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Logo: Heraeus Autumn School
Logo Leibniz Universität Hannover
Logo: Heraeus Autumn School
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Background and Objectives

Satellite-to-Satellite Tracking (SST) is a method to observe gravitational orbit perturbations for the determination of the spatial and temporal variations of the Earth’s gravity field. On the Gravity Recovery And Climate Experiment (GRACE) satellite mission, SST is done using a microwave ranging system between twin satellites orbiting the Earth in an altitude of about 400 km. The GRACE Follow-On mission will carry, for the first time, and in addition to the microwave ranging, a laser ranging interferometer for distance measurements with a ranging noise level of nanometers only.

In the data analysis, the SST observations are combined with measurements of orbital positions, of non-gravitational accelerations and of satellite attitude, and then introduced in a complex mathematical scheme to estimate orbit and gravity parameters such as coefficients of a spherical harmonic expansion.

The resulting global gravity models are very successfully used in the geodetic and geophysical community to determine the time variable mass distribution in the Earth system, e.g., to quantify the ice mass loss in Greenland and Antarctica, to determine the variability in ocean circulation, and to separate the contributions to the ongoing sea level rise.

After more than a decade of scientific analysis of SST data, the need to determine global and regional mass variations with better accuracy and spatial resolution becomes more and more urgent. Scientific efforts in many groups worldwide aim at achieving progress in SST measurement sensitivity, in the analysis of the overall SST satellite sensor system, and in the mathematical modeling of orbit and gravity parameters.

The aim of the autumn school “Global gravity field modeling from Satellite-to-Satellite Tracking data” is to review and teach mathematical approaches for the data analysis in the SST sensor system and for the estimation of orbit and gravity parameters from SST data. The school focuses on knowledge that is not yet found in textbooks. The program of the school will include intensive lectures on theory, evening lectures on complementary topics, as well as intensive computer exercises on the numerical implementation of the mathematical approaches using real GRACE SST data. The school will enable the students to compute their own global gravity field models from real GRACE and GRACE Follow-On data and will provide them with a sound basis for research on the further development of the modeling approaches and on improving the modeling accuracy.