Session programme

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.

In this Session, we will discuss new sensor measurement and mission concepts that apply advanced techniques for the study of the gravitational field of the Earth on ground and in space. Novel developments in quantum physics can excellently be used for geodetic applications, where new technologies and concepts lead to enhanced capabilities for satellite geodesy and terrestrial gravity sensing. Terrestrial gravity anomalies will be determined by observing free-falling atoms (quantum gravimetry) instead of using falling corner cubes. Additionally, changes in the gravity field can also be derived from GNSS displacement which play an increasingly important role due to their cheap and easy deployment and large number of available stations. This 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 with high spatial and temporal resolution.
Furthermore, highly precise optical clocks connected by dedicated fiber links have reached an accuracy level to measure differences of the gravity potential over long distances (relativistic geodesy), that is interesting for geodesy now. In future, relativistic geodesy might be applied for defining and realizing height systems in a new way, locally as well as globally. Moreover, accurate clocks help to improve the accuracy of the International Atomic Time standard TAI. They are important for all space geodetic techniques as well as for the realization of reference systems and their connections. One example of increasing importance is positioning and navigation with GNSS for terrestrial and space applications.
Finally, laser-interferometric ranging between test masses in space with nanometer accuracy does also belong to those novel developments. GRACE-FO will demonstrate it, and in the future even more refined concepts (tracking a swarm of satellites, space gradiometry) will be realized.
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 unforeseen 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.

The session is dedicated to aspects of high accuracy terrestrial gravity observations. Monitoring of long-term processes in geosciences with gravity meters yields many applications, e.g. in tectonics and land uplift, glacial isostatic adjustment and reveals trends in continental hydrology. Studies in these fields are subject of the session.
The International Gravity Reference System and Frame aims to provide A stable reference for absolute gravity measurements and is planned to rely on reference stations and distributed international and regional comparisons. In combination with continuous monitoring of gravity changes, a comparison function for the validation of absolute meters can be established, ensuring their traceability. Contributions to these aspects are invited. The infrastructure needed to make the frame accessible for the user on the level of national infrastructure, like updates of first order gravity networks, are within the scope of the session.
Advances in the instrumentation for absolute gravimetry are important. Contributions regarding the assessment of the uncertainty budget and systematic instrumental effects as well as the development and deployment of new technologies like quantum sensors are welcome.
The session addresses also the interpretation of high resolution temporal gravity changes, e.g. from superconducting and absolute gravimeters, including the analysis of Earth tides or the impact of water storage changes as well as geophysical applications like geothermal fields, volcano monitoring, the study of loading effects or the comparison with satellite gravity models.

Integrated modelling of gravity, magnetic, seismological and petrological data contributes to a wide range of geo-scientific research, from imaging the structure of the Solid earth and geodynamic processes (e.g. GIA and the coupling between Solid Earth and Cryosphere) to near surface investigations. The session especially welcomes contributions related to spatial and temporal variations of the Earth gravity and magnetic field at all scales and their application in an integrated context.

Many recent advances in aeronomy, space sciences, geomagnetism, and gravity arose from combining specific knowledge of these areas in interdisciplinary research. Current outstanding questions are, for example: What features of ionospheric currents do we discover when we understand the shape, strengths, and variation of the geomagnetic background field? What is the role of upward propagating atmospheric waves in energy and momentum transport into the ionosphere? Which ionospheric processes need to be better quantified to achieve complete knowledge of global core or crustal field variations? How does knowledge of the geometry of ionospheric and magnetospheric sources help in determining Earth’s conductivity in the geomagnetic field? How strongly do we need to consider Earth’s conductivity in quantifying ionospheric currents? How can we quantify and correct for ionospheric perturbations to achieve the best gravity field solutions? Finally, what can we learn about space sciences by studying ionospheric effects on geodetic measurements?

The session invites contributions on any of the subjects and in particular on results that benefit from interdisciplinary works in the areas of space science, geomagnetism, and gravity. Submissions are welcomed that contain analyses of global satellite or ground-based observations or modelling studies, including a combination of them.