Stability of the BIPM GNSS travelling calibrator

In the frame of the BIPM pilot project [8] on the accurate calibration aiming at unifying the UTC time link calibration uncertainties ≤ 2 ns, we studied the instability of the BIPM travelling calibrator (StdB). Using the time stability (Tdev), the closure measurements and the inter-comparison of the two independent receiver systems in the StdB, we analyzed one year data to investigate the short- and long-term variations and the accuracy of the calibration system consisting two or three independent receivers. It is concluded that the StdB is stable within or about 0.5 ns on average over one year therefore reliable enough to realize the goal of the pilot project.