OrbitalHub

For decades, the appeal of free-space optical communications from orbit has been obvious. A near-infrared laser beam carries orders of magnitude more spectrum than a comparable radio antenna, the beam is narrow enough to be effectively unjammable, and the photons cost almost nothing to produce. The catch has always been the last 50 kilometres of air. Index-of-refraction turbulence in the lower atmosphere bends the beam by microradians on millisecond timescales, smearing what should be a clean signal into a dancing speckle pattern on the receiver. Satellites have been talking to each other with optical links for years, but the moment a beam has to punch through clouds, fog, and temperature inversion layers, the system has to be either very large or staffed by a small army of optical engineers. On October 8, 2026, a Lithuanian startup called Astrolight, working with two Greek universities and the European Space Agency, showed that a 6U cubesat, a remote-controlled mountaintop terminal, and a piece of software that does not need a human to babysit it can do the job anyway, at 1 Gbps, with link margins to spare.

The piece of hardware in question is ATLAS-1, a laser communication terminal that Astrolight bolted to a nanosatellite called ERMIS-3, which the company says was deployed on a SpaceX rideshare launch (SatNews, October 8 2026). ERMIS-3 is funded through the Greek national space programme and the European Recovery Fund “Greece 2.0” initiative, with the National and Kapodistrian University of Athens running the Department of Aerospace side of the experiment and the Aristotle University of Thessaloniki operating the upgraded optical ground station. Astrolight’s job was the optics: the transmitter on the satellite, the receiver and beacon laser on the ground, and the software that joins them into a closed feedback loop. The ground station sits on Holomondas, a former astronomical observatory in northern Greece that Astrolight retrofitted earlier in 2026 with an 808-nanometre uplink beacon and a C-band optical receiver, and rebranded as OGS-2.5 (Intelligent CIO Europe, May 20 2026).

What the team reported on October 8 is more interesting than “it worked.” The link achieved first light on the satellite’s initial orbital pass over the ground station, transitioned to routine 1 Gbps downlinks within a week, and now runs two pre-scheduled passes per day, one in daylight and one at night, with no on-site operator. Closed-loop tracking held the beam down to elevations below 10 degrees; for passes above 15 degrees, link availability cleared 85%. The terminal re-acquired an interrupted signal in under 10 milliseconds, the speed the U.S. Space Development Agency now demands for inter-satellite optical links (SatNews, October 8 2026). That reacquisition budget is the operational number that matters. A low-Earth-orbit spacecraft flies past any single ground station in seven or eight minutes, and a slow reacquisition means lost megabits. Ten milliseconds is fast enough to hand the link off cleanly between stations on a single pass, which is what the commercial constellations are paying for.

The reason this is different from the inter-satellite optical links that SDA, Mynaric, and Tesat have been flying for several years is that those terminals never have to deal with the atmosphere. A beam from one satellite to another crosses nothing but vacuum, so the engineering reduces to narrow-beam pointing and high-fidelity wavefronts. A downlink to a mountaintop, by contrast, has to survive turbulence cells roughly 10 centimetres across near the ground, scintillation that flips the received power by a factor of three on second-long timescales, and weather. Holomondas sits at roughly 1,000 metres of elevation, which buys it less air column and fewer low-altitude turbulence cells than a sea-level site would. The 808 nm beacon Astrolight installed at the ground station gives the satellite’s coarse-pointing system a bright target to chase before the fine tracker takes over, and the C-band receiver behind it tolerates the same 1550 nm family of wavelengths that terrestrial fibre networks use, which means the same indium-gallium-arsenide photodetectors and erbium-doped fibre amplifiers can be repurposed from telecom inventory (Intelligent CIO Europe, May 20 2026).

The closed-loop trick is what closes the engineering gap. The beacon tells the satellite where the ground station is in inertial space; the satellite’s fast-steering mirror narrows the beam to a few hundred microradians, narrow enough that diffraction alone would put a metre-scale spot on the ground; the ground station’s wide-field detector sees the spot, measures its centroid, and pushes the offset back up the beacon. The whole loop runs at a few hundred hertz, well above the bandwidth of the turbulence that drives the worst scintillation. Once the loop is locked, the received power stabilises, and the link budget, which Astrolight quotes at 1 Gbps nominal and “up to 10 Gbps” headroom for the ATLAS-1 design, becomes a question of how much laser power the satellite can afford to spend per bit. A useful scaling relation is that the required transmit power scales as the square of the range, so a low-Earth-orbit link at 500 km needs roughly 10,000 times less power than a comparable geostationary link at 36,000 km — which is why nobody has ever put a useful optical downlink on a GEO satellite without a relay mirror in between.

The team has not talked publicly about the exact laser power, the modulation format, or the forward-error-correction scheme. Those numbers matter: at 1550 nm, the atmospheric transmission window is wider than at 1064 nm, and the eye-safety limit allows a few hundred milliwatts of average power before a ground telescope becomes a retinal hazard. The published numbers point toward on-off keying rather than the more exotic quadrature-amplitude-modulation formats that ground fibre uses, because residual scintillation still costs several decibels of margin if you try to ride a higher-order constellation through it. The “up to 10 Gbps” claim is therefore best read as a stretch goal in good seeing, not a guaranteed nightly rate.

What changes because of this is the small end of the market. The same architecture — a 1U-to-6U cubesat payload, a 30 centimetre ground receiver, and a software stack that runs itself — fits Earth-observation operators who today are stuck at tens of megabits per second over X-band because their satellite is too small for a steerable parabolic dish. Astrolight’s roadmap includes the ATLAS-2 and ATLAS-X-MINI terminals at 2.5 Gbps, and the larger ATLAS-X destined for ESA’s HydRON multi-orbit optical network in 2028 to 2029 (SatNews, October 8 2026). The company is also building a second optical ground station in Greenland with ESA, partly to chase high-elevation polar passes that Mediterranean sites cannot see, and partly to use the long Arctic nights as natural immunity against daytime turbulence. The first trans-Atlantic optical link from a commercial LEO satellite is no longer a 2030 problem.

The interesting historical echo is that this is, finally, what NASA and ESA have been quietly trying to build since the 1990s. Japan’s KIRARI satellite demonstrated a 1.5 Mbps optical downlink in 2006. The Lunar Laser Communication Demonstration returned 622 Mbps from the Moon in 2013. The European Data Relay System started operational optical service in 2016 at 1.8 Gbps between geostationary relay and LEO. The difference now is that a 6U cubesat, operated by a small team in Vilnius, can do the job, unattended, and the same company’s roadmap reaches deep into ESA’s flagship programmes. The orbit-to-ground bottleneck has been broken at the small end. What comes next is the same trick repeated a thousand times, every time a constellation operator looks at a 1 Gbps optical downlink and realises it no longer needs a ground crew to make it work.