Kalman timescale algorithm based on hydrogen clock ensemble

The selection of timescale algorithm will have a great influence on the accuracy and stability of timescale. To improve the accuracy and stability of timescale, this paper studied the stochastic model of the hydrogen clock and Hadamard deviation for researching the Kalman timescale algorithm based on the hydrogen clock ensemble, which is quite different from the traditional Kalman timescale algorithm based on the model of cesium-beam clock ensemble, mixed ensemble and Allen deviation. The Hadamard variance is used to describe the stability of clock frequency in this paper; it will improve the precision of the Hydrogen Clock Ensemble. By using Hadamard variance instead of Allen avariance, it can overcome the influence of frequency drift. In this paper, the clock whose stability is best is chosen as the reference clock so that the accuracy and stability of the hydrogen clock ensemble will be improved. The experiment data of the hydrogen clock ensemble in the timekeeping laboratory of National Institute of Metrology (NIM) in China were processed; the frequency stability can be improved to 10'15. The results verified that the Kalman timescale algorithm based on the hydrogen clock ensemble is effective.