On the Ionospheric Impact of Recent Storm Events on Satellite-Based Augmentation Systems in Middle and Low-Latitude Sectors

A. Komjathy, L. Sparks, A.J. Mannucci, X. Pi

Abstract:	Ionospheric correction algorithms have been characterized extensively for the mid-latitude region of the ionosphere where benign conditions usually exist. The United States Federal Aviation Administration s (FAA) Wide Area Augmentation System (WAAS) for civil aircraft navigation is focused primarily on the Conterminous United States (CONUS). Other Satellite-Based Augmentation Systems (SBAS) include the European Geostationary Navigation Overlay Service (EGNOS) and the Japanese Global Navigation Satellite System (MSAS). Other parts of the world, such as the South American region or India, provide a more serious challenge to addressing the impact of the ionosphere on navigation using SBAS. At equatorial latitudes, geophysical conditions produce the so-called Appleton- Hartree (equatorial) anomaly, which results in significantly larger ionospheric range delays and larger spatial gradients in these delays than are observed in the CONUS or European sectors. In this paper, we use GPS measurements obtained on geomagnetic storm days to perform a quantitative assessment of WAAS-type ionospheric correction algorithms in other parts of the world such as low-latitude Brazil and mid-latitude Europe. For the study, we access a world-wide network of 400+ dual-frequency GPS receivers. The network includes: 1) the Continuously Operating Reference Sites (CORS) in the United States; 2) stations in and near South America as part of the Brazilian Network of Continuous Monitoring of GPS (RBMC), operated by the Brazilian Institute of Geography and Statistics (IGBE); and (3) European and CONUS sites included in the International GPS Service (IGS) global network. Data sets have been selected to include 18 quiet and storm days upon which the WAAS ionospheric threat model is based. To provide groundtruth and calibrate GPS receiver and transmitter interfrequency biases, we process the GPS data using Global Ionospheric Mapping (GIM) software developed at the Jet Propulsion Laboratory to compute calibrated high resolution observations of ionospheric total electron content (TEC). In this research, we investigate major storm events of the last few years and evaluate their impact on WAAS ionospheric model performance in Brazil, Europe and CONUS. These storms include the worst-case CONUS storms such as those on July 15, 2000, and March 31, 2001; we investigate their impact on SBAS in Europe and Brazil. Results indicate that lesser known storms such as the one on April 5, 2000 had a more significant impact in Europe than a near worst-case storm in CONUS. Furthermore, in terms of planar fit residuals, we provide additional evidence that there is little difference between quiet and storm time behavior over Brazil. We find that the Brazilian planar fit residuals are 2 to 4 times higher (RMS) than those for Europe and CONUS.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	2769 - 2776
Cite this article:	Komjathy, A., Sparks, L., Mannucci, A.J., Pi, X., "On the Ionospheric Impact of Recent Storm Events on Satellite-Based Augmentation Systems in Middle and Low-Latitude Sectors," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 2769-2776.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In