Comparative Assessment of YUNYAO and COSMIC-2 Radio Occultation Bending-Angle Observations

GNSS radio occultation (RO) measurements are essential to global Earth observation systems. The YUNYAO constellation offers dense global coverage, high vertical resolution, and all-sky capabilities. This study proposes an improved bending-angle observation operator and presents a comprehensive evaluation of YUNYAO’s bending-angle observations against those from COSMIC-2 for December 2024. Our results indicate that YUNYAO achieves near-global coverage and provides substantially more observations than COSMIC-2. Within their region of overlap, the bending-angle quality of YUNYAO is broadly comparable to that of COSMIC-2, though YUNYAO shows a more pronounced negative relative bias above 30 km. In the vertical profile obtained by horizontally averaging the relative bias, YUNYAO exhibits a smaller bias than COSMIC-2 below 30 km. For both RO constellations, bending angles retrieved from Galileo signals exhibit a smaller relative bias than those retrieved from GLONASS in the upper atmosphere. Finally, performance differences are also evident among YUNYAO’s individual receivers.