K Börger

Combination of various observation techniques for regional modeling of the gravity field

Modeling a very broad spectrum of the Earths gravity field needs observations from various measurement techniques with different spectral sensitivities. Typically, high-resolution regional gravity data are combined with low-resolution global observations. To exploit the gravitational information as optimally as possible, we set up a regional modeling approach using radial spherical basis functions, emphasizing the strengths of various data sets by the flexible combination of high- and middle-resolution terrestrial, airborne, shipborne, and altimetry measurements. The basis functions are defined and located in the region of interest in such a manner, which the highest measure of information of the input data is captured. Any functional of the Earths gravity field can be derived, as, e.g., quasi-geoid heights or gravity anomalies. Here we present results of a study area in Northern Germany. A comprehensive cross validation to external observation data delivers standard deviations less than 5 cm. Differences to an existing regional quasi-geoid model count on average ±6 cm and proof the plausibility of our solution. The comparison with existing global models reaches higher standard deviations for the more sensitive gravity anomalies as for quasi-geoid heights, showing the additional value of our solution in the high frequency domain. Covering a broad frequency spectrum, our regional models can be used as basis for various applications, such as refinement of global models, national geoid determination, and detection of mass anomalies in the Earths interior.

Monitoring Space Weather at GSSAC

The sun emits electromagnetic waves as well as particles, i.e. electrons and protons, and the term space weather covers all phenomena and issues related to these radiations. Space weather in general affects technical systems and therefore it has to be monitored. As well as normal weather does, space weather shows regular, but sometimes irregular behaviour, and in particular the latter can lead to significant threats to technical systems. The principal mission of the German Space Situational Awareness Center (GSSAC) is to provide a recognized space picture, which comprises the detection, prediction and assessment of hazards coming from space for the safety of systems and operations. This definitely includes space weather, since it has an enormous impact on satellites, satellite’s subsystem functionality, communication and GPS. In this regard the ionosphere has a key role. The ionosphere represents the state and the behaviour of space weather in a suitable way. Surveying the ionosphere, modelling and forecasting are important subjects at GSSAC. Hence, this presentation deals with the GSSAC activities on space weather monitoring, where first of all observation methods and modelling approaches are considered.