HKO contributes to determination of Co-ordinated Universal Time

The Hong Kong Observatory (HKO) has been contributing to the determination of the Co-odinated Universal Time (UTC) since the middle of this year. The Bureau International des Poids Mesures (BIPM) in France determines UTC based on the time information from more than 200 atomic clocks located in more than 50 time service centres worldwide. The HKO is now one of these centres.

UTC was adopted as the international time standard in 1972. The Hong Kong Standard Time is UTC plus eight hours.

Early this year, the HKO installed a high accuracy time transfer system which employed the Global Positioning System Common-view Method to provide time information of HKO's atomic clock to BIPM for UTC determination. BIPM includes in its monthly time circular the difference between UTC and HKO's atomic clock. HKO can adjust its atomic clock based on the published time difference to maintain the accuracy of its atomic clock to within 1 microsecond (1 second = 1,000,000 microseconds).

BIPM is now hosting a calibration exercise for time service centres in the Asia-Pacific region including the National Time Service Centre of the Chinese Academy of Sciences, the National Institute of Information and Communications Technology of Japan and the HKO, etc. The Observatory has just received the calibration equipment provided by BIPM and will be collecting data in the following week. This calibration exercise provides quality assurance to the determination of UTC.

The HKO has been providing a time service since its establishment in 1883. Starting in 1980, HKO maintains the Hong Kong Standard Time with a Caesium beam atomic clock. To check the Hong Kong Standard Time, people can make use of HKO's six-pip time signals broadcast by the Radio Television Hong Kong or HKO's Telephone Information Enquiry System. They can also use the HKO's network time service to synchronise their computer clocks to the Hong Kong Standard Time. HKO's network time service provides fast and accurate time stamping for e-trade and other e-business. In 2003, HKO's Internet time server served more than 277 million time checks.