Introducing OpSTAR

Optical technologies are leading a revolution in satellite communications, as intersatellite laser links become standard features on many low Earth orbit satellites and are being demonstrated for deep-space operations.

Satellite navigation is poised to follow the same trajectory as optical technologies mature, offering the potential to redefine today’s system architectures which rely heavily on frequent ground contact, complex ground processing and highly stable complex onboard atomic clocks to provide services to end users.

Optical solutions have reached a level of readiness that makes them credible candidates for future use in operational satellite navigation systems, promising centimetre-level accuracy and picosecond-level time synchronisation, while also strengthening resilience against interference. Moreover, optical links benefit from less stringent regulatory constraints than those affecting signals in the radiofrequency spectrum. 

ESA’s OpSTAR in-orbit demonstrator mission aims to explore how optical links may be incorporated into satellite navigation for additional benefits.

OpSTAR will:

• Demonstrate the use of inter-satellite laser links to allow satellites to autonomously synchronise their clocks (timing), determine their orbit with high precision (ranging), and exchange mission data between each other.
• Demonstrate the use of optical links instead of radiofrequency signals to exchange PNT information between the satellites and the ground, making these links more resistant to interferences and jamming.
• Contribute to the creation of an international standard for optical timing and ranging in satellite navigation.
• Support the design of future satellite navigation architectures, interconnecting satellite navigation systems in geostationary (like EGNOS), medium (like Galileo) and low Earth orbit (like Celeste).

The OpSTAR in-orbit demonstrator mission will comprise two medium Earth orbit satellites equipped with both optical and navigation payloads, as well as two optical ground stations, a ground processing facility, a user test range as well as satellite control and reference systems.

As part of the demonstrator mission, European industry will have access to the Laser Communication and Ranging Terminal (LCRT). an interoperability testbench at ESA-ESTEC to validate their laser communication and ranging terminal solutions, while an end-to-end GNSS system simulator will allow to assess expected performance for alternative system concepts and novel PNT use cases.

The OpSTAR mission was approved at ESA Council at Ministerial Level of 2025 (CM25) and is financed by seven ESA Member States. The mission belongs to ESA’s FutureNAV programme, as part of its ‘Future PNT Demonstrators’ component.

The current Phase A/B1 activities are led by OHB System AG (Germany), supported by 36 subcontracting companies coming from 14 ESA member states.

The LCRT is expected to be inaugurated at ESA-ESTEC by the end of 2027.

In parallel, manufacturing, system integration and testing of the two Medium Earth Orbit satellites and associated ground infrastructure will continue, leading to full mission readiness.

The launch of the OpSTAR in‑orbit demonstrator is planned for the second half of 2029.