Ionospheric TEC estimation with the signals of various geostationary navigational satellites

With the development of receiver equipment and GNSS and SBAS constellations, the coherent dual-frequency L-band transmissions are now available from a number of geostationary satellites. These signals can be used for ionospheric total electron content (TEC) estimation. The quality of these data, i.e., the level of noise in such TEC estimation is of great interest and importance. We present results of comparisons of noise patterns in TEC estimation using signals of geostationary satellites of augmentation systems such as the Indian GAGAN, the European EGNOS and the American WAAS, as well as the signals from the Chinese Beidou navigation system. We used data from two receiving sites in the European part of Russia and the USA, which are equipped with JAVAD Delta receivers. We found out that the noise level in TEC estimation based on geostationary satellites of the Beidou system is one order smaller than that for SBAS and corresponds to those of GPS/GLONASS at the same elevation angles. Typically, the TEC RMS was about 0.05 TECU for GPS/GLONASS satellites at elevation range 5---15°, 0.06 TECU for Beidou geostationary satellites at elevation range 15---25°, 0.6 TECU for GAGAN at elevation range 15---25°, 0.7 TECU for WAAS at elevation 45°, and 5 TECU for EGNOS at elevation 20°. We also discuss the capabilities of geostationary TEC observations in connection with the recent G4 geomagnetic storm of March 2015 using six IGS MGEX stations in the American, Southeast Asian and Australian sectors. We demonstrate the hemispheric asymmetry in the ionospheric TEC response during this storm.