Development and validation of the TaiWan Ionosphere Model-2 using the COSMIC2, VIPIR, and GNSS data

Project Details


Accurate and precise real-time specification and modeling of the ionospheric electron density (Ne) are important to radio sky-wave communications and satellite navigation. In this scenario, the space based GPS/GNSS radio occultation (RO) technique is a novel approach for ionospheric monitoring and mapping. Due to the success of FS3/COSMIC, the joint U.S. and Taiwan RO team, lead separately by the National Oceanic and Atmospheric Administration (NOAA) and Taiwan's National Space Organization (NSPO), have moved forward with a COSMIC follow-on mission (called FS7/COSMIC2) that launched six low-inclination LEO satellites (24° inclination) in June of 2019. The GNSS RO payload can receive multi-channel GPS and GLONASS satellite signals and be capable of tracking more than 5,000 RO observations per day. It is expected that denser RO observations will be used to accurately structure and model the Earth’s equatorial and low-latitude ionosphere. This study will address new objectives and results of GNSS RO remote sensing in the ionosphere as well as new opportunities for future ionospheric weather and/or space weather missions. The first part of this project is proposed to improve the spherical harmonic analyses of TWIM parameter mapping from geodetic coordinates into geomagnetic coordinates. The second part of the project is proposed to improve the vertical Ne profile fitting from the α-Chapman-type function into the vary-Chap function, which has a continuously varying scale height. Further optimization analyses on the TWIM2 and validation works are also proposed. The sources of TWIM2 validation system include a Vertical Incidence Pulsed Ionospheric Radar (VIPIR) network located in east Asia and more than 150 local ground-based GPS/GNSS receivers in Taiwan. The East-Asia VIPIR network includes eight systems allocated in Japan (4 systems), Korea (2 systems), and Taiwan (2 systems). We note that the Longquan VIPIR station at South Taiwan is not in full operation and need to be fixed for full functions. The VIPIR is actually a high-frequency ionospheric sounding radar, i.e. ionosonde. The variation of the virtual height of reflection h’(f) as a function of the radio frequency is the fundamental ionosonde data product, and the records of these measurements are known as ionograms. Synoptic ionospheric measurements derived by vertical and oblique ionograms from the East-Asia VIPIR network can provide valuable information both for high-frequency radio propagation work and for validations of the ionospheric parameters, e.g. foF2, hmF2, foE, and hmE, estimated from TWIM2. We propose to finish the refurbishment of the Longquan VIPIR system and TWIM2 validation with the VIPIR data in the first year. Furthermore, more than one hundred of local ground-based GNSS receivers can provide STEC values for validation of TWIM2 in the second year
Effective start/end date1/07/2131/03/24


  • ionospheric electron density model
  • radio occultation
  • HF radar
  • GNSS


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