Ranging Errors Due to Disturbances in the Polar Ionosphere

G. J. Bishop and J. A. Klobuchar

Abstract:	Ionospheric total electron content (TEC)causes range and range rate errors in transionospheric RF systems. In middle-latitude regions, such as CONUS, simple models can statistically correct for more than half of the TEC contribution. The polar latitudes, however, have been shown to exhibit highly disturbed TEC behavior, for which adequate models do not yet exist. Short-term campaign observations of polar cap TEC near solar minimum have established that a basic diurnal TEC cycle exists, but there are frequent variations that can more than double background values over periods as short as ten minutes. These TEC variations were clearly linked to 'F-layer ionization patches' (ionospheric clouds) up to 1000 km in extent, with drift velocities to 1 preferential:! in h/s, which occurred the 1200-2400 UT period. Projections, based on polar cap foF2 measurements from ionospheric sounders, indicated that solar maximum would show a 2 to 3-fold increase in backsround TEC levels and a larqer increase in TEC variability. This projected increase invariation of the polar diurnal TEC cycle at solar maximum, is much- larger than the corresponding increase observed at typical mid-latitude sites. TEC measurements, made using GPS signals at Thule, Greenland, since October, 1987, are generally confirming such projected increases. These measurements show disturbances near solar maximum to be 3 to 4 times larger than the greatest TEC variations observed near solar minimum. Simple analytical results show that the range and range rate errors that a typical trans-ionospheric RF system will experience due to such TEC disturbances, will be highly dependent on the observation geometry of the system.
Published in:	Proceedings of the 3rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1990) September 19 - 21, 1990 The Broadmoor Hotel Colorado Spring, CO
Pages:	175 - 179
Cite this article:	Bishop, G. J., Klobuchar, J. A., "Ranging Errors Due to Disturbances in the Polar Ionosphere," Proceedings of the 3rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1990), Colorado Spring, CO, September 1990, pp. 175-179.
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