3 ms·
TAI is a weighted average of the clocks. The lower the estimated uncertainty of a clock, the more it contributes to the average. This is given in the second to
by fsh 5y ago
TAI is a weighted average of the clocks. The lower the estimated uncertainty of a clock, the more it contributes to the average. This is given in the second to last column in the first table of Circular T [1]. For example, in the last reporting period, Germany's PTB reported the lowest uncertainty, and therefore contributed most. Probably both their cesium fountains were running well. So a single much better clock would immediately improve the quality of TAI.
[1] https://webtai.bipm.org/ftp/pub/tai/Circular-T/cirt/cirt.409 https://webtai.bipm.org/ftp/pub/tai/Circular-T/cirt/cirt.409
- dataangel 5y agobut how do you estimate the uncertainty without another clock to compare against? It seems like a circular problem.... how do you prove you built a better clock without already having a better clock?
- fsh 5y agoEstimating the uncertainty is indeed quite difficult. Stability can be measured by comparing two uncorrelated clocks. This is why standard institutes tend to build them in pairs. Measuring absolute accuracy is a different beast, since two similar clocks will also have similar systematic errors. Of course, one can estimate the magnitude of these errors, but there can always be unknown contributions. It is therefore useful to compare different implementations, for example cesium fountain clocks built at different institutes. Still, there can always be some conceptual problem that affects all clocks in a similar way.