Gravity models from NGGM simulations


The Next Generation Gravity Mission (NGGM) represented by the Mass-change and Geosciences International Constellation (MAGIC) to be carried out in collaboration between ESA and NASA, will presumably be launched by the end of the present decade. The mission will acquire observations of inter-satellite distances between two pairs of satellites along two different orbits (Bender formation), with the objective of long-term monitoring of temporal variations of the Earth gravity field with high temporal (up to 3 days) and spatial (100 km) resolution. So in this project, a fundamental issue which is being considered is the study of the time-variable part of the Earth gravity field and the modelling of the aliasing effects, both tidal and non-tidal. 

Different strategies have been investigated at POLIMI for the application of the space-wise approach, since the mathematical model for the processing of the SST measurements (inter-satellite distances) can be based on different methods allowing to map the observed geometric quantity into a functional of the gravitational potential. As a result, the space-wise approach mathematical model has been adapted to deal with Low- Low Satellite-to-Satellite Tracking observations in terms of Line-of-Sight acceleration differences. The algorithm has been tested with numerical simulations based on NGGM simulated scenarios, leading to results comparable with those found in literature. In the gridding procedure, which is the core of the space-wise approach, the signal covariance adaptation will undergo further refinement, especially to model non-stationarity due to the time-variable signal.

The validation of the results of the application of the space-wise approach to NGGM simulated data is carried out at UNITN by comparison with the results of a “classic” solution for the estimation of the gravity field. 

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