G4.2 | Modern Concepts for Ground and Space Observations of the Earth Gravity Field
EDI
Modern Concepts for Ground and Space Observations of the Earth Gravity Field
Convener: Marvin ReichECSECS | Co-conveners: Jürgen Müller, Daniele Carbone, Elske van Dalfsen, Sébastien Merlet
Orals
| Thu, 01 May, 10:45–12:30 (CEST)
 
Room K2
Posters on site
| Attendance Thu, 01 May, 16:15–18:00 (CEST) | Display Thu, 01 May, 14:00–18:00
 
Hall X1
Orals |
Thu, 10:45
Posters on site
Thu, 16:15
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)".

Orals: Thu, 1 May | Room K2

Chairpersons: Marvin Reich, Jürgen Müller, Sébastien Merlet
10:45–10:50
5-minute convener introduction
Gravimetry
10:50–11:00
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EGU25-11695
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On-site presentation
Gravity and gravity gradient simultaneous survey in an urban environment 
Camille Janvier, Greta Firenze, Nuno Pires, Carlos Didelet, Antonio Marques, Yasser Omar, Cedric Majek, and Bruno Desruelle

In development since 2019, Exail’s Differential Quantum Gravimeter (DQG) is a double quantum gravimeter capable of measuring both gravity and vertical gravity gradient (VGG) at the same time [1]. In the laboratory it has shown sensitivities down do 250nm/s²/sqrt(tau) and 30E/sqrt(tau) as well as sub-10nm/s² and sub-1E stabilities. 

Here we show the performance of this instrument in the field by performing a dual gravity survey in the streets of Lisbon in order to detect a sewer system from the XVIIIth century. The survey was performed in collaboration with Lisbon city archeology laboratory (CAL). In total 26 stations in three days have been taken. The sewer system can be clearly observed on the gravity gradient signal, less so on the gravity signal, which is less resilient to the especially high environmental noise. The survey was performed in early October 2024 in mild temperature conditions but in the presence of wind and rain which necessitated the use of a tent.

Despite this DQG prototype not being originally designed for outdoor use, no issues were encountered during the measurements which bode well for future outdoor versions of this instrument, in particular for the automatized version in development within the FIQUgS project and which should improve significantly the rate of measurement.

We acknowledge fruitful discussions with Thomas Jacob from BRGM and Daniele Sampietro as well as Martina Capponi from GReD. Exail acknowledge funding from the Horizon-EUROPE project FIQUgS, grant number 101080144. YO acknowledge support from FCT – Fundação para a Ciência e a Tecnologia (Portugal), namely through project UIDB/04540/2020.[1] C. Janvier, V. Ménoret, B. Desruelle, S. Merlet, A. Landragin, and F. Pereira dos Santos, Compact differential gravimeter at the quantum projection-noise limit, Phys. Rev. A 105, 022801 (2022).

How to cite: Janvier, C., Firenze, G., Pires, N., Didelet, C., Marques, A., Omar, Y., Majek, C., and Desruelle, B.: Gravity and gravity gradient simultaneous survey in an urban environment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11695, https://doi.org/10.5194/egusphere-egu25-11695, 2025.

11:00–11:10
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EGU25-1677
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ECS
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On-site presentation
Calibration of superconducting gravimeters by combination with absolute quantum gravimeters 
Ezequiel D. Antokoletz, André Gebauer, Julian Glässel, and Hartmut Wziontek

Classically, the scale factor of superconducting gravimeters (SGs) can be determined by two approaches. A first estimate can be obtained by comparison of its observations with a theoretical Earth tide and precise ocean tide loading models, after correcting for the effects of polar motion and atmosphere on gravity. However, an independent estimation from existing tide models is preferred and can be achieved through the combination with parallel absolute gravity observations, usually performed with classical free-fall gravimeters. In this case, absolute gravity observations are carried out only over a few days to limit the mechanical wear of these instruments, and preferably during periods of spring tides to enhance the signal-to-noise ratio.

In this study, we investigate the use of the quantum gravimeters AQG by Exail for the calibration of superconducting gravimeters at the Geodetic Observatory Wettzell, Germany. To do so, continuous absolute gravity measurements were carried out for different periods of time and up to three months and combined with the SG observations. Scale factors were estimated through a least-squares adjustment, considering different time windows. Although the AQGs have a much larger scatter of individual experiments than FG5 absolute gravimeters, their benefit is considerably longer and continuous observation epochs, that are proved to be important also by synthetic data. A good agreement of the calibration factors with previous estimations was found, demonstrating the potential of quantum gravimeters to calibrate SGs.

How to cite: Antokoletz, E. D., Gebauer, A., Glässel, J., and Wziontek, H.: Calibration of superconducting gravimeters by combination with absolute quantum gravimeters, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1677, https://doi.org/10.5194/egusphere-egu25-1677, 2025.

