COMMISSION A : Electromaganetic Metrology

In Japan, the researches and developments on Time and Frequency (T&F) Standards and Time Transfer Technique are mainly carried out in the National Institute of Information and Communications Technology (NICT) and National Metrology Institute of Japan (NMIJ). NICT headquarters has been keeping UTC(NICT) and Japan Standard Time (JST). A maximum of eighteen Cs atomic clocks and four hydrogen masers are used for making the timescale. A new JST generation system including various upgrades was completed after four years for development and started operation in February 2006 [Nakagawa et al. 2005, Hanado et al. 2006, 2007]. The timescale algorithm of UTC(NICT) has been investigated by NICT staffs [Hosokawa et al. 2005], and some improvements have been added to suppress the undesirable effects of anomalous clocks. As for dissemination, two LF radio stations continuously transmit 40kHz and 60kHz respectively of JST time signal and the standard frequency signal. The field strength of LF signals during transmission was theoretically modeled. [Wakai et al. 2005]. To verify this model, two observation cruises on the Southeast Asian line and the North Pacific line using container ships were carried out in 2007. Results of the observation will be submitted to ITU-R WP7A in 2008. Public dial up time service via telephone lines has satisfied a large number of accesses. NICT newly developed a Network Time Protocol (NTP) server with high-performance and started a public time service from 2007. The number of access is about fifteen million per day [Toriyama et al. 2007]. A new protocol for high-speed network time transfer has been investigated by using this server [Iwama et al. 2006, 2007]. On-site calibration system for frequency standards at NICT was equipped with a new system and approved by a peer review in 2006. Accordingly measurement uncertainty was improved from 10 to 5x10. NICT has also started a remote calibration system since 2005[Saito et al. 2006]. NICT is regularly performing Two Way Satellite Time and Frequency Transfer (TWSTFT) between Germany (PTB) and Asian T&F institutes (KRISS, TL, NTSC, SPRING, and NMIJ), and calibrated their station delays for TL, KRISS and NMIJ. Obtained data by TWSTFT and GPS are reported to BIPM. The TWSTFT data for NICT/PTB link has been adopted for TAI link since April 2007 in place of GPS data [CIRCULAR T 231]. Researches about GPS carrier phase method and TWSTFT for a long baseline are in progress. NICT is developing a new TWSTFT method using dual Pseudo Random Noises (PRN). NICT and USNO plan to install a new TWSTFT relay station in Hawaii for their link. To distribute precise frequency by optical fiber, basic experiment using delay control has been