Impact of atomic clock and time-transfer noises in the formation of the international atomic time

2007 ◽  
Author(s):  
W. Lewandowski
Keyword(s):  
Atomic Clock ◽  
Time Transfer ◽  
Atomic Time

scholarly journals Remote atomic clock synchronization via satellites and optical fibers

2011 ◽  
Vol 9 ◽  
pp. 1-7 ◽  
Author(s):  
D. Piester ◽  
M. Rost ◽  
M. Fujieda ◽  
T. Feldmann ◽  
A. Bauch
Keyword(s):  
Time Scales ◽  
Optical Fibers ◽  
Time Scale ◽  
Distribution Systems ◽  
Clock Synchronization ◽  
Atomic Clock ◽  
Global Network ◽  
Current Status ◽  
Time Transfer ◽  
Uncertainty Level

Abstract. In the global network of institutions engaged with the realization of International Atomic Time (TAI), atomic clocks and time scales are compared by means of the Global Positioning System (GPS) and by employing telecommunication satellites for two-way satellite time and frequency transfer (TWSTFT). The frequencies of the state-of-the-art primary caesium fountain clocks can be compared at the level of 10−15 (relative, 1 day averaging) and time scales can be synchronized with an uncertainty of one nanosecond. Future improvements of worldwide clock comparisons will require also an improvement of the local signal distribution systems. For example, the future ACES (atomic clock ensemble in space) mission shall demonstrate remote time scale comparisons at the uncertainty level of 100 ps. To ensure that the ACES ground instrument will be synchronized to the local time scale at the Physikalisch-Technische Bundesanstalt (PTB) without a significant uncertainty contribution, we have developed a means for calibrated clock comparisons through optical fibers. An uncertainty below 40 ps over a distance of 2 km has been demonstrated on the campus of PTB. This technology is thus in general a promising candidate for synchronization of enhanced time transfer equipment with the local realizations of Coordinated Universal Time UTC. Based on these experiments we estimate the uncertainty level for calibrated time transfer through optical fibers over longer distances. These findings are compared with the current status and developments of satellite based time transfer systems, with a focus on the calibration techniques for operational systems.

The Compass Time System and its Interoperation

2012 ◽  
Vol 239-240 ◽  
pp. 548-551
Author(s):  
Shao Wu Dong
Keyword(s):  
Atomic Clock ◽  
Test System ◽  
Ground Control ◽  
Time System ◽  
Satellite Navigation System ◽  
System A ◽  
Timing System ◽  
Control Centre ◽  
Navigation Test ◽  
Atomic Time

We report on the time reference system of Compass global satellite navigation system and its interoperation with other GNSS’s. China has sent three satellites into geostationary orbit since 2000, and Compass Navigation Test System has been established. Compass time reference, named as BDT, is based on Atomic time, BDT is derived from the atomic clock ensemble in Compass ground control centre, and be traced to the international time, UTC. Interoperability is one of the most important aspect in the design of Compass timing system, a solution of time differences determination among BDT and other GNSS time scales are introduced in this paper.

scholarly journals Long term stability of atomic time scales

2012 ◽  
Vol 10 (H16) ◽  
pp. 209-210
Author(s):  
G. Petit ◽  
F. Arias
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Time Transfer ◽  
Long Term Stability ◽  
Relative Value ◽  
The Stability ◽  
Primary Standards ◽  
Stability And Accuracy ◽  
Atomic Time

AbstractWe review the stability and accuracy achieved by the reference atomic time scales TAI and TT(BIPM). We show that they presently are in the low 10−16 in relative value, based on the performance of primary standards, of the ensemble time scale and of the time transfer techniques. We consider how the 1 × 10−16 value could be reached or superseded and which are the present limitations to attain this goal.

scholarly journals Atomic time scales TAI and TT(BIPM): present performances and prospects

2009 ◽  
Vol 5 (H15) ◽  
pp. 220-221
Author(s):  
Gérard Petit
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Time Transfer ◽  
Relative Value ◽  
The Stability ◽  
Primary Standards ◽  
Stability And Accuracy ◽  
Atomic Time

AbstractWe review the stability and accuracy achieved by the reference atomic time scales TAI and TT(BIPM). We show that they presently are at the level of a few 10−16 in relative value, based on the performance of primary standards, of the ensemble time scale and of the time transfer techniques. We consider how the 1 × 10−16 value could be reached or superseded and which are the present limitations to attain this goal.

