Improving the Abel transform inversion using bending angles from FORMOSAT-3/COSMIC
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The FORMOSAT-3/COSMIC satellite constellation has become an important tool toward providing global remote sensing data for sounding of the atmosphere of the earth and the ionosphere in particular. In this study, the electron density profiles are derived using the Abel transform inversion. Some drawbacks of this transform in LEO GPS sounding can be overcome by considering the separability concept: horizontal gradients of vertical total electron content (VTEC) information are incorporated by the inversion method, providing more accurate electron density determinations. The novelty presented in this paper with respect to previous works is the use of the phase change between the GPS transmitter and the LEO receiver as the main observable instead of the ionospheric combination of carrier phase observables for the implementation of separability in the inversion process. Some of the characteristics of the method when applied to the excess phase are discussed. The results obtained show the equivalence of both approaches but the method exposed in this work has the potentiality to be applied to the neutral atmosphere. Recent FORMOSAT-3/COSMIC data have been processed with both the classical Abel inversion and the separability approach and evaluated versus colocated ionosonde data.
KeywordsGPS radio occultation Ionosphere Electron density Abel transform Separability FORMOSAT-3/COSMIC
The authors would like to express their gratitude to the University Corporation for Atmospheric Research (UCAR), the National Space Organization (NSPO) in Taiwan for the availability of FORMOSAT-3/COSMIC constellation data, the International GNSS Service (IGS) for making available IONEX files, the source of ionosonde data SPIDR and, Dr. David Altadill at Ebro Observatory for providing calibrated AS00Q ionosonde data. This work has been partially supported by the Spanish Ministry of Science and Technology and the European Social Funds under the program “Personal Técnico de Apoyo”, and the IBER-WARTK project ESP2007-62676.
- Anthes RA, Bernhardt PA, Chen Y, Cucurull L, Dymond KF, Ector D, Healy SB, Ho SP, Hunt DC, Kuo YH, Liu H, Manning H, McCormick C, Meehan TK, Randel WJ, Rocken C, Schreiner WS, Sokolovskiy SV, Syndergard S, Thompson DC, Trenberth KE, Wee TK, Yen NL, Seng Z (2008) The COSMIC/FORMOSAT-3 mission: early results. Bull Am Met Soc 89:313–333. doi: 10.1175/BAMS-89-3-313 CrossRefGoogle Scholar
- Davies K (1990) Ionospheric Radio, Chapter 5, IEE Electromagnetic Waves Series 31, Peter Peregrinus Ltd., ISBN 0 86341 186 X, pp 124–154Google Scholar
- Garcia-Fernandez M (2004) Contributions to the 3D ionospheric sounding with GPS data, Doctoral Thesis, Technical University of Catalonia (UPC), B.45104-2004/84-688-8156-2Google Scholar
- Hajj GA, Ao CO, Iijima BA, Kuang D, Kursinski ER, Mannucci AJ, Meehan TK, Romans LJ, de la Torre Juarez M, Yunck TP (2004) CHAMP and SAC-C Atmospheric occultation results and intercomparisons, J Geophys Res 109(D6). ISSN 0148-0227, pp D06109.1–D06109.24Google Scholar
- Hernandez-Pajares M, Juan JM, Sanz J (2000) Improving the Abel inversion by adding ground data LEO radio occultations in the ionospheric sounding. Geophys Res Lett 27:2743–2746Google Scholar
- Hernandez-Pajares M, Juan JM, Sanz J, Orus R, Garcia-Rigo A, Feltens J, Komjathy A, Schaer SC, Krankoswki A (2009) The IGS VTEC maps: a reliable source of ionospheric information since 1998, J Geod. doi: 10.007/s00190-008-0266-1
- Lei J, Syndergaard S, Burns AG, Solomon SC, Wang W, Zeng Z, Roble RG, Wu Q, Kuo YH, Holt JM, Zhang SR, Hysell DL, Rodrigues FS, Lin CH (2007) Comparison of COSMIC ionospheric measurements with ground-based observations and model predictions: preliminary results. J Geophys Res 112:A07308. doi: 10.1029/2006JA012240 CrossRefGoogle Scholar
- Schaer S, Gurtner W, Feltens J (1998) IONEX: the IONosphere Map EXchange. Format Version 1, Proceedings of the 1998 IGS Analysis Centres Workshop, ESOC, Darmstadt, Germany, Feb 9–11, pp 233–247Google Scholar
- Schreiner S, Sokolovskiy SV, Rocken C, Hunt DC (2008) Quality assessment of GPS radio occultation data from the COSMIC/FORMOSAT-3, CHAMP, GRACE missions, FORMOSAT-3/COSMIC 2008 Workshop, Taipei, Taiwan, Oct 1–3Google Scholar
- Shimazaki T (1955) World-wide daily variations in the height of the maximum electron density of the ionospheric F2-layer. J Radio Res Lab (Japan) 2(7):85–97Google Scholar
- Wickert J, Beyerle G, Hajj GA, Schwieger V, Reigber Ch (2002) GPS radio occultation with CHAMP: Atmospheric profiling utilizing the space-based single difference technique, Geophys Res Lett 29(8), doi: 10.1029/2001GL013982