Lunar laser: future of space communications

Ground station, White Sands, New Mexico
Date:3 April 2014 Author: Joe Pappalardo Tags:,

An experiment around the Moon heralds the next generation of space communications.

The future of space communications may come at the speed of photons instead of radio waves. Researchers for the first time have communicated with a spacecraft using a laser system.

In late October last year, the Lunar Laser Communications Demonstrator (LLCD) beamed data at 622 megabits per second – orders of magnitude faster than the current rate – back from the spacecraft, which was in lunar orbit. Don Cornwell, mission manager at Nasa’s Goddard Space Flight Centre, said that the LLCD “has been extremely successful, beyond expectations”.

During the test, the LLCD sent a string of binary code from the satellite orbiting the Moon to a ground station in New Mexico. It was the fastest download rate between the Moon and Earth. For scale, Nasa says that the spacecraft that’s carrying this laser experiment would take 639 hours to download an average-length HD movie using the standard S-band radio. LLCD could download the same film in less than 8 minutes.

The next step for laser space communications will occur closer to home. In 2016, the Laser Communications Relay Demonstration (LCRD) will hitch a ride into space on a communications satellite, where it will orbit Earth. In 2017, the LCRD will begin beaming 1,25 gigabits per second of test information from a ground station to the satellite and back to Earth to another ground station. The test spacecraft will be in orbit for two to five years, operating 24 hours a day, to prove the system is robust enough for commercial use. If it is, the test could open up new avenues of big-data-information exchange at the speed of light.

How it works
The spacecraft positions itself in the Moon’s orbit so the Lunar Laser Communications Demonstrator (LLCD) points at Earth.

An on-board detector scans for a signal from the ground terminal, telling LLCD where to aim its laser.

A 10 cm laser beam travels 383 000 km from the spacecraft orbiting the Moon to White Sands, New Mexico. Coded test information is transmitted at 622 megabits per second.

Why lasers?
Laser wavelengths are 10 000 times shorter than radio wavelengths, delivering much more data than even the best modern radio system, yet using less power. On the ground, collecting antennas can be smaller, easier to build and cheaper to maintain.


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