GNSS time and frequency transfers through national positioning, navigation and timing infrastructure

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Thayathip Thongtan ◽  
Sivinee Sawatdiaree ◽  
Chalermchon Satirapod
Keyword(s):  
Time Scale ◽  
Frequency Stability ◽  
Frequency Offset ◽  
Internal Clock ◽  
Time Transfer ◽  
Time Zone ◽  
Common View ◽  
Standard Format ◽  
Fractional Frequency ◽  
Atomic Time

Abstract GNSS signals have been a practical time transfer tool to realise a Coordinated Universal Time (UTC) and set civilian clocks around the world with respect to this atomic time standard. UTC time scale is maintained by the International Bureau of Weights and Measurements (BIPM) adjusted to be close to a time scale based on the Earth’s rotation. In Thailand, the official atomic time clocks are maintained by the National Institute of Metrology Thailand (NIMT) to produce UTC(NIMT) and Thailand standard time which is always 7 hours ahead of UTC(NIMT) because of the time zone differences between Greenwich and Bangkok. National Positioning, Navigation and Timing (PNT) infrastructure comprises of GNSS geodetic receivers uniformly distributed to continually observe GNSS signals, mainly for geodetic survey applications both real-time and post-processing services. NIMT is involved in order to provide time link to UTC and to determine the characteristics of GNSS receiver internal clocks; namely, fractional frequency offset and frequency stabilities by applying the GNSS time transfer techniques of common-view algorithms. Monitored time differences with respect to UTC(NIMT) are achieved from selected 4 ground stations in different parts of the country with observations of 21 days in order to determine the frequency stability at 1-day and 7-day modes. GNSS standard log files; in RINEX format, at these receivers are transformed into a time transfer standard format; CGGTTS, used to compute the time differences between two stations, the fractional frequency offset and the frequency stability. Averaged fractional frequency offsets are 2.8 × 10 − 13 Hertz/Hertz 2.8\times {10^{-13}}\hspace{2.38387pt}\text{Hertz/Hertz} and computed Allan deviation is around 1.5 × 10 − 13 Hertz/Hertz 1.5\times {10^{-13}}\hspace{2.38387pt}\text{Hertz/Hertz} for an averaging time of 1 day. The comparison of the national time scale and receiver clock offsets of every receivers in this national GNSS PNT infrastructure could be accomplished through common-view time transfer using GNSS satellites to maintain the time link of geodetic active control points to UTC as well as to determine receiver internal clock characteristics.

Geopotential Determination Between Ultra-Stable Distant Clocks Based on Two-Way Space Laser Time Transfer Links

2021 ◽  
Author(s):  
Abdelrahim Ruby ◽  
Wen-Bin Shen ◽  
Ahmed Shaker ◽  
Mostafa Ashry ◽  
Zhang Pengfei ◽  
...  
Keyword(s):  
Natural Science ◽  
Atomic Clock ◽  
Space Station ◽  
Signal Propagation ◽  
Gravity Potential ◽  
Time Transfer ◽  
Main Challenge ◽  
Satellite Links ◽  
Potential Applications ◽  
Beidou Satellites

<p>The Earth’s gravity potential (geopotential) field plays an important role in geodesy, for instance, it is the basis for defining the geoid and the International Height Reference System (IHRS). In chronometric geodesy, the main challenge for directly measuring geopotential differences between two stations lies in that a reliable link for time comparison is needed. Currently, most satellite links for time comparison are dealt with in the microwave domain, for which the ionospheric and tropospheric effects are major error sources that greatly influence the signal propagation compared to optical space links. Recently, accurate laser time transfer links between satellite and ground stations have already been planned and confirmed, such as Laser Time Transfer (LTT, China) on BeiDou satellites and Tiangong II / China's space station (CSS), Time Transfer by Laser Link (T2L2, French) on Jason-2 mission and European Laser Timing (ELT, Europe) on Atomic Clock Ensemble in Space (ACES). Therefore, in this study, we propose an approach for determining the geopotential difference between two ground atomic clocks based on the Two-way Laser Time Transfer (TWLTT) technique via a space station as a bridge, which could have potential applications in geoscience. This study is supported by the National Natural Science Foundations of China (NSFC) under Grants 42030105, 41721003, 41804012, 41631072, 41874023, Space Station Project (2020)228, and the Natural Science Foundation of Hubei Province of China under Grant 2019CFB611.</p>

Time transfer with nanosecond accuracy for the realization of International Atomic Time

Metrologia ◽  
2008 ◽  
Vol 45 (2) ◽  
pp. 185-198 ◽  
Author(s):  
D Piester ◽  
A Bauch ◽  
L Breakiron ◽  
D Matsakis ◽  
B Blanzano ◽  
...  
Keyword(s):  
Time Transfer ◽  
Atomic Time
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