Year: 2026
Type: article
Abstract: The National Physical Laboratory generates the UK’s local realisation of Coordinated Universal Time, UTC(NPL), using an active hydrogen maser steered by a caesium atomic fountain primary frequency standard. We present the results of improvements to the time scale steering algorithm used at NPL. The novel algorithm incorporates a technique for real-time estimation of the time offset between UTC and UTC(NPL), to maintain close alignment of the two in the interim period between monthly publications of Circular T by the Bureau International des Poids et Mesures. This technique is particularly effective in situations where the oscillator generating the time scale behaves unpredictably. Over such a period lasting one year the new algorithm reduced the maximum time offset between UTC and UTC(NPL) relative to a simulated application of the previous algorithm by either 11.9 ns or 1.0 ns, depending on whether Circular T or Rapid UTC reports were used as input to the phase lock. The success of this technique relies on the high uptime of the caesium fountain measuring the frequency of the maser flywheel. Here we explore the limits of such a technique and describe potential changes to the time scale operation to further improve the stability.
Source: Metrologia
Institution: National Physical Laboratory
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,325
OpenAlex ID: W7202286879