Current status of the UTC(NIM) and its application in metrology

The UTC(NIM) maintained by the National Institute of Metrology (NIM) in China is one of the physical realizations of Coordinated Universal Time (UTC) and serves as the foundation of China’s time and frequency metrology. In recent years, due to the integration of higher-performance hydrogen masers into the clock ensemble, optimization of the UTC(NIM) prediction and steering methods, and enhancements in comparison link performance, the time difference between UTC(NIM) and UTC has reduced from ±5 ns to ±3 ns since 2020. This paper presents the current performance of UTC(NIM) and its application in time and frequency metrology.