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 tele...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.展开更多
We report on studies of an optical lattice for a strontium clock performed at the National Time Service Center. Follow-ing tw o-stage laser cooling and trapping,88 Sr cold atoms w ith population of 105 and a longitudi...We report on studies of an optical lattice for a strontium clock performed at the National Time Service Center. Follow-ing tw o-stage laser cooling and trapping,88 Sr cold atoms w ith population of 105 and a longitudinal temperature of 8. 4 μK are loaded into a one-dimensional optical lattice. Spectroscopic analysis of the1S0-3P0 transition gives a linew idth of 180 Hz measured using magnetic field-induction,w hich mixes the3P1 state w ith the3P0 state. Rabi oscillations are observed. Because of the inhomogeneous excitation among the atoms,the Rabi π-pulse excitation at 5 ms show s a near 65% excitation of atoms. The transverse velocity distribution of the atomic beam and the absolute frequencies of the four inter-combination transitions of the isotopes w as measured precisely using velocity-selective fluorescence spectroscopy. By optical injection of tw o cascade external-cavity diode lasers,a single comb line at 689 nm from an optical femtosecond laser comb is filtered and amplified w ith a 37-d B side-mode suppression and a linew idth of less than 240 Hz. We describe recent w ork on a space optical clock concerning the physical vacuum system,thermal analysis,and a permanent-magnet Zeeman slow er for a space strontium optical clock. The first six mode frequencies are obtained and the corresponding oscillation modes are described in detail. We also simulate and analyze thermal profiles for both the physical and optical units installed in the cooling system. When the injected cooling w ater has a temperature of 21℃ or28℃,the units meet operational requirements for temperatures in a space environment. Using a series of permanent magnets,a Zeeman slow er is built that can w ithstand space launching and operating conditions for the space optical clock.展开更多
Due to high stable rotations, timing of pulsars provides a natural tool to correct the frequency deviation of spaceborne atomic clocks. Based on processing the observational data about a year of Crab pulsar given by X...Due to high stable rotations, timing of pulsars provides a natural tool to correct the frequency deviation of spaceborne atomic clocks. Based on processing the observational data about a year of Crab pulsar given by XPNAV-1 satellite, we study the possibility of correcting the frequency deviation of spaceborne atomic clocks using pulsar timing. According to the observational data in X-ray band and the timing model parameters from radio observations, the pre-fit timing residuals with a level of 67.66 μs are obtained. By fitting the slope of the timing residuals affected by the faked frequency-biased reference clock, we estimated successfully the relative frequency deviation of the reference clock. For a satellite clock with frequency deviation of the order about 10^(-12), a calibration accuracy with relative error of about 2% can be obtained from the Crab pulsar’s data for one year.The stability of the time scale based on Crab pulsar is about 10^(-12) for an interval of one year.展开更多
守时型原子钟主要包括氢原子钟和铯原子钟,为进一步探究不同类型守时原子钟计算时间尺度相关性能,本文开展全氢钟及氢铯联合时间尺度研究。首先依据国际权度局(Bureau International des Poids et Mesures,BIPM)发布的d公报将氢原子钟...守时型原子钟主要包括氢原子钟和铯原子钟,为进一步探究不同类型守时原子钟计算时间尺度相关性能,本文开展全氢钟及氢铯联合时间尺度研究。首先依据国际权度局(Bureau International des Poids et Mesures,BIPM)发布的d公报将氢原子钟进行分类,针对分类结果分别运用原子时尺度理论方法计算全氢钟时间尺度,并给出分析结果。随后计算全铯钟时间尺度,并分析探究两种不同的氢铯联合钟组时间尺度。结果表明,基于频率漂移量较小的氢钟组形成的时间尺度波动范围小,且稳定度优于频率漂移量较大的氢钟组形成的时间尺度。氢铯联合形成的时间尺度稳定度优于全铯钟时间尺度,不同的氢铯联合钟组计算得到的时间尺度结果相近。展开更多
时间频率数据是国家重要的信息资源,时间频率数据平台设计依托国家授时中心运行产生的时频数据、国际权度局(Bureau International des Poids et Mesures,BIPM)和国际地球自转服务机构(International Earth Rotation and Reference Syst...时间频率数据是国家重要的信息资源,时间频率数据平台设计依托国家授时中心运行产生的时频数据、国际权度局(Bureau International des Poids et Mesures,BIPM)和国际地球自转服务机构(International Earth Rotation and Reference Systems Service,IERS)公布的时间频率相关数据等实现,该数据平台可以为守时技术研究提供丰富的数据资源支撑。首先介绍时间频率数据平台的建设情况,随后利用数据平台汇交的本地守时系统比对和远距离链路比对数据开展守时技术研究,包括原子钟状态评估,主要分析原子钟异常跳变情况,研究跳变数据处理方法,针对不同类型守时钟,分析对比波动情况、稳定度等原子钟性能指标,此外基于ARIMA模型开展钟差预报研究。以上研究结果可为守时系统连续可靠运行提供重要参考。展开更多
The relationship and the mutual benefits of timekeeping and Global Navigation Satellite Systems(GNSS)are reviewed,showing how each field has been enriched and will continue to progress,based on the progress of the oth...The relationship and the mutual benefits of timekeeping and Global Navigation Satellite Systems(GNSS)are reviewed,showing how each field has been enriched and will continue to progress,based on the progress of the other field.The role of GNSSs in the calculation of Coordinated Universal Time(UTC),as well as the capacity of GNSSs to provide UTC time dissemination services are described,leading now to a time transfer accuracy of the order of 1-2 ns.In addition,the fundamental role of atomic clocks in the GNSS positioning is illustrated.The paper presents a review of the current use of GNSS in the international timekeeping system,as well as illustrating the role of GNSS in disseminating time,and use the time and frequency metrology as fundamentals in the navigation service.展开更多
基金supported by the National Natural Sci-ence Foundation of China(12273098).
