Intermittent optical frequency measurements to reduce the dead time uncertainty of frequency link

The absolute frequency of the ${}^{87}\mathrm{S}\mathrm{r}$ lattice clock transition was evaluated with an uncertainty of $1.1\times {10}^{-15}$ using a frequency link to the international atomic time (TAI). The frequency uncertainty of a hydrogen maser used as a transfer oscillator was reduced by homogeneously distributed intermittent measurement over a five-day grid of TAI. Three sets of four or five days measurements as well as systematic uncertainty of the clock at $8.6\times {10}^{-17}$ have resulted in an absolute frequency of $^{87}{\rm Sr}
{}^1S_0 - {}^3P_0$ clock transition to be 429 228 004 229 872.85 (47) Hz.