scholarly journals Current and future realizations of coordinate time scales

2009 ◽  
Vol 5 (S261) ◽  
pp. 95-101
Author(s):  
E. Felicitas Arias
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Proper Time ◽  
Frequency Stability ◽  
Reference Time ◽  
Weights And Measures ◽  
Coordinate Time ◽  
Future Improvement ◽  
Stability And Accuracy ◽  
Atomic Time

AbstractTwo atomic time scales maintained at the International Bureau of Weights and Measures (BIPM) are realizations of terrestrial time: International Atomic Time (TAI) and TT(BIPM). They are calculated from atomic clocks realizing proper time in national laboratories. The algorithm for the calculation of TAI has been designed to optimize the frequency stability and accuracy of the time scale. Plans for the future improvement of the reference time scales are presented.

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 We consider how the 1 × 10−16 value could be reached or superseded and which are the present limitations to attain this goal.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 The international atomic time, definition, realization

1986 ◽  
Vol 114 ◽  
pp. 297-297
Author(s):  
B. Guinot
Keyword(s):  
Time Scale ◽  
Proper Time ◽  
Tidal Effects ◽  
Coordinate Time ◽  
Atomic Time

The International Atomic Time TAI is a realized time scale which is ultimately used for comparisons between the observations and dynamical theories. Its definition should tell us unambiguously what an ideal TAI should be. It is also important know the uncertainties of the implementation of this definition.Concerning the definition, there is an apparent divergence between the physicists for whom TAI is a coordinate-time and the astronomers who often consider it as a proper time. This matter should be clarified and it might be advisable that IAU adopts a recommendation on this topic, based on the already existing CCDS and CCIR definitions, but completed for the specific uses in astronomy. The present TAI definition refers to the geoid. Some years will elapse before the tidal effects be observable. Nevertheless, it is desirable to have some exchanges of views on an improved definition.The accuracy (conformity with the definition), stability and precision of reading of TAI are progressively improving. Present and past properties will be briefly reported.

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.

scholarly journals GNSS-to-GNSS time offsets: study on the broadcast of a common reference time

GPS Solutions ◽  
2021 ◽  
Vol 25 (2) ◽  
Author(s):  
Ilaria Sesia ◽  
Giovanna Signorile ◽  
Tung Thanh Thai ◽  
Pascale Defraigne ◽  
Patrizia Tavella
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Reference Time ◽  
Single Time ◽  
Common Reference ◽  
Prediction Quality ◽  
Common Time ◽  
Time Offset ◽  
The Impact ◽  
Low Uncertainty

AbstractWe present two different approaches to broadcasting information to retrieve the GNSS-to-GNSS time offsets needed by users of multi-GNSS signals. Both approaches rely on the broadcast of a single time offset of each GNSS time versus one common time scale instead of broadcasting the time offsets between each of the constellation pairs. The first common time scale is the average of the GNSS time scales, and the second time scale is the prediction of UTC already broadcast by the different systems. We show that the average GNSS time scale allows the estimation of the GNSS-to-GNSS time offset at the user level with the very low uncertainty of a few nanoseconds when the receivers at both the provider and user levels are fully calibrated. The use of broadcast UTC prediction as a common time scale has a slightly larger uncertainty, which depends on the broadcast UTC prediction quality, which could be improved in the future. This study focuses on the evaluation of two different common time scales, not considering the impact of receiver calibration, at the user and provider levels, which can nevertheless have an important impact on GNSS-to-GNSS time offset estimation.

scholarly journals Geodesic stability and quasi normal modes via Lyapunov exponent for Hayward black hole

2020 ◽  
Vol 35 (30) ◽  
pp. 2050249
Author(s):  
Monimala Mondal ◽  
Parthapratim Pradhan ◽  
Farook Rahaman ◽  
Indrani Karar
Keyword(s):  
Black Hole ◽  
Lyapunov Exponent ◽  
Time Scale ◽  
Proper Time ◽  
Normal Modes ◽  
Schwarzschild Black Hole ◽  
Coordinate Time ◽  
Stability And Instability ◽  
The Stability ◽  
Asymptotic Observers

