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The ionosphere is the part of the Earth's atmosphere containing free electrons which effects radio wave propagation. The different travel times of multi-frequency signals allow the estimation of integrated electron density along the ray path ("Total Electron Content", TEC). Space-geodetic techniques, such as GNSS, DORIS or altimeter missions (e.g. Jason-1/2 and ENVISAT) can be used to estimate ionospheric parameters and provide valuable information for space weather monitoring.
 - Some space-geodetic techniques useful for ionosphere modeling
Within the last years, at DGFI, a multi-dimensional model has been developed describing the electron density in B-spline functions. By using trigonometric B-splines this approach can be used not only for regional but also for global modeling. Two main advantages of B-splines are (1) their localized feature and (2) the possibility to use them to construct scale functions and wavelets which allows the separation of the signal with different resolution. The separation of the electron density in a sum of bandpass filtered signal components equals a successive low-pass filter and is named multi-scale representation (MSR). The MSR allows effective data compression and has advantages when combining different input signals.
The existing modeling approaches are to be improved and to extend in the future. Additional input data types should be used (e.g. DORIS and TEC from different space-based GPS receiver on low earth orbiters) and combined as best as possible. In order to permit near real-time modeling of electron density we want to use kalman filter technique. This sequential parameter estimation technique allows the prediction of model parameters and is essential for the use of the model for real-time positioning purposes.
In the frame of a DFG-project (MuSIK) the consideration of physical model approaches will be taken into account. This project will be the basis of a data-driven physical ionosphere model which is not only useful for the correction of space-geodetic measurements and space weather monitoring but will also help to better understand the relations and interactions in the ionosphere.
Selected publicationsSchmidt M., Hugentobler U., Jakowski N., Dettmering D., Liang W., Limberger M., Wilken V., Gerzen T., Hoque M., Berdermann J.: Multi-scale model of the ionosphere from the combination of modern space-geodetic satellite techniques - project status and first results. EGU General Assembly 2012, Vienna, Austria, 2012-04-24 (Poster)  |
Schmidt M., Dettmering D., Liang W., Heinkelmann R.: Concepts for modeling VTEC as a multi-scale representation. EGU General Assembly 2011, Vienna, Austria, 2011-04-04/08, 2011-04-05 (Poster) |
Dettmering D., Heinkelmann R., Schmidt M.: Systematic differences between VTEC obtained by different space-geodetic techniques during CONT08. Journal of Geodesy 85(7), 443-451, DOI: 10.1007/s00190-011-0473-z, 2011 |
Dettmering D., Schmidt M., Heinkelmann R., Seitz M.: Combination of different space-geodetic observations for regional ionosphere modeling. Journal of Geodesy 85(12): 989-998, DOI: 10.1007/s00190-010-0423-1, 2011 |
Schmidt M., Dettmering D., Mößmer M., Wang Y., Zhang J.: Comparison of spherical harmonic and B spline models for the vertical total electron content. Radio Science, 46, RS0D11, DOI: 10.1029/2010RS004609, 2011 |
Dettmering D., Heinkelmann R., Schmidt M., Seitz M.: Die Atmosphäre als Fehlerquelle und Zielgröße in der Geodäsie. Zeitschrift für Vermessungswesen ZfV 135, Heft 2, S. 100-105, 2010 |
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