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

Schreiner, William S.; Sokolovskiy, Sergey; Rocken, Christian; Hunt, Douglas

doi:10.1029/1999rs900034

Cited by 350 publications

(394 citation statements)

References 13 publications

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“…In an ionospheric GPS radio occultation, the signals from a GPS satellite are received by a Low Earth Orbit (LEO) receiver as the GPS satellite sets or rises through the ionosphere [Hajj and Romans, 1998;Schreiner et al, 1999]. The signals are refracted due to electron density gradients, and since the ionosphere is a dispersive medium, the ray paths of the L1 and L2 signals will be slightly different.…”

Section: Introductionmentioning

confidence: 99%

A new algorithm for retrieving GPS radio occultation total electron content

Syndergaard

2002

Geophysical Research Letters

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A new algorithm for retrieving the relative ionospheric satellite‐to‐satellite total electron content during Global Positioning System (GPS) radio occultations is proposed. The algorithm consists of a linear combination of the L1 and L2 excess phase data using precise orbit information of the transmitter and receiver. The combination eliminates the effects of refractive bending and dispersion to first order. Simulations, representative of solar maximum conditions, show that using the “traditional” combination of the L1 and L2 phases, bending and dispersion may cause a systematic residual error of up to 20 TECU. Using only the L1 excess phase, the corresponding maximum residual error is about 7 TECU. The proposed combination results in a residual error due to bending and dispersion less than 0.1 TECU. Uncertainty in satellite orbit determination, as well as an unmodeled residual related to the geomagnetic field, result in a total systematic error of 1–2 TECU.

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Section: Introductionmentioning

confidence: 99%

A new algorithm for retrieving GPS radio occultation total electron content

Syndergaard

2002

Geophysical Research Letters

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“…Since the index of refractivity of the ionosphere depends mainly on the number of free electrons, the inversion of the measured signals can provide the vertical electron density profile (e.g. Hajj and Romans, 1998;Schreiner et al, 1999;Jakowski et al, 2002). Radio occultation measurements onboard CHAMP have been used since April 2002 to retrieve…”

Section: Introductionmentioning

confidence: 99%

Enhanced E-layer ionization in the auroral zones observed by radio occultation measurements onboard CHAMP and Formosat-3/COSMIC

Mayer

Jakowski

2009

Ann. Geophys.

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Abstract. Particle precipitation of magnetospheric origin causes additional ionization in the auroral zone at E-layer heights. During night-time, in particular at winter-night, the E-layer ionization may dominate over the F2-layer ionization level. To study the geophysical conditions and characteristics of the related ionospheric processes in more detail, we use GPS radio occultation electron density profile retrievals from CHAMP and Formosat-3/COSMIC to extract those vertical profiles which show the absolute maximum of ionization in the E-layer height range of 90-150 km. In order to select these profiles, we have developed an algorithm which can recognize the shape of a given profile by fitting an empirical Ansatz to it. Using data from CHAMP collected since 2002 and Formosat-3/COSMIC data starting from 2006, we are able to study both, the local-time dependence and the solarcylce variability of the observed processes.

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“…Inferring total electron content (TEC) on the ray path between the satellites is then a relatively straightforward task. Reviews of different analysis techniques have been given by Kursinski et al [1997] and Schreiner et al [1999].…”

Section: Introductionmentioning

confidence: 99%

Inverting ionospheric radio occultation measurements using maximum entropy

Hysell

2007

Radio Science

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[1] Practical aspects of the inversion of ionospheric radio occultation data using the Abel transform and its inverse are discussed. The linear inverse transform exhibits poor error propagation characteristics, producing significant artifacts preferentially at low altitudes where they might easily be mistaken for intermediate or sporadic layers in the ionosphere. Tikhonov regularization, which can be viewed as fixed linear filtering, reduces the artifacts at the expense of discarding fine structure in the profiles. Improved results are obtained using maximum entropy and Bayesian statistics. The maximum entropy algorithm can be viewed as a nonlinear adaptive filter which suppresses artifacts while preserving fine structure to the degree the data can support. Other advantages of and avenues for improving the basic maximum entropy algorithm are discussed.

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

Cited by 350 publications

References 13 publications

A new algorithm for retrieving GPS radio occultation total electron content

A new algorithm for retrieving GPS radio occultation total electron content

Enhanced E-layer ionization in the auroral zones observed by radio occultation measurements onboard CHAMP and Formosat-3/COSMIC

Inverting ionospheric radio occultation measurements using maximum entropy

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