Ionospheric tomography by combining vertical and oblique sounding data with TEC retrieved from a tri-band beacon

The development of the tri-band beacon brings hope to the high-resolution computerized ionospheric tomography (CIT) imaging. This is a major motivation for the proposed launch of a Chinese satellite carrying as a key payload a tri-band beacon for seismological studies. Due to the limited-angle geometry, the vertical precision of CIT still needs to be improved to meet the requirements of some applications, such as monitoring the ionospheric behaviors before earthquakes. To solve this problem, this paper puts forward a new bi-iteration method, which combines vertical and oblique sounding data with the total electron content (TEC) retrieved from an onboard tri-band beacon of a planned Chinese satellite for seismological studies transmitting VHF, UHF, and L-band frequencies. A ground-based high-resolution ionospheric observation network was built in northern China in April 2009. Based on this ground network and the planned satellite, high-resolution ionospheric structures can be reconstructed in real time for monitoring the ionospheric precursors of earthquakes over several seismic belts in northern China. The numerical simulations show that electron density distributions reconstructed from the three-frequency TEC are significantly improved after incorporating observation data of the ground-based vertical and oblique ionograms. Here, the oblique sounding data are assimilated in the CIT for the first time. The results in this paper help to ensure that the measurements to be made by this solid network will yield their potential.