Members of the DSOC team react to the first high-definition streaming video to be sent via laser from deep space. Image credits: NASA (CC BY 3.0).
For millennia, our communication was tethered to the physical world. You could either talk to someone directly or rely on a messenger on foot, horse, or a sailing ship to send a letter. The invention of the telegraph and radio changed all that. Suddenly, we could communicate to someone on the other side of the world. We wrapped the globe in signals that travel at the speed of light and today, our communications can reach almost any corner of the planet in a variety of different ways.
But this is not the end of the story. The more we started exploring our solar system, the more astronomers understood the limitations that come with using radio waves – and the advantages that could come with using lasers.
The key difference is in bandwidth. Both radio waves and laser light travel at the speed of light. However, laser light has a much higher frequency. This allows for more data to be encoded and means that laser systems can transmit data at much higher rates than even the most advanced radio systems. Another problem is that radio signals spread out and weaken dramatically over distances like millions of kilometers.
This is how the Deep Space Optical Communications (DSOC) program was born.
Faster Than Many Terrestrial Connections
Laser-based data transmission in space requires exceptional precision primarily due to the narrowness of the laser beam and the immense distances involved. Unlike radio waves, which spread out broadly and can cover a wide area, a laser beam is highly focused. To make matters even more challenging, the DSOC system must account for the spacecraft’s movement, the rotation of the Earth, and the immense travel time of light itself, all over the large scale of the solar system.
To achieve this, NASA engineers have developed sophisticated automated tracking systems. They use a powerful uplink beacon laser from NASA’s Table Mountain facility in California as a guide. This enables the spacecraft’s flight laser transceiver to lock on and beam its data back to the 200-inch Hale Telescope at Caltech’s Palomar Observatory.
Despite all this difficulty and complexity, the DSOC experiment has consistently performed better than expected.
Most of these efforts have involved the Psyche spacecraft, a NASA mission that aims to study the metallic asteroid 16 Psyche. The distance of Asteroid 16 Psyche from Earth is currently 460,152,806 km, and the shuttle is en route towards the asteroid.
The laser transmission system achieved “first light” on November 14, 2023. The DSOC team beamed a near-infrared laser encoded with test data from nearly 16 million km (10 million miles) away. For comparison, the Moon is “only” 384,400 km away. But this was just the start.
The major breakthrough took place a month later, when a 15-second video of Taters the cat chasing a laser pointer was transmitted from the Psyche spacecraft to Earth. Taters, a playful orange tabby, got its fifteen minutes of fame at the proposal of Joby Harris, a visual strategist at NASA’s Jet Propulsion Laboratory. However, this wasn’t just any video of a cat chasing a laser pointer; it was a video that travelled from deep space at a maximum speed of 267 megabits per second (Mbps). That is faster than the average internet connection in all but a handful of countries.
The first video sent from deep space.
Since then, the experiment has operated at even more extreme distances of 460 million km. Transmission speed decreased with distance, but the approach confirmed that optical communications can play a role in how we explore the solar system.
An Interplanetary Internet?
The success of optical communication technologies like DSOC is, first of all, useful for space missions. However, it is also an important step toward realizing an “Internet of Space.” This concept envisions a network of interconnected nodes across the solar system, allowing for a seamless data exchange between Earth, lunar bases, Martian colonies, and even distant probes.
This ambitious undertaking has been supported by Heidelberg Laureate Forum habitué Vinton “Vint” Cerf, widely recognized as one of the “fathers of the internet” and an ACM A.M. Turing Award recipient. Cerf realized that sending point-to-point data is just one part of the problem, you need networks that can distribute information efficiently. You need, essentially, a ‘space internet.’
In the 1970s, Cerf, along with Robert Kahn, co-designed the foundational architecture of the terrestrial internet: the Transmission Control Protocol/Internet Protocol (TCP/IP). This protocol (actually, a suite of protocols) was an instrumental stepping stone for the development of the Internet. TCP/IP enabled devices to communicate over diverse networks by breaking data into “packets” that can travel independently and be reassembled at their destination (something which we detailed in our dedicated story here). However, when it comes to space data transmission, classical TCP/IP is less well-suited.
This has led to the development of “Bundle Protocols,” a key component of what is known as Delay/Disruption Tolerant Networking (DTN). TCP/IP assumes a relatively stable and continuous connection, which will usually be true for Earth. Meanwhile, DTN is built for more unreliable environments. In a DTN system, if a data packet arrives at a node (a spacecraft or a lunar base, for instance) but the next link in the chain is unavailable (perhaps due to planetary rotation or orbital mechanics), the node stores the data until the connection is re-established. This “bundling” of data allows for reliable transmission over vast distances with unpredictable delays and disruptions.
The development of high-speed optical communication provides the high-bandwidth “pipes” necessary for such an interplanetary network to function in an efficient fashion. With this approach, we space explorers could realistically stream live video back to Earth or other bases, and Martian rovers could continuously upload large amounts scientific data to a network of orbital relays.
Another advantage of this DTN approach is that it can, in theory, work with both radio and laser waves. Engineers envision a synergistic approach where you have local networks (say, between a few moon bases or work stations), as well as a way to send data from the Earth to different faraway probes in deep space.
If that all sounds a bit like science fiction, well, there are already tangible steps from NASA to install 4G internet on the moon. In fact, an “internet of space” is quite necessary for a sustained human presence on the Moon, Mars, and beyond. It is still very much a work in progress, but the world is making tangible steps.
The fact that it was kickstarted with a cat video is just a bonus.