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The 8U ERMIS-3 CubeSat has established an optical communications link with the Holomondas ground station in Greece, ESA reported. The demonstration used an Astrolight ATLAS-1 terminal and marks Greece’s first optical link with a low Earth orbit satellite. It tested the precise pointing, acquisition and tracking needed to maintain a laser connection.
Greece’s ERMIS-3 CubeSat has established a laser communications link with the Holomondas Optical Ground Station, demonstrating that a small satellite can acquire and track a ground receiver while moving through low Earth orbit. The European Space Agency said the link was achieved weeks after the satellite’s commissioning and marks Greece’s first optical link with a LEO satellite.
The demonstration paired an ATLAS-1 optical terminal carried by ERMIS-3 with a terminal at Holomondas, a ground station in Greece developed by the Aristotle University of Thessaloniki. The satellite was developed by the National and Kapodistrian University of Athens, with optical terminals supplied by Lithuanian company Astrolight. ESA supported the mission with technical expertise.
The link tested a central challenge for laser communications: precise pointing, acquisition and tracking, often shortened to PAT. A satellite travels through orbit at several kilometres per second, while the laser beam is narrow and must be aimed accurately at a receiver. Both ends must locate and maintain the signal within a limited pass over the ground station.
Unlike radio-frequency systems, optical communications send data using laser light. ESA says this approach can support high data rates, but a connection can be blocked by clouds and its signal quality can be affected by atmospheric turbulence. The agency described ERMIS-3’s connection as a demonstration of one of the mission’s main objectives; the report did not state how much data was transferred or how long the link lasted.
Laser Links Could Ease Data Backlogs
The result is a step toward using optical communications on small satellites, which may help missions send large amounts of data to Earth. Earth-observation spacecraft, for example, can produce high-resolution and hyperspectral imagery that places demands on downlink capacity. A laser link could offer another way to move such data, although this demonstration alone does not establish its routine performance or operational advantage over radio.
The test also matters because it took place between a Greek satellite and a Greek ground station. It provides an in-orbit demonstration for the country’s space programme and shows cooperation among university teams, industry and ESA. For small spacecraft, proving that a compact terminal can point and track reliably is a necessary step before optical links can be considered for broader mission use.
Optical systems also have a practical limitation: weather can interrupt ground connections. Clouds may prevent a laser signal from reaching a station, and turbulence can degrade it. The demonstration confirms a successful link under the conditions at the time, not uninterrupted service in all weather or across repeated passes.
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A Greek In-Orbit Demonstration
ERMIS-3 launched on March 30, 2026, alongside ERMIS-1 and ERMIS-2. The three spacecraft are part of an in-orbit demonstration programme intended to test communications technologies for small satellites. ERMIS-3 is an 8U CubeSat, a compact satellite built from units based on a standard small-satellite format.
The mission forms part of Greece’s National Space Programme, implemented by ESA on behalf of the Greek government. ESA said its contribution included environmental testing and optical alignment at the European Space Research and Technology Centre in the Netherlands, as well as programme management, technical supervision and engineering support.
The ground receiver, Holomondas Optical Ground Station, is also known as HolOGS-1. The Aristotle University of Thessaloniki developed the station, while Astrolight provided optical terminals for the satellite and ground side. This arrangement allowed the team to test the complete link between a spacecraft terminal and a ground-based receiver.
“Using ATLAS-1 as a laser communications terminal has led to a unique collaboration and the first operations of a laser optical link on the CubeSat.”
— Professor Vaios Lappas and Antonis Paschalis, ERMIS principal investigators
Performance Beyond the Demonstration
The ESA report does not give the link duration, data volume, transmission rate or number of successful connection attempts. It also does not specify the weather or atmospheric conditions during the test. Those details would help readers judge how the system performed beyond the fact that a connection was established.
It remains unclear how frequently ERMIS-3 will attempt optical contacts, whether the satellite will demonstrate repeated links, and how the laser system will perform across different passes and conditions. The report describes a successful milestone, but does not say that the service is operational or that the link can replace radio communications.
Further Passes Will Test Reliability
The next evidence to watch for is whether ERMIS-3 can repeat the link in further passes and provide performance information such as data rate, connection duration and tracking reliability. Repeated demonstrations would offer a clearer picture of how the compact terminal works in orbit and how ground-station availability affects its use.
ESA and the ERMIS team have not announced a timetable for further tests in the report. The broader programme is intended to demonstrate technologies for small satellites, and results from continued operations could inform future missions seeking higher-capacity data links. Any operational use would still need to account for cloud cover and atmospheric effects.
Key Questions
What did ERMIS-3 achieve?
It established a laser communications link with the Holomondas Optical Ground Station in Greece, demonstrating the satellite’s ability to point, acquire and track a ground receiver.
Why is this link described as challenging?
The CubeSat moves rapidly through orbit and must aim a narrow laser beam precisely at the ground receiver during a limited contact window. The two terminals must acquire and track the signal, while clouds and atmospheric turbulence can affect the connection.
Who built the satellite and supplied the optical equipment?
The National and Kapodistrian University of Athens developed ERMIS-3. The spacecraft carries an ATLAS-1 terminal from Astrolight, while the Holomondas ground station was developed by the Aristotle University of Thessaloniki. ESA provided technical and programme support.
How much data did the satellite transmit?
The ESA report does not specify the amount of data, transmission rate or duration of the link. It confirms that the optical connection was established but does not provide those performance figures.
Does this mean optical links will replace radio communications?
No. The demonstration does not establish that optical links will replace radio systems. Laser communications can support high data rates, but clouds can block the connection, and the report does not describe the link as an operational replacement for radio.
Source: esa.int
