For decades, satellites have been beaming data from Earth to space and back via radio waves. But with the growing number of spacecraft in orbit and the increasing quantities of data beaming back to Earth, radio spectrum is hitting its physical limits. For about a decade, companies and research institutions have been working on higher-bandwidth, optical technologies that would remove current data transmission bottlenecks. Perhaps the most ambitious among those companies is Singapore-based deep-tech start-up Transcelestial, which has been testing its commercial-grade Earth-to-space laser communication terminal in trials in space in the past few weeks.
The company, which has sold hundreds of ground-to-ground internet-beaming laser terminals, launched its demonstration payload to space in November aboard the 6GStarLab satellite developed by UK-headquartered Open Cosmos, and has further satellite launches scheduled for later this year. The satellites, Transcelestial says, will form the backbone of a future constellation that will provide fiber-grade level connectivity from orbit to the world’s unconnected by the end of this decade.
Other companies have been using laser terminals to beam data between satellites. SpaceX Starlink has been relying on space-to-space laser terminals since 2021, forming an orbital mesh network that can route vast amounts of data through space in real time without needing a ground station. The constellation, however, still requires conventional radio waves to beam connectivity to users on Earth, meaning there is only so much data that can pass through the overall network at any given moment.
But using lasers to beam data to Earth comes with challenges that so far have been difficult to solve. Transcelestial and other companies, however, believe they’ve finally cracked the problem.
High-Speed Laser Internet Technology
Laser light transmits at higher frequencies than radio waves, and can therefore pack more data by orders of magnitude. SpaceX’s Starlink constellation offers a peak user bandwidth of 200 megabits per second—which gets diluted as the number of users in an area grows. By comparison, Transcelestial’s test satellite can beam data to Earth at rates up to 1 gigabit per second. The company’s upcoming satellites will provide an even greater bandwidth of up to 10 Gbps. In the future, Transcelestial’s CEO and co-founder Rohit Jha estimates that every satellite could beam 100 Gbps or more to Earth.
“Scaling for an optical system is actually quite easy,” Jha says. “Ultimately, we can deliver 100 Gbps per second just by putting more terminals on the satellite. It will be like undersea cables from space.”
Other Earth-to-space laser data transmission experiments have been conducted, says Mohammad Danesh, Transcelestial’s co-founder and chief technology officer, but they required bespoke science-grade equipment costing millions of dollars. In 2023, NASA tested a record-breaking 200 Gbps laser link between a ground station and NASA’s Pathfinder Technology Demonstrator 3 satellite in low-Earth orbit. That same year, the Chinese Academy of Sciences conducted a more modest demo with a 10 Gbps laser connection between low-Earth orbit and the ground.
Transcelestial believes it can take the technology mainstream by reducing costs through a combination of supply chain management and manufacturing experience that the company has acquired over the years developing its point-to-point laser communication systems for internet distribution in hard-to-reach areas on Earth.
“The biggest challenge is building a reliable and scalable optical ground station network,” Danesh said, referring to the stations that communicate with satellites in orbit. “The optical ground stations that people are building today cost millions of dollars, and that’s not scalable. You need to be able to manufacture these at scale at a commercial rate, where you can have dozens of these all around the world. And that’s the approach we’ve been taking.”
The multiple ground stations, Danesh adds, will help overcome the difficulty laser light has to get through clouds by providing alternative downlink and uplink locations all over the world.
“If location A is cloudy or rainy or for whatever reason is not working really well, then you start relaying information and find another location where you can download the data,” Danesh says. “This will be a game-changer in space because even with RF, this capability doesn’t fully exist yet, and it can sometimes take days to access your data.”
Secure Laser Communication in Space
Transcelestial is just one of a constellation of companies developing laser communication technologies for space. Lasers, in addition to higher bandwidth, are also much narrower and more focused compared to radio waves. This means they are far more resilient to jamming and interception. This inherent security has come to the fore since the war in Ukraine exposed the vulnerabilities of radio frequency communications to jamming and spoofing.
“In case of laser communications, you have to be literally within the line of sight of the communication beam to be able to disrupt it,” says Laurynas Mačiulis, the CEO of Astrolight. “It’s practically very difficult.”
Astrolight, based in Lithuania, has also developed a space-to-ground laser communications terminal, which it plans to launch to space later this month aboard two small satellites developed by the National Kapodistrian University of Athens and the Aristotle University of Thessaloniki in Greece. The company has a more modest goal than Transcelestial, hoping to enable operators of Earth-observing satellites to get their data down faster and provide back-up communications for users needing extra security.
The company previously tested secure laser communication links to transmit data between two ships on the sea and between two ground stations as part of NATO’s REPMUS and DiBax exercises. In both cases, the terminals passed the tests with flying colors, providing reliable high-bandwidth communications even in rainy and foggy weather, 24 hours a day, for two weeks.
According to media reports, SpaceX CEO Elon Musk hinted that his company is also looking at ground-to-space laser communication technology to overcome the bandwidth bottleneck that currently plagues Starlink users in more densely populated areas.
Jha thinks that laser communications is the future as the technology can deliver a cost per transmitted bit orders of magnitude better compared to radio frequency systems, despite the initially higher price tag. He believes Transcelestial could even leapfrog Starlink, offering fiber-grade connectivity across the equatorial band (where billions of the world’s least connected people live) with a constellation of only 40 satellites—compared to more than ten thousand for Starlink.
Instead of beaming internet directly to individual users on Earth like Starlink does, Transcelestial envisions delivering tens to hundreds of gigabits to local telecom companies, who would further distribute connectivity to users via local ground-based infrastructure. In the future, Jha envisions orbital lasers replacing even undersea cables, offering a cheaper, more reliable service that could not be easily disrupted by adversaries or natural disasters.
Joachim Horwath, the chief technology officer of Germany-based laser communications developer Mynaric, cautions that the challenges presented by the atmospheric interference might be more difficult to surmount than some think.
“Laser communications offer clear advantages for space-to-ground links, particularly when it comes to very high data throughput, inherent security, and the ability to deploy the technology without relying on scarce RF spectrum,” says Horwath. “However, atmospheric conditions remain a key technical challenge. Clouds, turbulence, and weather variability can affect optical link performance, which means these systems require strategies like site diversity or hybrid architectures to ensure reliability. Because of this, we don’t expect laser communications to replace RF entirely.”