文摘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.
文摘We report on studies of an optical lattice for a strontium clock performed at the National Time Service Center. Follow-ing tw o-stage laser cooling and trapping,88 Sr cold atoms w ith population of 105 and a longitudinal temperature of 8. 4 μK are loaded into a one-dimensional optical lattice. Spectroscopic analysis of the1S0-3P0 transition gives a linew idth of 180 Hz measured using magnetic field-induction,w hich mixes the3P1 state w ith the3P0 state. Rabi oscillations are observed. Because of the inhomogeneous excitation among the atoms,the Rabi π-pulse excitation at 5 ms show s a near 65% excitation of atoms. The transverse velocity distribution of the atomic beam and the absolute frequencies of the four inter-combination transitions of the isotopes w as measured precisely using velocity-selective fluorescence spectroscopy. By optical injection of tw o cascade external-cavity diode lasers,a single comb line at 689 nm from an optical femtosecond laser comb is filtered and amplified w ith a 37-d B side-mode suppression and a linew idth of less than 240 Hz. We describe recent w ork on a space optical clock concerning the physical vacuum system,thermal analysis,and a permanent-magnet Zeeman slow er for a space strontium optical clock. The first six mode frequencies are obtained and the corresponding oscillation modes are described in detail. We also simulate and analyze thermal profiles for both the physical and optical units installed in the cooling system. When the injected cooling w ater has a temperature of 21℃ or28℃,the units meet operational requirements for temperatures in a space environment. Using a series of permanent magnets,a Zeeman slow er is built that can w ithstand space launching and operating conditions for the space optical clock.
基金supported by the National SKA Program of China(No.2020SKA0120103)the National Natural Science Foundation of China(Nos.U1831130 and U1531112).
文摘Due to high stable rotations, timing of pulsars provides a natural tool to correct the frequency deviation of spaceborne atomic clocks. Based on processing the observational data about a year of Crab pulsar given by XPNAV-1 satellite, we study the possibility of correcting the frequency deviation of spaceborne atomic clocks using pulsar timing. According to the observational data in X-ray band and the timing model parameters from radio observations, the pre-fit timing residuals with a level of 67.66 μs are obtained. By fitting the slope of the timing residuals affected by the faked frequency-biased reference clock, we estimated successfully the relative frequency deviation of the reference clock. For a satellite clock with frequency deviation of the order about 10^(-12), a calibration accuracy with relative error of about 2% can be obtained from the Crab pulsar’s data for one year.The stability of the time scale based on Crab pulsar is about 10^(-12) for an interval of one year.
文摘守时型原子钟主要包括氢原子钟和铯原子钟,为进一步探究不同类型守时原子钟计算时间尺度相关性能,本文开展全氢钟及氢铯联合时间尺度研究。首先依据国际权度局(Bureau International des Poids et Mesures,BIPM)发布的d公报将氢原子钟进行分类,针对分类结果分别运用原子时尺度理论方法计算全氢钟时间尺度,并给出分析结果。随后计算全铯钟时间尺度,并分析探究两种不同的氢铯联合钟组时间尺度。结果表明,基于频率漂移量较小的氢钟组形成的时间尺度波动范围小,且稳定度优于频率漂移量较大的氢钟组形成的时间尺度。氢铯联合形成的时间尺度稳定度优于全铯钟时间尺度,不同的氢铯联合钟组计算得到的时间尺度结果相近。
文摘时间频率数据是国家重要的信息资源,时间频率数据平台设计依托国家授时中心运行产生的时频数据、国际权度局(Bureau International des Poids et Mesures,BIPM)和国际地球自转服务机构(International Earth Rotation and Reference Systems Service,IERS)公布的时间频率相关数据等实现,该数据平台可以为守时技术研究提供丰富的数据资源支撑。首先介绍时间频率数据平台的建设情况,随后利用数据平台汇交的本地守时系统比对和远距离链路比对数据开展守时技术研究,包括原子钟状态评估,主要分析原子钟异常跳变情况,研究跳变数据处理方法,针对不同类型守时钟,分析对比波动情况、稳定度等原子钟性能指标,此外基于ARIMA模型开展钟差预报研究。以上研究结果可为守时系统连续可靠运行提供重要参考。
文摘The relationship and the mutual benefits of timekeeping and Global Navigation Satellite Systems(GNSS)are reviewed,showing how each field has been enriched and will continue to progress,based on the progress of the other field.The role of GNSSs in the calculation of Coordinated Universal Time(UTC),as well as the capacity of GNSSs to provide UTC time dissemination services are described,leading now to a time transfer accuracy of the order of 1-2 ns.In addition,the fundamental role of atomic clocks in the GNSS positioning is illustrated.The paper presents a review of the current use of GNSS in the international timekeeping system,as well as illustrating the role of GNSS in disseminating time,and use the time and frequency metrology as fundamentals in the navigation service.
