Ionosphere Effects at the Nanosecond Level Observed in Common-View Time Transfer

Robin P. Giffard

Abstract:	The single-channel "Common-View" GPS time-transfer technique is frequently used to minimize the inaccuracy caused by satellite clock errors, including Selective Avail-ability. Even when carefully conducted, these measure-ments are subject to receiver noise, satellite ephemeris errors, multipath effects, and variable propagation delays. Many of these errors can be reduced if continuous mea-surements are made on all of the satellites that are in com-mon view. We report results using this method with multi-channel, modular, L1, time receivers over a 4,000 km East-West baseline. The effect of averaging on the sources of error is discussed. The experiments show measurement noise at the level of about 1 nanosecond for averaging times between 100 seconds and 2 days without post-pro-cessing. In addition, significant diurnal effects at the level of up to 10 nanoseconds peak-to-peak are often observed. These appear to be due to the expected differences between the actual ionospheric delays and the predictions of the built-in model. Techniques for mitigating these errors are discussed.
Published in:	Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997) September 16 - 19, 1997 Kansas City, MO
Pages:	1099 - 1106
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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