Summary

Galileo Second Generation (G2G) represents a major evolution of Europe’s satellite navigation system, introducing more resilient, accurate and flexible satellites for next-generation navigation services. One of the key innovations lies in the development of new atomic clocks, which are essential to positioning accuracy and signal reliability.

Safran Electronics & Defense in Switzerland plays a central role in this effort through the development of advanced spaceborne timing technologies, including the innovative Mercury Ion Clock. Objectives: improve stability, robustness and long-term operational performance for GNSS missions.

Background & project scope

Satellite navigation systems rely on ultra-precise atomic clocks to calculate positioning accurately. “Since navigation signals travel at the speed of light, even extremely small timing errors can significantly affect positioning performance,” explains Michela Pirozzi, Dr Program Manager at Safran Electronics & Defense. “A deviation of one nanosecond can generate a positioning error of approximately 30 centimeters.”

Galileo’s current satellites already use highly stable rubidium atomic clocks and passive hydrogen masers to provide world-leading navigation accuracy. Safran Electronics & Defense has been a key contributor to this success through its space-qualified rubidium clocks developed in Switzerland.

The G2G program is designed to further enhance navigation precision, signal robustness and long-term system resilience for upcoming Galileo satellites, including digital navigation payloads, enhanced signal flexibility, Inter-satellite communication links and more advanced timing architectures.

The Mercury Ion Clock

Among the technologies selected by ESA for further development is Safran Electronics & Defense’s Mercury Ion Clock. Research activities are conducted through Safran’s Swiss timing expertise centers, where advanced space clock technologies are designed and engineered for demanding space environments.

The Mercury Ion Clock system uses time-varying electric fields to trap a cloud of mercury ions without physical contact with the surrounding vacuum tube walls. This architecture offers major advantages for space applications. “Because the ions are confined within a trap, the clock is less sensitive to environmental perturbations, particularly thermal variations,” confirms Christian Schori, scientist at Safran Electronics & Defense. “In addition, the technology delivers excellent long-term frequency stability”.

These characteristics make the Mercury Ion Clock particularly attractive for future GNSS missions, where stability, robustness and operational lifetime are critical. The new system is expected to enhance overall Galileo performance by:

• Increasing navigation accuracy,
• Improving synchronization stability,
• Ensuring greater robustness in harsh space environments,
• Expanding technological diversity within the Galileo programme.

Beyond Galileo itself, these developments reinforce Europe’s strategic autonomy in critical timing technologies used in navigation, telecommunications, defense and scientific infrastructures.

Conclusion

The Galileo Second Generation is a strategic step forward for Europe’s satellite navigation capabilities. At the heart of this evolution are new atomic clock technologies capable of delivering greater precision and long-term operational resilience.

Through the development of the Mercury Ion Clock and next-generation timing technologies, Safran Electronics & Defense is helping shape the future of European satellite navigation while reinforcing Europe’s leadership in precision timing for space applications.