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High-Precision Laser Time-Frequency Synchronization in Space Based on an Improved Kalman Filtering Method
Boao Sun1,2, Xiaoqing Wang1,3, Zhibin Sun1,2
1National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China.
Sensors (Basel, Switzerland)
|June 12, 2026
Summary
This study presents an improved Kalman filtering method for free-space optical time-frequency synchronization, enhancing accuracy by 41% and improving time stability. The method addresses beam drift and link variations for reliable space applications.
Area of Science:
- Optical communications
- Space technology
- Signal processing
Background:
- Future space applications require precise time-frequency synchronization.
- Free-space optical links face challenges like beam drift and dynamic link variations.
- Existing methods may lack adaptability to real-time environmental changes.
Purpose of the Study:
- To investigate the impact of beam drift and link variations on free-space laser synchronization.
- To develop and validate an improved method for free-space optical time-frequency synchronization and ranging.
- To provide a ground-based experimental reference for space-based optical synchronization systems.
Main Methods:
- Established a bidirectional free-space laser time-frequency synchronization and ranging system.
- Modeled the synchronization process and proposed an improved Kalman filtering method with innovation consistency.
- Implemented a strong tracking mechanism for adaptability and an adaptive observation noise modeling strategy.
Main Results:
- Time synchronization accuracy improved from 78.32 ps to 45.64 ps (41% enhancement).
- Time deviation (TDEV) reduced significantly at averaging times of 1 s and 800 s.
- Ranging performance achieved a standard deviation of 15.2 mm over 321 m.
Conclusions:
- The proposed method enhances time synchronization accuracy and stability in free-space optical links.
- The approach effectively handles model mismatch and time-varying noise properties.
- Demonstrated high-precision and stable state estimation for integrated free-space laser synchronization and ranging systems.
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