Absolute frequency measurement of the ¹⁷¹Yb optical lattice clock at KRISS using TAI for over a year

We report a measurement of the absolute frequency of the 1 S 0 – 3 P 0 transition in the 171 Yb optical lattice clock at KRISS (KRISS-Yb1) for 14 months, which was referenced to the SI second by primary and secondary standards worldwide via International Atomic Time. The determined absolute frequency is 518 295 836 590 863.75(14) Hz with the relative frequency uncertainty of 2.6 × 10 −16 , which agrees well with other reports. This result is expected to contribute to the future update of the CIPM recommendation frequency of the secondary frequency standards.