EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2026-4663 Global Sampling Characteristics and Coverage Complementarity of 12 GNSS Radio Occultation Constellations Lu Wenqiang https://orcid.org/0000-0002-1191-257X 1 2 3 9 Chen Ran 4 5 9 Xu Na 1 2 3 Meng Xiangguang 4 5 Xue Lei 6 Liao Mi 1 2 3 Liu Yan 7 Guo Peng 8 Yang Guanglin 1 2 3 Hu Xiuqing 1 2 3 Zhao Xiangang 1 2 3 Sun Yueqiang 4 5 National Satellite Meteorological Center/National Center for Space Weather, Beijing 100081, China Innovation Center for Fengyun Meteorological Satellite (FYSIC), Beijing 100081, China Key Laboratory of Radiometric Calibration and Validation for Environmental Satellites, CMA, Beijing 100081, China National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China National Meteorological Information Center, China Meteorological Administration, Beijing 100081, China Earth System Modeling and Prediction Center, China Meteorological Administration, Beijing 100081, China Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China These authors contributed equally to this work. 10 08 2026 2026 1 31 Copyright: © 2026 Wenqiang Lu et al. 2026 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-4663/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-4663/egusphere-2026-4663.pdf

This study uses observations from COSMIC-2, FY-3, GRACE-C/D, KOMPSAT-5, MetOp-A/C, PAZ, PlanetiQ, Sentinel-6A, Spire, TerraSAR-X/TanDEM-X, TM-1, and YY-1 during 1–7 January 2026 to compare their spatial distributions, grid coverage, local-time sampling, and retrieval accuracy; it also assesses the benefits of multi-mission integration and the potential effects of COSMIC-2 retirement on the integrated observing capability. The results show that orbital configuration determines latitudinal and local-time sampling, whereas event abundance and constellation size primarily control grid coverage. Large constellations such as YY-1 and TM-1 provide the strongest global continuity, while missions with different orbital inclinations offer complementary sampling across latitude bands. Combining all missions substantially reduces spatial gaps and provides near-global coverage at 1.0° and 2.0° resolutions. Within 6 h windows, joint coverage reaches 70.98 % at 2.0° resolution. The combined observations also broaden local-time sampling, whereas COSMIC-2 remains particularly important for equatorial coverage. Therefore, the retirement of COSMIC-2 would reduce equatorial sampling capability and should be considered in the development of future multi-mission GNSS-RO observing systems. Comparisons with ERA5 indicate broadly consistent retrieval accuracy among most missions between 10 and 35 km, with larger differences in the lower troposphere. These findings demonstrate the value of integrating missions with diverse orbital configurations and highlight the need to sustain complementary sampling after the retirement of key missions.

 National Natural Science Foundation of China U2542214 U2442216