NASA to test laser communication system between space and Earth

Getting data back to Earth from space quickly and efficiently is more complicated than it looks; to achieve this, NASA wants to use fiber optic technology … but without fiber.

One of the major challenges of space is obviously the distance. As soon as one wishes to visit celestial bodies other than the Moon, it becomes very important; this therefore requires engineers to develop new means of communication. This is the case of the Laser Communications Relay Demonstration (LCRD), which will soon be tested by NASA.

In essence, the agency wants to more or less imitate the concept of fiber optics, namely to use light to transport a large amount of information over long distances and at high speed. But how will they be able to stretch cables in space? The answer lies in the name of the technology: NASA and its industrial partners want to do without it altogether.

Exit, the sheath that protects and supports fiber optic cables on Earth; here, NASA has refined the concept as much as possible by removing all the physical support to keep only the essential element, namely the light through which information passes. To transmit it, they will use what NASA refers to as “laser links”. On paper, this technology has many of the advantages of fiber optics, but without the flaws associated with its physical medium.

Optimizing an old idea

The concept itself has nothing new; as early as 1995, the Japanese space agency had already used a laser to communicate with one of its satellites. And since then, NASA and other aerospace players have also proposed several concepts based on this technology. ESA, for example, has developed the European Data Relay Satellite System, or EDRS; this technology, already deployed today, allows the satellites concerned to communicate by laser at up to 1.8 Gbits / s.

The LCRD program will synthesize all the progress made on laser communication in one and the same technology, optimized specifically for communication between Earth and space. Because the point that NASA will seek to optimize as a priority is the return information about our planet. Indeed, even devices that already communicate by laser – like two from the EDRS – still widely use the radio waves to bring the signal back to Earth.

It is largely the fault of its atmosphere, which tends to cause laser signal distortion. The same goes for bad weather and other meteorological phenomena, which can easily degrade the signal. NASA will therefore deploy a geostationary satellite which will be specially dedicated to the exploration of this technology. This will allow NASA engineers to understand in what conditions laser communication is viable, and how to treat it for preserve its integrity.

Remove bottlenecks and densify the network

Ultimately, this system should allow a whole constellation of satellites to communicate with each other at very high speed, as the EDRS already does. This is important, because it becomes crucial to increase the capacity of these networks; indeed, these communication channels are now starting to saturate, especially since the start of the new space race. There is therefore an urgent need to densify the network.

But the most important thing is the return of information to Earth. The radio waves which are used to repatriate data through the atmosphere allow a much lower flow rate than the laser; this step is therefore a real bottleneck which slows down the whole process. As it is, the network not only begins to saturate, but in addition, it is quite difficult to recover such data in a short time. A logistical dead end therefore NASA seeks to extract itself at all costs.

This is where the LCRD comes in. By replacing radio waves with a laser, it would make it possible to considerably widen this bottleneck, if not to blow it up completely. In practice, we could not only communicate much faster with our space equipment, but also unclog the entire network. A tempting prospect for all projects in this industry, from space tourism to fundamental research and the deployment of colonies.

But that doesn’t mean we’ll be giving up on our good old ways anytime soon. Until the LCRD is mature, we will stay radio wave dependent to repatriate this data despite the vagaries of the atmosphere. But eventually, once this system is up and running and deployed, it could be a high-performance mesh network, which will allow engineers to transmit large amounts of data in no time.

Leave a Comment