The shape of our planet deviates substantially from an ideal sphere in many ways. First of all, the Earth is roughly an ellipsoid because of its rotation, bulged at the equator and flattened at the poles. Additionally, high mountains on the continents and deep valleys in the oceans crumple its surface.

More interesting from a geoscientific point of view, however, are the spatial and temporal variations of the Earth's gravitational field that produce additional deviations from the ideal sphere. These deviations are caused by large scale mass variations due to mantle convection currents resulting in motions of the whole Earth body (e.g. variation of Earth’s rotation) or parts of it (e.g. deformation of the lithosphere visible in the Mid Atlantic ridge, at subduction zones, in plate kinematics, volcanism, or Earth quakes). Additionally, luni-solar and planetary gravitation, atmospheric pressure and winds, ocean circulation and tides, ocean loading, variations in the continental water cycle or melting of ice in Polar regions and glacier systems cause spatial and temporal variations in the gravity field. 

To observe these mass distribution and mass variation in System Earth on a global scale, with homogeneous accuracy and over long time periods dedicated gravity satellite missions are required.

Section 1.2 develops and operates these missions in strong collaboration with German Industry, NASA, ESA, DLR and the German Satellite Operations Center (GSOC). Analysis of the mission science data is performed using our own developed Earth Parameter and Orbit System (EPOS) software using up to date international standards.

GFZ-1, the first satellite of the GFZ, designed as a small, passive satellite and equipped with 60 retro-reflectors to be illuminated from the ground by the global network of satellite laser ranging (SLR) systems has been used end of last century together with various other geodetic satellites to improve our knowledge of the Earth’s gravity field. A completely new generation of Low Earth Orbiting (LEO) satellites, equipped with onboard GPS receivers and highly precise inter-satellite and accelerometry instrumentation, enabled scientists since beginning of this century not only to observe the Earth‘s gravitational field with much higher spatial resolution but also, for the very first time, its temporal variability.

The individual satellites CHAMP (CHAllenging Minisatellite Payload, 2000-2010) and GOCE (Gravity field and steady-state Ocean Circulation Explorer, 2009-2013), as well as the twin satellites of the GRACE (Gravity Recovery and Climate Mission, 2002-2017) mission can exactly measure even the smallest accelerations caused by gravity changes. GFZ played a leading role in the development, operation and analysis of these modern satellite missions and were part of the joint US/German GRACE Science Data System (SDS), provided the GRACE Deputy Operations Mission Manager and were member within ESA’s GOCE High Level Processing Facility. Together with NASA we developed the GRACE-FO (Follow-on) mission which was successfully launched on May 22, 2018 and which now continues the time series of GRACE.

Together with the DLR, we are currently developing the third GRACE mission called GRACE-C (Continuity), which, after GRACE-FO, will again extend the time series after launch end of 2028. Here, we are again part of the SDS and again responsible for mission operations after launch. For this purpose, we also operate the primary receiving station for both missions in Ny-Ålesund on  Spitsbergen. The monthly release 06 Level-2 (represented in spherical harmonic coefficients) and Level-3 (user-friendly, post-processed gridded data) are provided to the international users free of charge and on a regular basis via the ISDC (Information System and Data Center) and GravIS  (Gravity Information System).

In order to further improve the data quality of GRACE and GRACE-FO, we are leading the DFG-funded research group NEROGRAV (New Refined Observations of Climate Change from Spaceborne Gravity Missions) and are working on two subprojects.

GRACE-C is planned to form the Mass-change And Geoscience International Constellation (MAGIC) together with an ESA Next Generation Gravity Mission from 2032 to significantly increase the temporal and spatial resolution of the previous monthly gravity fields. Here, the section is involved in various simulation studies for ESA here.

The analysis of these data includes instrument data pre-processing, precision orbit determination and routine generation of various static and time-variable EIGEN (European Improved Gravity model of the Earth by New techniques) gravity field models which are used for many applications in Earth system science such as monitoring the continental global water cycle, melting of large glacier systems, or analysis of deep ocean currents. These so-called 'static satellite only models (purely derived from satellite data)' are of special interest as they have been derived independent from terrestrial data. These models are further combined (within Working Group 2) with terrestrial gravimetry data to ultra-high spatial resolution global models.

Below you find some recent publications of the working group 1. The section's complete list of publications can be found here. A list of GRACE/GRACE-FO related publications can be found here.

Dahle, C., Boergens, E., Sasgen, I., Döhne, T., Reißland, S., Dobslaw, H., Klemann, V., Murböck, M., König, R., Dill, R., Sips, M., Sylla, U., Groh, A., Horwath, M., Flechtner, F. (2025): GravIS: mass anomaly products from satellite gravimetry. - Earth System Science Data, 17, 2, 611-631.
https://doi.org/10.5194/essd-17-611-2025

Wilms, J., Hauk, M., Panafidina, N., Murböck, M., Neumayer, K. H., Dahle, C., Flechtner, F. (2025): Optimized gravity field retrieval for the MAGIC mission concept using background model uncertainty information. - Journal of Geodesy, 99, 21.
https://doi.org/10.1007/s00190-024-01931-5

Ince, E. S., Abrykosov, O., Förste, C. (2024): GDEMM2024: Global Digital Elevation Merged Model 2024 for surface, bedrock, ice thickness, and land-type masks. - Scientific Data, 11, 1087.
https://doi.org/10.1038/s41597-024-03920-x

Koch, F., Gascoin, S., Achmüller, K., Schattan, P., Wetzel, K., Deschamps‐Berger, C., Lehning, M., Rehm, T., Schulz, K., Voigt, C. (2024): Superconducting Gravimeter Observations Show That a Satellite‐Derived Snow Depth Image Improves the Simulation of the Snow Water Equivalent Evolution in a High Alpine Site. - Geophysical Research Letters, 51, 24, e2024GL112483.
https://doi.org/10.1029/2024GL112483

Meyer, U., Lasser, M., Dahle, C., Förste, C., Behzadpour, S., Koch, I., Jäggi, A. (2024): Combined monthly GRACE-FO gravity fields for a Global Gravity-based Groundwater Product. - Geophysical Journal International, 236, 1, 456-469.
https://doi.org/10.1093/gji/ggad437

Shihora, L., Liu, Z., Balidakis, K., Wilms, J., Dahle, C., Flechtner, F., Dobslaw, H. (2024): Accounting for residual errors in atmosphere–ocean background models applied in satellite gravimetry. - Journal of Geodesy, 98, 27.
https://doi.org/10.1007/s00190-024-01832-7

Voigt, C., Sulzbach, R., Dobslaw, H., Weise, A., Timmen, L., Deng, Z., Reich, M., Stolarczuk, N., Peters, H., Fietz, M., Thomas, M., Flechtner, F. (2024): Non‐tidal ocean loading signals of the North and Baltic Sea from terrestrial gravimetry, GNSS, and high‐resolution modeling. - Geophysical Research Letters, 51, 13, e2024GL109262.
https://doi.org/10.1029/2024GL109262