Implementation and Performance Analysis of a GNSS Receiver–CSAC Based Precision Timing System for LEO Navigation Satellite Applications

Jaeeun Lee, Jinsil Lee, Eunsung Lee, Daehee Won*

Precise time synchronization is a critical requirement for navigation satellites, including Low Earth Orbit (LEO) navigation systems. However, small LEO satellites often face constraints in size, power, and cost, which limit the use of high-performance space-qualified atomic clocks. In this study, a precision timing device based on a commercial GNSS receiver and a Chip-Scale Atomic Clock (CSAC) is developed, and its applicability to LEO navigation satellites is analyzed. The proposed system disciplines a CSAC-based reference clock using the 1 PPS signal generated by the GNSS receiver. Timing stability is evaluated by measuring the time difference between the GNSS 1 PPS and the CSAC-based 1PPS signals. The performance of the system is analyzed under both normal GNSS tracking conditions and holdover conditions when GNSS signals are unavailable. Experimental results show that the proposed system can maintain stable time synchronization when GNSS signals are available, and it can sustain acceptable timing accuracy for a certain duration during GNSS outages using the holdover capability of the CSAC. These results indicate that the proposed low-cost precision timing architecture based on a commercial GNSS receiver and CSAC can be a practical solution for timing maintenance in LEO navigation satellite payloads.
Keywords: LEO, PNT, clock, CSAC

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