A New Technique for Estimating Frequency from GPS Carrier-Phase Time Transfer Data
C Hackman, Judah Levine, Tom Parker, Dirk Piester, Juergen Becker
GPS carrier-phase time transfer (GPSCP1T) offers high frequency stability at short averaging times, approaching a fractional frequency stability of 10-15 at averaging times of one day. However, a discontinuity occurs in the time transfer estimates between the end of one processing batch (typically 1-3 days in length) and the beginning of the next. Though techniques exist for estilnating and removing these steps, the removal of each step introduces additional uncertainty into the results. The conventional procedure for computing frequency from GPSCPTT data over a multi-day epoch has been to remove the discontinuities between the batch solutions and then to compute the frequency from the resulting continuous set of time transfer estimates. In this paper, a new technique is presented in which a frequency is computed from each batch solution and then an average of these frequency values taken in order to obtain a mean frequency value for the epoch of interest. Frequency values obtained from the new technique are compared with those obtained using the conventional technique and those obtained from two way satellite time and frequency transfer (TWSTFT) measurements. When measuring the frequency difference between clocks located in Braunschweig, Germany and Boulder, Colorado during October and December of 2003, the frequency values obtained from the GPSCP1T data using the new method agreed with those obtained using the conventional method at 2-3 x 10-16, implying that it may be feasible to replace the conventional method with the new method. The frequencies obtained from the GPSCPTT data using either method agreed with those obtained from the TWSTFT data at a few to several parts in 1016, implying that both TWSTFT and GPSCPTT are approaching frequency-transfer performance sufficient for use during simultaneous fountain evaluations.
Proc. IEEE Intl. Ultrasonics, Ferroelectrics, and Frequency Control Anniversary Joint Conf.
August 24-27, 2004
Montreal, 1, CA
IEEE Intl. Ultrasonics, Ferroelectrics, and Frequency Control Conf.
carrier phase time transfer, frequency transfer, GPS, GPS carrier phase time transfer, GPSCPTT, time transfer, two way satellite time transfer, TWSTFT, TWSTT
, Levine, J.
, Parker, T.
, Piester, D.
and Becker, J.
A New Technique for Estimating Frequency from GPS Carrier-Phase Time Transfer Data, Proc. IEEE Intl. Ultrasonics, Ferroelectrics, and Frequency Control Anniversary Joint Conf., Montreal, 1, CA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=50087
(Accessed November 29, 2023)