Time Scales Comparisons using Simultaneous Measurements in Three Frequency Channels

Petr Panek and Alexander Kuna

Abstract:	Simultaneous time transfer in three frequency channels can be performed after implementing new GPS signals. It leads to improving the accuracy on the one hand by increasing the number of measurements entering the statistical processing, and on the other hand by improving the characteristics of the time transfer based on ionospheric free solution. This paper describes the design of optimal methods for processing the results of measurements in several frequency channels based on the Best Linear Unbiased Estimation (BLUE). The optimal estimate was derived for a number of elementary models (no ionospheric delay, first-order ionospheric delay, first- and second-order ionospheric delay), and the contribution of using measurements in three frequency channels was evaluated compared to procedures used up to now. We show that the optimal estimates are in some cases equal to already used linear combination of measurements (e.g. L3P) and thus these classical procedures can be considered optimal. We confirm the fact that the ionospheric free solution is always redeemed with significant increase of impact of random errors. The impact is increased by factor of three concerning the measurements in two frequency channels compared to measurement in a single frequency channel. We show that improvement of 15 % can be achieved if measurements in three frequency channels are performed. Results of experimental measurement are also presented. The measurement aimed to look into the real behavior of random errors when using five GPS signals broadcast in three frequency channels, namely the amount of their correlation, which plays an important role in processing the results of several simultaneous measurements. We show that the correlation between measurement errors caused by multipath propagation is low despite the small span between the L2 and L5 frequency channels, and that one can benefit by including the measurements in the L5 frequency channel in the processing.
Published in:	Proceedings of the 44th Annual Precise Time and Time Interval Systems and Applications Meeting November 26 - 29, 2012 Hyatt Regency Reston Town Center Reston, Virginia
Pages:	301 - 310
Cite this article:	Panek, Petr, Kuna, Alexander, "Time Scales Comparisons using Simultaneous Measurements in Three Frequency Channels," Proceedings of the 44th Annual Precise Time and Time Interval Systems and Applications Meeting, Reston, Virginia, November 2012, pp. 301-310.
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