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: Jürgen Müller | Co-conveners: Daniele Carbone, Sébastien Merlet, Marvin Reich, Elske de Zeeuw - van Dalfsen, Sergei Kopeikin, Wenbin Shen
Orals
| Wed, 26 Apr, 08:30–10:15 (CEST), 10:45–12:30 (CEST)
 
Room D3
Posters on site
| Attendance Wed, 26 Apr, 16:15–18:00 (CEST)
 
Hall X2
Posters virtual
| Attendance Wed, 26 Apr, 16:15–18:00 (CEST)
 
vHall GMPV/G/GD/SM
Orals |
Wed, 08:30
Wed, 16:15
Wed, 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 possibilities 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 the application to various fields 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. We also 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.).
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 H2020 project “New Tools for Terrain Gravimetry (NEWTON-g)”.

Orals: Wed, 26 Apr | Room D3

Chairpersons: Jürgen Müller, Sébastien Merlet
08:30–08:35
Chronometric Geodesy
08:35–08:55
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EGU23-13573
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solicited
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Highlight
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On-site presentation
Miltiadis Chatzinikos, Pacôme Delva, and Guillaume Lion

Atomic clocks went through tremendous evolutions and ameliorations since their invention in the middle of the twentieth century. The constant amelioration of their accuracy and stability permitted numerous applications in the field of metrology and fundamental physics. For a long time cold atom Caesium fountain clocks remained unchallenged in terms of accuracy and stability. However, this is no longer true with the recent development of optical clocks. This new generation of atomic clock opens new possibilities for applications in chronometric geodesy.

With this progress in clock technology heading towards a relative clock accuracy of 1018, geodetic applications become feasible, such as determining gravity potential differences over large distances at the level of 0.1 m2 s2. In this context, the effect of temporal gravity field variations on the new observable has to be considered. In addition, the clocks could provide results with a high temporal resolution (e.g. 7 to 1 h or less) for understanding the daily to annual evolution of corresponding phenomena, which makes the clocks unique in their ability to continuously monitor regional variations of the gravity potential field, especially when using a well-distributed clock network.

The goal of this paper is firstly to present an extensive review on the contribution of chronometric geodesy to the study of geodynamic phenomena. The second one is to present and analyze the mathematical framework for the estimation of the spatial-temporal variations of the gravity potential field using temporal networks of clocks. The mathematical background of this analysis was inspired from the 4-dimensional integrated geodesy developed in the last decades of the twentieth century.

How to cite: Chatzinikos, M., Delva, P., and Lion, G.: The contribution of atomic clocks to the study of spatial-temporal variations of the earth's gravity potential field, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13573, https://doi.org/10.5194/egusphere-egu23-13573, 2023.

08:55–09:05
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EGU23-5312
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ECS
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On-site presentation
Dennis Philipp, Eva Hackmann, and Claus Laemmerzahl

We derive exact expressions for the relativistic redshift and timing between observers in various configurations in stationary spacetimes for the purpose of chronometry, i.e., relativistic gravimetry based on clocks. These observers are assumed to be equipped with standard clocks and move along arbitrary worldlines. It is shown how redshift observations can be used to infer the (mass) multipole moments of the underlying spacetime, i.e., a decomposition of the gravito-electric potential. In particular, an Earth-bound observer is considered that is meant to model a standard clock on the Earth's surface (or on the geoid).  Its clock is continuously compared with a clock on a satellite to determine from redshift measurements a relativistic gravity potential in the vicinity of the Earth. Results shown here are in agreement with the Newtonian potential determination from the so-called energy approach. The framework is intended for applications within relativistic geodesy and is exemplified in different exact vacuum spacetimes for illustration.

How to cite: Philipp, D., Hackmann, E., and Laemmerzahl, C.: Chronometry: On the redshift and relativistic gravity potential determination in GR, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5312, https://doi.org/10.5194/egusphere-egu23-5312, 2023.

09:05–09:15
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EGU23-11940
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On-site presentation
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Ziyu Shen, Wen-Bin Shen, Tengxu Zhang, Lin He, and Pengfei Zhang

We propose an approach for testing the gravitational redshift based on frequency signals transmitted between a spacecraft and a ground station. The main idea is to integrate one uplink signal from the ground to the spacecraft and two downlink signals from the spacecraft to the ground. Based on the integration and specific correction models, the gravitational shift of the signals between the spacecraft and the ground station can be detected at a high precision level. The gravitational redshift effect can be tested at about E-6 to E-8 levels in different cases for less than one month if the stability of onboard the atomic clock reaches E-17/day. Compared to the scheme of the Gravity Probe-A (GP-A) experiment conducted in 1976, in the new approach, any onboard signal transponder is not required, and the frequency values of the three links can be relatively arbitrary. Since the hardware requirement is decreased, any spacecraft can be a candidate for gravitational redshift experiment if it can emit two different frequency signals and receive a frequency signal from the ground. This study is supported by the National Natural Science Foundation of China (NSFC) (Grant Nos. 42030105, 41721003, 41631072, 41874023, 41804012), Space Station Project (2020)228, and Natural Science Foundation of Hubei Province (Grant No. 2019CFB611).

