Abstract
The accuracy of time synchronization can be significantly increased by enhancing the performance of atomic clocks. Future-generation time-frequency loads will be equipped with the latest ultrahigh-precision atomic clocks (with a day stability better than 10−17) and will leverage advantages of the space environment such as microgravity and low interference to operate a new generation of high-performance time-frequency payloads on low-orbit spacecraft. Moreover, using the high-precision time-frequency system of ground stations, low-time-delay high-performance time-frequency transmission networks, which have the potential to achieve ultrahigh-precision time synchronization, will be constructed. By considering full link error terms above the picosecond level, this paper proposes a new space-to-ground microwave two-way time synchronization method for scenarios involving low-orbit spacecraft and ground stations. Using the theoretical principles and practical application scenarios related to this method, a theoretical and simulation verification platform was developed to research the impact of the attitude, phase center calibration, and orbit determination errors on the single-frequency two-way time synchronization method. The effectiveness of this new method was verified. The results showed that when the attitude error is less than 72 arc seconds (0.02°), the phase center calibration error is less than 1 mm, and the precision orbit determination (POD) error is less than 10 cm (three-axis). After disregarding nonlink error terms such as equipment noise, this method can attain a space-to-ground time synchronization accuracy of better than 1.5 ps, and the time deviation (TDEV) of the transfer link is better than 0.7 ps @ 100 s, which results in ultrahigh-precision space-to-ground time synchronization.
Highlights
Introduction iationsAt present, optical fiber link time comparison technology [1], which can achieve the highest picosecond time synchronization accuracy, is the most accurate of the commonly used long-distance time transfer methods
The space-to-ground thethe new space-to-ground two-way time synchronization method proposed in thistime paper synchronization result
Thisstudy study presented space-to-ground time time synchronization method. This presented aasingle-frequency single-frequency space-to-ground synchronization based on a low-orbit spacecraft in a highly environment
Summary
The integration of next-generation high-performance atomic clocks and related equipment is referred to as a new generation of space time-frequency payloads. 42◦ ) to operate a new generation of space atomic clocks that can obtain a time-frequency reference that is several orders of magnitude higher than that of the ground and achieve high-precision space-to-ground time synchronization through high-performance space-toground microwave links. China has proposed establishing a high-precision time-frequency generating and operating system (space-precision time-frequency reference) in space and has constructed a highprecision time-frequency network based on microwave links to meet the high-precision time requirements of various spacecraft and users. To achieve this goal, a stable and reliable time synchronization method needs to be redesigned to support the realization of ultrahigh-precision time synchronization.
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