Satellite project measures gravity, predicts deluges
The European Gravity Service for Improved Emergency Management (EGSIEM) project aims at improving the methods to predict deluges. "In view of the climate change, the frequency of extreme weather conditions is increasing significantly", says Adrian Jäggi from the Astronomical Institute of the University of Bern. "For this reason it is becoming increasingly important to have reliable and relevant data at one’s disposal to take appropriate measures to save life, infrastructure and property in time."
But how can a satellite capture, and even predict the probability of a deluge? The measurement principles utilised by the Bern researchers are anything but self-explanatory and straightforward. First, to predict an inundation, it is important to know the saturation of the subsoil with water. Ironically, the subsoil can be monitored best from space. The GRACE (Gravity Recovery and Climate Experiment) satellite system, launched already in 2002, enables users to analyse terrestrial mass changes. The distribution of masses (for instance, water) directly influences the terrestrial field of gravity. This, in turn, affects the satellite orbit.
In the case that water is gathering in a certain region, the mass of this region increases, and the satellite orbit is changing. Though the deviation is only marginal – the orbit changes by the thickness of a hair – it can be measured: Within the GRACE system, two identical satellites follow each other in a correlated polar orbit; they continuously measure their mutual distance by means of microwaves. If the leading satellite approaches a region with increased gravity, it experiences a slight acceleration. Measuring this effect allows highly accurate conclusions as to the earth gravity. This enables the scientists to predict the regions where natural and artificial reservoirs are filled and at which speed.
Within the EGSIEM project, the institute for terrestrial measurements (IfE) at the University of Leipzig assumes the task of analysing the GRACE sensor data. In this context, a team of researchers led by Prof. Jakob Flury will develop sensor data deviation models that will enable modelling the earth’s field of gravity at even higher accuracy.
The system will also enable the prediction of droughts. However, predicting droughts is less time-critical since acridities announce themselves over weeks.
Members of the EGSIEM consortium are, besides the university of Bern and the IfE, the university of Luxembourg, the Deutsches GeoFoschungsZentrum (GFZ) in Potsdam (Germany), Géode & Cie (Toulouse, France) and the technical University of Graz (Austria).
Related information:
Gravity Recovery And Climate Experiment
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