Daphna G. Enzer and David W. Murphy, Jet Propulsion Laboratory, California Institute of Technology

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GPS can be used as an effective tool for comparing frequencies across large distances to better than 1 part in 10-16 . At the Jet Propulsion Laboratory (JPL) we process GPS receiver data using GIPSY-OASIS (GPS-Inferred Positioning System and Orbit Analysis Simulation Software) which uses wide-lane phase bias ambiguity resolution as part of its PPP (Precise Pointing Positioning) algorithm. To process GPS data for the Deep Space Atomic Clock (DSAC) mission, we further devised an algorithm and software for concatenating daily files and correcting for phase jumps and data gaps. Here we compare the frequency-transfer performance of this GIPSY_PPP technique, applied to ground receivers, against the well-proven IPPP technique used at the International Bureau of Weights and Measures (BIPM). We process 10 months of Germany to United States link data between two International GNSS Service (IGS) stations, both referenced to stable clocks steered to Universal Coordinated Time (UTC). We then subtract two-way satellite time and frequency transfer (TWSTFT) link data to remove the long-term clock instability component. These same link data were processed with IPPP and reported on by Petit and Meynadier at last year’s PTTI conference. We compare the two techniques and discuss the viability of using GIPSY_PPP instead of IPPP for transcontinental frequency transfer.