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.

Tropospheric delays must be taken into account when analyzing GNSS data. Several tropospheric delay models and mapping functions are available, for instance the Vienna Mapping Functions 1 (VMF1) and the Global Mapping Function (GMF). Recently, a refined version of VMF1, VMF3, has been released. This study aims to assess the performance of VMF3 for GNSS observations in Indonesia, by analyzing the data using Bernese GNSS Software, version 5.2 with Precise Point Positioning method.

The precise knowledge of the orientation of an Earth fixed coordinate system with respect to space is of great importance for all tasks of positioning and navigation. In this work we investigated the potential of combining measurements of Very Long Baseline Interferometry and a large ring laser gyroscope to derive highly resolved parameters describing this orientation. The ring laser is not yet at the same level of accuracy and therefore does not substantially influence the results.