New Trends in Two-Way Time and Frequency Transfer via Satellite

Abstract : Recent developments performed with SATRE two-way time transfer (TWSTFT) modems resulted in significant performance upgrades and operational improvements of the TWSTFT method These are aimed to reduce : manpower effort and to provide reliable, real-time data via a centralized monitoring and control facility, which can be easily integrated into larger systems or ground-station installations. New operational modes and advanced modulation techniques are aimed to significantly reduce transponder and other operational costs. Clock performance requirements at secondary sites can be significantly reduced as soon as two-way links operate on frequent schedule. The results of a two-week test campaign to evaluate frequency transfer using carrier phase between USN0 and MST are presented This technique opens another upgrade path exhibiting improved performance from 2-way links via satellite A precision of 2 ps for a I-second integration time has been achieved via two different, standard communication satellites. The initial frequency-transfer accuracy is on the order of SE-14 for a 30 min observation time period. The frequency transfer stability approaches lE-14 for a 100 s integration interval. Further tests are planned to extend the characterization to longer time periods. Remote control via Internet and centralized data collection have been used throughout the experiment.