanometer laser that launched to the space station aboard a SpaceX Falcon 9 Dragon capsule on 18 April. The space station's Dextre robotic arm installed OPALS on the outside of the orbital outpost in preparation for the demonstration.

The latest test hit a maximum data rate of 50 megabits per second during a transmission test lasting 148 seconds. Such rates allowed OPALS to transmit the video message within just 3.5 seconds versus traditional downlink communication that would have taken more than 10 minutes.

But the laser aboard the space station didn't work alone. OPALS also depends on a ground telescope located within the Optical Communications Telescope Laboratory at the Jet Propulsion Laboratory facilities on Table Mountain in Wrightwood, Calif. That telescope uses orbital predictions to track the space station as the latter moves across Earth's sky at more than 28 000 kilometers per hour. Meanwhile, the laser aboard the space station detected a beacon attached to the ground telescope and used the beacon's signal to guide its own laser beam.

The latest demonstration already appears to have exceeded the original performance estimates for the OPALS project, which suggested a conservative data transmission rate of 10 megabits per second during the approximately 100 seconds that the space station laser and ground telescope could maintain line of sight.

Success with such tests could benefit both people on Earth as well as deep-space missions. Laser communications can enable higher definition video from satellites orbiting Earth, from distant Mars rovers, or possibly future human missions to the red planet. Last year, NASA achieved a milestone by using a laser-equipped lunar orbiter to beam data back to Earth at up to 622 megabits per second.

http://spectrum.ieee.org/tech-talk/aerospace/space-flight/space-station-laser-beams-video-message-to-earth