ERMIS-3, a Greek CubeSat, has established a laser connection with the Holomondas Optical Ground Station in Greece. ESA reported the demonstration on November 2, 2026, identifying it as Greece’s first optical link with a satellite in low Earth orbit. The spacecraft carries a miniature terminal that sends information through a precisely directed beam of light.
Developed by the National and Kapodistrian University of Athens, the eight-unit CubeSat communicated with HolOGS-1, the ground station developed by Aristotle University of Thessaloniki. Lithuanian company Astrolight supplied the optical equipment. The connection demonstrated pointing, acquisition, and tracking, three functions that allow a moving spacecraft and a ground terminal to establish and maintain contact.
Connecting the Spacecraft and Ground Station
ERMIS-3 uses Astrolight’s ATLAS-1 terminal. At Holomondas, the company upgraded the ground equipment to its OGS-2.5 configuration for the related PeakSat mission. In an October 8 announcement, Astrolight reported that its team in Lithuania operated both ends of the connection remotely.
The company reported data transmission at one gigabit per second and two links per day after commissioning. Both terminals achieved their first optical contact during the satellite’s first active pass over the station. By the third pass, Astrolight said the equipment had completed calibration and was operating autonomously according to a schedule.
Astrolight also reported link availability above 85% for passes higher than 15 degrees of elevation following calibration. Elevation describes the satellite’s angle above the local horizon. The company reported that interrupted links were reacquired in less than 10 milliseconds, supporting recovery when the optical path was briefly obstructed. These figures describe the company’s reported performance during the commissioning and early operations period.
How a Laser Downlink Works
An optical downlink carries information from a spacecraft to a ground receiver using light. NASA’s explanation of laser communications describes systems operating at infrared wavelengths, which are much shorter than radio wavelengths. The higher optical frequency supports transmission of more information through a single link.
The concentrating optics also keep the beam narrow. Pointing directs the terminal toward its counterpart, acquisition establishes the connection, and tracking maintains alignment as the geometry changes. A spacecraft in low Earth orbit travels several kilometers per second, so the direction between it and a fixed ground station changes throughout the pass.
This alignment function was central to ERMIS-3’s mission design. The satellite and ground equipment establish contact during the interval when the spacecraft is visible from the station. Their control systems maintain the connection as it crosses the sky.
The atmosphere is part of the transmission path. Clouds can block an optical beam, and turbulence can disturb its propagation. NASA locates optical ground facilities at sites selected for favorable atmospheric conditions. For the Greek demonstration, Astrolight’s reported rapid reacquisition describes how its terminals resumed contact after temporary interruptions.
Optical terminals can also provide a compact way to transmit large data volumes. NASA notes that laser systems typically use less volume, mass, and power than comparable radio systems. These properties are relevant to small spacecraft, where communications equipment shares limited resources with instruments, computers, and power hardware.
A Communications Experiment With an Imaging Application
ERMIS-3 launched on March 30, 2026, aboard the Transporter-16 mission. It flew with ERMIS-1 and ERMIS-2, which have different communications assignments. ESA’s launch account described those two satellites as test platforms for satellite-enabled Internet of Things connectivity using 5G technology and for radio-frequency intersatellite links.
ERMIS-3’s optical experiment focuses on the connection to Earth. ESA described a planned demonstration of rapid hyperspectral-image transfer using the spacecraft’s camera, with precision agriculture as an intended application. The mission brings together the collection of imagery and a communications method for returning that information during a ground-station pass.
The link is direct to the ground. Optical communications also support connections between satellites, allowing information to move through relay networks before reaching Earth. New Space Economy’s satellite laser communications primer explains these separate uses: direct downlinks return onboard data during a contact, and intersatellite links move information between spacecraft. ERMIS-3 demonstrates the former configuration.
ESA supported the spacecraft through environmental testing and optical alignment at the European Space Research and Technology Centre in the Netherlands. The work forms part of Greece’s National Space Programme, which ESA implements on behalf of the Greek government. The completed demonstration connects a university-built spacecraft with a Greek optical ground station for remotely operated data transmission.
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