11:10–11:20
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EGU25-13302
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ECS
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On-site presentation
Regularization Approach in Tidal Analysis for Absolute Gravimetry 
Adam Ciesielski and Przemysław Dykowski

Superconducting and quantum gravimeters, through continuous precise relative and accurate absolute gravity measurements, provide deep insight into monitoring the Earth's gravity field, rheology, and temporal changes. The major obstacle in the analysis of gravimetric data is refining the correct tidal model to be subtracted from the measurements. The main limitation in tidal analysis is the resolution - coarse tidal groups. The recent, innovative Earth Tides Analysis software, RATA (Regularized Approach to Tidal Analysis), abandons this 100-year-old concept of groups, and by restricting overfitting possibilities, it provides the finest solution. 

For practical reasons, the concept of groups is still present in RATA as data-driven "reference groups." This remains a useful feature for applications such as gravimetry, since the only available software uses PRETERNA or TSOFT formats. They not only require groups but also allow a limited number of them, not easily distinguishing between various tidal degrees. We implemented functions that transform the outcome model from RATA into PRETERNA and TSOFT formats. Afterwards, we investigated the differences in the resulting synthetic time series using various approaches (e.g., theoretical tides with ocean corrections, local RATA and ETERNA models) for various stations. 

Moreover, since the aim and feature of RATA is to achieve super-resolution that even highly violates the Rayleigh criterion in tidal analysis, we investigated how the length of the analysed time series affects the outcome RATA model. For analyses of various stations from the IGETS database, we also studied the change of residual time series. Additionally, we compared the gravity time series between the superconducting gravimeter (SG) with the absolute quantum gravimeter (AQG) operating simultaneously at Borowa Góra Observatory for longer than three months (part of Innoglobo QuGrav NCBR project). Finally, we investigated how much tidal information we could extract from the AQG and compared it with RATA tidal models resulting from the SG. 

How to cite: Ciesielski, A. and Dykowski, P.: Regularization Approach in Tidal Analysis for Absolute Gravimetry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13302, https://doi.org/10.5194/egusphere-egu25-13302, 2025.

11:20–11:30
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EGU25-20699
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On-site presentation
Quantum Pathways Institute contributions to a roadmap for technical implementation and scientific interpretation of a spaceborne quantum gravity gradiometer. 
Srinivas Bettadpur, Ufuk Topcu, Seth Bank, Dan Wasserman, Murray Holland, Dana Anderson, Penina Axelrad, Marco Nicotra, Dan Blumenthal, Michael Watkins, and Michelle Stephens

The Quantum Pathways Institute (QPI), sponsored by NASA/STMD, is a collaborative effort between UT Austin, CU Boulder, Caltech, UC Santa Barbara, and NIST. The QPI is focused on advancing quantum sensing technology for next-generation Earth science applications, and its vision targets 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 reports progress on two fronts. First a short summary status of QPI team’s work is presented, on quantum sensing research, conceptual development, and experimental results targeted towards a gravity gradiometer system. Second, we present progress in developing a roadmap to science mission implementation, including progress in addressing some key technical spaceflight and data analysis challenges.

How to cite: Bettadpur, S., Topcu, U., Bank, S., Wasserman, D., Holland, M., Anderson, D., Axelrad, P., Nicotra, M., Blumenthal, D., Watkins, M., and Stephens, M.: Quantum Pathways Institute contributions to a roadmap for technical implementation and scientific interpretation of a spaceborne quantum gravity gradiometer., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20699, https://doi.org/10.5194/egusphere-egu25-20699, 2025.

11:30–11:40
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EGU25-20735
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On-site presentation
Optomechanical inertial sensors and their applications to Earth and Planetary science 
Felipe Guzman

Accelerometry has become crucial for monitoring mass change and geophysical phenomena within the Earth, as well as dynamics on planetary systems. Optomechanical inertial sensors are novel alternative instruments that feature characteristic advantages such as lower cost, size, weight and power (CSWaP) with acceleration sensitivities on par with GRACE. Reduced CSWaP makes these instruments suitable for enhancing mission reliability as redundant accelerometers, and can also improve science data quality by providing measurements of thruster firings and transient effects, among others.

Moreover, low CSWaP optomechanical instruments would enable cost-effective mission designs, spacecraft miniaturization, simplified architectures, as well as the deployment of constellations of satellite pairs flying at lower altitudes.

We will discuss some of the potential science cases that can be addressed with this technology, as well as current status and progress in the development of these novel low-frequency optomechanical inertial sensing technologies.

We will present updates on recent measurements, showing noise floors in the order of 8 pico-g above 60 mHz in our laboratory, as well as their planned use in upcoming space demonstrations.

How to cite: Guzman, F.: Optomechanical inertial sensors and their applications to Earth and Planetary science, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20735, https://doi.org/10.5194/egusphere-egu25-20735, 2025.

