Geodesy is a fundamental Earth sciences discipline that describes the Earth’s place in space (i.e., shape, size, orientation, gravity field) over time. Although often invisible, geodesy is widely used in various sectors where precise positioning, navigation, and timing are required, and is essential for socio-economic development. In the coming decade, the use of geospatial information is expected to grow substantially (e.g., for hazard risk assessment, natural resource monitoring, pandemic prevention), leading to increased demand for geodetic services2. But where do we stand today? Are we fully aware of the critical role of geodesy for societal needs? And what challenges are we facing?
This session will present the First Joint Development Plan for Global Geodesy, along with the concept of a global geodesy supply chain. The panellists will discuss key weaknesses3 as well as implementation of potential practical solutions to increase the visibility of geodesy. The session will also explore ways to improve cooperation between different scientific groups and policymakers to strengthen the global geodesy supply chain for the benefit of humanity and the planet.

Remarkable advances over recent years prove that geodesy today develops under a broad spectrum of interactions, including theory, science, engineering, technology, observations, and practice-oriented services. Geodetic science accumulates significant results in studies towards classical geodetic problems and problems that only emerged or gained new interest, in many cases due to synergistic activities in geodesy and tremendous advances in the instrumentations and computational tools. In-depth studies progressed in parallel with investigations that led to a broadening of the traditional core of geodesy. The scope of the session is conceived with a certain degree of freedom, even though the session intends to provide a forum for all investigations and results of a theoretical and methodological nature.

Within this concept, we seek contributions concerning problems of reference frames, gravity field, geodynamics, and positioning, but also studies surpassing the frontiers of these topics. We invite presentations discussing analytical and numerical methods in solving geodetic problems, advances in mathematical modelling and statistical concepts, or the use of high-performance facilities. Demonstrations of mathematical and physical research directly motivated by geodetic practice and ties to other disciplines are welcome. In parallel to theory-oriented results, examinations of novel data-processing methods in various branches of geodetic science and practice are also acceptable.

This session aims to showcase novel applications of methods from the field of artificial intelligence and machine learning in geodesy.

In recent years, the exponential growth of geodetic data from various observation techniques has created challenges and opportunities. Innovative approaches are required to efficiently handle and harness the vast amount of geodetic data available nowadays for scientific purposes, for example when dealing with “big data” from Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR). Likewise, numerical weather models and other environmental models important for geodesy come with ever-growing resolutions and dimensions. Strategies and methodologies from the fields of artificial intelligence and machine learning have shown great potential not only in this context but also when applied to more limited data sets to solve complex non-linear problems in geodesy.

We invite contributions related to various aspects of applying methods from artificial intelligence and machine learning (including both shallow and deep learning techniques) to geodetic problems and data sets. We welcome investigations related to (but not limited to): more efficient and automated processing of geodetic data, pattern and anomaly detection in geodetic time series, images or higher-dimensional data sets, improved predictions of geodetic parameters, such as Earth orientation or atmospheric parameters into the future, combination and extraction of information from multiple inhomogeneous data sets (multi-temporal, multi-sensor, multi-modal fusion), feature selection and sensitivity, downscaling geodetic data, and improvements of large-scale simulations. We strongly encourage contributions that address crucial aspects of uncertainty quantification, interpretability, and explainability of machine learning outcomes, as well as the integration of physical relationships into data-driven frameworks.

By combining the power of artificial intelligence with geodetic science, we aim to open new horizons in our understanding of Earth's dynamic geophysical processes. Join us in this session to explore how the fusion of physics and machine learning promises advantages in generalization, consistency, and extrapolation, ultimately advancing the frontiers of geodesy.

Precise orbit determination is of central importance for many applications of geodesy and earth science. The challenge is to determine satellite orbits in an absolute sense at the centimeter or even sub-centimeter level, and at the millimeter or even sub-millimeter level in a relative sense. Four constellations of GNSS satellites are available and numerous position-critical missions (e.g. altimetry, gravity, SAR and SLR missions) are currently in orbit. Altogether, outstanding data are available offering new opportunities to push orbit determination to the limit and to explore new applications.

