A Comparison of the Highest Precision Commonly Available Time Transfer Methods: TWSTT and GPS CV

Abstract : The U.S. Naval Observatory (USNO) in Washington, D.C., is now operating its Alternate Master Clock (AMC), located at Falcon Air Force Base, Colorado. UTC(USNO)-UTC(AMC) is determined independently by the Global Positioning System (GPS) common view (CV) and the Two-Way Satellite Time Transfer (TWSTT) method. The GPS CV time transfer data are joined from strict 13- minute common-view tracks. The TWSTT data are single 5-minute runs taken once every hour. In this study, the performances of the GPS CV time transfers from Standard Positioning Service (SPS) CIA code single-channel receivers using the modeled ionosphere, Precise Positioning Service (PPS) dual-frequency receivers using the measured ionosphere, and TWSTT are compared.