This study focuses on the comparison of different solar radiation pressure (SRP) strategies combined with a-priori information and empirical SRP parameterization. Analysis of precise orbits as well as estimated empirical SRP parameters based on various SRP strategies shows visible differences and indicates the deficiencies of a-priori model or empirical parameterization. The orbit difference patterns presented in this study may give the view on how to improve the current SRP models.

The HY-2A calibration microwave radiometer (CMR) water vapor product is validated using ground-based GNSS observations along the coastline and shipborne GNSS observations over the Indian Ocean. The validation result shows that HY-2A CMR PWV agrees well with ground-based GNSS PWV, with 2.67 mm in rms within 100 km and an RMS of 1.57 mm with shipborne GNSS for the distance threshold of 100 km. Ground-based GNSS and shipborne GNSS agree with HY-2A CMR well.

The paper focuses on the analyses of the global occurrence of equatorial plasma bubble events using S4 data that were calculated from GPS radio occultation measurements of the FormoSat-3/COSMIC mission. The advantage in using radio occultation data is that we get information not only on the occurrence and intensity of the equatorial bubble events, but also on the altitude distribution. We analyzed a 10.5-year time series of COSMIC data and demonstrated a strong dependence on the solar cycle.

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The recent dramatic development of multi-GNSS constellations brings great opportunities and potential for more enhanced precise positioning, navigation, timing, and other applications. In this contribution, we develop a numerical weather model (NWM) constrained PPP processing system to improve the multi-GNSS precise positioning. Compared to the standard PPP solution, significant improvements of both convergence time and positioning accuracy are achieved with the NWM-constrained PPP solution.