This session aims to make accessible the technical challenges of orbit determination and modelling to the wider community and to quantify the nature of the impact of dynamics errors on the various applications. Contributions are solicited from, but not limited to, the following areas: (1) precise orbit determination and validation; (2) satellite surface force modelling; (3) advances in modelling atmospheric density and in atmospheric gravity; (4) advances in modelling earth radiation fluxes and their interaction with space vehicles; (5) analysis of changes in geodetic parameters/earth models resulting from improved force modelling/orbit determination methods; (6) improvements in observable modelling for all tracking systems, e.g. SLR, DORIS, GNSS and their impact on orbit determination; (7) advances in combining the different tracking systems for orbit determination; (8) the impact of improved clock modelling methods/space clocks on precise orbit determination; (9) advances in modelling satellite attitude; (10) simulation studies for the planned co-location of geodetic techniques in space mission GENESIS.

A global Terrestrial Reference Frame (TRF) is fundamental for monitoring the Earth's rotation in space, and to many Earth science applications that need absolute positioning and precise orbit determination of near-Earth satellites. An accurate and stable TRF is especially needed for the quantification of global change phenomena such as sea level rise and current ice melting. This session generally welcomes contributions on both the computation and use of TRFs.

The computation of TRFs relies on space geodetic observations acquired by ground networks of stations and requires the estimation of a large number of parameters including station positions and Earth Orientation Parameters. Nowadays, measurement biases and imperfect background models are the main factors limiting the accuracy of TRFs. This session therefore welcomes contributions that develop strategies to overcome systematics in space geodetic observing systems such as long-term mean range biases in SLR observations, gravitational deformation of VLBI antennas, GNSS antenna phase patterns, etc.

The second objective of this session is to bring together contributions from individual technique services, space geodetic data analysts, ITRS combination centers and TRF users to discuss the TRF solutions produced by different groups, with a special focus on their comparison, evaluation and updates. The understanding of the discrepancies between the terrestrial scale observed by the different space geodetic techniques, the determination of new local tie vectors at co-location sites, the improvement of geocentre motion determination and the assessment of observed non-linear station motions by comparison with physics-based deformation models are of particular interest. Finally, with the development of the GENESIS mission, contributions on the handling and the impact of co-located instruments of individual techniques onboard satellite missions (space ties) for TRF realization are also highly welcome.

In general, presentations regarding any type of development that could improve future TRF solutions are warmly encouraged.

The Global Geodetic Observing System (GGOS) relies on the geodetic infrastructure established and managed by a large international scientific community organised under the auspices of the International Association of Geodesy (IAG). In particular, the Scientific Services of the IAG facilitate the global coordination of geodetic activities and ensure reliable products not only for other Earth sciences but also for a diverse and growing number of daily applications. The observing system built on this solid and broad base acts as a unifying umbrella for the IAG Services to ensure a comprehensive and integrated monitoring of the Earth’s shape, gravity field and rotation.
The GGOS is committed not only to advancing geodetic methods and addressing the relevant science issues of geodesy and geodynamics, but also issues relevant to society (global risk management, geo-hazards, natural resources, climate change, severe storm forecasting, sea level estimations and ocean forecasting, space weather, and others). To this end, the current GGOS strategy seeks strong cooperation within the geodetic, geodynamic and geophysical communities, and with organisations involved in global Earth observation and with UN bodies related to geodesy.
This session encourages contributions related to, but not limited to, the activities of the IAG Services, from data acquisition and delivery to the release of final products from either single or multiple techniques; identification and storage of geodetic data; status and potential extension of observing networks; development of basic concepts as essential variables for Earth system monitoring; international cooperation with the UN and other stakeholders; efforts to promote data sharing and improve observing networks; emerging techniques, and future programs and missions relevant for geodesy.

