Time synchronization is fundamental to critical technologies, ranging from global navigation and secure communications to frontier research in physics. Traditional methods, including those based on pseudocode, are generally limited to sub-nanosecond precision, often compromised by atmospheric interference, hardware-induced noise, and relativistic effects. These challenges have restricted synchronization reliability, particularly for satellite-to-ground systems operating in dynamic conditions. The need for improved accuracy has driven researchers toward more advanced methodologies.

A study published in *Satellite Navigation* by researchers from the National Time Service Center of the Chinese Academy of Sciences introduces a novel carrier-phase-based method for satellite-ground synchronization. Tested using the China Space Station (CSS)-ground system, this technique delivers an unprecedented level of precision, far surpassing the limitations of traditional pseudocode-based approaches.

This method uniquely combines pseudocode with carrier phase observations, enabling a robust synchronization framework. Laboratory tests validated its exceptional stability, with picosecond-level precision confirmed in experimental settings. Further satellite-to-ground testing reinforced these findings, demonstrating a substantial leap in synchronization accuracy. Allan Deviation analysis showed that the new technique improves stability by nearly an order of magnitude compared to conventional methods.

One of the method's standout advantages is its ability to compensate for multiple sources of error. Motion delays, relativistic time dilation, and atmospheric perturbations are significantly mitigated through a triple-frequency mode that corrects for ionospheric and tropospheric distortions. By incorporating precise orbit determination and real-time atmospheric data, the researchers enhanced the synchronization system's overall accuracy. Moreover, the technique minimizes hardware biases and short-term fluctuations, ensuring consistent performance even in highly dynamic environments. The result is a groundbreaking time synchronization solution offering both unparalleled precision and remarkable stability.

Dr. Shuaihe Gao, the lead researcher on the project, highlighted the significance of this advancement: "Our carrier-phase-based method is a game-changer in satellite-ground time synchronization. Achieving picosecond-level accuracy sets a new benchmark for high-precision synchronization, which is essential for the future of space exploration and fundamental physics research."

The impact of this development extends well beyond laboratory settings. For global navigation satellite systems (GNSS), this enhanced synchronization capability promises substantial improvements in positioning accuracy, benefiting industries such as transportation, logistics, and telecommunications. In deep space exploration, precise timekeeping is crucial for navigation and interstellar communication, making this advancement particularly valuable. Furthermore, in fundamental physics, the technology supports high-precision experiments such as tests of relativity and quantum mechanics. Additionally, this method could contribute to refining global clock networks, improving scientific measurements, and enabling the accurate dissemination of time signals worldwide. With such far-reaching applications, this breakthrough represents a transformative step forward in time synchronization technology, with potential benefits spanning Earth sciences, space missions, and beyond.

Research Report:An improved carrier-phase-based method for precise time synchronization using the observations from the China Space Station-ground synchronization system

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