TY - JOUR
T1 - A neural network based error correction method for radio occultation electron density retrieval
AU - Pham, Viet Cuong
AU - Juang, Jyh Ching
N1 - Funding Information:
This research was financially supported by National Science Council Taiwan , under Grant NSC 101-2221-E-006-191-MY3 . We acknowledge the Taiwan's National Space Organization (NSPO) and the University Corporation for Atmospheric Research (UCAR) for providing FORMOSAT-3/COSMIC data. We thank the Telecommunications/ICT for Development (T/ICT4D) Laboratory of the Abdus Salam International Centre for Theoretical Physics, Trieste, Italy for providing the NeQuick2 model source code. The NeQuick2 web model is available at: http://t-ict4d.ictp.it/nequick2/nequick-2-web-model . We are grateful to the National Geophysical Data Center, National Oceanic and Atmosphere Administration (NOAA) for providing the R12 index. We also acknowledge the Jicamarca Radio Observatory and the International GNSS Service for providing ISR data and global TEC map, respectively.
Publisher Copyright:
© 2015.
PY - 2015/12/1
Y1 - 2015/12/1
N2 - Abel inversion techniques have been widely employed to retrieve electron density profiles (EDPs) from radio occultation (RO) measurements, which are available by observing Global Navigation Satellite System (GNSS) satellites from low-earth-orbit (LEO) satellites. It is well known that the ordinary Abel inversion might introduce errors in the retrieval of EDPs when the spherical symmetry assumption is violated. The error, however, is case-dependent; therefore it is desirable to associate an error index or correction coefficient with respect to each retrieved EDP. Several error indices have been proposed but they only deal with electron density at the F2 peak and suffer from some drawbacks. In this paper we propose an artificial neural network (ANN) based error correction method for EDPs obtained by the ordinary Abel inversion. The ANN is first trained to learn the relationship between vertical total electron content (TEC) measurements and retrieval errors at the F2 peak, 220. km and 110. km altitudes; correction coefficients are then estimated to correct the retrieved EDPs at these three altitudes. Experiments using the NeQuick2 model and real FORMOSAT-3/COSMIC RO geometry show that the proposed method outperforms existing ones. Real incoherent scatter radar (ISR) measurements at the Jicamarca Radio Observatory and the global TEC map provided by the International GNSS Service (IGS) are also used to valid the proposed method.
AB - Abel inversion techniques have been widely employed to retrieve electron density profiles (EDPs) from radio occultation (RO) measurements, which are available by observing Global Navigation Satellite System (GNSS) satellites from low-earth-orbit (LEO) satellites. It is well known that the ordinary Abel inversion might introduce errors in the retrieval of EDPs when the spherical symmetry assumption is violated. The error, however, is case-dependent; therefore it is desirable to associate an error index or correction coefficient with respect to each retrieved EDP. Several error indices have been proposed but they only deal with electron density at the F2 peak and suffer from some drawbacks. In this paper we propose an artificial neural network (ANN) based error correction method for EDPs obtained by the ordinary Abel inversion. The ANN is first trained to learn the relationship between vertical total electron content (TEC) measurements and retrieval errors at the F2 peak, 220. km and 110. km altitudes; correction coefficients are then estimated to correct the retrieved EDPs at these three altitudes. Experiments using the NeQuick2 model and real FORMOSAT-3/COSMIC RO geometry show that the proposed method outperforms existing ones. Real incoherent scatter radar (ISR) measurements at the Jicamarca Radio Observatory and the global TEC map provided by the International GNSS Service (IGS) are also used to valid the proposed method.
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U2 - 10.1016/j.jastp.2015.10.013
DO - 10.1016/j.jastp.2015.10.013
M3 - Article
AN - SCOPUS:84945248291
SN - 1364-6826
VL - 135
SP - 77
EP - 84
JO - Journal of Atmospheric and Solar-Terrestrial Physics
JF - Journal of Atmospheric and Solar-Terrestrial Physics
ER -