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Panfilo G.,International Bureau of Weights and Measures BIPM
EFTF 2012 - 2012 European Frequency and Time Forum, Proceedings | Year: 2012

A new quadratic prediction algorithm is used in UTC calculation starting from August 2011. The positive effects in term of long-term stability are already evident. The results obtained after the implementation of the new algorithm are presented and discussed. © 2012 IEEE.


Davis R.S.,International Bureau of Weights and Measures BIPM
Journal of Chemical Education | Year: 2015

The definition of the kilogram, the unit of mass in the International System of Units (SI), has not changed in more than 125 years. The kilogram is still defined by the mass of a Pt-Ir cylinder conserved at the International Bureau of Weights and Measures. Science and technology have progressed to the point where it is likely the kilogram will be redefined in 2018 in terms of a constant of physics - the Planck constant, which is closely linked to the Avogadro and atomic mass constants. In this article, we illustrate by means of a simple experiment on how analytical chemistry is contributing to this project, how the new definition of the kilogram will be put into practice and what it may mean for chemists. Surprisingly, perhaps, this simple experiment allows us to determine the mass of an aluminum-27 atom, the mass of a carbon-12 atom (and the atomic mass constant), the Avogadro constant, and the Planck constant - all with uncertainty less than 1% - in close analogy to the way the most accurate experiment of this type achieves an uncertainty of parts in 108. Finally, we point out that a very different area of modern technology, namely voltage and resistance measurements using quantum electrical devices, provides a second high-accuracy way to implement the new definition. © 2015 The American Chemical Society and Division of Chemical Education, Inc.


Palinkas V.,Research Institute of Geodesy | Liard J.,Natural Resources Canada | Jiang Z.,International Bureau of Weights and Measures BIPM
Metrologia | Year: 2012

FG5 absolute gravimeters are the most accurate gravimeters available at present and have significant influence on the realization of a gravity reference through international comparisons of absolute gravimeters. The latter comparisons are the only way to maintain the traceability of absolute gravimetry to the International System of Units (SI). Sources of systematic error such as the self-attraction effect (SAE) have to be taken into account when determining accurate values of the acceleration due to gravity, as needed, for example, for the watt balance project or the International Gravity Reference System. In this paper the SAE for two types of FG5 gravimeter is estimated using two independent methods. The resulting SAEs are 1.2(0.2)Gal and 1.7(0.2)Gal for FG5 with fibre and bulk interferometer types, respectively. The importance of accurately defining the measurement height is emphasized in the context of the SAE. The accuracy and advantages of referring gravity measurements to an effective position of the free-fall solution are demonstrated together with a simple and accurate empirical estimation of this effective position. © 2012 BIPM & IOP Publishing Ltd.


Jiang Z.,International Bureau of Weights and Measures BIPM | Lewandowski W.,International Bureau of Weights and Measures BIPM
Metrologia | Year: 2012

At present, the applicable spatial techniques used in UTC (Coordinated Universal Time) computation are GPS, TWSTFT (Two-Way Satellite Time and Frequency Transfers) and GLONASS. To enable accuracy and robustness for the generation of UTC, a multi-technique strategy for UTC time transfer is indispensable. Over the last two decades efforts have been made to use GLONASS for accurate time transfer. The first GLONASS time link that presents in UTC was introduced in November 2009, BIPM Circular T 263. For present and future accurate time transfers, GLONASS is comparable to GPS with the same types of observations. In this paper, we first recall principles of the GNSS Common-View and All in View time transfers; we present the technical issues for the use of GLONASS in UTC, i.e. short- and long-term stabilities, frequency biases, calibration and its practical implementation. Finally, we outline the prospects for the use of GLONASS in accurate time transfer. © 2012 BIPM & IOP Publishing Ltd.


Arias E.F.,International Bureau of Weights and Measures BIPM
Revista Mexicana de Astronomia y Astrofisica: Serie de Conferencias | Year: 2014

The International Bureau of Weights and Measures, in coordination with international organizations and national institutes, maintains and disseminates Coordinated Universal Time (UTC). Other timescales exist for different purposes. This article describes the state-of-the-art in the elaboration of these time scales.

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