Definition and realization of UTC (BSNC)

UTC (BSNC) is the Coordinated Universal Time maintained by Beijing Satellite Navigation Center. It’s frequency accuracy reaches 10-14 magnitudes. Monthly stability reaches 10-15 magnitudes.

UTC (BSNC) is realized according to comprehensive atomic time concept, established and maintained by time frequency system. Time frequency system consists of atomic clock set, internal measurement unit, external comparison unit, data processing unit and signal production unit. The diagram below shows the composition of the system.

Figure 1 Time Frequency System structure

The system conducts timekeeping with more than ten hydrogen masers, which formulate atomic clock set and provide time and frequency signals. The internal measurement unit observes the initial time frequency signals inside the clock set. The time and frequency difference is given in cycled measurement. The difference between UTC (BSNC) and other time standards is measured with external measurement unit. Data processing unit calculates a relatively unified time standard with a certain algorithm on the basis of the measurement information given out by internal measurement unit and external measurement unit, and takes it as time reference for the navigation system. Signal production unit conducts frequency control towards the main clock frequency signal of the atomic clock and produces real time physical time signal.