分类： 天文学 >> 天文仪器与技术 提交时间： 2024-09-30 合作期刊: 《天文技术与仪器（英文）》
摘要： A time and frequency system is a critical component of Very Long Baseline Interferometry (VLBI) stations, providing stable and reliable standards that directly impact data processing quality. At the Tianma 65 m radio telescope(TMRT), this system has been meticulously designed to ensure long-term reliability and high performance. It incorporates high-performance hydrogen atomic clocks, high-precision time standards, automatic signal switching, and robust system software. This comprehensive approach has enabled the system to achieve long-term reliable operation, successfully supporting both major national engineering tasks and daily scientific observations. The effectiveness of the system is evidenced by its consistent delivery of the precision and stability required for radio astronomy. This article provides an in-depth exploration of the design and operation of the time and frequency system at the Tianma 65 m telescope, examining various aspects of its architecture, implementation, and performance. By sharing these insights, we aim to contribute knowledge that could benefit similar systems at other VLBI stations, greatly advancing radio astronomy infrastructure.
分类： 物理学 >> 地球物理学、天文学和天体物理学 分类： 信息科学与系统科学 >> 信息科学与系统科学基础学科 提交时间： 2024-06-09
Wenlong Sun
Fengfeng Shi
Yuting Lin
Jinfeng Xu
Shaofeng He
Yongxin Lin
Guocheng Wang
Run Zhao
Pei Ma
摘要： The precise estimation of the satellite clock bias (SCB) holds considerable importance in ensuring accurate timekeeping, navigation, and positioning. This studyintroduces a novel SCB prediction approach that integrates variational mode decomposition (VMD) and long short-term memory (LSTM) network techniques, combining signal decomposition with deep learning methodologies. Initially, the raw SCB data undergoespreprocessing, followed by decomposition using the VMD method to generate multiple intrinsic mode functions (IMFs). These decomposed IMFs serve as inputs for LSTM, where several independent LSTM models are established for training and prediction purposes. Subsequently, the predicted outcomes are aggregated and reconstructed to derive the finalSCB prediction. Experimental findings demonstrate notable advancements in clock bias prediction for the spaceborne hydrogen atomic clock for BDS, with prediction accuracies of 0.048 ns, 0.204 ns and 1.397 ns for 6 hours, 3 days and 15 days, respectively. These results exhibit significant enhancements compared to both the LSTM network and the Back Propagation (BP) neural network, with improvements of 56%, 84% and 83% for the aforementioned time intervals in comparison to LSTM, and enhancements of 59%, 82% and 83% relative to the BP neural network.
分类： 天文学 >> 天文仪器与技术 提交时间： 2024-04-18 合作期刊: 《天文技术与仪器（英文）》
摘要：Optical frequency combs, as powerful tools for precision spectroscopy and research into optical frequency standards, have driven continuous progress and significant breakthroughs in applications such as time-frequency transfer, measurement of fundamental physical constants, and high-precision ranging, achieving a series of milestone results in ground-based environments. With the continuous maturation and evolution of femtosecond lasers and related technologies, optical frequency combs are moving from ground-based applications to astronomical and space-based applications, playing an increasingly important role in atomic clocks, exoplanet observations, gravitational wave measurements, and other areas. This paper, focusing on astronomical and space-based applications, reviews research progress on astronomical frequency combs, optical clock time-frequency networks, gravitational waves, dark matter measurement, dual-comb large-scale absolute ranging, and high-resolution atmospheric spectroscopy. With enhanced performance and their gradual application in the field of space-based research, optical frequency combs will undoubtedly provide more powerful support for astronomical science and cosmic exploration in the future.
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