Optical technology is emerging as an alternative solution for positioning, navigation, and timing (PNT), with applications ranging from GNSS-denied or lacking environments like Mars to potential integration into future GNSS systems themselves. The European Space Agency (ESA) has recently taken a significant step forward by initiating a definition study for OpSTAR (Optical Synchronized Time And Ranging), contracting with a consortium of 33 European companies led by OHB System.
Optical links, which transmit data using laser beams instead of radio signals, have established their reliability in satellite communications. However, their adaptation for navigation requires addressing unique challenges in precision time synchronization and ranging. The OpSTAR project proposes a testbed comprising two identical satellites and ground stations, enabling experiments with bi-directional optical links for time-transfer and ranging applications.
The OpSTAR initiative represents the first step toward a potential in-orbit demonstrator, which will validate intersatellite optical links before their integration into operational satellite navigation systems. The project involves comprehensive testing of critical optical system elements to consolidate future PNT system concepts and inform decisions about incorporating optical technology in operational systems. OpSTAR will also contribute to defining an international interoperability standard for optical timing and ranging in PNT.
Through programs like FutureNAV, ESA ensures that Europe remains a leader in navigation technologies while supporting innovation in space-based PNT technologies. The foundation for optical PNT builds upon the matured technology of Optical Inter-Satellite Links (OISL), which has demonstrated its reliability in space communications. This proven technology can be adapted to achieve precise ranging capabilities as well as time and frequency transfer between satellites and ground stations. The advantages of optical systems over traditional microwave technology are substantial, offering superior frequency stability through optical clocks and enhanced ranging precision via optical links, as well as less susceptibility to jamming. These capabilities position optical technology as a key enabler for next-generation navigation systems, on Earth and beyond.
Image Credit: NASA / Dave Ryan – Laser Communication Relay Demonstrator communicating over laser links
ESA to develop optical technology for navigation https://www.esa.int/Applications/Satellite_navigation/ESA_to_develop_optical_technology_for_navigation
ESA Opstar contract signature https://www.esa.int/ESA_Multimedia/Images/2025/02/Opstar_contract_signature
Paper: Optical Technologies for Future Global Navigation Satellite Systems https://elib.dlr.de/195226/2/Optical_Technologies_for_Future_Global_Navigation_Satellite_Systems.pdf
OpSTAR: A New (Laser) Era for PNT Systems https://www.ion.org/itm/abstracts.cfm?paperID=15056