11:40–11:50
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EGU25-9728
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On-site presentation
Investigating Satellite Control Algorithms for Formation Flying in Gravity Field Recovery 
Andreas Leipner, Stefanie Bremer, and Meike List

Satellite formation flying has emerged as a promising approach for high-precision gravity field recovery, complementing and extending the capabilities of double-satellite missions such as GRACE and GRACE-FO. The use of multiple satellites in formations allows for improved spatial and temporal resolution in gravity field recovery and reducing alising effects.

Despite its advantages, maintaining precise satellite formations over long mission durations poses significant challenges. Orbital perturbations, such as atmospheric drag, differential gravitational forces, and solar radiation pressure, can degrade the formation geometry, compromising the accuracy of gravity field measurements.

This study investigates the feasibility and effectiveness of advanced control algorithms for maintaining satellite formations optimized for gravity field recovery.
 
We employ numerical simulations to model a satellite formation in low-Earth orbit. The satellites are configured in optimized formations, such as triangels rotating around a center point, to maximize sensitivity to gravitational variations. Advanced control algorithms are implemented to counteract perturbations and maintain the formation. The performance of these algorithms is evaluated in terms of formation accuracy and robustness to external disturbances.

The presented results represent our current progress in developing control algorithms for satellite formation flying. The study also highlights the sensitivity of formations to perturbations and proposes control schemes.

How to cite: Leipner, A., Bremer, S., and List, M.: Investigating Satellite Control Algorithms for Formation Flying in Gravity Field Recovery, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9728, https://doi.org/10.5194/egusphere-egu25-9728, 2025.

Relativistic Geodesy
11:50–12:00
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EGU25-14188
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ECS
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On-site presentation
Determination of geopotential at ground station using China Space Station microwave links 
Pengfei Zhang, Chenxiang Wang, Lihong Li, Lei Wang, Wei Xu, Ziyu Shen, Rui Xu, An Ning, Abdelrahim Ruby, and Wenbin Shen

The China Space Station (CSS) is currently in orbit and carries the high-precision optical atomic clock with stability of 2.0×10-15/√τ in its experiment module. We have developed a model to determine the geopotential at the ground based on the gravity frequency shift equation and have created both one-way and dual-frequency transfer models up to c-4. These models consider influence from the troposphere, ionosphere, and solid Earth tides. The proposed model is suitable for measurements at the magnitude of 10-19. Based on the CSS mission, we conducted the simulation experiments. The results indicate that, based on the CSS microwave links, we can obtain the geopotential difference between two sites on the ground with centimeter-level accuracy.

This study is supported by the National Natural Science Foundations of China (NSFC) (Grant Nos. 42030105, 42388102, and 42274011) and the China Postdoctoral Science Foundation (Certificate Number: 2024M752480).

How to cite: Zhang, P., Wang, C., Li, L., Wang, L., Xu, W., Shen, Z., Xu, R., Ning, A., Ruby, A., and Shen, W.: Determination of geopotential at ground station using China Space Station microwave links, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14188, https://doi.org/10.5194/egusphere-egu25-14188, 2025.

12:00–12:10
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EGU25-11356
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On-site presentation
Simulating spaceborne high-precision optical clocks and their potential for measuring relativistic gravity 
Noa Wassermann, Dennis Philipp, and Meike List

Highly precise optical clocks are advancing rapidly and hold the promise of enabling gravity measurements with unprecedented accuracy, particularly through the deployment of spaceborne clocks on satellites. Satellite mission simulations need to improve their accuracy alongside, in order to be able to thoroughly plan such satellite missions and interpret measurements correctly. Therefore, we develop a clock model for our simulation tool that incorporates even small relativistic effects as well as calculations of the clock’s uncertainty due to thermal perturbations. We use these models and our satellite simulator VENQS to study the potentials of future generations of optical clocks, their precision and ability to detect very small relativistic effects like the gravitomagnetic clock effect. We also study their potential use for future relativistic geodesy satellite missions. This talk will present the current state of our research.

How to cite: Wassermann, N., Philipp, D., and List, M.: Simulating spaceborne high-precision optical clocks and their potential for measuring relativistic gravity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11356, https://doi.org/10.5194/egusphere-egu25-11356, 2025.

12:10–12:20
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EGU25-16496
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ECS
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On-site presentation
Chronometric assessment of relativistic degrees of freedom of the gravity field
(withdrawn)
Dennis Philipp
12:20–12:30
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EGU25-4906
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ECS
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Virtual presentation
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Simulating Gravitational Redshift Test Using the European Laser Timing (ELT) Experiment on the ACES Mission 
Abdelrahim Ruby, Wenbin Shen, Ahmed Shaker, Pengfei Zhang, and Ziyu Shen

Gravitational redshift (GRS), a fundamental prediction of general relativity (GR), serves as a critical test of the Einstein Equivalence Principle (EEP) by comparing time flow rates between differing gravitational potentials. Over the decades, GRS experiments in astronomical observations, terrestrial measurements, and space-based investigations have achieved precision levels as fine as 10-5. However, most GRS experiments depend on microwave links for time and frequency transfer, with only a few exploring optical time and frequency transfer methods. Optical time transfer links provide a transformative alternative, offering superior resistance to atmospheric perturbations and higher modulation bandwidths, which enable sub-picosecond synchronization and exceptional time transfer precision. In 1975, Professor Carroll Alley (1927–2016) and his team at the University of Maryland (UMD), USA, demonstrated the feasibility of the optical time transfer method for GRS testing, achieving 10-2 accuracy using cesium clocks with 2×10-14 stability per day and laser pulses of 0.5 mJ energy, 0.1 ns duration, and 10 pulses per second. Modern advancements in optical timing experiments, such as the Chinese Laser Timing (CLT) on the China Space Station (CSS) mission, launched in October 2022, and the European Laser Timing (ELT), part of the upcoming Atomic Clock Ensemble in Space (ACES) mission aboard the International Space Station (ISS), promise unprecedented precision in future GRS experiments.

This study investigates GRS testing by simulating ELT data. The ACES mission features atomic clocks with instabilities of about 2×10-16, including a hydrogen maser achieving 1.5×10-15 after 10,000 seconds and a cesium clock with stability of 1.1×10-13​√τ, where τ is the integration time in seconds. Additionally, the ELT payload is equipped with a novel single photon detector with a timing stability of < 3 ps @ 300 s and an event timer with precision of < 1 ps. Our simulation results indicate that using the two-way laser time transfer (TWLTT) link via the ELT experiment achieves precision levels 3–4 orders of magnitude higher than those obtained in the Alley experiment 50 years ago, thanks to the advanced atomic clocks aboard the ACES mission. This study is supported by the National Natural Science Foundations of China (NSFC) (Grant Nos. 42030105, 42388102, and 42274011) and the Space Station Project (2020-228).

How to cite: Ruby, A., Shen, W., Shaker, A., Zhang, P., and Shen, Z.: Simulating Gravitational Redshift Test Using the European Laser Timing (ELT) Experiment on the ACES Mission, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4906, https://doi.org/10.5194/egusphere-egu25-4906, 2025.

Posters on site: Thu, 1 May, 16:15–18:00 | Hall X1

Display time: Thu, 1 May, 14:00–18:00
Chairpersons: Daniele Carbone, Elske van Dalfsen
X1.130
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EGU25-4113
First results from the comparison of absolute gravimeters WETCAG-2024 at the Geodetic Observatory Wettzell, Germany 
Hartmut Wziontek, Vojtech Pálinkáš, Ezequiel D. Antokoletz, Henri Baumann, Jean-Daniel Bernard, Mirjam Bilker-Koivula, Erik Brachmann, Adam Ciesielski, Danilo Contrafatto, Przemysław Dykowski, Andreas Engfeldt, Alessio Facello, André Gebauer, Fillipo Greco, Domenico Iacovone, Juraj Janák, Johannes Konrad, Jakub Kostelecký, Alexander Lothhammer, Sébastien Merlet, Alfio Messina, Jyri Näränen, Juraj Papčo, Andrea Prato, Marvin Reich, René Reudink, and Christian Rothleitner

The validation of compatibility and long-term stability of absolute gravimeters is a key component for the realization of the International Terrestrial Gravity Reference Frame (ITGRF) of IAG and is relevant for metrology, in particular for the realization of the kilogram. Because a natural reference for the absolute value of gravity acceleration is not accessible, international comparisons of absolute gravimeters are well established. The gravity reference is realized based on a set of accurate absolute measurements and the functional model for their processing. 
After the CCM.G-K2.2023 key comparison supplemented by additional comparison ICAG-2023 held in September 2023 at Table Mountain Geophysical Observatory (TMGO) Boulder, Colorado, USA, there was a need to distribute the gravity reference further to institutions in Europe. Therefore, the EURAMET key comparison of absolute gravimeters EURAMET.M.G-K2.2023 and additional comparison WETCAG-2024 was organized at the Geodetic Observatory Wettzell, Germany, in May and June 2024, where 15 institutions participated with 17 absolute gravimeters. The link to CCM.G-K2.2023 is provided by three gravimeters that took part in both comparisons. Additionally, deviations from the verticality and Eötvös/Coriolis accelerations during the free fall were determined for most of the gravimeters. 
We present first results for the equivalence of the participating gravimeters as well as for the verticality and Eötvös effects. Further, we evaluate and discuss the stability of the reference values over decades, based on a reference function deduced from the registration of the superconducting gravimeter GWR SG030, repeated absolute gravity observations since 2010 and several regional comparisons performed at this station, in particular with the comparison EURAMET.M.G-K3 held at Wettzell in 2018. 
Quantum gravimeters are represented in WETCAG-2024 with two instruments. This allows to compare the new technology with the reference established at the Wettzell station over 15 years, specifically in the context of stability of gravimeters and the upcoming realization of the ITGRF.  

 

How to cite: Wziontek, H., Pálinkáš, V., Antokoletz, E. D., Baumann, H., Bernard, J.-D., Bilker-Koivula, M., Brachmann, E., Ciesielski, A., Contrafatto, D., Dykowski, P., Engfeldt, A., Facello, A., Gebauer, A., Greco, F., Iacovone, D., Janák, J., Konrad, J., Kostelecký, J., Lothhammer, A., Merlet, S., Messina, A., Näränen, J., Papčo, J., Prato, A., Reich, M., Reudink, R., and Rothleitner, C.: First results from the comparison of absolute gravimeters WETCAG-2024 at the Geodetic Observatory Wettzell, Germany, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4113, https://doi.org/10.5194/egusphere-egu25-4113, 2025.

X1.131
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EGU25-20592
Modeling a broad spectrum of hydrodynamically nonlinear ocean tides and their observation by continuously recording terrestrial gravimeters 
Henryk Dobslaw, Roman Sulzbach, Christian Voigt, and Hartmut Wziontek

Ocean tide variability can be decomposed into a vast spectrum of individual partial tides with distinct tidal periodicities. Besides the ~10 dominant frequencies well constrained by satellite altimetry, there is a wide range of smaller oscillations that are much less well determined by observations. Besides other tidal subgroups (e.g., radiational tides and degree-3 ocean tides) these comprise hydrodynamically nonlinear ocean tides, which are generated due to the interactions of major tides. The frequencies of these tides are the sums and differences of the generating major tides and do not necessarily have a counterpart in the tide-generating potential. Nonlinear ocean tides possess significantly large amplitudes, especially in shallow waters as they can be found along the coast of the North Sea in Northern Germany.
We present in this contribution new hydrodynamical simulations of the global dynamics of non-linear ocean tides with the numerical shallow-water model TiME (Tidal Model forced by Ephemerides; Sulzbach et. al, 2021). The simulations benefit from an online implementation of self-attraction and loading, which can simultaneously represent this effect for ocean tides from long to sub-semidiurnal periods. Additionally, the model employs an updated implementation of bottom friction, which considers the shear within the vertical flow direction of the tidal transport. The model results are validated with a network of terrestrial superconducting gravimeters, which are sensitive to both local and global mass anomalies induced by ocean tides. Therefore, gravimeters are not only sensitive to the local sea surface anomaly but integrate this information over a larger area. As they additionally possess a very low noise level and their respective time series have considerable length, gravimeters are well suited to detect these spatially extended mass anomalies of low amplitude. Periods considered in this work range from 1 month down to 4 hours. Depending on the generation type of the different nonlinear tides it can be shown that the observed tidal variability can be well reduced by employing TiME predictions for selected frequencies.

How to cite: Dobslaw, H., Sulzbach, R., Voigt, C., and Wziontek, H.: Modeling a broad spectrum of hydrodynamically nonlinear ocean tides and their observation by continuously recording terrestrial gravimeters, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20592, https://doi.org/10.5194/egusphere-egu25-20592, 2025.

X1.132
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EGU25-10971
On the importance of accounting for instrumental effects when applying gravimetry to volcano monitoring 
Filippo Greco, Daniele Carbone, Danilo Contrafatto, Alfio Alex Messina, and Luca Timoteo Mirabella

Repeated and continuous gravity measurements have long been performed to monitor active volcanoes and study the processes that may lead to unrest and eruptions. Possible instrumental effects must be accurately accounted for, since they can be behind apparent gravity changes even stronger than the real (i.e., volcano-related) ones.

At tall volcanoes, where, due to the rough topography, the difference between the gravity field values at external and summit stations can be hundreds of mGal, strong time changes in gravity may arise from changes in the calibration factor of the device used to perform campaign measurements. For example, a difference in the value of the gravity field between reference station and summit active area of 300 mGal implies an apparent time change of 60 µGal, if a shift of 100 ppm occurs in the calibration factor of the gravimeter. To avoid this, the calibration factor of the instrument used to perform campaign measurements should be regularly checked.

The instrumental drift of relative gravimeters can make it difficult to detect long-term (months to years) gravity changes through continuous measurements. This shortcoming may also affect data from superconducting gravimeters (much more stable than spring gravimeters), especially if relatively small gravity changes are to be detected over time scales of several months, or longer. To address this issue, absolute gravity measurements must be performed at the same site where the continuously recording gravimeter is installed. Here we present some examples from Mt. Etna volcano, where instrumental effects, potentially leading to apparent time changes of some tens of µGal, were detected through suitable measurement strategies.

How to cite: Greco, F., Carbone, D., Contrafatto, D., Messina, A. A., and Mirabella, L. T.: On the importance of accounting for instrumental effects when applying gravimetry to volcano monitoring, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10971, https://doi.org/10.5194/egusphere-egu25-10971, 2025.

X1.133
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EGU25-15763
Determination of physical heights via time transfer 
Klarissa Emma Lachmann, Jürgen Müller, Anja Schlicht, and Peter Vollmair

We present a project from the research unit (RU) "TIME" (Clock Metrology: A Novel Approach to TIME in Geodesy), which seeks to determine gravity potential or height differences between distant locations by comparing optical clocks. A strontium optical lattice clock at the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig will be connected to the German Research Centre for Geosciences (GFZ) in Potsdam via a delay-compensated optical fiber link. Optical time transfer will then be applied between the geodetic observatories in Potsdam and Wettzell (hosting a second optical clock) through the Atomic Clock Ensemble in Space (ACES) using Satellite Laser Ranging (SLR) telescopes.

Additionally, a third optical clock located in Grasse, France, will be included for comparison. This clock, assumed to have similar characteristics to the one in Braunschweig, will connect to PTB via microwave terminals and to Wettzell using both laser and microwave links, forming a triangular measurement configuration.

The innovative aspect of this approach lies in utilizing time transfer, rather than frequency transfer, and employing free-space links over an extended period to measure physical height differences. Key challenges include managing clock and link variations, atmospheric disturbances, visibility limitations, and data gaps. The clock and link errors are modeled specifically for this constellation, involving the ACES system.

This approach demonstrates the accurate determination of physical height differences via time transfer, particularly for Global Geodetic Observing System (GGOS) core stations such as the Geodetic Observatory Wettzell (GOW).

We discuss the underlying principles, unique properties, and specific challenges of this measurement scenario. Additionally, we provide preliminary estimates of the expected accuracies for the various components and the resulting height differences, based on simulations with varying error budgets for comparison.

We acknowledge the support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 490990195 – FOR 5456.

How to cite: Lachmann, K. E., Müller, J., Schlicht, A., and Vollmair, P.: Determination of physical heights via time transfer, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15763, https://doi.org/10.5194/egusphere-egu25-15763, 2025.

X1.134
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EGU25-11309
Absolute Quantum Gravimeter for Field Applications 
Jeremie Richard, Laura Antoni-Micollier, Romain Gautier, Paul Bertier, Pierre Vermeulen, Camille Janvier, Cédric Majek, Bruno Desruelle, and Vincent Menoret

Absolute gravity measurements at the level of 1 µGal using cold atom quantum technology have been demonstrated in the laboratory in 1992 and have ever since received an increasing interest from the geophysics community [1]. In 2015, Exail launched on the marketplace the Absolute Quantum Gravimeter (AQG) [2]. Cutting-edge technology developments brought the necessary easy-of-use, autonomy, and robustness for field deployment.

In 10 years of production, more than 20 units have since been produced for various geophysical applications, including hydrology and volcanology. We present here an overview on the results obtained over this large panel of instruments. Comparison of the sensitivity of the instruments at our premises prior to shipping, shows reproducible performance in the range of 600-800 nm/s²/sqrt(Tau), reaching a stability better than 10 nm/s² after approximately one hour of integration.

Ongoing work focuses on two main axes: the completion and improvement of a budget of systematic effects, that is necessary to evaluate the trueness of the instruments, several instruments already delivered with such a budget; and the improvement of remote operability with the development of a self-leveling tripod.

[1] M. Kasevich, S. Chu. Measurement of the gravitational acceleration of an atom with a light-pulse atom interferometer. Applied Physics B, 1992, vol. 54, p. 321-332.
[2] V. Ménoret et al, Gravity measurements below 10-9 g with a transportable absolute quantum gravimeter. Scientific Reports, 2018, 8, pp.12300.

How to cite: Richard, J., Antoni-Micollier, L., Gautier, R., Bertier, P., Vermeulen, P., Janvier, C., Majek, C., Desruelle, B., and Menoret, V.: Absolute Quantum Gravimeter for Field Applications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11309, https://doi.org/10.5194/egusphere-egu25-11309, 2025.

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EGU25-16499
Results and Findings from the Worldwide First Joint Measurements with 5 Absolute Quantum Gravimeters 
Sébastien Merlet, Marvin Reich, Przemyslaw Dykowski, Pierre Vermeulen, Maxime Arnal, Andre Gebauer, Mohamed Sobh, Nawel Addi, Nicolas Le Moigne, Heiko Thoss, Marcin Sekowski, Jan Bergmann, and Ludger Timmen

Quantum gravimeters have been in use as laboratory instruments by various research groups for some time and have been available as user-friendly commercial devices since 2014. In contrast to traditional absolute gravimeters such as the FG5, which employ corner cubes as a falling test mass, these devices utilise laser-cooled cold-atom clouds. The Absolute Quantum Gravimeter (AQG) produced by the French company Exail is available in two model series: indoor observatory devices (A-series) and outdoor capable devices (B-series).

In this contribution, we present the results of the world's first AQG comparison, conducted in January 2024 at Leibniz University Hanover (Germany) in the gravimetric laboratory of the HiTec building.

