Products of Space Geodesy and Links to Earth Science and Astronomy

Products of Space Geodesy such as Earth Orientation Parameters, polar motion and precise positioning, as well as various applications of these products are of importance to both Earth Sciences and Astronomy. Global geodetic site positions and velocities find application in geodynamics, on a local and global scale, including plate mobility and tectonics, on time scales varying from sub-seconds to millions of years. Precise orbit determination provides information on Earth’s gravity field and changing shape, it also allows calibration of satellite platforms which measure ocean and ice levels. Nuisance parameters such as observable delays due to the ionosphere and atmosphere provide additional information about total electron content and integrated water vapour. Global reference frames on Earth, and celestial reference frames in the universe are maintained and linked to one another, providing unique positioning capability on Earth and in space. Accuracies and precision of techniques and instrumentation are such now that even relativistic parameters can be tested to new levels. Future developments are very promising as the scientific community moves towards implementation of the Global Geodetic Observing System (GGOS), where sub-cm accuracy on global scales is the objective, requiring a factor ten improvement in measurement accuracies and improved models in terms of factors which affect measuring accuracies. The different Space Geodesy techniques will be discussed briefly with examples of their applications, their links to astronomy and the earth sciences, as well as current and future developments, and South Africa’s role currently and in the near future.