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Comparison of the multi-national SIM time scale to UTC and UTCr



J. M. Lopez, Michael A. Lombardi, E. de Carlos, N. Munoz, C. Ortiz, M. Gertsvolf, R. de Carvalho, R. Solis


The Sistema Interamericano de Metrologia (SIM) is one of the world's five major Regional Metrology Organizations (RMO's) recognized by the International Committee for Weights and Measures (CIPM). With the goal of allowing SIM National Metrology Institutes (NMI's) to track the performance of their time and frequency standards in near real time, the SIM Time and Frequency Metrology Working Group (SIM TFWG) established the SIM Time Network (SIMTN) in 2005. As of June 2018, 25 SIM nations participate in the SIMTN. Since 2008 the SIM TFWG has produced the SIM Time Scale (SIMT), a multi-national ensemble computed every hour from time difference measurements collected by the SIMTN every 10 minutes. SIMT, the first continuously maintained multi-national ensemble time scale that is generated and published in real time, complements the world's official time scale, Coordinated Universal Time (UTC), by providing real-time support to the operational timing and calibration systems at SIM NMIs. SIMT provides a real- time approximation of UTC with a timing uncertainty near 10 ns. In this paper, we present a SIMT evaluation based on data from November 2016 to June 2018 by comparing SIMT performance to that of UTC and rapid UTC (UTCr).
IEEE Transactions on Instrumentation and Measurement


atomic clocks, international comparisons, time, time scales


Lopez, J. , Lombardi, M. , de Carlos, E. , Munoz, N. , Ortiz, C. , Gertsvolf, M. , de Carvalho, R. and Solis, R. (2020), Comparison of the multi-national SIM time scale to UTC and UTCr, IEEE Transactions on Instrumentation and Measurement (Accessed April 17, 2024)
Created July 1, 2020, Updated April 27, 2023