Journal of Geodesy

, Volume 87, Issue 9, pp 813–823

A technique for routinely updating the ITU-R database using radio occultation electron density profiles

  • Claudio Brunini
  • Francisco Azpilicueta
  • Bruno Nava
Original Article

DOI: 10.1007/s00190-013-0648-x

Cite this article as:
Brunini, C., Azpilicueta, F. & Nava, B. J Geod (2013) 87: 813. doi:10.1007/s00190-013-0648-x

Abstract

Well credited and widely used ionospheric models, such as the International Reference Ionosphere or NeQuick, describe the variation of the electron density with height by means of a piecewise profile tied to the F2-peak parameters: the electron density,\(N_m \mathrm{F2}\), and the height, \(h_m \mathrm{F2}\). Accurate values of these parameters are crucial for retrieving reliable electron density estimations from those models. When direct measurements of these parameters are not available, the models compute the parameters using the so-called ITU-R database, which was established in the early 1960s. This paper presents a technique aimed at routinely updating the ITU-R database using radio occultation electron density profiles derived from GPS measurements gathered from low Earth orbit satellites. Before being used, these radio occultation profiles are validated by fitting to them an electron density model. A re-weighted Least Squares algorithm is used for down-weighting unreliable measurements (occasionally, entire profiles) and to retrieve \(N_m \mathrm{F2}\) and \(h_m \mathrm{F2}\) values—together with their error estimates—from the profiles. These values are used to monthly update the database, which consists of two sets of ITU-R-like coefficients that could easily be implemented in the IRI or NeQuick models. The technique was tested with radio occultation electron density profiles that are delivered to the community by the COSMIC/FORMOSAT-3 mission team. Tests were performed for solstices and equinoxes seasons in high and low-solar activity conditions. The global mean error of the resulting maps—estimated by the Least Squares technique—is between \(0.5\times 10^{10}\) and \(3.6\times 10^{10}\) elec/m\(^{-3}\) for the F2-peak electron density (which is equivalent to 7 % of the value of the estimated parameter) and from 2.0 to 5.6 km for the height (\(\sim \)2 %).

Keywords

Ionosphere F2-peak parameters ITU-R maps updating International Reference Ionosphere (IRI) NeQuick  Radio-occultation 

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Claudio Brunini
    • 1
    • 2
  • Francisco Azpilicueta
    • 2
    • 1
  • Bruno Nava
    • 3
  1. 1.GESA, Facultad de Ciencias Astronómicas y GeofísicasUniversidad Nacional de La PlataLa PlataArgentina
  2. 2.Consejo Nacional de Investigaciones Científicas y TécnicasLa PlataArgentina
  3. 3.The Abdus Salam International Centre for Theoretical PhysicsTriesteItaly