Analysis and validation of GPS/MET radio occultation data in the ionosphere

Global positioning system (GPS) radio occultation signals received by a low Earth orbit satellite provide information on the global distribution of electron density in the ionosphere. Two radio occultation inversion algorithms are examined. The first algorithm utilizes the Abel integral transform, which assumes spherical symmetry of the electron density field. The second algorithm is a three-dimensional inversion constrained with the horizontal structure of a priori electron density fields. The Abel and 3-D constrained algorithms are validated by statistically comparing 4 days of inversions with critical frequency data from a network of 45 ionosonde stations and with vertical total electron content data from the global network of GPS ground receivers.