Last March, a laser-ranging system on the United Statesâ€™ East Coast beamed a tiny image of the Mona Lisa to NASAâ€™s Lunar Reconnaissance Orbiter. The transmission, which reached the spacecraft while it was in orbit around the moon, was just a trickle of data by Earth standards, topping out at 300 bits per second.
Soon, that modest demonstration could be trumped by a much faster, two-way link. On 6 September, the Lunar Laser Communication Demonstration (LLCD) is set to launch to the moon. Once in orbit, it is expected to be able to receive data from Earth via laser at a rate of 20 megabits per second and send data back at up to 620 Mb/s. If all goes well, researchers say, the experiment could someday enable spacecraft to send high-definition video from other planets and allow high-bandwidth communication with astronauts who venture beyond the moon.
Over the years, a number of Earth-orbiters have tested laser links with the ground and between spacecraft, and a few proof-of-principle laser pings have been sent to a spacecraft en route to Jupiter and exchanged with another headed to Mercury. But LLCD, which will orbit a good 10 times as far from Earth as geosynchronous satellites, â€œwill be the longest laser communications link ever attempted,â€ says Don Boroson, who led the design team for the instrument at MITâ€™s Lincoln Laboratory. LLCD will attempt to receive data using an onboard 10-centimeter telescope and transmit it back with a half-watt laser.