How to cite: Shen, Z., Shen, W.-B., Zhang, T., He, L., and Zhang, P.: Test of gravitational redshift by combining tri-frequency links between spacecraft and ground station, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11940, https://doi.org/10.5194/egusphere-egu23-11940, 2023.

09:15–09:25
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EGU23-12980
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ECS
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On-site presentation
Noa Wassermann, Andreas Leipner, Dennis Philipp, Jan Scheumann, Stefanie Bremer, and Meike List

One major objective of Geodesy is the observation of the Earth, its gravity field and climate. To study subtle but impactful changes in the gravitational field, novel paradigms and high-precision measurement schemes are emerging.

According to Einstein’s Theory of General Relativity, the proper time of a clock is the four-dimensional length of its worldline through curved spacetime. Thus, the comparison of clocks always is a comparison of local spacetime geometries. Thereupon, clock comparison could be used as a new method, termed chronometry, for gravity field recovery (GFR) via high-precision timing and redshift measurements. With the fast development of new, better, and smaller time measurement devices, optical clocks are a promising tool for GFR. Such clocks can be compared using, e.g., a light signal propagating in free space. For the determination of all gravitational degrees of freedom, it is necessary to relocate at least one clock around the planet. This can be done via moving clocks on satellites. To interpret these precise measurements correctly, it is essential to consider all influences on the laser signal used.

For this purpose, DLR and ZARM developed a simulation platform called XHPS in the scope of the DFG Collaborative Research Center 1464 TerraQ to model the environmental effects on satellites. It is used to study the influences on the laser signal between a ground station and satellites (or between two satellites). In particular, we want to simulate the signal loss caused by the Earth’s atmosphere, as well as other influences such as the relativistic redshift. It might also be interesting to compare the magnitude of redshift and atmospheric perturbations. This work will present the current state of our research.

How to cite: Wassermann, N., Leipner, A., Philipp, D., Scheumann, J., Bremer, S., and List, M.: Simulation of relativistic and environmental influences on laser signals used for gravity field recovery with spaceborne optical clocks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12980, https://doi.org/10.5194/egusphere-egu23-12980, 2023.

09:25–09:35
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EGU23-11934
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On-site presentation
Massimo Visco, Alessando Di Marco, Feliciana Sapio, David Lucchesi, Marco Cinelli, Emiliano Fiorenza, Carlo Lefevre, Pasqualino Loffredo, Marco Lucente, Carmelo Magnafico, Roberto Peron, Francesco Santoli, Natalia Gatto, and francesco vespe

Within the G4S_2.0 (Galileo for Science) project, funded by the Italian Space Agency (ASI), two activities in the field of Fundamental Physics are under investigation and development: a new measure of the Gravitational Red Shift (GRS) and a search for possible Dark Matter (DM) candidates in the form of domain walls. Both researches are based on data from high-accuracy clocks aboard the satellites.

The GRS measurement exploits the two Galileo satellites DORESA and MILENA injected in 2014 into a wrong orbit characterized by a too high eccentricity. The corrected orbit, still has a relatively high eccentricity (about 0.16) suitable for gravitational measurements. Consequently, the clocks frequency of these two satellites is modulated with the changes of the Earth’s gravitational potential at the height of the satellite.

The search for DM matter is done by looking for the expected rapid perturbations in on-board clocks when a structure like a domain wall crosses Earth’s orbit and the Galileo constellation.  If this occurs, on-board clocks would have to change their frequency relative to a reference clock on Earth.

For both targets, a careful knowledge of the satellite’s position is required, to be obtained with a Precise Orbit Determination (POD) in which the main non gravitational perturbations, such as direct solar radiation pressure, are adequately modeled and accounted for. Furthermore, the clock data needs to be cleaned up by removing long-term drift and fast time jumps unrelated to the effects we want to measure.

We will present the preliminary results obtained within these activities.

How to cite: Visco, M., Di Marco, A., Sapio, F., Lucchesi, D., Cinelli, M., Fiorenza, E., Lefevre, C., Loffredo, P., Lucente, M., Magnafico, C., Peron, R., Santoli, F., Gatto, N., and vespe, F.: Measures in Fundamental Physics within the Galileo for Science (G4S_2.0) project using the data of the Galileo Satellite Constellation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11934, https://doi.org/10.5194/egusphere-egu23-11934, 2023.

