Review of GPS Carrier-Phase and Two-Way Satellite Time Transfer Measurement Results between Schriever Air Force Base and theUnited States Naval Observatory

Lisa M. Nelson, Kristine M. Larson, Judah Levine

Abstract:	We are investigating the use of GPS carrier-phase for high accuracy time transfer measurements. We have conducted a long-term time transfer experiment between the United States Naval Observatory (USNO) Master Clock and Alternate Master Clock (AMC). These clocks are located at the USNO in Washington D.C. and Schriever Air Force Base near Colorado Springs, Colorado, respectively. At both locations two-way satellite time transfer (TWSTT) measurements are made nearly every hour and geodetic dual-frequency GPS carrier-phase data are collected every 30 seconds. The data are analyzed using a geodetic software package developed by the Jet Propulsion Laboratory combined with precise satellite orbits determined by the International GPS Service (IGS) global tracking network [1,2]. The radial accuracy of these orbits is approximately 10 cm. Instead of computing the difference between the GPS observables, as is common in high-accuracy geodetic GPS analyses, the software explicitly estimates the receiver and satellite clocks at each data epoch. The technical GPS issues investigated include the importance of carrier-phase ambiguity resolution, troposphere modeling, thermal effects, and multipath noise. Given that the error spectra for the GPS and TWSTT systems are quite distinct, we hope to learn more about each system's accuracy potential.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	1023 - 1034
Cite this article:	Nelson, Lisa M., Larson, Kristine M., Levine, Judah, "Review of GPS Carrier-Phase and Two-Way Satellite Time Transfer Measurement Results between Schriever Air Force Base and theUnited States Naval Observatory," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 1023-1034.
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