Atomic Time and Frequency Standards Development at Shanghai Observatory, China

The performance characteristics of several types of our atomic frequency standards are described. All of these standards are designed, developed, and fabricated in China. The hydrogen maser is the only type developed by the Shanghai Observatory. This paper also describes briefly the basic consideration for system implementation, calculation approach, and experiment results in the generation of the Shanghai Observatory atomic time scale AT(SO). Based on available frequency standards-one prototype laboratory model of cesium clock, three hydrogen clocks, and several (3-6) rubidium clocks-the AT(SO) was established in 1978. The laboratory cesium clock is used to provide the basic calibration reference of the second in 1979, while hydrogen clocks and rubidium clocks are used as the working clocks to ensure the continuity of the time scale.