In recent years, we have observed steady progress in signals, services, and satellite deployment of Global Navigation Satellite Systems (GNSS). Consequently, modernizing existing GNSS systems and developing new constellations have moved us towards a new era of multi-constellation and multi-frequency GNSS signal availability. Meanwhile, the technology development provided high-grade GNSS user receivers to collect high rate, low noise, and multipath impact measurements. Also, recent extraordinary progress in low-cost GNSS chipsets, smartphones, and sensor fusion must be acknowledged. Such advancements boost GNSS research and catalyze an expansion of traditional satellite navigation to novel areas of science and industry. On one side, the developments stimulate a broad range of new GNSS applications. On the other side, they result in new challenges in data processing. Hence, algorithmic advancements are needed to address the opportunities and challenges in enhancing high-precision GNSS applications' accuracy, availability, interoperability, and integrity.
This session is a forum to discuss advances in high-precision GNSS algorithms and their applications in geosciences such as geodesy, geodynamics, seismology, tsunamis, ionosphere, troposphere, etc.
We encourage but do not limit submissions related to:
- Processing algorithms in high-precision GNSS,
- Multi-GNSS benefits for Geosciences,
- Multi-constellation GNSS processing and product standards,
- High-rate GNSS,
- Low-cost receiver and smartphone GNSS observations for precise positioning, navigation, and geoscience applications,
- Precise Point Positioning (PPP, PPP-RTK) and Real Time Kinematic (RTK),
- GNSS and other sensors (accelerometers, INS, etc.) fusion,
- GNSS products for high-precision applications (orbits, clocks, uncalibrated phase delays, inter-system and inter-frequency biases, etc.),
- Troposphere and ionosphere modeling with GNSS,
- CORS services for Geosciences (GBAS, Network-RTK, etc.),
- Precise Positioning of EOS platforms,
- GNSS for natural hazards prevention,
- Monitoring crustal deformation and the seismic cycle of active faults,
- GNSS and early-warning systems,
- GNSS reflectometry.

The precise positioning at centimeter level with GPS has been available for decades, which is lately strengthened by the emerging Global Navigation Satellite Systems (GNSS), such as the European Galileo, Chinese BeiDou, and Russian GLONASS, making positioning cost-effective and compact. OEM boards of various qualities and single-board microcontrollers allow construction of low-cost/mass-market/consumer-grade GNSS receivers that are used for applications requiring precise positioning, sensor synchronisation, GNSS reflectometry, phase time delay and signal attenuation. These applications are spread over fields such as geodesy, hydrology, (hydro-)meteorology, volcanology, natural hazards, cryospheric and biospheric sciences and (urban) navigation. Moreover, they are valuable for deriving and monitoring geophysical phenomena such as sea-level rise, crustal or surface deformation. We solicit abstracts on instrumentation and innovative applications in different fields of research, as well as algorithms, and sensor calibration and integration. We welcome any other contributions that highlight the challenges of using low-cost GNSS receivers and antennas.

GNSS Interferometric Reflectometry (GNSS-IR) is an emerging ground-based remote sensing technique that uses reflected GNSS signals. This technique has been applied to measure a variety of variables including water level, significant wave height, snow accumulation, permafrost melt, soil moisture, vegetation water content and coastal subsidence. As the number of developers and users of GNSS-IR continues to grow, this session seeks to highlight advances in the (near real-time) acquisition, processing, analysis and application of GNSS-IR data in environmental sensing. The session welcomes contributions related to the algorithmic and technical improvement of GNSS-IR models, as well as the development of open-source hardware and software. We encourage discussions on GNSS-IR delivery products and their validation, the optimal exploitation of geodetic and affordable GNSS sensors for applications in interferometric reflectometry and initiatives for (near) real-time monitoring of environmental variables.

This session invites innovative Earth system and climate studies employing geodetic observations and methods. Modern geodetic observing systems have been instrumental in studying a wide range of changes in the Earth’s solid and fluid layers at various spatiotemporal scales. These changes are related to surface processes such as glacial isostatic adjustment, the terrestrial water cycle, ocean dynamics and ice-mass balance, which are primarily due to changes in the climate. To understand the Earth system response to natural climate variability and anthropogenic climate change, different time spans of observations need to be cross-compared and combined with several other datasets and model outputs. Geodetic observables are also often compared with geophysical models, which helps in explaining observations, evaluating simulations, and finally merging measurements and numerical models via data assimilation.

We look forward to contributions that:​

1. Utilize geodetic data from diverse geodetic satellites including altimetry, gravimetry (CHAMP, GRACE, GOCE and GRACE-FO, SWOT), navigation satellite systems (GNSS and DORIS) or remote sensing techniques that are based on both passive (i.e., optical and hyperspectral) and active (i.e., SAR, Sentinel, NISAR) instruments.​

2. Cover a wide variety of applications of geodetic measurements and their combination to observe and model Earth system signals in hydrological, ocean, atmospheric, climate and cryospheric sciences.​

3. Show a new approach or method for separating and interpreting the variety of geophysical signals in our Earth system and combining various observations to improve spatiotemporal resolution of Earth observation products.​

4. Work on simulations of future satellite mission (such as MAGIC and NGMM) that may advance climate sciences.​

5. Work towards any of the goals of the Inter-Commission Committee on "Geodesy for Climate Research" (ICCC) of the International Association of Geodesy (IAG).​

We are committed to promoting gender balance and ECS in our session. With author consent, highlights from this session will be shared on social media with a dedicated hashtag during the conference in order to increase the impact of the session.

Accurate modeling and prediction of Earth rotation is important for numerous applications in geodesy, astronomy and navigation. In recent years, geodetic observation systems have made significant progress in monitoring the temporal variability of the Earth's rotation, which is largely related to dynamic processes in the planet's fluid components. The increase in observation accuracy must go along with the improvement of theories and models.
We welcome contributions that highlight new determinations and analyses of Earth Orientation Parameters (EOP), including combinations of different geodetic and astrometric observational techniques for deriving UT1/length-of-day variations and polar motion. We welcome discussions of EOP solutions in conjunction with a consistent determination of terrestrial and celestial frames. We are interested in the latest achievements in EOP forecasting, especially reports exploring the potential of innovative techniques, such as machine learning, in improving forecast accuracy.
We invite contributions on the dynamical links between Earth rotation, geophysical fluids, and other geodetic quantities, such as the Earth gravity field or surface deformation, and of explanations for the physical excitations of Earth rotation. Besides tidal influences from outside the Earth, the principal causes for variable EOP appear to be related to angular momentum exchange from motions and mass redistribution of the fluid portions of the planet.
We welcome contributions about the relationship between EOP variability and the variability in fluids due to climate effects or global change. Forecasts of these impacts are important especially for the operational determination of EOP, and the effort to improve predictions is an important topic.
We are interested in the progress in the theory of Earth rotation. We seek contributions that are consistent internally with the accurate observations at the mm-level, to meet the requirements of the Global Geodetic Observing System and respond to IAG 2019 Res. 5 and IAU 2021 Res. B2. We also welcome contributions on the variability and excitation of the rotation of other planetary bodies.

Glacial Isostatic Adjustment (GIA) refers to the Earth's response to changes in ice sheets, leading to surface deformation, changes in gravity, rotation, and the state of stress. This process is primarily driven by ice-sheet dynamics and Earth's structure, impacting other Earth systems like the cryosphere and hydrosphere. A wealth of standardized observational data, such as GNSS measurements, relative sea levels, and satellite gravimetry, helps refine GIA models. These models enhance our understanding of ice-sheet history, sea-level changes, and Earth's rheology.

We welcome contributions on GIA's effects across various scales, including geodetic measurements, complex GIA modelling, GIA-induced sea-level changes, and the Earth's response to current ice-mass changes. We also invite abstracts on GIA's impact on nuclear waste sites, groundwater, and carbon resources. This session is co-sponsored by the SCAR sub-committee INSTANT-EIS, Earth - Ice - Sea level, in view of instabilities and thresholds in Antarctica (https://www.scar.org/science/instant/home/) and the IAG/IACS sub-commission 3.4 “Cryospheric Deformation”.

The redistribution of fluid mass across the Earth’s surface and near-surface, driven by water cycle dynamics and its extremes, can cause measurable load-induced deformation. In recent decades, increasingly accurate and available space geodetic measurement techniques (e.g., GNSS, InSAR, satellite gravimetry, satellite altimetry) have enriched our understanding of this response. Accurate observations of crustal deformation, combined with geophysical models, can be used to quantify hydrological loads, providing new insights into related hydrological processes. This session aims to attract research that advances our ability to accurately quantify hydrological mass loads across different temporal and spatial scales, involving various hydrological compartments (e.g., groundwater, surface water, snow, ice). We invite studies focusing on innovative measurement and modeling approaches, and on reconciling observations from different geodetic measurement techniques used to study hydrological loading. Research that assesses the strengths and limitations of each approach and proposes strategies for seamless and accurate integration is highly encouraged. Additionally, we seek studies that conduct intercomparisons of different hydrological model data (e.g., from land surface models and hydrological models) and geodetic measurement techniques to understand their relative strengths, weaknesses, and accuracies.

We are looking for studies that investigate how tectonic plates move, how this movement is accommodated in deformation zones, and how elastic strain builds up and is released along faults and in subduction zones. These studies should use space geodetic data and sea floor geodetic measurements in combination with observations like seismicity, geological slip rates and rakes, sea-level, and gravity. How can the observed elastic strain buildup best be used to infer the likelihood of future earthquakes? How persistent are fault asperities over multiple earthquake cycles? Are fault slip rates from paleoseismology identical to those from geodetic data? What portion of plate motion results in earthquakes, and where does the rest go? How fast are mountains currently rising? How well can we constrain the stresses that drive the observed deformation? How much do the nearly constant velocities of plates vary during the earthquake cycle, and does this influence the definition of Earth's reference frame?

This session focuses on the hydrogeodetic measurement of water bodies such as rivers, lakes, floodplains and wetlands, groundwater and soil. The measurements relate to estimating water levels, extent, storage and discharge of water bodies through the combined use of remote sensing and in situ measurements and their assimilation in hydrodynamic models.

Monitoring these resources plays a key role in assessing water resources, understanding water dynamics, characterising and mitigating water-related risks and enabling integrated management of water resources and aquatic ecosystems. While in situ measurement networks play a central role in the monitoring effort, remote sensing techniques provide near real-time measurements and long homogeneous time series to study the impact of climate change from local to regional and global scales.

During the past three decades, a large number of satellites and sensors has been developed and launched, allowing to quantify and monitor the extent of open water bodies (passive and active microwave, optical), the water levels (radar and laser altimetry), the global water storage and its changes (variable gravity). River discharge, a key variable of hydrological dynamics, can be estimated by combining space/in situ observations and modelling, although still challenging with available spaceborne techniques. Interferometric Synthetic Aperture Radar (InSAR) is also commonly used to understand wetland connectivity, floodplain dynamics and surface water level changes, with more complex stacking processes to study the relationship between ground deformation and changes in groundwater, permafrost or soil moisture.

Traditional instruments contribute to long-term water level monitoring and provide baseline databases. Scientific applications of more complex technologies like Synthetic Aperture Radar (SAR) altimetry on CryoSat-2, Sentinel-3A/B and Sentinel-6MF missions are maturing, including the Fully-Focused SAR technique offering very-high along-track resolution. The SWOT mission, recently lauched and commissioned, now opens up many new hydrology-related opportunities. We also welcome submissions of pre-launch studies for CRISTAL, Sentinel-3C/3D/3NG-Topography, Sentinel-6NG, MAGIC/NGGM and and other proposed missions such as Guanlan, HY-2 and SmallSat constellations such as SMASH, and covering forecasting.

Tides influence a wide range of ocean and Earth system processes, from the coasts to the deep ocean. Together with storm surges, they play a central role in driving coastal flooding. Tides provide the mechanical energy that fuels ocean mixing and sustains large-scale circulation, affecting marine biogeochemistry, ecosystems, and interacting with ice sheet and sea ice dynamics.
Tides and storm surges act as key drivers of coastal processes, exerting a combined influence on coastal hazards such as flooding, morphological changes, pollution, and infrastructure resilience. The behaviour and interaction of tides and storm surges, in combination with other coastal processes, represents an active research field that will be discussed in this session.
Both tides and storm surge patterns exhibit short and long-term temporal variability across different spatial scales and are modified by sea-level rise, climate change, sea ice, and human activities such as dredging and estuarine modifications. These changes have implications for coastal flooding, tidal energy generation, ocean stratification, mixing and large-scale ocean circulation. Further back in geological time, changes in continental configuration and sea level profoundly altered tidal dynamics, with potentially far-reaching effects on ocean circulation, mixing and evolutionary processes.
Observations (in-situ measurements and remote sensing), models (numerical and data-driven) and geological reconstructions are important tools in understanding how tides and storm surges vary across space and time. The aim of this session is to share innovative approaches, technical advancements in observation and modelling techniques, and recent improvements in understanding of these tide- and surge-driven processes and their implications for coastal, ocean and Earth system processes. Submissions are encouraged both from regional and global-scale studies on all aspects of tides and surges in the past, present and future, including those from estuaries, rivers, lakes, and even other planetary bodies.

Vertical motions of the Earth’s lithosphere away from an isostatically compensated state provide a powerful lens into the dynamic behavior of the sublithospheric mantle. These motions can now be monitored geodetically at unprecedented precision. At the same time, geological records provide invaluable spatial-temporal information about the history of vertical lithosphere motion, for instance through provenance, stratigraphic and other proxies. Altogether, the combination of geodetic and geologic observations provide extraordinary opportunities to constrain deep earth processes in geodynamic forward and inverse models of past mantle convection. The challenges of using Earth's surface records to better understand deep Earth processes involve (1) signal separation from other uplift and subsidence mechanisms, such as isostasy and plate tectonics, and (2) different spatial resolutions and scales between models and observables.

In this session, we aim to bring together researchers interested in the surface expression of deep Earth processes from geodetic to geological time scales using multi-disciplinary methods, including (but not limited to) geodetic, geophysical, geochemical, geomorphological, stratigraphic, and other observations, as well as numerical modeling. We welcome studies that tackle challenges and address questions surrounding mantle convection and its surface manifestation in the Mesozoic and Cenozoic times. Studies using a multidisciplinary approach are particularly encouraged.

New observations about earthquakes keep accumulating that contribute to unveil every time a bit more our understanding of earthquake processes and related earthquake cycle. Methods have significantly improved in geophysics, in geodesy, and in paleoseismology-geomorphology. Hence, on one hand the number of earthquakes with well-documented rupture process and deformation pattern has increased significantly. Similarly, the number of studies documenting long time series of past earthquakes, including quantification of past deformation has also increased. On the other hand, the modeling communities, both numerical and analogue, which are working on rupture dynamics and/or earthquake cycle are also making significant progresses. Thus, this session is the opportunity to bring together these different contributions to foster further collaboration between the different groups focusing all on the same objective of integrating earthquake processes into the earthquake cycle and crustal deformation framework. Hence, in this session we welcome contributions documenting earthquake ruptures and crustal deformation processes, both for ancient events or recent events, from seismological, geodetic, or paleoseismological perspective. Contributions documenting deformation during pre-, post-, or interseismic periods, which are highly relevant to earthquake cycle understanding, are also very welcomed. Finally, we seek for any contribution looking at the earthquake cycle from the modeling perspective, especially including approaches integrating data and modeling.

For more than two decades, satellite missions dedicated to the determination of the Earth's gravity field have enabled a wide variety of studies related to climate research as well as other geophysical or geodetic applications. Continuing the successful, more than 15 years long data record of the Gravity Recovery and Climate Experiment (GRACE, 2002-2017) mission, its Follow-on mission GRACE-FO, launched in May 2018, is currently in orbit providing fundamental observations to monitor global gravity variations from space. Regarding the computation of high-resolution static gravity field models of the Earth and oceanic applications, the Gravity field and steady-state Ocean Circulation Explorer (GOCE, 2009-2013) mission plays an indispensable role. Complementary to these dedicated missions, observations from other non-dedicated missions such as Swarm as well as satellite laser ranging (SLR) have shown to be of significant importance, either to bridge gaps in the GRACE/GRACE-FO time series or to improve gravity field models and scientific results derived thereof. The important role of satellite gravimetry in monitoring the Earth from space has led to various ongoing initiatives preparing for future gravity missions, including simulation studies, the definition of user and mission requirements and the investigation of potential measurement equipment and orbit scenarios.

This session solicits contributions about:
(1) Results from satellite gravimetry missions as well as from non-dedicated satellite missions in terms of
- data analyses to retrieve time-variable and static global gravity field models,
- combination synergies, and
- Earth science applications.
(2) The status and study results for future gravity field missions.

Recent developments in different fields have enabled new applications and concepts in the space- and ground-based observation of the Earth’s gravity field. In this session, we discuss the benefit of new sensors and techniques and their ability to provide precise and accurate measurements of Earth’s gravity.
We encourage the dissemination of results from geoscience applications of absolute quantum gravimeters, which are gradually replacing devices based on the free-fall of corner cubes, since they allow nearly continuous absolute gravity measurements and offer the possibility to measure the gravity gradient. Quantum sensors are also increasingly considered for future gravity space missions. In addition, we welcome results from gravimeters based on other technologies (e.g., MEMS or superconducting gravimeters) that have been used to study the redistributions of subsurface fluid masses (water, magma, hydrocarbons, etc.) in permanent deployment or field surveys.
Besides gravimeters, other concepts can provide unique information on the Earth’s gravity field. According to Einstein’s theory of general relativity, frequency comparisons of highly precise optical clocks connected by optical links give direct access to differences of the gravity potential (relativistic geodesy) over long baselines. In future, precise optical clock networks can be applied for defining and realizing a new international height system or to monitor mass variations.
Laser interferometry between test masses in space with nanometer accuracy – successfully demonstrated through the GRACE-FO mission – also belongs to these novel concepts, and even more refined concepts (tracking swarms of satellites, space gradiometry) will be realized in the near future.
We invite presentations illustrating the state of the art of those novel techniques, that will open the door to a vast bundle of applications, including the gravimetric observation of the Earth-Moon system with high spatial-temporal resolution as well as the assessment of terrestrial mass redistributions, occurring at different space and time scales and providing unique information on the processes behind, e.g., climate change and volcanic activity.
This session is organized jointly with the IAG (International Association of Geodesy) project "Novel Sensors and Quantum Technology for Geodesy (QuGe)".

Launched in November 2013, the ESA Earth Explorer Swarm satellite trio has provided, for one solar cycle, continuous accurate measurements of the magnetic field, accompanied by plasma and electric field measurements, precise navigation, and accelerometer observations.
The polar-orbiting Swarm satellites are augmented with absolute magnetic scalar and vector data from the low-inclination Macau Science Satellite 1 (MSS-1, since May 2023, 41° inclination, covering all Local Times within 2 months) and with absolute scalar field measurements from the CSES satellite (since 2018, fixed 02/14 LT near-polar orbit) which significantly extend the data coverage in space and time.
In addition, the ESA Scout NanoMagSat constellation consisting of one near-polar and two 60° inclination satellites, is now also in the pipeline, with a sequence of launches planned to start at the end of 2027 for full operation in 2028. It will acquire absolute vector magnetic data at 1 Hz, very low noise scalar and vector magnetic field data at 2 kHz, electron density data at 2 kHz and electron temperature data at 1 Hz. It will also acquire navigation data, enabling top-side TEC retrieval, and collect ionospheric radio-occultation profiles.

This session invites contributions on investigations in geomagnetism, ionospheric and thermospheric sciences related to Earth and near-Earth processes, with focus on existing and planned Low-Earth-Orbiting satellites. Combined analyses of satellite- and ground-based or model data are welcome.

Modelling the subsurface structure of planetary bodies using gravity and magnetic data has been extensively applied across a range of celestial bodies, including the Earth, Moon, terrestrial planets (i.e., Mars, Mercury, Venus), and icy satellites (e.g., Ganymede, Europa, Callisto and Enceladus). In combination with measurements of surface topography and shape, the interior properties of celestial bodies, such as thickness and density of internal layers, can be inferred. These studies are pivotal for the understanding of their geological evolution. This session will explore the latest methods and approaches in developing planetary gravity and magnetic field models, conducting topographical analyses, and carrying out data modelling techniques to unravel the internal structures of planets and satellites. Contributions spanning various aspects of planetary research, including theoretical studies, observational data, and the development of potential field solutions are welcome. Additionally, presentations on innovative data processing and interpretation methods, advances in subsurface modeling techniques, and specific case studies of geological interest are encouraged. New insights from the analysis of potential field data from past missions, combined with contributions on the preparation and anticipated findings from recent and upcoming missions (e.g., BepiColombo, JUICE, Europa Clipper, Veritas, EnVision), as well as advanced applications, will offer the community a comprehensive understanding of this dynamic area of planetary research.

Geodesy contributes to atmospheric science by providing some of the essential climate variables of the Global Climate Observing System. In particular, water vapor is currently under-sampled in meteorological and climate observing systems. Thus, obtaining more high-quality humidity observations is essential for weather forecasting and climate monitoring. The production, exploitation and evaluation of operational GNSS Meteorology for weather forecasting is well established in Europe thanks to over 20 years+ of cooperation between the geodetic community and the national meteorological services. Improving the skill of NWP models, e.g., to forecast extreme precipitation, requires GNSS products with a higher spatio-temporal resolution and shorter turnaround. Homogeneously reprocessed GNSS data have high potential for monitoring water vapor climatic trends and variability. With shorter orbit repeat periods, SAR measurements are a new source of information to improve NWP models. Using NWP data within RT GNSS data analysis can initialize PPP algorithms, thus reducing convergence times and improving positioning. GNSS signals can also be used for L-band remote sensing when Earth-surface reflected signals are considered. GNSS-R contributes to environmental monitoring with estimates of soil moisture, snow depth, ocean wind speed, sea ice concentration and can potentially be used to retrieve near-surface water vapor.
We welcome, but not limit, contributions on:
• Estimates of the neutral atmosphere using ground- and space-based geodetic data and their use in weather forecasting and climate monitoring
• Retrieval and comparison of tropospheric parameters from multi-GNSS, VLBI, DORIS and multi-sensor observations
• Now-casting, forecasting, and climate research using RT and reprocessed tropospheric products, employing NWP and machine learning
• Assimilation of GNSS tropospheric products in NWP and in climate reanalysis
• Production of SAR tropospheric parameters and assimilation thereof in NWP
• Homogenization of long-term GNSS and VLBI tropospheric products
• Delay properties of GNSS signals for propagation experiments
• Exploitation of NWP data in GNSS data processing
• Techniques for soil moisture retrieval from GNSS data and for ground-atmosphere boundary interactions
• Detection and characterization of sea level, snow depth and sea ice changes, using GNSS-R
• Investigating the atmospheric water cycle using satellite gravimetry

The Global Geodetic Observing System (GGOS) Focus Area on Geodetic Space Weather Research of the International Association of Geodesy (IAG) invites researchers to explore the critical role of geodetic techniques in advancing our understanding of space weather dynamics. This session aims to bring together scientists and researchers to discuss modelling methodologies and accuracy of space-based observations for advancing the accuracy and resilience of space weather modeling, monitoring, and forecasts. Emphasis is placed on the use of geodetic observations (e.g., GNSS, GNSS-RO, VLBI, DORIS, InSAR) to provide insights into the ionosphere, plasmasphere, and thermosphere.

This session will explore recent advancements in total electron content (TEC) estimation and prediction, in three-dimensional ionospheric modelling techniques such as tomography, in using data assimilation and machine learning techniques, in electron density retrieval from recent GNSS radio-occultation missions, and ionospheric scintillation impacts on GNSS data. We also encourage studies assessing the impacts of atmospheric drag on low Earth orbit (LEO) satellites, aiming to improve neutral density estimation within the thermosphere through precise orbit determination (POD) and high-resolution accelerometer observations. Additionally, we welcome contributions on monitoring space weather events through geodetic observations, including but not limited to geomagnetic storms, ionospheric plasma bubbles, and traveling ionospheric disturbances. Discussions on the implications of these space weather phenomena for positioning and navigation systems are also encouraged. We also welcome the integration of geodetic observations with data from dedicated instruments, such as ionosondes, in-situ Langmuir probes, and incoherent scatter radars.

In this session we welcome contributions of general interest within the geodesy community. The session is open to all branches of geodesy and related fields of research, particularly those topics that are not covered by other sessions.