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 coordinates of radio telescopes, which are part of the emerging VLBI Global Observing System, were estimated in a least squares unconstrained adjustment. The higher number of observations per time with better sky coverage, which these telescopes can produce, was optimally utilized by testing different intervals for the tropospheric delay estimation. We found that a short estimation interval of 15 min for the tropospheric gradients with a 45 min interval for the zenith wet delay perform best.

For the documentation of time and space variations of water vapor in atmosphere during the Nawdex campaign (fall 2016), a ground network of more than 1200 continuously operation reference GNSS stations has been analyzed. This network spreads from Caribbeans to Morocco through Greenland. This study presents the retrieval of Integrated Water Vapor content from GNSS measurements and their use in the evaluation of the European Centre for Medium-Range Weather Forecasts reanalyses ERAI and ERA5.

Correctly determining the orbit of Earth-orbiting satellites requires to account multiple background effects which appear in the system Earth. Usually, these effects are introduced by various complex force models, which are not always easy to handle. We publish and validate a data set of commonly used models to make it easier to track down potential issues when applying such background forces in orbit and gravity field determination.