The US/German GRACE Follow-on (GRACE-FO) mission, successfully launched on 22 May 2018, prolongs the observations of the Gravity Recovery and Climate Experiment (GRACE). Satellite gravimetry missions such as GRACE, GRACE-FO and the Gravity field and steady-state Ocean Circulation Explorer (GOCE) have showed their fundamental impact for climate research studies and other geophysical or geodetic applications. The gravity field solutions can be complemented by data from other non-dedicated satellite missions like SWARM.
The great success of these missions clearly shows that global gravity variations can be at best monitored from space. Therefore, various initiatives are ongoing to prepare for future gravity missions: simulation studies have been performed, user and mission requirements have been defined and potential measurement equipment and orbit scenarios have been investigated.

This session solicits contributions about
(1) results from satellite gravimetry missions as well as from non-dedicated missions in terms of
- data analyses
- combination synergies
- Earth science applications
(2) status and study results for future gravity field missions.

Current developments in quantum physics will enable novel applications and measurement concepts in geodesy and Earth observation. In this Session, we will discuss new sensors and mission concepts that apply advanced techniques for the study of the gravitational field of the Earth on ground and in space. Terrestrial gravity anomalies will be determined by observing free-falling atoms (quantum gravimetry) gradually replacing the falling corner cubes. This technique can also be applied for future gradiometric measurements in space.
According to Einstein’s theory of general relativity, frequency comparisons of highly precise optical clocks connected by optical links give access to differences of the gravity potential (relativistic geodesy) for gravity field recovery and height determination. In future, precise optical could clouds be applied for defining and realizing height systems in a new way, and moreover, help to improve the accuracy of the International Atomic Time scale TAI. They are important for all space geodetic techniques as well as for the realization of reference systems and their connections.
Additionally, laser interferometry between test masses in space with nanometer accuracy – which has been realized in the GRACE-FO mission – belongs to these novel concepts, and in the future even more refined concepts (tracking a swarm of satellites, space gradiometry) will be realized.
Finally, changes in the gravity field can be derived from GNSS displacements which play an increasingly important role due to the relatively cheap and easy deployment of new GNSS receivers and the large number of available stations.
These techniques will open the door for a vast bundle of applications such as fast local gravimetric surveys and exploration, and the observation of Earth system processes from space with high spatial and temporal resolution.
We invite presentations to illustrate the principles and state of the art of those novel techniques and the application of the new methods for terrestrial and satellite geodesy (where local and global mass variations and surface deformations will be observed with substantially improved accuracy and resolution, variations that reflect changes in the Earth system), navigation and fundamental physics. We also welcome papers for further applications and invite contributions covering the theoretical description of the new methods, introducing novel theoretical concepts as well as new modelling schemes.

Gravity and magnetic field data contribute to a wide range of geo-scientific research, from imaging the structure of the earth and geodynamic processes (e.g. mass transport phenomena or deformation processes) to near surface investigations. The session is dedicated to contributions related to spatial and temporal variations of the Earth gravity and magnetic field at all scales. Contributions to modern potential field research are welcome, including instrumental issues, data processing techniques, interpretation methods, innovative applications of the results and data collected by modern satellite missions (e.g. GOCE, GRACE, Swarm), potential theory, as well as case histories.

Terrain gravimetry is a powerful geophysical tool that, through sensing changes in subsurface mass, can supply unique information on the dynamics of underground fluids, like water, magma, hydrocarbons, etc. This is critically important for energy industry (not just petroleum and natural gas, but also geothermal), resource management (particularly, with regard to water), and natural hazards (especially volcanoes).
Despite its potential, terrain gravimetry is currently underexploited, owing to the high cost of available instrumentation and the difficulty in using it under harsh environmental conditions and to the major challenge posed by retrieving useful information from gravity changes in noisy environments.
Major technology developments have recently occurred in instrumentation and methodology and are being demonstrated, opening up new perspectives to increase the capability of terrain gravimetry. On one hand, new types of sensors are being developed and ruggedized, expanding the measurement capabilities. On the other hand, methodologies and workflows are developed to exploit more efficiently hybrid networks of sensors. As an example, a recently funded H2020 project, called NEWTON-g, targets the development and field application of a “gravity imager” exploiting MEMS (relative) and quantum (absolute) gravimeters. These advancements will give new impulse to terrain gravimetry, thus helping its transition from a niche field into a cornerstone resource for geophysical monitoring and research. However, for this transition to succeed, technology developments must be complemented by constructive feedback from the gravimetry community
This session aims at bringing together instrument and tool developers and end-users of terrain gravimetry in a variety of fields, including, but not limited to, hydrology, volcanology and petroleum geology. We aim at discussing the state of the art of terrain gravimetry and the added value it provides with respect to other geophysical techniques, as well as the exciting opportunities offered by the new technologies under development.