The Compass and its time reference system

Dong, Sining; Wu, Haitao; Li, Xiaohui; Guo, Shuren; Yang, Qianqian

doi:10.1088/0026-1394/45/6/s08

Cited by 10 publications

(6 citation statements)

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“…Receiver error is about 3ns, including receiver noise error, the receiver delay error, inter-frequency bias, multipath errors, etc; (5). The error of time interval counter measurement is about 0.5ns; (6). The reference clock error of about 2ns; (7).…”

Section: A Error Budget For System Time Offset Monitoringmentioning

confidence: 99%

“…Therefore, every GNSS system has its own time reference system, the system time of GPS is GPST, which is traceable to UTC (USNO); GLONASS system time is GLONASST, traceable to UTC (SU); Galileo system is GST (Galileo System Time), was controled to the TAI or UTC by the Time Service Provider (TSP). BDs system time is referred as BDT, BDT using a continuous time scale which is no leap second insertion, and it traces to international TAI or UTC through UTC (NTSC) [6,7]. In the multi-mode navigation applications, the use of satellite clock correction broadcast by satellite navigation message, GPS pseudorange correction to GPST, GLONASS pseudoranges correction to GLONASST and BDs pseudorange correction to the BDT.…”

Section: Introductionmentioning

confidence: 99%

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A method of GNSS system time offset monitoring

Zhang

Zhu

et al. 2013

2013 Joint European Frequency and Time Forum &Amp; International Frequency Control Symposium (EFTF/IFC)

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With the progress of Global Navigation Satellite Systems(GNSSs),which mainly includes GPS, GLONASS, GALILEO as well as BeiDou, multi-system joint working mode has become research focus and application trend. But, Each satellite navigation system has its own independent system time, such as GPST, GLONASST, GST and BDT. The System time offset between the two satellite navigation systems is one of the most important aspects of their interoperability. It will cause combined navigation position solution bias and time solution. Therefore, it is necessary and significant to monitor and research system time offset. A method of GNSS System Time Offset monitoring which is called Signal-in-Space Reception method is put forward and its principle is described. In this method, UTC(NTSC) time scale is regarded as reference time scale on account of its status of standard time and frequency resources. Then, The time offset between each satellite navigation system time and UTC(NTSC) which include UTC(NTSC)-GPST, UTC(NTSC)-GLONASST, UTC(NTSC)-BDT,UTC(NTSC)-GST can be acquired. Thus, system time offset among satellite navigation systems, such as GPST-GLONASST, can be acquired with about 5ns (1 σ ) precision.On the basis of above described method, GNSS System time offset monitoring system has been set up since 2011 and it is gradually improved and perfected. A great deal of monitoring data has been collected. Addition to common error sources, some special error sources related to GNSS timing receiver such as receiver delay, inter-system hard delay bias, inter-frequency biases and so on are analyzed, as they can effectively affect monitoring results and precision. The monitoring data and IGS precision orbit as well as corresponding data published by BIPM Circular T Bulletin are combined together to determine above error values. The results of the error items and GNSS system time offset monitoring results are to be showed.

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Section: A Error Budget For System Time Offset Monitoringmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A method of GNSS system time offset monitoring

Zhang

Zhu

et al. 2013

2013 Joint European Frequency and Time Forum &Amp; International Frequency Control Symposium (EFTF/IFC)

Self Cite

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“…In design processes of common communication and navigation satellite payloads, it is essential to equip satellites with a series of high-precision frequency or time references onboard, particularly in scenarios involving high-precision navigation and physics research. [7][8][9][10][11][12][13][14] This is due to the fact that the time or frequency output of the satellite's onboard clock not only provides a reference for the time dissemination of the satellite ephemeris but also supports the operation of a series of onboard radio-frequency (RF) devices and digital systems. With the continuous development of miniaturization technology for atomic clocks, an increasing number of communication and navigation satellites start to incorporate atomic clocks as part of their payloads, which has significantly enhanced the performance of positioning, navigation, and timing (PNT) applications in recent years.…”

Section: Introductionmentioning

confidence: 99%

Proposal for a realtime Einstein-synchronization-defined satellite virtual clock

Yan 严,

Tang 汤,

Wang 王

et al. 2024

Chinese Phys. B

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The realization of high performance satellite onboard clock is vital for various PNT applications. For further improvement of the synchronization-based satellite time and frequency references, this paper proposes a geosynchronous (GEO) satellite virtual clock concept based on ground–satellite synchronization and presents a beacon transponder structure for its implementation (scheduled for launch in 2025), which does not require atomic clocks to be mounted on the satellite. Its high performance relies only on minor modifications to the existing transponder structure of GEO satellites. We carefully modeled the carrier phase link and analyzed the factors causing link asymmetry within the special relativity. Considering that the performance of such synchronization-based satellite clocks is primarily limited by the link’s random phase noise, which cannot be adequately modeled, we designed a closed-loop experiment based on commercial GEO satellites for pre-evaluation. This experiment was aimed at extracting the zero-means random part of the ground-satellite Ku-band carrier phase via a feedback loop. Ultimately, we obtained a 1σ value of 0.633 ps (two-way link), following the Gaussian distribution. From this result, we conclude that the proposed real-time Einstein-synchronization-defined satellite virtual clock can achieve picosecond-level replication of onboard time and frequency.

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“…GNSS satellite clocks are aligned with terrestrial time (TT) [11][12][13][14], which is annually realized by the Bureau International des Poids et Mesures (BIPM) as "TT BIPM * * " (" * * " indicates the year of calculation) [15]. Although TT is currently the most accurate and stable timescale, the post-processed timescale is not suitable for real-time applications.…”

Section: Introductionmentioning

confidence: 99%

Characterizing Periodic Variations of Atomic Frequency Standards via Their Frequency Stability Estimates

Cheng

Nie

Zhu

2023

Sensors

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The onboard atomic frequency standard (AFS) is a crucial element of Global Navigation Satellite System (GNSS) satellites. However, it is widely accepted that periodic variations can influence the onboard AFS. The presence of non-stationary random processes in AFS signals can lead to inaccurate separation of the periodic and stochastic components of satellite AFS clock data when using least squares and Fourier transform methods. In this paper, we characterize the periodic variations of AFS using Allan and Hadamard variances and demonstrate that the Allan and Hadamard variances of the periodics are independent of the variances of the stochastic component. The proposed model is tested against simulated and real clock data, revealing that our approach provides more precise characterization of periodic variations compared to the least squares method. Additionally, we observe that overfitting periodic variations can improve the precision of GPS clock bias prediction, as indicated by a comparison of fitting and prediction errors of satellite clock bias.

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The Compass and its time reference system

Cited by 10 publications

References 0 publications

A method of GNSS system time offset monitoring

A method of GNSS system time offset monitoring

Proposal for a realtime Einstein-synchronization-defined satellite virtual clock

Characterizing Periodic Variations of Atomic Frequency Standards via Their Frequency Stability Estimates

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