Carrier-phase two-way satellite frequency transfer over a very long baseline

Abstract

In this paper we report that carrier-phase two-way satellite time and\nfrequency transfer (TWSTFT) was successfully demonstrated over a very long\nbaseline of 9,000 km, established between the National Institute of Information\nand Communications Technology (NICT) and the Physikalisch-Technische\nBundesanstalt (PTB). We verified that the carrier-phase TWSTFT (TWCP) result\nagreed with those obtained by conventional TWSTFT and GPS carrier-phase (GPSCP)\ntechniques. Moreover, a much improved short-term instability for frequency\ntransfer of $2\\times10^{-13}$ at 1 s was achieved, which is at the same level\nas previously confirmed over a shorter baseline within Japan. The precision\nachieved was so high that the effects of ionospheric delay became significant\nwhich are ignored in conventional TWSTFT even over a long link. We compensated\nfor these effects using ionospheric delays computed from regional vertical\ntotal electron content maps. The agreement between the TWCP and GPSCP results\nwas improved because of this compensation.\n