Ground-to-satellite optical communications using existing inter-satellite terminals

Proven in orbit by Cailabs and Kepler Communications

Cailabs has successfully demonstrated that satellite-to-ground optical communications can be achieved using already deployed inter-satellite optical terminals, unlocking new possibilities for secure, resilient space connectivity.

The innovation

Cailabs, in partnership with Kepler Communications, has demonstrated a new approach: Reusing existing satellite-to-satellite optical terminals for direct satellite-to-ground communication

This eliminates the need for new payloads in orbit and enables:

• Rapid deployment of optical downlinks
• Reduced infrastructure costs
• Immediate scalability using existing constellations

Proven in orbit

Cailabs has been conducting tests at the request of the Canadian company Kepler Communications Inc., aiming at validating compliance with SDA standards using satellite-to-satellite communication terminals. The validation is performed with an operational Kepler LEO satellite equipped with two Tesat SCOT80 bidirectional mounted at the front and rear of the satellite. More than forty sat-to-ground tests have been conducted and these campaigns demonstrated error-free optical communication above 20° elevation and reliable acquisition down to 10° elevation, with several gigabytes of data transmitted per satellite pass.

In May 2025, Kepler announced the achievement of full SDA-standards acquisition and data rates in multiple space-to-ground scenarios between its Pathfinder optical satellite in low Earth orbit (LEO) and Cailabs Optical Ground Station (OGS) in Rennes, France. This milestone confirms that satellite-to-ground connectivity is feasible using already deployed satellite-to-satellite terminals.

Why it matters

This breakthrough delivers immediate value to operators, institutions, and defense stakeholders:

Faster deployment: No need to wait for new satellites, leverage existing infrastructure.

Cost efficiency: Avoid additional payload development and launch costs.

Enhanced security: Optical communications are inherently resistant to jamming and interception.

Operational flexibility: Adaptable to a wide range of missions, from commercial data transfer to defense communications.

Already launched or planned constellations with optical intersatellite links can be leveraged to offer satellite-to-ground optical links, delivering new services such as secure data downlink, tactical communications, rapid data exfiltration, or high-speed Earth observation data transfer without additional space assets.

A new paradigm for space communications

By extending the role of optical inter-satellite terminals to ground communications, Cailabs is enabling a new generation of hybrid optical networks, more resilient, scalable, and ready for immediate deployment.

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