Application of SCORE to Extract Protonospheric Electron Content from GPS/NNSS Observations

G. J. Bishop, D. S. Coco, N. Lunt,C. Coker,A. J. Mazzella, L. Kersley

Abstract:	Protonospheric (or plasmaspheric) electron content is included in GPS measurements of ionospheric total electron content (TEC), since the GPS satellites’ altitude is 20,000 km and the ionosphere is almost entirely below 1000 km altitude. Accurate measurement of this protonospheric content remains a significant issue in the use of GPS TEC data for space weather modeling or for providing ionospheric TEC data to aid other systems. The Self-Calibration Of pseudoRange Errors (SCORE) algorithm uses the GPS TEC measurements to calibrate GPS two-frequency receivers for all system components' contributions to pseudorange error, supporting improved GPS TEC accuracies. A recent study has shown that SCORE can maintain mid-latitude GPS TEC accuracy at better than the 2 TEC units (1 TECu = 1x10 16 electrons/m 2 integrated along the raypath, 2 TECu » 1 ns delay at L1). One approach used in that study was to compare SCORE-calibrated GPS TEC to measures of TEC recovered from the Navy Navigation Satellite System (NNSS, now re-named the Navy Ionospheric Measuring System, NIMS). Examination was limited to comparisons nearly overhead the observing station. In this paper we extend the GPS/NIMS comparisons over wide geographic regions, taking advantage of the fact that NIMS produces an essentially north-south cross section of the regional ionospheric TEC in a few minutes and SCORE-calibrated GPS produces a highly accurate regional TEC map for the entire day. The aim of this study was to obtain protonospheric electron content through differencing these two profiles, since the NIMS satellites only observe the ionospheric contribution. This paper investigates this differencing technique and provides insight into the advantages of using GPS and dense GPS networks to map the ionosphere and protonosphere. The preliminary results indicate that these methods have good potential for monitoring protonospheric electron content from the mid latitudes.
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:	207 - 216
Cite this article:	Bishop, G. J., Coco, D. S., Lunt, N., Coker, C., Mazzella, A. J., Kersley, L., "Application of SCORE to Extract Protonospheric Electron Content from GPS/NNSS Observations," Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997), Kansas City, MO, September 1997, pp. 207-216.
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