We derive proper time Lyapunov exponent [Formula: see text] and coordinate time Lyapunov exponent [Formula: see text] for a regular Hayward class of black hole. The proper time corresponds to [Formula: see text] and the coordinate time corresponds to [Formula: see text], where [Formula: see text] is measured by the asymptotic observers both for Hayward black hole and for special case of Schwarzschild black hole. We compute their ratio as [Formula: see text] for time-like geodesics. In the limit of [Formula: see text] that means for Schwarzschild black hole this ratio reduces to [Formula: see text]. Using Lyapunov exponent, we investigate the stability and instability of equatorial circular geodesics. By evaluating the Lyapunov exponent, which is the inverse of the instability time scale, we show that, in the eikonal limit, the real and imaginary parts of quasi-normal modes (QNMs) is specified by the frequency and instability time scale of the null circular geodesics. Furthermore, we discuss the unstable photon sphere and radius of shadow for this class of black hole.

scholarly journals Impact of new frequency standards on the international time scales

2009 ◽  
Vol 5 (H15) ◽  
pp. 223-224
Author(s):  
E. Felicitas Arias ◽  
Gianna Panfilo
Keyword(s):  
Time Scales ◽  
World Wide ◽  
Clock Frequency ◽  
Time Transfer ◽  
Reference Time ◽  
Weights And Measures ◽  
International Bureau ◽  
Frequency Standards ◽  
Remote Sites ◽  
Primary Frequency

AbstractThe reference time scales maintained at the International Bureau of Weights and Measures (BIPM) are constructed with data from industrial clocks and primary frequency standards operated in national metrology laboratories and observatories world-wide distributed. Clocks are compared making use of techniques of time transfer between remote sites. The algorithm of calculation relies on clock weighting and clock frequency prediction. We briefly present hereafter the influence of some clocks on the scales, as well as the possibilities for improvement.

scholarly journals Multi-scale event synchronization analysis for unravelling climate processes: A wavelet-based approach

2017 ◽  
Author(s):  
Ankit Agarwal ◽  
Norbert Marwan ◽  
Maheswaran Rathinasamy ◽  
Bruno Merz ◽  
Jürgen Kurths
Keyword(s):  
Time Series ◽  
Time Scales ◽  
Time Scale ◽  
Temporal Dynamics ◽  
Multiple Scales ◽  
Nonlinear Interactions ◽  
Reference Time ◽  
Multi Scale ◽  
Spatio Temporal ◽  
Different Time Scales

Abstract. The temporal dynamics of climate processes are spread across different time scales and, as such, the study of these processes only at one selected time scale might not reveal the complete mechanisms and interactions within and between the (sub-) processes. For capturing the nonlinear interactions between climatic events, the method of event synchronization has found increasing attention recently. The main drawback with the present estimation of event synchronization is its restriction to analyse the time series at one reference time scale only. The study of event synchronization at multiple scales would be of great interest to comprehend the dynamics of the investigated climate processes. In this paper, wavelet based multi-scale event synchronization (MSES) method is proposed by combining the wavelet transform and event synchronization. Wavelets are used extensively to comprehend multi-scale processes and the dynamics of processes across various time scales. The proposed method allows the study of spatio-temporal patterns across different time scales. The method is tested on synthetic and real-world time series in order to check its replicability and applicability. The results indicate that MSES is able to capture relationships that exist between processes at different time scales.

scholarly journals Pulsar Astrometry and Improved Terrestrial Clocks

1996 ◽  
Vol 160 ◽  
pp. 113-114
Author(s):  
Demetrios N. Matsakis ◽  
Frederick J. Josties ◽  
Roger S. Foster
Keyword(s):  
Inverse Problem ◽  
Time Scales ◽  
Time Scale ◽  
World Wide ◽  
State Of The Art ◽  
Frequency Standards ◽  
A Value ◽  
The World ◽  
Averaging Time ◽  
Atomic Time

AbstractRecent improvements in cesium and hydrogen terrestrial frequency standards have brought the frequency precision of International Atomic Time (TAI) to a value of 2.5E-15 s/s over an averaging time of a month. In this paper we illustrate the improvement graphically, and discuss the state of the art for frame ties between the radio, dynamical, and optical frames. In a larger paper, available via the World Wide Web, we illustrate the measured accuracy curves of the frequency standards, show their effect on the ensemble time scales, explain the reasons for the confusing array of available time scales, and discuss the inverse problem of using pulsar data to correct the terrestrial time scale.

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