Ground- and space-based GPS data ingestion into the NeQuick model |
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| Authors: | C Brunini F Azpilicueta M Gende E Camilion A Aragón Ángel M Hernandez-Pajares M Juan J Sanz Dagoberto Salazar |
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| Institution: | (1) School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK;(2) Research Group of Astronomy and Geomatics, Technical University of Catalonia (gAGE/UPC), Mod. C3, Campus Nord UPC, Jordi Girona 1, 08034 Barcelona, Spain;(3) IFAC-CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy |
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| Abstract: | This paper presents a technique for ingesting ground- and space-based dual-frequency GPS observations into a semi-empirical
global electron density model. The NeQuick-2 model is used as the basis for describing the global electron density distribution.
This model is mainly driven by the F2 ionosphere layer parameters (i.e. the electron density, N
m
F2, and the height, h
m
F2 of the F2 peak), which, in the absence of directly measured values, are computed from the ITU-R database (ITU-R 1997). This database was established using observations collected from 1954 to 1958 by a network of around 150 ionospheric sounders
with uneven global coverage. It allows computing monthly median values of N
m
F2 and h
m
F2 (intra-month variations are averaged), for low and high solar activity. For intermediate solar activity a linear interpolation
must be performed. Ground-based GNSS observations from a global network of ~350 receivers are pre-processed in order to retrieve
slant total electron content (sTEC) information, and space-based GPS observations (radio occultation data from the FORMOSAT-3/COSMIC
constellation) are pre-processed to retrieve electron density (ED) information. Both, sTEC and ED are ingested into the NeQuick-2
model in order to adapt N
m
F2 and h
m
F2, and reduce simultaneously both, the observed minus computed sTEC and ED differences. The first experimental results presented
in this paper suggest that the data ingestion technique is self consistent and able to reduce the observed minus computed
sTEC and ED differences to ~25–30% of the values computed from the ITU-R database. Although sTEC and ED are both derived from
GPS observations, independent algorithm and models are used to compute their values from ground-based GPS observations and
space-based FORMOSAT-3/COSMIC radio occultations. This fact encourages us to pursue this research with the aim to improve
the results presented here and assess their accuracy in a reliable way. |
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