HR: 14:30h
AN: A53C-03 INVITED     [Abstracts]
TI: Improved Abel transform inversion: First application to COSMIC/FORMOSAT-3
AU: * Aragon-Angel, A
EM: angela@ma4.upc.edu
AF: Res. group Astron. & Geomatics Technical Univ. Catalonia (gAGE/UPC), Mod. C3 Campus Nord UPC Jordi Girona 1, Barcelona, E08034, Spain
AU: Hernandez-Pajares, M
EM: manuel@ma4.upc.edu
AF: Res. group Astron. & Geomatics Technical Univ. Catalonia (gAGE/UPC), Mod. C3 Campus Nord UPC Jordi Girona 1, Barcelona, E08034, Spain
AU: Juan, J
EM: miguel@fa.upc.edu
AF: Res. group Astron. & Geomatics Technical Univ. Catalonia (gAGE/UPC), Mod. C3 Campus Nord UPC Jordi Girona 1, Barcelona, E08034, Spain
AU: Sanz, J
EM: jaume@ma4.upc.edu
AF: Res. group Astron. & Geomatics Technical Univ. Catalonia (gAGE/UPC), Mod. C3 Campus Nord UPC Jordi Girona 1, Barcelona, E08034, Spain
AB: In this paper the first results of Ionospheric Tomographic inversion are presented, using the Improved Abel Transform on the COSMIC/FORMOSAT-3 constellation of 6 LEO satellites, carrying on-board GPS receivers.[- 4mm] The Abel transform inversion is a wide used technique which in the ionospheric context makes it possible to retrieve electron densities as a function of height based of STEC (Slant Total Electron Content) data gathered from GPS receivers on board of LEO (Low Earth Orbit) satellites. Within this precise use, the classical approach of the Abel inversion is based on the assumption of spherical symmetry of the electron density in the vicinity of an occultation, meaning that the electron content varies in height but not horizontally. In particular, one implication of this assumption is that the VTEC (Vertical Total Electron Content) is a constant value for the occultation region. This assumption may not always be valid since horizontal ionospheric gradients (a very frequent feature in some ionosphere problematic areas such as the Equatorial region) could significantly affect the electron profiles. [- 4mm] In order to overcome this limitation/problem of the classical Abel inversion, a studied improvement of this technique can be obtained by assuming separability in the electron density (see Hernández-Pajares et al. 2000). This means that the electron density can be expressed by the multiplication of VTEC data and a shape function which assumes all the height dependency in it while the VTEC data keeps the horizontal dependency. Actually, it is more realistic to assume that this shape fuction depends only on the height and to use VTEC information to take into account the horizontal variation rather than considering spherical symmetry in the electron density function as it has been carried out in the classical approach of the Abel inversion.[-4mm] Since the above mentioned improved Abel inversion technique has already been tested and proven to be a useful tool to obtain a vertical description of the ionospheric electron density (see García-Fernández et al. 2003), a natural following step would be to extend the use of this technique to the recently available COSMIC data. The COSMIC satellite constellation, formed by 6 micro-satellites, is being deployed since April 2006 in circular orbit around the Earth, with a final altitude of about 700-800 kilometers. Its global and almost uniform coverage will overcome one of the main limitations of this technique which is the sparcity of data, related to lack of GPS receivers in some regions. This can significantly stimulate the development of radio occultation techniques with the use of the huge volume of data provided by the COSMIC constellation to be processed and analysed updating the current knowledge of the Ionospheres nature and behaviour. In this context a summary of the Improvel Abel transform inversion technique and the first results based on COSMIC constellation data will be presented. Moreover, future improvements, taking into account the higher temporal and global spatial coverage, will be discussed. [-4mm] References:M. Hernández-Pajares, J. M. Juan and J. Sanz, Improving the Abel inversion by adding ground GPS data to LEO radio occultations in ionospheric sounding, GEOPHYSICAL RESEARCH LETTERS, VOL. 27, NO. 16, PAGES 2473-2476, AUGUST 15, 2000.M. Garcia-Fernández, M. Hernández-Pajares, M. Juan, and J. Sanz, Improvement of ionospheric electron density estimation with GPSMET occultations using Abel inversion and VTEC Information, JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. A9, 1338, doi:10.1029/2003JA009952, 2003
DE: 2494 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly