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)" and the Horizon Europe project EQUIP-G (Grant ID 101215427).
Gravitational redshift, one of the fundamental predictions of general relativity, describes the relationship between the oscillation frequency of clocks and the gravitational field. Testing the gravitational redshift effect with higher precision not only provides an important verification of general relativity but may also reveal new physical phenomena. In this study, an uplink and two downlink signals are established between a geostationary satellite (S) and a ground station (E). By combining three signals with different frequencies, the first-order Doppler effects, as well as influences from the ionosphere and troposphere, can be effectively suppressed, allowing high-precision extraction of the gravitational redshift signal. This research presents simulated experimental results. The geostationary satellite, a BeiDou-3 satellite, is linked to the ground station located at the Luojia Time and Frequency Laboratory in Wuhan. Both the satellite and the ground are equipped with optical atomic clocks, each with a stability of 2×10−18 at 1 day. The uplink signal frequency is 1 THz, while the two downlink signals’ frequencies are 1.1 THz and 0.8 THz, respectively. The simulation results indicate that after 10 days of continuous observation, the accuracy in determining the geopotential difference between the average positions of the ground station and the satellite is better than 10 cm. This enables testing of the gravitational redshift effect at a precision level of 2×10−8. This study provides valuable insights and references for future high-precision gravitational redshift tests utilizing geostationary or even arbitrary satellites, with potential applications in gravity potential measurements. This study is supported by the National Natural Science Foundation of China (NSFC) (Grant Nos. 42388102, 42030105, and 42274011).
How to cite: Ning, A., Li, L., Wang, L., Zhang, P., Shen, Z., Xu, R., Xie, Y., and Shen, W.: Simulation experiments for testing gravitational redshift using three optical frequency signals between satellite and ground station, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4633, https://doi.org/10.5194/egusphere-egu26-4633, 2026.
Transportable high-performance optical atomic clocks are currently being developed worldwide. Apart from applications in metrology and fundamental physics studies, due to the relativistic gravitational redshift of clock frequencies they serve as quantum sensors of the local gravity potential. If they are connected to distant atomic clocks via high-performance frequency comparison links, the frequency difference between the clocks measured remotely enables a direct determination of gravity potential differences with high spatial and temporal resolution. This method is called chronometric leveling [1].
We have been operating a transportable strontium lattice clock for ten years and have used it for chronometric leveling. Here we describe our second-generation transportable atomic clock [2], which has been operational since 2023 and has demonstrated centimeter height resolution in the field. Taking all frequency shifts into account, its total systematic uncertainty is evaluated to be 2.1×10-18, which via the gravitational redshift corresponds to a height uncertainty of 1.9 cm. This is close to the currently lowest achieved physical height uncertainties in geodesy, determined by the mostly satellite-based GNSS/geoid approach [3]. The atomic clock is installed in an air-conditioned car trailer and has been successfully operated after transportation several times.
We briefly review recent off-campus measurement campaigns in England [4], southern Germany and Italy, and we lay out plans for future measurements aiming to demonstrate how a next-generation height system with cm accuracy can be established and controlled in practice. These measurements are expected to benefit from the extended European core time-frequency network (C-TFN), which forms a tripod in Germany with PTB at the hub, thus enabling, for example, the detection of 2D tilt in the current height reference system.
References:
[1] T. E. Mehlstäubler et al., Rep. Prog. Phys. 81(6), 064401, 2018.
[2] I. Nosske et al., Quant. Sci. Technol. 10(4), 045076, 2025.
[3] H. Denker et al., J. Geod. 92(5), 487-516, 2018.
[4] International Clock and Oscillator Networking Collaboration, arXiv:2410.22973, 2024.
How to cite: Nosske, I., Vishwakarma, C., Lücke, T., Dörscher, S., Kuhl, A., Mukherjee, S., Kronjäger, J., and Lisdat, C.: Transportable optical atomic clock for geodesy at the centimeter height level, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13866, https://doi.org/10.5194/egusphere-egu26-13866, 2026.
Here we propose a single-clock measurement scheme for determining the geopotential difference between two stations using a single clock combined with GNSS Precise Point Positioning (PPP) time-frequency transfer. An experiment was conducted on two remote stations, with a distance 129 km and a height difference 1245 m, using a single hydrogen maser. Utilizing the International GNSS Service (IGS) time as reference, the geopotential frequency shift between the two stations was extracted by comparing the frequency differences between the hydrogen maser and the IGS time before and after clock transportation, and the measured geopotential difference between the two stations is 12075.9±118.5 m2/s2, which shows consistency with the value derived from the EIGEN-6C4 global gravity field model, with a deviation of (-79±119) m2/s2. Compared with traditional dual-clock methods, this approach obviates the need for inter-clock calibration, reduces operational complexity and equipment investment costs, and improves data utilization efficiency. In the future, the integration of optical clocks into the GNSS observation system is anticipated achieving methodological breakthroughs. Hence, we expect the geopotential difference measurement by integrating optical-clock technology into the GNSS-based single-clock scheme. The prospects include the GNSS receivers connected with optical clock signals, the high-stability optical-to-radio frequency conversion, and the establishment of an integrated space–ground optical frequency network comprising satellite-borne optical clocks and fiber-connected ground stations. This approach is envisioned to enable high-precision geodetic applications, such as equi-frequency geoid definition, centimeter-level orthometric height transfer, global height datum unification, while providing a novel platform for fundamental physics investigations (such as gravitational waves and dark matter detections). These capabilities underscore the transformative potential of optical-clock-enhanced GNSS technology across both geodetic science and fundamental physic. This study is supported by the National Natural Science Foundation of China (NSFC) (Grant Nos. 42388102, 42030105, and 42274011), and Gravitation Center Project (NGL-2025-004).
How to cite: Wang, L., Shen, W., Li, L., Zhang, P., Ning, A., Xu, R., Xie, Y., and Shen, Z.: A GNSS-Based Single-Clock Method for Geopotential Difference Determination and Its Outlook with Optical Clocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15794, https://doi.org/10.5194/egusphere-egu26-15794, 2026.
Relativistic geodesy exploits the gravitational redshift predicted by General Relativity (GR) to determine differences in the Earth’s gravitational potential (geopotential) through high-precision clock comparisons. Recent advances in optical atomic clocks and optical time-transfer techniques have achieved fractional frequency uncertainties at or below 10-18 , corresponding to a geopotential variation sensitivity of approximately 0.1m2s-2. This level of precision is sufficient to enable high-resolution chronometric leveling. Compared with conventional microwave time-transfer methods, optical links provide superior resilience to atmospheric perturbations, higher modulation bandwidths, and unambiguous time-transfer observables, making them particularly well suited for relativistic geodesy applications. Motivated by the European Laser Timing (ELT) experiment and the high-precision cesium cold-atom clock aboard the Atomic Clock Ensemble in Space (ACES) mission, characterized by a fractional frequency stability and accuracy of approximately 10-16, we propose and analyze a triple optical time-transfer model for determining the Earth’s geopotential. The model is formulated within a consistent relativistic framework based on post-Newtonian theory, which adequately supports atomic clock comparisons at the accuracy level of 10-18.
In the absence of actual ELT/ACES optical data and considering the limitations of current ground-based laser ranging stations, where heterogeneous time and frequency standards exhibit insufficient long-term stability for relativistic geodesy, a high-fidelity numerical simulation framework is developed. This framework incorporates representative ELT/ACES mission parameters, including a ground-based optical clock with a fractional frequency instability of 10⁻¹⁸. Simulation results show that approximately 70% of ELT/ACES mission passes yield geopotential bias estimates within (-0.180±0.846) m2s-2 relative to the reference value, corresponding to centimeter-level height sensitivity. These results demonstrate that optical time and frequency transfer links, when combined with state-of-the-art optical clocks, can support free-space measurement networks capable of global chronometric leveling. Such networks hold significant potential for the realization of a unified height reference system and for advancing high-precision geodetic applications. This study is supported by the National Natural Science Foundation of China (NSFC) (Grant Nos. 42388102, 42030105, and 42274011) and the Space Station Project (2020-228). National Gravitation Laboratory, Huazhong University of Science and Technology, Wuhan 430074, P.R. China.
How to cite: Ruby, A., Shen, W., Shaker, A., Zhang, P., and Shen, Z.: Geopotential Determination Using an Optical Link and a Cold-Atom Cesium Clock Aboard the ACES Mission, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3237, https://doi.org/10.5194/egusphere-egu26-3237, 2026.
The Quantum Pathways Institute (QPI), sponsored by NASA/STMD, is a collaborative effort between UT Austin, CU Boulder, Caltech, UC Santa Barbara, and NIST. At the time of this presentation, the QPI will be at the half-way mark of a five-year program to advance to TRL-3 at the systems level the quantum sensing technology for next-generation Earth science applications. Arising from this work, we envision eventual 1 micro-Eotvos precision gravity gradient measurements in orbit, requiring femto-meter/s^2 inertial sensing. Such a gravity gradiometer system could target ice-mass loss measurements within 10 Gt/year, ocean heat uptake inference within 0.1 W/m^2, and better than 0.1 mm/year sea-level rise inference.
This paper provides a status update on our progress on two fronts. First a summary status of QPI team’s work is presented, on quantum sensing research, its conceptual development, and experimental results targeted towards a gravity gradiometer system. Second, we present progress in developing a roadmap to eventual science mission implementation, including progress in addressing some key technical spaceflight and data analysis challenges.
How to cite: Bettadpur, S., Holland, M., LeDesma, C., Anderson, D., Axelrad, P., Nicotra, M., Bank, S., Topcu, U., Wasserman, D., Blumenthal, D., Stephens, M., and Watkins, M.: Innovation and Progress at the Quantum Pathways Institute - A status Update, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22263, https://doi.org/10.5194/egusphere-egu26-22263, 2026.
High-precision gravity observation relies critically on the performance of sensor systems. Ground performance testing is of great importance for cutting-edge gravity measurement sensors, including satellite gravimetry payloads, gravimeters, MEMS accelerometers and other high-precision sensors. Since the precision level of these instruments is from 10-9 m/s2/Hz1/2 to 10-12 m/s2/Hz1/2 or even higher, the performance tests are primarily limited by seismic noise. This necessitates ground-based testing facilities with seismic isolation performance surpassing the target sensor noise floor. Huazhong University of Science and Technology has carried out extensive researches on low-frequency seismic isolation and inertial sensor performance testing. From 2015, a low-frequency horizontal vibration insensitive pendulum based on translation-tilt compensation has been proposed and tested, the residual noise reached 1×10-9 m/s2/Hz1/2 at 0.1 Hz. Since 2021, an active controlled four-wire pendulum has been presented. Combining with a precision gravitational calibration unit, an integrated performance test facility was built in 2023, with a direct resolution test of 50 pg level for inertial sensors. By using the electromagnetic excitation on the pendulum, it can realize the sensitivity calibration, amplitude–frequency response analysis, and resolution calibration of high-precision sensors. In 2025, an electrostatic accelerometer with low self-noise was used as the motion sensor of the active controlled four-wire pendulum, the residual noise on the bench was 1×10-9 m/s2/Hz1/2 at 0.5 Hz. Recently, a new two-stage active-passive hybrid vibration isolation system was designed by integrating a four-wire pendulum and a translation-tilt compensation pendulum. The residual noise measured by an out-of-loop Guralp 3T seismometer reached a minimum level of 4×10-10 m/s2/Hz1/2 at 0.1 Hz. These works provide effective means to improve the ground-based test ability and long-term stability evaluation of high-precision inertial sensors. They also support the development of next-generation space gravity missions, quantum gravimeters, lunar and planetary seismometers and gravimeters, etc.
How to cite: Ma, C., Bai, Y., Liu, L., Li, M., Qu, S., and Zhou, Z.: Low-frequency seismic isolation and high-precision inertial sensor ground performance testing facility for satellite gravimetry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6130, https://doi.org/10.5194/egusphere-egu26-6130, 2026.
Absolute quantum gravimeters based on atom interferometry achieve outstanding accuracy and long-term stability, but their operation in real-world environment critically depends on an efficient compensation of ground vibrations, generally provided by auxiliary classical sensors. These sensors are most often commercial devices, which can limit flexibility and system optimization.
In this work, we present the development of a homemade inertial sensor designed to be coupled with the absolute quantum gravimeter of Exail [1]. We demonstrate the successful hybridization of an atomic gravimeter with an interferometric inertial sensor. This constitutes a proof of concept for the direct interfacing of an atomic sensor with a laboratory-developed classical sensor.
The inertial sensor is an interferometric accelerometer operating in the 0.01–100 Hz band. It consists of a leaf-spring suspended proof mass with a natural frequency of 2.8 Hz and a compact mechanical structure. The proof-mass motion is measured using a custom homodyne quadrature Michelson interferometer, providing a displacement resolution of 2 × 10⁻¹³ m/√Hz at 10 Hz. These characteristics allow the sensor to meet the requirements for vibration compensation in atom-interferometric gravimetry.[2]
We describe the mechanical and electronic integration of the interferometric sensor within the gravimeter.
Experimental results show that the gravimeter remains operational when driven with the homemade sensor, demonstrating the robustness of the hybridization and validating the overall concept. Although further improvements are required to the targeted gravity measurement performance, these results open a clear path toward customizable hybrid quantum–classical gravimetric systems.
[1] Ménoret, V., Vermeulen, P., Le Moigne, N. et al. Gravity measurements below 10−9 g with a transportable absolute quantum gravimeter. Sci Rep 8, 12300 (2018)
[2] A. Amorosi, L. Amez-Droz, M. Zeoli, B. Thibaut, M. Teloi, M.H. Lakkis, A. Sider, C. Di Fronzo, C. Collette. (2025)
On broadening techniques for a high-resolution optical accelerometers. In Sensors and Actuators.
How to cite: Teloi, M., Thibaut, B., Amorosi, A., Collette, C., Ménoret, V., Antoni-Micollier, L., and Janvier, C.: Hybridization of an Absolute Quantum Gravimeter with a Homemade Interferometric Sensor for Ground Motion Compensation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6435, https://doi.org/10.5194/egusphere-egu26-6435, 2026.
With the advancement of high-precision absolute gravimeters, absolute/relative hybrid observation systems now enable the detection of terrestrial time-varying gravity signals, offering insights into density changes and mass redistribution within seismogenic zones. However, extracting weak gravity signals related to earthquakes remains challenging due to complex surface processes and unclear mechanisms. This study investigates gravity changes before three major earthquakes, such as the 2013 Lushan Ms7.0, 2021 Yangbi Ms6.4, and 2022 Menyuan Ms6.9 events on the eastern Tibetan Plateau. To address issues such as nonlinear drift and scale-factor variability in relative gravimeters, a Bayesian gravity adjustment method is introduced to enable quantification of observational uncertainties. Then, after correcting for hydrological and vertical deformation effects, residual gravity changes possible related to deep tectonic mass transport are derived. For quantitative description, a mass source model inversion method is used to quantify potential links between gravity changes and crustal mass transfer in seismogenic regions. Finally, combined with historical seismicity, velocity, and electrical structure models, we constructed several mass source models for understanding the mechanism of deep mass migration before strong earthquakes.
How to cite: Wang, L., Chen, S., and Jia, L.: Time-Variable Gravity Observations from the Chinese Mainland Seismic Gravity Network Reveal Deep Mass Migration during Large-Earthquake Preparation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2234, https://doi.org/10.5194/egusphere-egu26-2234, 2026.
Superconducting gravimeters (SGs) provide direct, high-precision observations of gravity variations, reflecting hydrological mass redistribution and other geophysical processes. SGs can thus be used to evaluate terrestrial water storage simulations from hydrological models. Conversely, hydrological model output, together with independent observational data, helps better interpret the hydrological signals present in SG time series.
However, comparing modeled terrestrial water storage with SG measurements remains challenging, as hydrological models simulate processes at regional to continental scales, whereas SG observations represent an integrated signal in which local, regional, and larger-scale contributions cannot be readily distinguished.
We evaluate high-resolution simulations of the Community Land Model version 5.0 fork eCLM, both with and without GRACE/-FO data assimilation, at spatial resolutions of 12 km and 2.8 km over Europe, and compare them with the global Catchment Land Surface Model (CLSM) with respect to their consistency with gravity observations for selected European SGs. We selected four stations - Medicina, Wettzell, Yebes, and Todenfeld - to cover different climate regimes and to make use of long, well-assessed time series, with Todenfeld included as a new station. For the deseasonalized time series, after correcting for atmospheric loading, we find correlations between simulated and observed gravity variations of up to 73%, indicating that a substantial fraction of the SG signal can be attributed to hydrological mass changes represented in the models. At the same time, discrepancies in amplitude and phase are observed, suggesting contributions from hydrological processes that are insufficiently represented, such as groundwater dynamics, snow accumulation in the vicinity of the instrument, or highly localized hydrological signals.
In particular, we analyze two years of data from the iGrav-043 superconducting gravimeter operated by the University of Bonn. The instrument was installed in 2023 in Todenfeld near Bonn at a former satellite-geodetic observatory on a grassland hill. In addition to modeled terrestrial water storage, the SG observations are interpreted using independent data sets, including remotely sensed soil moisture as well as precipitation data sets, enabling a detailed investigation of selected hydrological events.
Our results highlight that SGs can provide a robust observational basis for validating hydrological model output, particularly within well-distributed networks. This first-ever comparison between regional high-resolution hydrological model simulations and gravity observations from the SG at Todenfeld reveals a remarkable consistency, demonstrating that the station is a well-suited location for hydrological studies.
Remaining discrepancies highlight the importance of complementary observations at the station scale. In situ measurements of soil moisture, ideally separated by depth and type, as well as other station-based measurements of water cycle variables, such as snow cover, are required to better separate individual hydrological contributions to the gravity signal. In particular, a GNSS site is planned to be installed in Todenfeld to constrain the spatial scale of hydrological processes, since GNSS observations are sensitive to loading over a broader spatial footprint than SGs.
How to cite: Daubenspeck, A., Springer, A., Ewerdwalbesloh, Y., Karegar, M., and Kusche, J.: Disentangling Hydrological Signals in Superconducting Gravimeter Time Series with High-Resolution Models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18080, https://doi.org/10.5194/egusphere-egu26-18080, 2026.
As ocean tides move massive quantities of water over the Earth, they cause fluctuations in local gravity which must be accounted for in the calibration of inertial guidance systems, measurement of geodetic surveys, and analysis of local hydrological processes. Ocean tide models, which contain detailed hydrodynamics and assimilated data, are used to predict these gravity fluctuations. We evaluate the accuracy of several common ocean tide models—including the DTU, EOT, FES, and TPXO families of models—against reference superconducting gravimeter (SG) data provided by the International Geodynamics and Earth Tides Service (IGETS) of the International Association of Geodesy (IAG). Other geophysical models, such as solid Earth tide and atmospheric loading, are removed from the SG data, and the reduced data is compared against ocean tide model predictions computed using the “Some Programs for Ocean-Tide Loading” (SPOTL) software suite developed by Scripps Institution of Oceanography. By comparing how well the various ocean tide models fit the SG data, these models can be ranked in terms of their absolute accuracy relative to the IGETS measurements, and such analysis can be used to inform model selection for downstream processing.
How to cite: Feuge-Miller, B., Hughes, J. C., Malnar, J., and Olson, C.: An Accuracy Comparison of Ocean Tide Models using a Global Superconducting Gravimeter Network, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22063, https://doi.org/10.5194/egusphere-egu26-22063, 2026.
Gravity exploration and monitoring have the potential to transform a wide range of commercial and scientific applications, including geodesy, hydrography, resource exploration, navigation, civil engineering, and long-term observation of subsurface dynamics.
At Nomad Atomics, we are developing compact, drift-free, quantum gravity sensors. Our cold atom-based sensor is designed to overcome the key limitations of existing commercial instruments, i.e., combining the stability and accuracy of absolute gravimeters with the portability and accessibility of relative gravimeters. Our continuous efforts to reduce the size and weight of our sensor to a volume <20 L and a weight <20 kg, with, e.g. our collaboration with Fraunhofer IZM to integrate our optics in a glass chip [1], make our quantum absolute gravimeter ideal for large scale surveying and monitoring applications.
In this talk, we will report on the latest development of our compact survey-style absolute quantum gravimeters. We will discuss the usage of this sensor for groundwater monitoring in the Berlin-Brandenburg area [2] and present preliminary performances comparison with the state-of-the-art GAIN absolute quantum sensor from Humboldt University.
[1]: IBB ProFit Program, Grant 10206866
[2]: BMBF Project ATOMAQUA (https://www.quantensysteme.info/projektatlas/projekte/q/atomaqua)
How to cite: Cordier, M., Leykauf, B., Hedges, S., Wrobel, A., Ross, K., MacKenzie, S., Freier, C., Wigley, P., and Hardman, K.: Quantum absolute gravimeter designed for field surveys, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23076, https://doi.org/10.5194/egusphere-egu26-23076, 2026.
The FIQUgS project aims at developing advanced field quantum gravimeters with enhanced resilience to temperature variations, reduced size, and lower power consumption. Two instruments are being developed within the project: a new version of Exail's Absolute Quantum Gravimeter (AQG) and a Differential Quantum Gravimeter (DQG) [1,2]. Both instruments have benefited from design improvements that eliminate the need for a power-intensive air-conditioning unit.
Here, we report on the first tests of the FIQUgS DQG conducted at LNE-OP/LTE laboratories in 2025. These tests follow similar ones carried out in 2022 with the DQG prototype [3] and include:
- A comparison of the absolute measurements of the DQG against AQG-B01* for gravity measurement and against a CG6* for vertical gravity gradients.
- A two weeks long measurement and a comparison with a superconducting gravimeter, see figure 1.
- An evaluation of the effect of temperature on measurement stability under varying temperature conditions.
- A comparison of the internal time and wavelength references against national standards.
Overall, the instrument performed well within an 18-35 °C range. Preliminary results for the comparison with AQG-B01 show an agreement within 100nm/s² and gravity gradients measured using a CG6 show an agreement within 30E (1E=1nm/s²/m).
Further work will aim at robustifying the system and extend the thermal operating range. Nonetheless, these results provide a solid foundation for field surveys planned with FIQUgS in mid-2026.
Figure 1: 2 weeks long simultaneous gravity and vertical gravity gradient measurement of the FIQUgS DQG at LNE-OP/LTE.
The FIQUgS project is funded by the European Comission under the Horizon Europe program, grant number 101080144
*AQG-B01 and CG6 are instruments of INSU-CNRS French National Parc of Instruments PIN PGravi.
[1] https://www.fiqugs.eu/
[2] L. Antoni-Micollier et al., "Absolute Quantum Gravimeters and Gradiometers for Field Measurements," in IEEE Instrumentation & Measurement Magazine, vol. 27, no. 6, pp. 4-10, September 2024, doi: 10.1109/MIM.2024.10654720.
[3] Janvier, C., Merlet, S., Rosenbusch, P., Ménoret, V., Landragin, A., Pereira dos Santos, F., and Desruelle, B.: Operational evaluation of an industrial differential quantum gravimeter, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5171, https://doi.org/10.5194/egusphere-egu23-5171, 2023.
How to cite: Janvier, C., Myneni, N., Caldani, R., Addi, N., Pereira dos Santos, F., Merlet, S., and Sidorenkov, L.: Preliminary metrological assessment for a field differential quantum gravimeter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6496, https://doi.org/10.5194/egusphere-egu26-6496, 2026.
Abstract—Underwater gravity measurement systems typically consist of the strapdown inertial navigation system (SINS), the doppler velocity log (DVL), the depth gauge (DG), and other underwater sensors. Although SINS can provide continuous autonomous navigation parameters, the results obtained from pure inertial navigation diverge over time due to gyro drift and accelerometer biases during prolonged operation. Therefore, relying solely on SINS cannot meet the accuracy requirements for gravity measurements. The DVL can accurately measure the carrier’s velocity and compensate for SINS errors to obtain higher navigation precision. However, in areas with complex seabed topography or when the carrier operates far above the seafloor, the DVL-measured water-relative velocity does not reflect the true motion relative to the seabed. Such velocity errors severely degrade underwater positioning accuracy and consequently compromise gravity measurement quality. To address this issue, we propose a SINS/DVL/DG underwater gravity measurement model considering unknown ocean current velocity based on Cubature Kalman Filter (CKF). By exploiting the short-term stability of ocean currents, a nonlinear state equation is established incorporating attitude, velocity, and current velocity. Measurement equations are formulated based on velocity errors from the DVL’s bottom-tracking and water-tracking modes, respectively. The system state and covariance are updated via the third-degree spherical-radial cubature rule, enabling real-time estimation of the carrier’s attitude and velocity, as well as current velocity. After compensating for velocity errors, high-reliability gravity data are derived from the corrected navigation information. The proposed method was validated using sea trial data collected in a 500-meter-deep area. Results show that the estimated ocean current velocity error remains below 0.01 m/s, and the internal consistency of repeated gravity survey lines reaches 1.00 mGal. Compared to traditional integrated navigation approaches, the proposed method significantly improves positioning accuracy by effectively compensating for DVL water-track velocity errors, thereby delivering high-precision gravity measurements even under unknown ocean current conditions.
Index Terms—underwater gravity, integrated navigation, effect of ocean current, inertial Navigation, internal accuracies
Fig.1 Flow chart of the SINS/DVL/DG underwater gravimetry method considering the unknown ocean current velocity
Fig. 2 Comparison chart of gravimetry results
How to cite: Xie, Y., Xiong, Z., Cao, J., Cai, S., Guo, Y., Luo, K., Yu, R., and Wu, M.: An Underwater Gravimetry Method Considering Unknown Ocean Current Velocity Based on SINS/DVL/DG, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9443, https://doi.org/10.5194/egusphere-egu26-9443, 2026.
We are investigating the underwater use of gravimeters to search for dumped munitions in the Baltic Sea. After the second world war, a lot of munition, bombs and chemical weapons were dumped into the ocean. These hazardous substances pose a danger to people, maritime life and the construction of infrastructure such as wind farms, pipelines and submarine cables. Optical sensors require clear visibility, which is quickly reduced with increasing depth and by murky water. Gravimeters may be able to identify dump sites regardless of visibility, including those covered by sediments. Additionally, gravimeters are able to determine the total mass of a found site which can otherwise be easily underestimated and thus is very helpful for salvage and disposal.
In the past, gravimeters have already been used on board of ships and remotely operated vehicles. Applications cover geophysical and oceanographic research, and the search and monitoring of natural resources. The search for sunken munitions is more difficult because the masses are smaller. We expect the magnitude of the signal to be around 10nm/s^2 depending on the objects and the distance of the sensor. This scenario is a big challenge with current gravimeters.
We are in the process of developing a realistic simulation environment in which we compare different scenarios and propose a set of requirements necessary for the successful operation of such a mission. We plan to formulate requirements for the gravimeter, the mobile platform including supporting sensors and the survey path. In practice the supporting sensors will be crucial for the success. This will allow future (quantum) gravimeters to be designed suitable for this application.
We will present an overview of our project, show the simulated signal for a real munition dump and the first evaluations of such a signal embedded into the environment observed in different scenarios.
How to cite: Fock, M., Schilling, M., and Weigelt, M.: Simulating the Gravity Signature of Underwater Ammunition Dumps, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9217, https://doi.org/10.5194/egusphere-egu26-9217, 2026.
The accurate determination of the Arctic marine gravity field is crucial for applications such as marine resources exploration, geological structure detection, and underwater navigation. However, the extensive sea-ice cover makes the inversion of Arctic marine gravity field challenging using traditional radar altimetry due to waveform contamination and limited lead detections, resulting in lower precision compared to mid-latitude oceans. While ICESat-2 offers smaller footprints (~11 m) ideal for lead detection and a theoretical advantage for sea surface height measurement, the official ATL07 product, which provide surface heights and surface-type classifications in the Arctic, suffers from inaccurate classification errors and high uncertainty in sea surface height estimation over leads. This study presents a refined processing chain for ICESat-2 ATL03 data to enhance sea surface height (SSH) and marine gravity field retrieval in the Arctic. A two-step denoising algorithm was developed to remove noise photons and mitigate after-pulse effects, improving the surface height precision of the strong beams from 0.12 m to 0.08 m as validated against airborne measurements. Furthermore, this study integrated Sentinel-2 imagery with a combined unsupervised and supervised machine learning approach to achieve high-accuracy classification of sea ice, leads, and open water. Validation with Sentinel-2 imagery demonstrated that this refined classification increased lead identification accuracy from 46.6% to 98.6%. By integrating the processed ICESat-2 data with multi-mission radar altimeter data (Cryosat-2, SARAL, Sentinel-3a), a new Arctic marine gravity field model was developed. When compared with the models SIO V32.1 and DTU21, the standard deviations of the discrepancies of our model are 3.76 mGal and 3.15 mGal, respectively. Comparison with the ArcGP gravity dataset indicated an improvement of approximately 0.5 mGal in gravity anomaly accuracy north of 80°N after incorporating ICESat-2 data. Further comparison with the GEBCO_2024 bathymetric model revealed that the inclusion of ICESat-2 data also resulted in an enhancement in the resolution of marine gravity model over ice-covered oceans. This study demonstrates that incorporation of high-precision ICESat-2 data might enhance the accuracy of marine gravity field in sea ice-covered regions.
How to cite: Sun, H., Jin, T., and Liu, W.: Refining Arctic Marine Gravity Field in Ice-Covered Regions using ICESat-2, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10213, https://doi.org/10.5194/egusphere-egu26-10213, 2026.
High-quality and -resolution marine geoid models provide a physically meaningful reference for water-level information and support navigation and bathymetric mapping. However, the realisation of accurate geoid-based reference surfaces in offshore regions is often limited by a lack of reliable gravity observations, due to factors ranging from significant time and cost constraints to geopolitical restrictions. The high-resolution KaRIn sea surface height observations from the SWOT (Surface Water and Ocean Topography) altimetry mission have the potential to offer an alternative approach to global marine geoid determination. Discrete offshore geoidal heights can be derived by removing modelled instantaneous estimates of dynamic ocean topography from the observed sea surface heights. A unified geoid surface model, together with its associated standard errors, can then be determined following least-squares collocation principles. Employing the geodetic infrastructure of the Baltic Sea region for the development and validation of the method, an agreement of just a few centimetres (standard deviation of 2.2 cm for the entire Baltic Sea) was achieved with the recently developed high-resolution gravimetric BSCD2000 geoid model. Since the SWOT-based geoid surface maintains high quality even in the near-shore zone, a seamless geoid model for land and offshore can be established by blending, with the land portion determined using the conventional gravimetric approach. Beyond the Baltic Sea region, the method's applicability is demonstrated in other parts of the world, showcasing how SWOT altimetry observations can facilitate an alternative to conventional gravimetric marine geoid determination.
How to cite: Varbla, S. and Gruber, T.: Development of geoid-based offshore reference surfaces using SWOT altimetry observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4307, https://doi.org/10.5194/egusphere-egu26-4307, 2026.
A high-fidelity gravity background field is essential for gravity-aided navigation. Existing gravity models, which predominantly rely on satellite gravimetry, are often insufficient in terms of both accuracy and spatial resolution for practical navigation applications. It is therefore crucial to enhance these models with near-surface gravimetric measurements. While spatial interpolation is commonly used to grid such observations, current approaches suffer from significant shortcomings: function-fitting methods prioritize mathematical optimization over the physical structure of the gravity field, while conventional Kriging techniques do not adequately incorporate spatial continuity between adjacent grid points. To overcome these limitations, this paper proposes a novel Gravity‑Characteristics Iterative Optimization Kriging (GC‑IOK) method, which explicitly integrates the spatial covariance and continuity properties of the gravity field. The approach employs a local gravity anomaly covariance function to quantify stochastic uncertainty in Kriging interpolation and further utilizes the continuous distribution characteristics of the field to iteratively refine local gridding results, thereby improving overall model accuracy. Validation was conducted using EIGEN‑6C4 model data across diverse geomorphological regions in China—including deserts, plateaus, karst mountains, oceans, and plains. Results show that in gravity backgrounds rich in local extrema and dominated by high‑frequency signals, the proposed method more effectively captures local continuity and reduces the average RMSE by 0.3–0.7 mGal compared to Ordinary Kriging. This study thus provides a transferable framework for high‑fidelity grid‑based gravity background modeling.
How to cite: Xie, X., Luo, K., Cai, S., Xiong, Z., Yu, R., Cao, J., Guo, Y., and Wu, M.: GC-IOK: An Iterative Optimization Kriging with Covariance and Continuity Constraints of Gravity Characteristics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16854, https://doi.org/10.5194/egusphere-egu26-16854, 2026.
The Sichuan–Yunnan region is characterized by strong tectonic deformation, high seismicity, and frequent destructive earthquakes. Consequently, constructing accurate crustal physical models is essential for elucidating seismogenic mechanisms and tectonic processes. However, owing to inconsistencies in observational datasets, differences in data processing strategies, and limitations in computational approaches, crustal models proposed by different researchers for this region remain partially inconsistent.
To address these issues, this study first derives a representative common model by integrating multiple existing geophysical models using a Hidden Markov Random Field (HMRF) framework. Based on this common model, a three-dimensional crustal density structure model is constructed through Bayesian inversion, incorporating constraints from Bouguer gravity anomaly.
The results reveal pronounced spatial variations in density structure beneath major faults in the region. Distinct positive lateral density anomalies are identified beneath the Yuanmou, Qujing, Chenghai, Lijiang–Xiaojinhe, Xianshuihe, and Zhaotong–Ludian faults, whereas comparable anomalies are absent beneath several other fault zones. In addition, density distributions exhibit significant along-strike heterogeneity within individual faults, reflecting variations in deep crustal architecture. Notably, the Lijiang–Xiaojinhe fault displays the most prominent signatures of deep-seated material intrusion, while density anomalies associated with the Red River fault show a systematic deepening trend from east to west.
How to cite: Li, Y., Chen, S., Li, H., and Zhang, B.: Gravity-Constrained Three-Dimensional Crustal Density Structure of the Sichuan–Yunnan Region Based on HMRF Model Integration and Bayesian Inversion, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2893, https://doi.org/10.5194/egusphere-egu26-2893, 2026.
Every point on Earth has a specific gravity and gravity potential value. Surfaces that connect points with equal gravity potential are referred to as equipotential or level surfaces. Among these, the geoid—an equipotential surface that closely approximates mean sea level—plays a fundamental role in the study of the Earth's gravity field within the framework of physical geodesy. However, gravity measurements obtained on the Earth's physical surface cannot be used directly; they must first be transformed into gravity anomalies to enable meaningful geophysical and geodetic analysis.
This paper evaluates the free-air and simple Bouguer gravity anomalies derived from both terrestrial and airborne gravity measurements. The consistency between terrestrial and airborne gravity-derived anomalies is also examined to assess the advantages of integrating multi-source datasets for regional gravity field modeling. Moreover, the study investigates how the selection of gravity anomaly type affects the accuracy, resolution, and overall reliability of the gravimetric geoid in a mountainous area of the Colorado test region. The results contribute to a better understanding of gravity anomaly behavior in complex topographic environments and provide insights into improving regional geoid determination strategies.
How to cite: Tütüncü, M. and Yılmaz, N.: Evaluation of Terrestrial and Airborne Gravity in Determining Gravity Anomalies and the Geoid in Colorado, USA, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1452, https://doi.org/10.5194/egusphere-egu26-1452, 2026.
The FIeld QUantum Gravity Sensors (FIQUgS) project aims to advance quantum gravimetry from controlled laboratory environments to robust field operations for geophysical surveying. A central outcome of the project is the Differential Quantum Gravimeter (DQG), which enables the simultaneous acquisition of gravity acceleration and its vertical gradient. This dual-observable capability represents a substantial methodological improvement over conventional gravimetric instruments, increasing sensitivity to near-surface mass variations while reducing the influence of regional or distant sources.
To support efficient and repeatable field deployment, the DQG is operated on a dedicated robotic carrier specifically designed to handle the instrument’s weight and operational constraints. The platform also integrates a project-specific Spectral Ground Penetrating Radar system allowing coordinated multi-physics data acquisition and enhanced near-surface imaging. In this contribution, we present an overview of the status of FIQUgS DQG as well as the overall survey concept and acquisition strategies adopted for three representative outdoor field sites selected within the project. The first site, located in Reims (France), targets the detection and characterization of shallow anthropogenic cavities in urban environment. The second site, in the Netherlands, is designed to assess the detection limits of the DQG over a known dipping underground tunnel. The third site, in the Nièvre region (France), focuses on surveying a structurally complex geological setting.
These sites provide complementary test conditions to evaluate instrument performance, survey design, and data integration workflows. The presented framework highlights the potential of quantum gravity instrumentation, when combined with robotic deployment and multi-sensor approaches, to open new perspectives for high-resolution near-surface and engineering geophysics.
How to cite: Capponi, M., Sampietro, D., Jacob, T., Streich, R., Janvier, C., Soriano, A., and Orman, M.: Field Deployment of a Differential Quantum Gravimeter on a Robotic Multi-Physics Platform: Outdoor Test Sites and Survey Strategies within the FIQUgS Project, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7526, https://doi.org/10.5194/egusphere-egu26-7526, 2026.
Atom gravimeters based on atom interferometry offer measurement capabilities, by combining high sensitivities and accuracies at the best level of a few tens of nm s−2 with the possibility to perform continuous measurements. Being absolute meters, their scale factor is accurately determined and do not need calibration.
We have developed a laboratory state-of-the-art cold atom gravimeter (CAG). The measurement is based on atomic interferometry techniques using stimulated Raman transitions on free-falling 87Rb atoms. The phase shift of the atomic interferometer is proportional to g, the acceleration due to gravity, which we measure with a sensitivity greater than that of conventional absolute gravimeters (5.7ng/rac(Hz)) and with greater accuracy (2ng).
The instrument being movable, participated to international comparisons since 2009 and became the French reference standard. Its limitations have been identified and several improvements are ongoing to achieve the 10-10 range in terms of accuracy and stability. It will then come back to the reference gravimetric station at LNE, the French National Metrological Institute. These activities take part the European Qu-Test project [1] and of MetriQs-France platform [2].
The poster will present the instrument and improvements and next steps from tests and metrology characterization to its involvement in the European project EQUIP-G [3] as it will participate to the project final comparison in 2028.
Qu-Test project is funded by the European Commission under the Horizon Europe program, grant number 101112931
EQUIP-G project is funded by the European Commission under the Horizon Europe program, grant number 101215427
[1] https://qu-test.eu
[2] https://www.lne.fr/fr/metriqs-france/plateforme-hub
[3] https://www.equip-g.eu
How to cite: Caldani, R., Gonçalves Benvenutti, D., Pereira Dos Santos, F., and Merlet, S.: Improving performances of LNE-OP/LTE Cold Atom Gravimeter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14730, https://doi.org/10.5194/egusphere-egu26-14730, 2026.
Aligned with the objective of strengthening EU’s strategic autonomy and competitiveness, the Horizon Europe project EQUIP-G [1] started in June 2025. The main objective is to establish a European perennial Research Infrastructure managing a shared park of quantum sensors and a terrestrial reference gravity network. Ten absolute commercially available quantum sensors will be acquired: seven gravimeters, two dual gravi-gradiometers and one onboarded gravimeter. Some activities of the project aim to provide comprehensive quality control to all these new instruments, and traceability over time and use cases to ensure a consistent park of instruments. This includes consolidation of measurement protocols and quantum sensor validation.
Every instrument will be tested as comprehensively as possible at LNE, the French National Metrological Institute, which is already involved in the implementation of the RIA Qu-Test project [2]. At this site, a reference gravimetric station has been operational and monitored with state-of-the-art gravity instrumentation since 2003. It is part of MetriQs-France platform [3] and allows the concurrent installation of six mobile gravimeters at the same time.
The first tests are carried out in a laboratory environment and are followed by outdoor tests. This allows to characterize each instrument and detect any faults, before sending it out for deployment under field conditions to run the measurement activities within planned project use cases. One of these use cases involves the installation of a network of quantum gravimeters at the O-ZNS site, 100 km away from LNE. In addition to the importance of this use case for the project, the fact that the two sites are close to each other allow us to extend the tests on each instrument with the execution of field measurement at O-ZNS.
In order to guarantee the quality of the measurements carried out in the frame of the different EQUIP-G use cases and to ensure the traceability and quality of the measurements from the gravimeters, two absolute comparisons will be organized in 2026 and 2028. They involve other absolute gravimeters, owned by consortium partners, which have taken part in all metrological International KC and European (EURAMET) comparisons in the last 20 years. In addition, the LNE-OP/LTE and UBER self-made laboratory quantum instruments will participate in the final comparison, which will strengthen the evaluation of the final results, in particular through the comparison of sensors based on different technologies and tested to the state-of-the-art level of performance.
These testing and metrology activities of EQUIP-G project will be presented in the poster.
EQUIP-G project is funded by the European Commission under the Horizon Europe program, grant number 101215427
[1] https://www.equip-g.eu
[2] https://qu-test.eu
[3] https://www.lne.fr/fr/metriqs-france/plateforme-hub
How to cite: Merlet, S., Caldani, R., Dykowski, P., Ciesielski, A., Carbone, D., Nuttunen, E., Näränen, J., Bilker-Koivula, M., Reich, M., Reudink, R. H. C., Jacob, T., Boujoudar, M., Azaroual, M., and Lautier-Gaud, J.: Quantum sensor testing activities within EQUIP-G project, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12409, https://doi.org/10.5194/egusphere-egu26-12409, 2026.
Gravimetry is becoming increasingly important in various fields of geodesy and the geosciences. For example, it can be used to quantify climate change by measuring changes in mass distribution and can assist in the search for raw material deposits.
Airborne gravimetry can be used to close the gap between small scaled ground gravimetry and satellite gravimetry which allows for global measurements. Until now, relative gravimeters are used in flight gravimetry, which have various disadvantages, like a high drift and limited resolution. These and additional problems can be mostly reduced or eliminated with quantum gravimeters, which leads to numerous applications. So far, absolute gravimeters are mostly used in static environments, but have been tried on slowly and uniformly moving platforms (shipborne gravimetry).
Unfortunately, the high velocity and its changes, as well as small rapid changes in the motion of an aircraft superimpose the sought-after gravitational acceleration. Therefore, to extract the gravitational acceleration from the measurements, the aircraft motion needs to be reconstructed as accurate as possible, which is to be realized through multiple sensor data fusion.
The project AeroQGrav aims to develop and operate an absolute quantum optical sensor on a moving platform. To this end, we are currently simulating the expected measurements. We hope to incorporate first in-flight measurements concerning the movement and velocity of the plane to make the simulation-results more realistic with respect to the environment of the aircraft.
How to cite: Hillig, M. and Schilling, M.: Advancing airborne gravimetry with quantum technology (AeroQGrav), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11187, https://doi.org/10.5194/egusphere-egu26-11187, 2026.
EQUIP-G aims at demonstrating the possibilities of quantum gravimeters through the execution of continuous and repeated observation in Europe, under different geological and geodynamical settings.
To showcase the possibilities enabled by quantum gravimeters when used to address geophysical challenges and the advantages they may offer with respect to devices based on other technologies (spring and superconducting relative gravimeters, free fall corner cube absolute gravimeters), several use cases (UCs) will be carried out during the course of the project. When defining the set of project UCs, the EQUIP-G consortium took into account different perspectives, including the need to tackle urgent and relevant societal topics (e.g., management of natural risks and resources) and the time scale of the gravity changes produced by the phenomena in the target of the different UCs, which must be compatible with the duration of the project.
In the frame of EQUIP-G’s terrestrial use cases (TUCs), quantum gravimetry will be applied to hydrology, volcanology, climatology, geothermic, and geodesy. In particular, among the eight TUCs that will be implemented, two deal with hydrological processes, two focus on time gravity changes developing at active volcanoes, one involves activities framed within the safety analysis of geological repositories for nuclear waste, one focuses on climate monitoring, one is devoted to demonstrating the applicability of quantum gravimetry to geothermal reservoir monitoring, one will be undertaken to assess the feasibility and advantages of using quantum devices for the execution of gravity surveys over extended areas.
Furthermore, two onboard use cases (OBUCs) will be carried out. OBUC1 aims to demonstrate mobile gravity mapping onboard a fixed-wing aircraft, using a commercial quantum sensor in combination with high-quality GNSS observations. OBUC2 will be implemented using an innovative airship platform, instead of the fixed-wing aircraft. Since measurements must be averaged in time, a slow-moving platform will result in higher resolution of the spatial mapping.
Here we provide a description of the EQUIP-G’s UCs, including how each of them will contribute to the assessment of the project’s goals.
How to cite: Reich, M., Carbone, D., Dykowski, P., Enzlberger Jensen, T., Lautier-Gaud, J., and Merlet, S. and the EQUIP-G Use Cases Team: Terrestrial and onboard use cases to demonstrate quantum gravimetry within the EQUIP-G project, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18194, https://doi.org/10.5194/egusphere-egu26-18194, 2026.
An Absolute Quantum Gravimeter (AQG-B07) was deployed in western Greenland to evaluate the robustness, repeatability, and uncertainty of measurements under transport-intensive, harsh and completely remote field conditions. The campaign was conceived as a traceability experiment, linking laboratory reference measurements to remote field sites, with the Arctic environment being an extreme case scenario. A key objective was to assess the feasibility and credibility of absolute gravity measurements at the Kangia North (KAGA) permanent GNSS station near the calving front of the Ilulissat Glacier, one of the fastest-flowing and most dynamically active glaciers in Greenland.
Absolute gravity observations were first carried out at the Borowa Góra Geodetic-Geophysical Observatory (Poland), an ITGRF reference site with repeated absolute gravity measurements, including an international comparison campaign in 2025, and continuous gravity monitoring with a superconducting gravimeter (iGrav) since 2016. These measurements provide a reference baseline for instrument validation prior and subsequent to transport. Before the expedition, outdoor field tests were performed at the observatory in Poland to simulate remote site conditions.
The measurement protocol followed a closed-loop sequence, with the AQG being deployed under progressively less controlled conditions: from Borowa Góra Observatory, through intermediate measurements in the Ilulissat airport hangar (following shipment by sea), to the bedrock near the glacier front (reached by helicopter flight) approximately 50 km inland from Ilulissat within a UNESCO-protected area. Then, the gravimeter returned to the Ilulissat hangar for an additional benchmark observations and, after approximately two months of sea transport, measurements were repeated at Borowa Góra. This procedure enables a direct assessment of instrumental stability, drift, reproducibility and transport-related effects. The measurements were conducted under different microseismic noise conditions, ranging from stable low-noise laboratory and outdoor pillar at Borowa Góra, through semi-controlled hangar conditions with occasional human-induced disturbances, to highly variable and unpredictable (natural origin) noise levels at the glacier site. Throughout the campaign, auxiliary accelerometer data (with which the AQG is equipped) were recorded to characterize site-dependent noise and to quantify its influence on absolute gravity estimates.
We discuss the implications of these results for the uncertainty and credibility of absolute gravity measurements in remote cryospheric environments, with particular emphasis on transport effects, site noise characterization, and operational repeatability of AQGs. Practical solutions and identified limitations for AQG operation under outdoor and Arctic field conditions are presented.
The measurements at Borowa Góra were supported by the QuGrav project (National Centre for Research and Development, Innoglobo III Programme). The Greenland campaign was carried out within the project EQUIP-G (funded by the European Commission under the Horizon Europe program, grant number 101215427) and with support from the Danish Climate Data Agency, serving as a pilot study for future repeated quantum gravimetry observations in Greenland planned for 2028.
How to cite: Ciesielski, A., Jensen, T. E., and Dykowski, P.: Can a quantum gravimeter survive the Arctic? A journey from Poland to Greenland and back, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14936, https://doi.org/10.5194/egusphere-egu26-14936, 2026.
Ocean tide signatures are omnipresent in geodetic observations. This applies to direct observations of sea surface height variations or tidal transports, as well as to geodetic observables that are implicitly affected by them, including horizontal and vertical deformation of the solid Earth, tidal variations of the terrestrial magnetic field, and most importantly, the terrestrial gravity field. Since ocean tide-induced oscillations often have a significant magnitude, they can introduce artefacts into observation time series and thereby degrade the overall observation quality if they are not corrected by a skilful model. A prominent example is tidal aliasing in satellite gravimetric observations, caused by imperfections in ocean tide models, which still contribute significantly to the GRACE(-FO) uncertainty budget.
While modern ocean tide atlases have achieved high accuracy through the incorporation of satellite altimetric observations, several parts of the ocean tide spectrum remain insufficiently known. This particularly includes shallow-water tides excited by hydrodynamical nonlinearity, which can reach high amplitudes in extended shelf seas. Consequently, they can strongly impact, for example, altimetric and gravimetric observations. Due to their small amplitudes and short wavelengths, shallow-water tides are more difficult to observe from space; therefore, modern ocean tide atlases rely heavily on purely numerical modelling. However, the underlying hydrodynamical processes are still not well understood and are only approximately parameterised. Although purely numerical models succeed in reproducing general patterns of shallow-water tides, they are not yet accurate enough to yield a meaningful variance reduction in geodetic observations. For instance, the M4 tide from the TiME22 ocean tide atlas achieved a variance reduction of only 15–25 %.
In this contribution, we combine several approaches to improve the modelling accuracy of TiME over the European shelf – a well-suited test region due to high tidal amplitudes and the availability of long gravimetric time series at near-coastal locations. Modelling strategies include (i) increasing the model resolution to obtain a more realistic representation of bathymetry, (ii) accounting for wetting and drying processes—particularly important in the Wadden Sea—and (iii) representing the divergence between the alignment of mean and bottom-layer flow. While each of these effects improves the overall model performance, their combination substantially enhances the large-scale (temporal and spatial) prediction accuracy of shallow-water tidal dynamics and enables the generation of a geodetic correction atlas for a wide range of nonlinear tides.
How to cite: Sulzbach, R. and Dobslaw, H.: Towards Improved Shallow-Water Tide Modelling for Gravimetric Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10637, https://doi.org/10.5194/egusphere-egu26-10637, 2026.
INGV is currently developing the Italian Fiducial Gravimetric Network, which will consist of approximately ten stations evenly distributed across the national territory. The network will include several INGV stations, equipped with superconducting or absolute (quantum and ballistic) gravimeters, currently the only instruments capable of providing high-precision and stable gravity measurements over long periods, operating in continuous or quasi-continuous mode.
The primary aim of the network is to monitor long-term and long-wavelength variations of the gravitational field over the Italian territory. This network supports the newly established National Reference Gravimetric (G0) and Height (H0) Network. Four stations of the network managed by INGV — Cascina, Napoli, Nicolosi and Sos Enattos — are already operational and acquiring data. Among these four stations, two are equipped with superconducting relative gravimeters (iGravs, manufactured by GWR Instruments): iGrav#25 at Nicolosi and iGrav#70 at Sos Enattos. The Nicolosi station, operational since 2016, is of particular interest for the monitoring of Mt. Etna volcano. The Sos Enattos station, located at the Italian candidate site for the Einstein Telescope (the future European gravitational-wave observatory), was installed in September 2025 at a preliminary location and will be relocated to its final site in early 2026. In November and December 2025, two Absolute Quantum Gravimeters (AQGs, manufactured by Exail) were deployed at Cascina (AQG-A09, installed at the EGO site, where the Virgo gravitational-wave detector is hosted) and Naples (AQG-B06, installed at the CeSMA, University of Naples “Federico II”). All stations are remotely controlled.
Since the installation of each gravimeter, daily analysis of the incoming signal has been carried out. Here we present preliminary results from the already available data. In this first stage, the main objective has been to characterise the recorded signals, evaluating instrumental sensitivity and stability, as well as analysing the environmental noise. In the subsequent phase, the focus will move to the estimation and separation of local contributions from regional-scale signals. To this end, the sites have been or will be equipped with sensors to measure key meteorological parameters, GNSS receivers to monitor ground deformation and, where possible, piezometers to measure the oscillations of the local groundwater table.
How to cite: Dottore, N. and the team: The Italian Fiducial Gravimetric Network based on high-precision continuous gravity measurements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12928, https://doi.org/10.5194/egusphere-egu26-12928, 2026.
We announce the establishment of ENIGMA (East-Asian Network Initiative for Gravity Measurement Alliance), a high-precision observational network of superconducting gravimeters spanning South Korea, Japan, Taiwan, and mainland China. By strategically deploying a parallel observation belt along the major seismogenic zones—including the Japan Trench, Ryukyu Trench, and Nankai Trough—ENIGMA aims to monitor subtle micro-gravity fluctuations associated with the circum-Pacific "Ring of Fire." This spatial configuration enables the systematic analysis of seismic events across diverse magnitudes, focal mechanisms, and depths.
Central to this initiative is the development of a dedicated data hub designed to standardize data formats, facilitate seamless sharing, and provide high-performance computing resources for collaborative research. Beyond traditional geophysics, the network’s exceptional sensitivity offers a novel frontier for fundamental physics, such as searching for dark matter candidates within the Earth’s interior. This presentation outlines the scientific roadmap and various high-impact use cases enabled by the integration of GWR Instruments’ superconducting gravimeters and the ENIGMA data infrastructure.
How to cite: Kim, H., Kim, J., Oh, J. J., Son, E. J., Dehghan, M. J., and Kim, J. W.: ENIGMA: East-Asian Network Initiative for Gravity Measurement Alliance, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17212, https://doi.org/10.5194/egusphere-egu26-17212, 2026.
We present the operational status and performance of the Yemi Micro-Gravity Observatory (YeMiGO) following the installation of the iGrav#001 superconducting gravimeter (SG) at Yemi underground laboratory (YemiLab), South Korea, in October 2022. Situated at a depth of 1,003 m below the surface (118 m below mean sea level), YeMiGO provides a unique ultra-low-noise environment for high-precision geodynamic studies.
Noise characterization using data from September 2023 demonstrates exceptional stability, particularly within the seismic frequency band, confirming the site’s suitability for high-sensitivity gravity monitoring. A calibration factor of -94.38±0.14 μGal/V was determined through a joint observation campaign with the FG5-231 absolute gravimeter.
During the initial 587-day observing run (O1), the SG successfully captured numerous seismic events, including a significant co-seismic gravity offset of 0.561 μGal triggered by a magnitude 6.2 earthquake 765 km away. Preliminary comparative analysis between the iGrav and conventional seismometers suggests that the SG exhibits a more stable response to earthquake distance, offering complementary data for broad-band seismic research.
How to cite: Kim, J., Dehghan, M. J., Kim, H., Oh, J. J., Son, E. J., and Kim, J. W.: Status of YeMiGO: Underground micro-gravity observatory in South Korea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18287, https://doi.org/10.5194/egusphere-egu26-18287, 2026.
This study presents a comparative evaluation of the seismic detection capabilities between the iGrav superconducting gravimeter (SG) at the Yemi Micro-Gravity Observatory (YeMiGO) and conventional broadband seismometers. We analyzed the initial 587-day observation period following the SG's installation to assess their relative response characteristics across varying epicentral distances.
Under a unified analysis framework, the YeMiGO SG identified 398 seismic events, while the regional broadband seismometer network recorded 282 events.
The preliminary results reveal a difference in relative sensitivity: whereas the detection threshold of broadband seismometers exhibits a more pronounced degradation as a function of distance, the SG maintains a relatively stable signal-to-noise ratio for far-field events. These findings suggest that the iGrav SG is less susceptible to the sensitivity loss typically associated with increasing epicentral distance. Consequently, the SG provides a more robust and extended detection range, serving as a powerful complementary tool to traditional inertial sensors for global seismic monitoring and deep-earth structure studies.
How to cite: Son, E. J., Kim, H., Kim, J., Oh, J. J., and Kim, J. W.: Comparative Performance Analysis of Seismic Sensitivity: Superconducting Gravimeter vs. Broadband Seismometer, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18504, https://doi.org/10.5194/egusphere-egu26-18504, 2026.
This study presents a Gauss–Markov model (GMM) for gravity field determination, in which the disturbing potential is parameterized using adjusted spherical cap harmonics (ASCH) in local spherical coordinates (r, θ, α). The ASCH parametrization within W = V+ Z (Z = centrifugal potential) means a gravity field representation over a spherical area placed round the local cap pole (φ0, λ0) with an opening angle θ0, and the scaling s=π/2·θ0, using the generalized Legendre polynomial Pn(k),m. With the relation kSCHA ≈ (1/s)·nSH much less ASCH parameters p are needed for the same resolution as for SH.
The GMM related to the above ASCH parametrization, developed in recent years at the Laboratory for GNSS and Navigation at Karlsruhe University of Applied Sciences and implemented in the is presented. The GMM includes direct observations or a priori information on the ASCH parameters (C'n(k),m, S'n(k),m), which can be derived from global spherical harmonic (SH) models. In addition, geometric fitting points (H B, L, h) are used to reduce long-wavelength components of geoid or quasi-geoid models N = h − H resulting from the ASCH parametrization. Furthermore, surface gravity observations g(x) are incorporated as observation equations. Topographic and isostatic reductions are not applied within the ASCH GMM.
Latvia is one of the few countries where at present high-quality vertical direction (VD) observations for the astronomical latitude and longitude (Φ, Λ)x, observed by digital zenith camera, developed at the Institute of Geodesy and Geoinformatics of the University of Latvia, are available (~450 points). This enables the design of an integrated hybrid gravimetric and vertical direction (VD) network. The implementation of the corresponding highly nonlinear Gauss–Markov observation equations for astronomical latitude and longitude, formulated in terms of the ASCH parameters (C'n(k),m, S'n(k),m), is discussed. In this way reduction free surface observations (Φ, Λ)x can be used, while vertical deflections (ξ, η)x require, depending on the type of modeling reductions, and do not provide any additional information.
In the second part, this study introduces a comprehensive methodological framework for the optimization of a hybrid gravity and vertical direction (VD) network within the above GMM parametrized by ASCH. As a first approach, a network reduction method is applied for the 1st order design, enabling the optimization of the number and spatial distribution of combined gravity g(x) and vertical direction (φ, Λ)x observations within a given area. As a second approach, a spectral optimization method based on eigenvalue analysis is employed to solve the first-order design problem. The proposed framework provides a robust basis for optimizing future measurement campaigns and for improving regional gravity field and quasi-geoid modelling.
How to cite: Runde, K. and Jäger, R.: Gauss-Markov Model (GMM) of an Integrated Approach for Regional Gravity Field Determination and Design Optimization of a Hybrid Gravimetric and Vertical Directions Network Using Adjusted Spherical Cap Harmonics (ASCH) Modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15045, https://doi.org/10.5194/egusphere-egu26-15045, 2026.
The Laser Ranging Interferometer (LRI) on GRACE FO provided orders of magnitude improved precision satellite-to-satellite ranging measurements over the microwave ranging instrument. The LRI successes have resulted in the next evolution of GRACE mission architectures (GRACE C and NGGM) to baseline the LRI as the main science instrument. The optical cavity assembly was critical to the success of the LRI, as it provides the laser frequency stability required for precision measurement of nanometer-scale range changes between two spacecraft. This optical cavity has been developed over the last 20 years at BAE Systems SMS (formerly Ball Aerospace) under internal and NASA/JPL funding. The optical cavity design successfully flew and operated on GRACE FO for the duration of LRI measurements. The locked laser frequency noise performance is 30 Hz/sqrt(Hz) down to mHz frequencies.
For GRACE C, several key improvements were made to the cavity to improve its manufacturability, reliability, and compatibility with GRACE C LRI architecture (accommodation of the Scale Factor Unit). The cavity is based on a Fabry-Perot etalon at center wavelength 1064nm, with free spectral range of 1.93 GHz and Finesse of ~50,000. The cavity has integrated photodiodes for sensing the transmitted and reflected beams from the etalon, and a photodiode pre-amplifier which provides the feedback signal to the Laser Ranging Processor for performing the Pound-Drever-Hall Lock for laser stabilization. BAE Systems SMS has delivered 3 tested and qualified optical cavities to JPL for integration into the LRI instrument for the GRACE C mission, anticipated to launch in 2028. A very similar optical cavity is baselined for the LISA mission, and BAE Systems SMS’s cavity design can be adapted to other space platform with laser stability needs.
How to cite: Lee, J., Craig, R., Drobot, S., and Lindensmith, C.: Optical Cavity Developments for GRACE-like Architectures, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15184, https://doi.org/10.5194/egusphere-egu26-15184, 2026.
CARIOQA (Cold Atom Rubidium Interferometer in Orbit for Quantum) is a European initiative to demonstrate quantum sensing from space, paving the way for next-generation, gravimetry-based climate and Earth-system observations. By deploying a cold atom interferometer on a dedicated satellite, CARIOQA seeks to validate the operational feasibility of quantum sensors in a space environment, thereby strengthening Europe’s technological sovereignty in quantum technologies and pushing the boundaries of space-based science.
The first part of CARIOQA – the Pathfinder Mission Preparation (PMP) – started in late 2022. It focuses on the development of an engineering model of the quantum accelerometer accompanied by the scientific background and considerations for the operation in orbit. Phase A (PHA), executed from early 2024 to mid-2025, defined the mission architecture, established requirements on the mission, instrument and satellite, and successfully demonstrated the technical feasibility of a Quantum Space Gravimetry Pathfinder Mission within the next decade. Building on this progress, Phase B (PHB) officially began in October 2025 and will span 24 months. During this phase, the mission concept will be consolidated, and critical technologies for both the quantum payload and satellite platform will be advanced to Technology Readiness Level (TRL) 6. This milestone will validate the maturity and space worthiness of key components, positioning CARIOQA for future flight implementation.
While the primary objective of CARIOQA is the technological demonstration of a spaceborne quantum accelerometer, the mission also addresses scientific questions. These include the potential of quantum sensors to achieve higher accuracy in Earth’s gravity field recovery, probe the density of the upper layers of the atmosphere and the feasibility of upgrading the accelerometer into a spaceborne gradiometer. Such capabilities could revolutionise the ability to monitor mass transport processes—such as the distribution of water masses—offering vital data for climate change modelling, sea-level rise assessment, and sustainable water resource management.
This contribution presents the current status and scientific vision of CARIOQA-PHB, highlighting the scientific possibilities of a quantum pathfinder mission.
CARIOQA-PHB is a joint European project, funded by the European Union (id: 101189541), including experts in satellite instrument development (TAS, exail, ZARM, LEONARDO), quantum sensing (LUH, LTE, LP2N, ONERA, FORTH), space geodesy, Earth sciences and users of gravity field data (LUH, TUM, POLIMI), mission analysis (GMV) as well as in impact maximisation and assessment (PRAXI Network/FORTH, G.A.C. Group), coordinated by the French and German space agencies CNES and DLR under CNES lead.
How to cite: Biskupek, L. and the CARIOQA Consortium: CARIOQA Phase B - The next step on the European path to quantum sensors in space, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9366, https://doi.org/10.5194/egusphere-egu26-9366, 2026.
Satellite gravity missions are a powerful tool to measure the global Earth’s gravity field and consequently provide important information for geosciences. However, improvements in spatial and temporal resolution are required for many applications. Simulation studies are performed to quantify the influence of improved sensors, orbit parameters and measurement concepts on the recovered gravity field solution. The investigations focus primarily on accelerometers by evaluating the concept of Cold Atom Interferometry (CAI) accelerometers and their combination with electrostatic accelerometers for future satellite gravity missions. CAI accelerometers with their long-term stability would complement the classical electrostatic accelerometers very well.
Different accelerometer performance levels and orbit designs are tested within a closed-loop simulation in order to quantify their impact on the gravity field solution. The modelling of the CAI behavior accounts for several noise sources and systematics such as the detection noise, laser frequency noise, wavefront aberration, and sources of contrast loss. The effects of satellite rotations and their compensation by a counter-rotation mirror are also considered. Furthermore, the benefit of a quantum gyroscope is investigated. The measurement of the rotation rate is a critical factor for the required rotation compensation and also in gradiometry scenarios.
Additionally, simulation results for the pathfinder mission Cold Atom Rubidium Interferometer in Orbit for Quantum Accelerometer (CARIOQA) are presented. CARIOQA will demonstrate the application of a CAI as an accelerometer in space. As preparation of the pathfinder mission, closed-loop simulations for gravity field recovery are performed for two scenarios: 1) The CARIOQA pathfinder mission involves a single satellite utilizing high-low satellite-to-satellite tracking. 2) A possible future quantum space gravimetry mission consists of a constellation of multiple satellites operating in a low-low satellite-to-satellite tracking mode.
We acknowledge the support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – EXC-2123 Quantum-Frontiers – 390837967 and the European Union for the project CARIOQA-PMP (Project-ID 101081775). This work is also supported by the Federal Ministry for Economic Affairs and Climate Action (BMWK), Project 50NA2310A (SpaceQNav).
How to cite: Knabe, A., HosseiniArani, A., Fletling, N., Beaufils, Q., Sreekantaiah, A. C., Pereira dos Santos, F., Müller, J., and Schön, S.: Benefit of Cold Atom Interferometry Inertial Sensors for Future Satellite Gravity Missions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16553, https://doi.org/10.5194/egusphere-egu26-16553, 2026.
More precise determination of mass-redistribution processes in the Earth system demands novel measurement concepts and sensors for future satellite gravimetry missions. On the sensor side, atomic clocks are interesting candidates due to the gravitational red-shift effecting the clock’s frequency. However, clocks also experience a red-shift due to their state of motion. Hence their velocity needs to be known very precisely. This problem can be solved by utilizing a classical time-wise variational equation approach for gravity field recovery. In this approach the satellite's orbit in terms of position and velocity is adjusted together with the gravitational field coefficients and hence no prior high accuracy knowledge of the satellite's (clock's) velocity is needed.
This contribution gives detailed insights into satellite-based clock measurements used in gravity-field recovery. We present the mathematical foundations for an idealised measurement and a realistic one-way frequency comparison via laser. Results are evaluated in a closed-loop approach for multiple scenarios, like GRACE, Bender, Helix, and High-Low.
We investigated the performance of clock measurements between satellites in different mission scenarios, noise levels and clock integration times under consideration of increasingly realistic simulation and processing conditions. Comparison of these analyses to KBR measurements gives insights into the limits and required technological improvements concerning atomic clocks that are needed to benefit from clocks in gravimetric missions.
This work has been part of the Collaborative Research Center 1464 TerraQ and funded by DFG.
How to cite: Huckfeldt, M., Wöske, F., and Rievers, B.: Atomic Clocks in Satellite Gravimetry, Investigation of Precision Requirements by Closed Loop Simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18419, https://doi.org/10.5194/egusphere-egu26-18419, 2026.
Posters virtual: Thu, 7 May, 14:00–18:00 | vPoster spot 3
EGU26-15725 | Posters virtual | VPS25
Geopotential Difference Determination via BDS and Galileo Multi-Frequency Time-Frequency SignalsThu, 07 May, 14:12–14:15 (CEST) vPoster spot 3
Traditional methods for determining geopotential and height require successive transfers of leveling and gravity measurements, which are prone to error accumulation, face challenges in transoceanic applications, and are generally time-consuming, labor-intensive, and inefficient. Based on the principles of general relativity, an alternative approach using high-precision time-frequency signals to determine geopotential can overcome these limitations. In this study, simulation experiments were conducted to determine geopotential differences using BDS and Galileo five-frequency undifferenced carrier phase time-frequency transfer technology. The simulations employed clocks with different performance characteristics, utilizing precise clock offsets and multi-frequency observation data from both systems. The results show that the frequency stability achieved by BDS and Galileo five-frequency undifferenced carrier phase time-frequency transfer can reach approximately 3×10⁻¹⁷. The root mean square of the determined geopotential differences corresponds to centimeter-level equivalent height accuracy, and the convergence accuracy of the geopotential difference by the final epoch can reach better than 3.0 m²·s⁻². Given the rapid development of GNSS multi-frequency signals and ongoing improvements in the precision of products such as code and phase biases, geopotential determination based on Galileo and BDS multi-frequency signals is expected to have broader application prospects in the future. This study was supported by the National Natural Science Foundation of China project (No. 42304095), the Key Project of Natural Science Research in Universities of Anhui Province (No. 2023AH051634), the Chuzhou University Research Initiation Fund Project (No. 2023qd07).
How to cite: Xu, W. and Song, J.: Geopotential Difference Determination via BDS and Galileo Multi-Frequency Time-Frequency Signals, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15725, https://doi.org/10.5194/egusphere-egu26-15725, 2026.