Five AQG units (B-series) participated in the comparison, operated by teams from France, Poland and Germany. The measurement activities were conducted over a five-day period, comprising 12-hour tracking series conducted both during the day and night. In contrast with traditional gravity comparisons, the primary objective of these joint measurements was to enhance the understanding of the operational principles of AQGs. In addition to the long measurements each device carried out on 3 out of 5 available pillars, dedicated tests were conducted jointly on all instruments, including tiltmeter calibrations and accelerometer response. The data processing and evaluation focused on device characteristics, stability over time, individual noise levels, and statistical uncertainties of individual measurements.

The joint AQG measurements were independently supported by classical relative and absolute gravity measurements with CG6 and FG5 gravimeters.

How to cite: Merlet, S., Reich, M., Dykowski, P., Vermeulen, P., Arnal, M., Gebauer, A., Sobh, M., Addi, N., Le Moigne, N., Thoss, H., Sekowski, M., Bergmann, J., and Timmen, L.: Results and Findings from the Worldwide First Joint Measurements with 5 Absolute Quantum Gravimeters, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16499, https://doi.org/10.5194/egusphere-egu25-16499, 2025.

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EGU25-17252
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ECS
Gravimetry platform for evaluation and characterization of quantum technologies 
Nawel Addi, Franck Pereira Dos Santos, and Sébastien Merlet

The Horizon Europe project “Qu-Test” [1] aims to establish a European infrastructure open to industry for the characterization and testing of components, subsystems, and instruments developed from quantum technologies. As part of this project, led by a consortium of Research Technology Institutes and National Metrology Institutes within the European Union, we are developing a platform for the functional and metrological characterization of quantum gravimeters.

In my poster, I will present our reference site, which comprises our laboratory, characterized instruments, and models derived from 20 years of measurements.

Our laboratory, located in the Paris region, features a 6 m × 5.5 m × 2 m concrete platform supported by 12 m long legs that reach the Fontainebleau sands layer. Initially constructed for the LNE Watt Balance [2], our activities have since expanded to include the use, study, characterization, and calibration of various types of instruments. Relative spring-based gravimeters, such as portable Scintrex CG5 and CG6 models, enable us to map and model gravity differences throughout the laboratory's 40 m³ volume. A superconducting relative gravimeter iGrav, allows continuous monitoring of temporal changes of g. The absolute reference value is provided by the atomic gravimeter CAG [3], which calibrates the iGrav’s scale factor [4] and evaluates its drift.

The laboratory's size facilitates the simultaneous accommodation of several gravimeters, enabling regular comparison campaigns. The first comparison in 2006 involved only absolute gravimeters of the FG5 type, while recent comparisons have also included atomic gravimeters like AQGs [5]. The site is routinely used to assess the performance and verify the functionality of the French national gravimeter park (PIN PGravi) [6], particularly before participating in international comparisons with FG5 (#206 and #228) [7] and AQG-B01 [8].

This open-access reference site allows users to verify their instruments before field missions, calibrate spring-based relative gravimeters such as the gPhoneX, and test new developments, including quantum gravimeter and dual gravi-gradio-meter systems.

[1] https://qu-test.eu

[2] M. Thomas et al (2017) metrologia 54

[3] R. Karcher et al (2018) New J. Phys 20

[4] S. Merlet et al (2021) J Geod 95

[5] V. Ménoret et al (2018) Sci Rep 8

[6] S. Merlet et al (2024) IEEE Instrum Meas Mag 27

[7] H. Wziontek et al (2025) G4.2 EGU

[8] S. Merlet et al (2025) G4.2 EGU

How to cite: Addi, N., Pereira Dos Santos, F., and Merlet, S.: Gravimetry platform for evaluation and characterization of quantum technologies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17252, https://doi.org/10.5194/egusphere-egu25-17252, 2025.

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EGU25-19523
The CARIOQA Project - A Cold Atom Rubidium Interferometer in Orbit for Quantum Accelerometry 
Liliane Biskupek and the CARIOQA Consortium

The CARIOQA (Cold Atom Rubidium Interferometer in Orbit for Quantum) project aims for the preparation of a pathfinder mission with an atom interferometric accelerometer for a deployment in future missions for earth observation. Atom interferometers offers drift-free, long-term stable measurements, complementing established technology, and consequently the expectation of improved data recovery at low frequencies.

To date, comer cialisation of atom interferometers is ongoing, they were deployed on mobile platforms, and atom optics payloads were adapted to and operated on a zero-g plane, a drop tower, sounding rockets, and a space station. The next step would be embarking such a system on a dedicated satellite to verify its functionality, the goal of CARIOQA.

The project is currently being worked on in two parts, the Pathfinder Mission Preparation (PMP) and the Phase A (PHA). The focus of PMP is on the development of an engineering model of the quantum accelerometer accompanied by the scientific background and considerations for the operation in orbit. PHA is investigating the feasibility of a quantum space gravimetry pathfinder mission within the next decade.

This contribution will outline the background and introduce the CARIOQA project.

