Volume 27, Issue 16 p. 2473-2476
Free Access

Improving the Abel inversion by adding ground GPS data to LEO radio occultations in ionospheric sounding

M. Hernández-Pajares

M. Hernández-Pajares

Group of Astronomy and Geomatics, Universitat Politècnica de Catalunya, Barcelona, Spain

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J. M. Juan

J. M. Juan

Group of Astronomy and Geomatics, Universitat Politècnica de Catalunya, Barcelona, Spain

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J. Sanz

J. Sanz

Group of Astronomy and Geomatics, Universitat Politècnica de Catalunya, Barcelona, Spain

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First published: 15 August 2000
Citations: 87

Abstract

GPS radio occultations allow the sounding of the Earth's atmosphere (i.e. troposphere and ionosphere). The basic observable of this technique is the additional delay, due to the refractivity index, of a radio signal when passing through the atmosphere. This additional delay is proportional to the integrated refractivity, in such a way that we can obtain an estimation of the vertical refractivity profiles using observations at different elevation angles by solving an inverse problem. Traditionally, the solution of this inverse problem is obtained by using the Abel inversion algorithm assuming a refractivity index that only depends on the altitude. In this paper we present a modified Abel inversion algorithm for ionospheric sounding that overcomes the spherical symmetry assumption of the traditional Abel inversion algorithm. Processing a set of simulated data and 1 day of real data with this algorithm, a clear improvement over the traditional one can be obtained when comparing the derived critical frequencies with the ionosonde measurements. It is also shown that this improvement is sufficient to measure critical frequencies associated with the ionospheric E layer.