Two-way satellite time transfer activities in asian-pacific region

摘要

Two-Way Satellite Time Transfer (TWSTT) is one of the most precise time transfer techniques, and time transfer using this method has been used between European and North American Time and Frequency laboratories on a regular bases. In the Asia-Pacific Region four Time and Frequency laboratories have been involved in establishing a precise time transfer network using the TWSTT technique. After several continuous 24-hour TWSTT experiments between Communications Research Laboratory (CRL) in Japan and National Measurement Laboratory (NML) in Australia, a regular, twice weekly TWSTT link has been established since April 1998 using a Ku-band transponder on INTELSAT satellite 702 located at 177 deg. E. CRL and Shaanxi Astronomical Observatory of Chinese Academy of Science (CSAO) have just established a precise time transfer link using the TWSTT technique from October, 1998. For this time transfer link we are using a Ku-band transponder on the JCSAT-3 satellite, which is owned by Japanese satellite communication company and is located at 128 deg. E. National Research Laboratory of Metrology (NRLM) in Japan is also planning to join the TWSTT link network with a link to CRL also using JCSAT-3 from March 1999. For the next step toward a global TWSTT network we are planning to connect the Asia-Pacific TWSTT link to European and North American time and frequency laboratories. Such a network of precise time transferlinks will not only by itself be useful in contributing to TAI and UTC but also provide an accurate time transfer reference for other precise time transfer techniques such as the GPS carrier phase method.