HR: 15:50h
AN: A53C-09    [Abstracts]
TI: Impact of the Combination of GNSS and Altimetry Data on the Derived Global Ionosphere Maps
AU: Todorova, S
EM: stodo@mars.hg.tuwien.ac.at
AF: Institute of Geodesy and Geophysics, Vienna University of Technology, Gusshausstr. 27- 29, Vienna, 1040, Austria
AU: * Schuh, H
EM: harald.schuh@tuwien.ac.at
AF: Institute of Geodesy and Geophysics, Vienna University of Technology, Gusshausstr. 27- 29, Vienna, 1040, Austria
AU: Hobiger, T
EM: hobiger@nict.go.jp
AF: Space-Time Standards Group, Kashima Space Research Center, NICT, 893-1 Hirai, Kashima, 314-0012, Japan
AU: Hernandez-Pajares, M
EM: manuel@ma4.upc.edu
AF: Group of Astronomy and Geomatics, Univ. Politecnica de Catalunya, Jordi Girona 1, C3, Barcelona, 08034, Spain
AB: The classical input data for development of Global Ionosphere Maps (GIM) of the Total Electron Content (TEC) is the so called "geometry free linear combination", obtained from the dual-frequency Global Navigation Satellite System (GNSS) observations. Such maps in general achieve good quality of the ionosphere representation. However, the GNSS stations are inhomogeneously distributed, with large gaps particularly over the sea surface, which lowers the precision of the GIM over these areas. On the other hand, the dual-frequency satellite altimetry missions such as Jason-1 and TOPEX/Poseidon provide information about the parameter of the ionosphere precisely above the sea surface, where the altimetry observations are preformed. Due to the limited spread of the measurements and some open issues related to systematic errors, the ionospheric data from satellite altimetry is used only for cross-validation of the GNSS GIM. It can be anticipated however, that some specifics of the ionosphere parameter derived by satellite altimetry will partly balance the inhomogeneity of the GNSS data. Such important features are complementing in the global resolution, different biasing and the absence of additional mapping, as it is the case in GNSS. In this study we create two-hourly GIM from GNSS data and additionally introduce satellite altimetry observations, which help to compensate the insufficient GNSS coverage of the oceans. The combination of the data from around 180 GNSS stations and the satellite altimetry mission Jason-1 is performed on the normal equation level. The comparison between the integrated ionosphere models and the GNSS-only maps shows a higher accuracy of the combined GIM over the seas. A further effect of the combination is that the method allows the independent estimation of daily values of the Differential Code Biases (DCB) for all GNSS satellites and receivers, and of the systematic errors affecting the altimetry measurements. Such errors should include a hardware delay similar to the GNSS DCB as well as the impact of the topside ionosphere, which is not sampled by Jason-1. At this stage, for testing purposes we estimate a constant daily value, which will be further investigated. The final aim of the study is the development of improved combined global TEC maps, which make best use of the advantages of each particular type of data and have higher accuracy and reliability than the results derived by the two methods if treated individually.
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1295 Integrations of techniques
DE: 2435 Ionospheric disturbances
DE: 2447 Modeling and forecasting
DE: 2494 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly