Global ionosphere maps based on GNSS, satellite altimetry, radio occultation and DORIS
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Global ionosphere maps (GIMs) provided by the global navigation satellite systems (GNSS) data are essential in ionospheric research as the source of the global vertical total electron content (VTEC). However, conventional GIMs experience lower accuracy and reliability from uneven distribution of GNSS tracking stations, especially in ocean areas with few tracking stations. The orbits of ocean altimetry satellite cover vast ocean areas and can directly provide VTEC at nadir with two different wavelengths of radio waves. Radio occultation observations and the beacons of Doppler orbitography and radio positioning integrated by satellite (DORIS) are evenly distributed globally. Satellite altimetry, radio occultation and DORIS can compensate GNSS data in ocean areas, allowing a more accurate and reliable GIMs to be formed with the integration of these observations. This study builds GIMs with temporal intervals of 2 h by the integration of GNSS, satellite altimetry, radio occultation and DORIS data. We investigate the integration method for multi-source data and used the data in May 2013 to validate the effectiveness of integration. Result shows that VTEC changes by −11.0 to −7.0 TECU after the integration of satellite altimetry, radio occultation and DORIS data. The maximum root mean square decreases by 5.5 TECU, and the accuracy of GIMs in ocean areas improves significantly.
KeywordsGlobal ionosphere maps Total electron content GNSS Satellite altimetry Radio occultation DORIS
We thank CDDIS for providing GNSS and DORIS observation data, CNES and NOAA for providing Jason-1 and Jason-2 GDR data, respectively, NOAA for providing ionosonde data and CDAAC for providing COSMIC “ionprf” data. This study was funded by the National Natural Science Foundation of China (41404031) and Key Laboratory of Geo-informatics of State Bureau of Surveying and Mapping (201420).
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