Section 1.1: GPS/GALILEO Technologies

To better understand something that is very close, it often helps to view it from a distance. This is also true for Earth science research, where the perspective from near-Earth space allows a completely new look at our planet. For example, the orbits of satellites can give us information about the shape of the Earth and its gravitational field. If the mass of the Earth were uniformly distributed in its interior, our home planet would have the shape of an ideal sphere. In reality however, the inside of the Earth is anything but homogeneous. Thick sedimentary layers alternate with huge blocks of granite. The roots of the high mountain ranges reach deep into the Earth, while the crust under the oceans is relatively thin. Variations in the density of the material in the Earth's mantle and core also influence its gravitational field and through that, the Earth's shape. These differences affect the details of a satellite's orbit. Through precision measurements of the satellites' paths, we can infer differences in gravity from one place to another and through time. These differences provide information about the structure of the Earth's interior and clues about the dynamic changes within.

In addition to the precise determination of satellite orbits, we analyse recordings from many different sensors on numerous satellites. Among them are the altitude sensors for precise surveying of ocean and ice surfaces. The signals from current GPS and future Galileo satellites give information about the figure and movements of the Earth's crust. They define the reference system against which such measurements as the rise in sea level are determined. They also can be used to assess the condition of the atmosphere. We also analyse images taken by remote sensing satellites, in order to understand the effects of climate change and to develop strategies to reduce the risk caused by natural catastrophes.

The interplay of information from all these measurements gives a dynamic overview of the Earth which forms the basis for computer modelling of the past history of the measured parameters, and their future development. Our simulations range from the dynamics of the Earth's core and its surface to the investigation of the interactions between atmosphere, the oceans and the solid Earth.