Time Transfer Experiments Using GLONASS P-code Measurements from RINEX Files

Abstract

We have used GLONASS P-code measurements from different geodetic GPS/GLONASS receivers involved in the IGEX campaign to perform frequency/time transfer between remote clocks. GLONASS time transfer is commonly based on the clock differences between GLONASS system time and the local clock computed by a time transfer receiver. We choose to analyze the raw P-code data available in the RINEX files. This also allows working with the data from geodetic receivers involved in the IGEX campaign. As a first point, we show that the handling of the external frequency in some of the IGEX receivers is not suited for time transfer applications. We also point out that the GLONASS broadcast ephemerides give rise to a considerable number of outliers in the time transfer, compared to the precise IGEX ephemerides. Due to receiver clock resets at day boundaries, which is a characteristic of the R100 receivers from 3S-Navigation, continuous data sets exceeding one day are not available. Invthis context, it is therefore impossible to perform RINEX-based precise frequency transfer with GLONASS P-codes on a time scale longer than one day. Because the frequencies used by GLONASS satellites are different, the time transfer results must be corrected for the different receiver hardware delays. After this correction, the final precision of our time transfer results corresponds to a root-mean-square (rms) of 1.8 nanoseconds (ns) (maximum difference of 11.8 ns) compared to a rms of about 4.4 ns (maximum difference of 31.9 ns) for time transfer based on GPS C/A code observations. © 2001 John Wiley & Sons, Inc.