CARIOQA is a joint European project, funded by the European Union, including experts in satellite instrument development (Airbus, Exail SAS, TELETEL, LEONARDO), quantum sensing (LUH, SYRTE, LP2N, LCAR, ONERA, FORTH), space geodesy, Earth sciences and users of gravity field data (LUH, TUM, POLIMI, DTU), 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: The CARIOQA Project - A Cold Atom Rubidium Interferometer in Orbit for Quantum Accelerometry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19523, https://doi.org/10.5194/egusphere-egu25-19523, 2025.

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EGU25-17732
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ECS
CARIOQA Pathfinder Mission Development towards Future Quantum Space Gravimetry Missions  
Nina Fletling, Annike Knabe, Jürgen Müller, Manuel Schilling, Liliane Biskupek, and Matthias Weigelt

For over two decades, satellite gravimetry missions have been measuring the Earth’s gravity field globally providing valuable observations for geosciences. Successor missions are already in development to extend this time series. Future objectives include achieving higher spatial and temporal resolutions of gravity field products as well as enhancing the measurement accuracy, currently constraint by, among other aspects, instrument performances. While some adaptations have already been made or are foreseen for the upcoming MAGIC constellation, a significant advancement could be made by replacing or combining the commonly used electrostatic accelerometer on board the satellites with quantum-based sensors to overcome currently existing limitations.

Before launching a dedicated quantum space gravimetry mission, however, the application of a cold atom interferometer as an accelerometer in space needs to be demonstrated to reach the necessary technology readiness level. This shall be achieved by a quantum pathfinder mission which is prepared in the framework of the Cold Atom Rubidium Interferometer in Orbit for Quantum Accelerometer (CARIOQA) project in the Horizon Europe funding programme. The ongoing Pathfinder Mission Preparation (CARIOQA-PMP) project involves developing an engineering model as well as a comprehensive study on the potential scientific outcome of both the quantum pathfinder mission and a future quantum space gravimetry mission. In parallel to PMP, a Phase A (CARIOQA-PHA) study defining requirements on the mission, instrument and satellite, and assessing the overall feasibility of a quantum space gravimetry pathfinder mission is nearing its completion.

This contribution will present simulated gravity field solutions considering the CARIOQA pathfinder mission, a single satellite in high-low satellite-to-satellite tracking mode, and possible future quantum space gravimetry missions consisting of a satellite constellation utilizing low-low satellite-to-satellite tracking. Closed-loop simulations were carried out to assess the benefits of a quantum-based accelerometer compared to the commonly used electrostatic one and to identify remaining challenges.

CARIOQA-PMP is a joint European project, including experts in satellite instrument development (Airbus, Exail SAS, TELETEL, LEONARDO), quantum sensing (LUH, SYRTE, LP2N, LCAR, ONERA, FORTH), space geodesy, Earth sciences and users of gravity field data (LUH, TUM, POLIMI, DTU), 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. The CARIOQA-PHA project includes key partners (CNES, DLR, ADS-F, ADS-G, FORTH) from the CARIOQA-PMP consortium, plus a new industrial partner for the mission analysis (GMV).

We acknowledge the funding by the European Union for the projects CARIOQA-PMP (Project-ID 101081775) and CARIOQA-PHA (Project-ID 101135075).

How to cite: Fletling, N., Knabe, A., Müller, J., Schilling, M., Biskupek, L., and Weigelt, M.: CARIOQA Pathfinder Mission Development towards Future Quantum Space Gravimetry Missions , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17732, https://doi.org/10.5194/egusphere-egu25-17732, 2025.

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EGU25-17773
CARIOQA-PMP: preliminary results of gravity field recovery simulations for the pathfinder mission by the space-wise approach 
Lorenzo Rossi, Mirko Reguzzoni, Amir Mohammad Eslami, Khulan Batsukh, and Federica Migliaccio

The Cold Atom Rubidium Interferometer in Orbit for Quantum Accelerometry - Pathfinder Mission Preparation project (CARIOQA-PMP) is funded under the EU HORIZON program with the aim of developing quantum accelerometers for space applications. Such technology will be used for satellite-based Earth science to support monitoring climate change and the development of mitigation and adaption measures.

The aim of the current work is to assess the expected gravity field recovery performance of the CARIOQA pathfinder mission by running end-to-end simulations based on possible mission configurations. The satellite will be equipped with a single-arm quantum accelerometer and a GNSS receiver. Orbital parameters and instrumental error models are provided by the technological partners of the project. In particular, three orbital scenarios are considered (circular, elliptical and variable-altitude orbits) and a CAI accelerometer with 10-10 m/s2 accuracy level is assumed.

The simulations are performed by applying the space-wise approach developed at POLIMI. The results show that the CARIOQA pathfinder mission is promising for the estimation of the very low degrees of the time variable gravity field, thanks to the almost flat error power spectral density of the cold atom interferometer.

 

How to cite: Rossi, L., Reguzzoni, M., Eslami, A. M., Batsukh, K., and Migliaccio, F.: CARIOQA-PMP: preliminary results of gravity field recovery simulations for the pathfinder mission by the space-wise approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17773, https://doi.org/10.5194/egusphere-egu25-17773, 2025.