Perspectives on the Systematic (Type B) Uncertainties of UTC-UTC(k)

Abstract

The systematic uncertainties in the difference between Coordinated Universal Time (UTC) and UTC realizations like UTC(k) are analyzed with a semi-historical algorithm using the uncertainties of the calibrations of only the extant time-transfer links and their covariance with clock predictions. It is important that the network has matured through recalibration, and that UTC was once generated with only GPS. This approach covers all types of links, including redundant links and cross links. The uncertainties of non-GPS links depend on the uncertainties of the pivot lab’s GPS system and the other system(s) used in the link. Clock predictions of labs not linked by GPS must be adjusted whenever the pivot lab’s GPS receiver is recalibrated. The resulting uncertainties differ by up to 45% from the results given in a recently published alternative proposal. Aging of the uncertainties leads to a blending of this approach with the current algorithm used by the International Bureau of Weights and Measures (BIPM).