Novick, A.
and López Romero, J.
(2025),
The SIM Time Network - Twenty Years of Operation, 2025 Proceedings of the European Time and Frequency Forum (EFTF), Queretaro, MX, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=960081
(Accessed November 22, 2025)
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The SIM Time Network - Twenty Years of Operation
Published
Author(s)
, Jose Mauricio López Romero
Abstract
The SIM Time Network (SIMTN) was established two decades ago to provide real-time time and frequency comparisons among National Metrology Institutes (NMIs) across the Americas. Since its inception, SIMTN has played a crucial role in strengthening regional time and frequency capabilities by enabling continuous monitoring, promoting traceability to UTC, and supporting the realization of UTC(k) time scales. Currently the SIMTN comprises 26 labs. This paper presents a comprehensive overview of the design, operational evolution, and achievements of the SIMTN over twenty years of continuous operation. Key aspects include the initial system architecture based on GPS common-view methods, the deployment of decentralized data centers, and the development of custom software for data acquisition, processing, and dissemination. We discuss the significant upgrades introduced to enhance reliability, automation, and measurement precision, as well as the network's contribution to international timekeeping activities. Finally, we outline the near future perspectives for the SIMTN, including dual-frequency receivers to decode both the L1 (1575.42 MHz) and L2 (1227.6 MHz) carrier frequencies. This allows a measurement of the actual delay of the signals through the ionosphere instead of relying on calculated models. We demonstrate that this approach significantly enhances positioning accuracy and reduces delay variations caused by diurnal fluctuations, enabling time comparisons within the SIMTN with a combined uncertainty (k = 2) of less than 2 nanoseconds.Proceedings Title
2025 Proceedings of the European Time and Frequency Forum (EFTF)
Conference Dates
May 13-16, 2025
Conference Location
Queretaro, MX
Conference Title
2025 IFCS-EFTF International Frequency Control Symposium / European Time and Frequency Forum
Pub Type
Conferences
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Keywords
time, frequency, time transfer, coordinated universal time
Citation
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Created May 16, 2025, Updated November 17, 2025