Direct comparisons of European primary and secondary frequency standards via satellite techniques

TL;DR

This study compares European primary and secondary frequency standards using satellite techniques over 26 days, achieving high precision in frequency difference measurements of optical and fountain clocks.

Contribution

It introduces an enhanced statistical analysis method for satellite-based frequency comparisons, improving uncertainty estimation for optical and fountain clocks.

Findings

Optical clock comparisons uncertainty: 1.8×10⁻¹⁶ to 3.5×10⁻¹⁶

Fountain clock differences: max 6.9×10⁻¹⁶

Uncertainty ranges: 4.8×10⁻¹⁶ to 7.7×10⁻¹⁶

Abstract

We carried out a 26-day comparison of five simultaneously operated optical clocks and six atomic fountain clocks located at INRIM, LNE-SYRTE, NPL and PTB by using two satellite-based frequency comparison techniques: broadband Two-Way Satellite Time and Frequency Transfer (TWSTFT) and Global Positioning System Precise Point Positioning (GPS PPP). With an enhanced statistical analysis procedure taking into account correlations and gaps in the measurement data, combined overall uncertainties in the range of $1.8 \times 10^{-16}$ to $3.5 \times 10^{-16}$ for the optical clock comparisons were found. The comparison of the fountain clocks yields results with a maximum relative frequency difference of $6.9 \times 10^{-16}$, and combined overall uncertainties in the range of $4.8 \times 10^{-16}$ to $7.7 \times 10^{-16}$.