Communicating via Long-Distance Lasers
A NASA partnership made lasers viable for satellite communications
Visible light has been used to communicate for centuries: lanterns on ships and Morse code flashes allowed information to be conveyed at a distance. But now there’s a new way to use light to communicate over even further distances and with far more accuracy – lasers.
A laser beam can carry information in a similar way to radio waves. By modifying the beam a certain way, the varying modulation can transmit a digital signal. Space is a perfect use for the technology, because there’s no atmosphere or buildings to impede the beam’s path, and compared to other communications standards, lasers offer a wide range of benefits. Light waves can support a high data rate, and take less power to run. On Earth, fiber optic cables provide similar benefits to laser communications, but using lasers in “freespace” over a longer distance has proved more challenging.
In 2013, a demonstration on the Lunar Atmosphere and Dust Environment Explorer (LADEE) relayed video between ground stations on Earth and the orbiter. The orbiter was able to transmit 622 megabits of data, enough to carry 30 HDTV channels. While future lunar astronauts might not need to watch reruns, the ability to transmit that much data could be a game changer for space exploration. To further explore how this technology could work, NASA’s Goddard Space Flight Center in Greenbelt, Maryland looked into partnering with the private sector.
“Building systems like this is very costly,” said Hossin Abeldayem, senior technology officer at Goddard’s Strategic Partnerships Office. “Doing it this way means there’ll be more competition and better technology in the end.”
Bridging the Communications Gap
Denver, Colorado based BridgeComm, formerly known as BridgeSat, was founded in 2015 to dive into the opportunities presented by using lasers to communicate in space. The company had earlier reached out to NASA centers pitching, among other ideas, a new generation of Tracking and Data Relay Satellites, the backbone of NASA’s communications network in space. They sent their proposal to Goddard’s call for partners and ultimately won the competition, signing a Space Act Agreement soon afterward.
Over the course of this and the other following agreements, BridgeComm engineers met with their counterparts at NASA, either in person or on the phone, several times to discuss development of their systems. A large portion of the collaboration was this consulting, ensuring that the researchers at BridgeComm had access to a wide knowledge base. While working with Goddard, the company also made agreements with NASA Headquarters, NASA’s Ames Research Center in Silicon Valley, and Glenn Research Center in Cleveland, Ohio. With all these centers on board, the company could apply NASA expertise to every part of their system.
There are a few key parts to make these systems work. Compared to the wide area a radio signal can cover, lasers from space can only be received across an area covering the size of a football field. To allow ground stations to reliably pick up the signals from space, BridgeComm and NASA teams brainstormed a way to ensure the beam remained trained on a spot on the planet below. By mounting the entire laser system on a gimbal and using fine steering mirrors, the engineers could ensure the beam didn’t wander as the satellite moved through its orbit. Barry Matsumori, CEO of BridgeComm says that the expertise gained from NASA helped to make the company’s ability to precisely aim the beam on a receiver work.
Also key to the system are amplifiers. While the lasers can travel a great distance, they need to be bright to travel the potentially interplanetary distances needed for NASA missions. BridgeComm’s amplifiers are able to keep the beams bright, while being small enough to fit on a satellite.
According to Abeldayem, when the time came to renew the agreement with Goddard in early 2020, BridgeComm didn’t need the center’s assistance anymore, as the company had successfully built out its own systems.
Shining Lights on the Horizon
BridgeComm’s primary customers are those that need high-speed communications but don’t want to compete for bandwidth on the already crowded radio channels.
“Radio-frequency spectrum is in short supply,” said Matsumori. “By going optical, we can transmit more data without using any of it.”
Since the completion of the Goddard agreement, BridgeComm has made waves in the private sector. They’ve received additional funding from Boeing to further build out BridgeComm’s communications technology, making additional ground stations for future satellites that might use their system.
There are already interested customers for the BridgeComm system as well. The company is working on laser communications equipment for the geospatial data company HySpecIQ, which hopes to use the light amplifiers and specialized gimbals on their new satellite constellation. With the award of the HySpecIQ contract, BridgeComm is one of the first companies to commercialize optical wireless communication technology in space, and Matsumori thanks NASA for the kickstart it gave to the company.