Future Satellite Gravimetry
09:35–09:45
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EGU23-14485
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Virtual presentation
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Olivier Carraz, Aaron Strangfeld, Luca Massotti, Guenther March, Arnaud Heliere, Ilias Daras, and Pierluigi Silvestrin

In the past twenty years, gravimetry missions have demonstrated a unique capability to monitor not only major climate-related changes of the Earth directly from space - quantifying the melt of large glaciers and ice sheets, global sea level rise, continental draught, major flooding events, and also effects of large earthquakes and tsunamis. Adding to fundamental knowledge of the Earth, a quantum gravimetry mission will provide essential climate variables (ECV) of unprecedented quality for ground water, mass balance of ice sheets and glaciers, heat and mass transport,.. as demonstrated – within limits of past technology – by successful missions like GOCE and GRACE (FO). In order to respond to the increasing demand of the user community for sustained mass change observations at higher spatial and temporal resolution, ESA and NASA are at the moment coordinating their activities and are harmonizing their cooperation scenarios in an implementation framework, called MAGIC (MAss change and Geosciences International Constellation). In future post -MAGIC mission, a combination of classical sensors with CAI, or at a later stage a full quantum sensor will bring up the Quantum Missions for Climate to sensitivity that will open to many applications and user needs with respect to water management and hazard prevention among others [1] [2]. Special note must be taken also on the adoption of Quantum Technology (QT) for Earth Observation by the European Commission (COM), notably in the Horizon Europe programme, under the thrust of Commissioner T. Breton, and of the inclusion of QT in ESA Agenda 2025.

COM and ESA are setting up a process that would realize a Pathfinder Mission to demonstrate the scientific and technical maturity of quantum gravimetry in space with a view to implement a ground-breaking Quantum Mission for Climate and other applications in the next decade.

Several studies related to these new sensor concepts were initiated at ESA, mainly focusing on technology development for different instrument configurations (gravity gradiometers and satellite-to-satellite ranging systems) and including validation activities, e.g. two successful airborne surveys with a CAI gravimeter. A new study has been initiated in 2022, the Quantum Space Gravimetry for Earth Mass Transport (QSG4EMT) with the focus on QSG mission architectures that monitor Earth's mass transport processes and development of QSG user requirements.

A technology roadmap will also be outlined for potential implementation of a Quantum Space Gravimetry Pathfinder mission before the end of this decade, aimed at improving state of the art accelerometers in the low frequency band and pave the way to developing a Quantum Mission for Climate in continuity and enhancement of MAGIC.

 

[1] ESA-EC User Requirements workshop for Space Gravimetry Mission, Nov 2021.

[2] Towards a sustained observing system for mass transport to understand global change and to benefit society, NASA/ESA Interagency Gravity Science Working Group (IGSWG), TUD-IGSWG-2016-01.

How to cite: Carraz, O., Strangfeld, A., Massotti, L., March, G., Heliere, A., Daras, I., and Silvestrin, P.: ESA Activities and Perspectives on Quantum Space Gravimetry, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14485, https://doi.org/10.5194/egusphere-egu23-14485, 2023.

09:45–09:55
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EGU23-13280
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ECS
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Highlight
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On-site presentation
Christian Struckmann, Ernst M. Rasel, Peter Wolf, and Naceur Gaaloul

Quantum sensors based on the interference of matter waves provide an exceptional performance to test the postulates of General Relativity by comparing the free-fall acceleration of matter waves of different composition. Space-borne quantum tests of the universality of free fall (UFF) promise to exploit the full potential of these sensors due to long free-fall times, and to reach unprecedented sensitivity beyond current limits.

In this contribution, we present a simulator for satellite-based atom interferometry and demonstrate its functionality in designing the STE-QUEST mission scenario, a satellite test of the UFF with ultra-cold atoms to 10^-17 as proposed to the ESA Medium mission frame [https://arxiv.org/abs/2211.15412]. Moreover, we will highlight the possibility of this simulator to design Earth Observation missions going beyond state of the art such as the CARIOQA concept [https://arxiv.org/abs/2211.01215].

This work is supported by DLR funds from the BMWi (50WM2263A-CARIOQA-GE and 50WM2253A-(AI)^2).

How to cite: Struckmann, C., Rasel, E. M., Wolf, P., and Gaaloul, N.: Simulating space-borne atom interferometers for Earth Observation and tests of General Relativity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13280, https://doi.org/10.5194/egusphere-egu23-13280, 2023.

09:55–10:05
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EGU23-14264
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ECS
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Highlight
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On-site presentation
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Philipp Zingerle, Roland Pail, Thomas Gruber, and Petro Abrykosov

With the evolution of cold atom interferometry (CAI), an adaptation for spaceborne applications may become possible in the near future. One of the applications which may benefit from such CAI instruments are next-generation satellite gravity field missions (NGGMs), since they rely heavily on the accelerometer performance. Here, either future satellite-to-satellite tracking (SST) missions (such as GRACE/-FO) or satellite gravity gradiometry (SGG) missions (such as GOCE) are feasible. Until now, only electrostatic accelerometers have been used. However, all suffer from an increased long-term instability which affects the accuracy of the long wavelengths of the retrieved gravity field. In this contribution we investigate the impact of CAI sensors on various NGGM mission concepts (either SST or SGG variants) and quantify the instrument-only error separately from the full gravity field retrieval error (which is hampered by temporal aliasing). Knowing that temporal aliasing currently poses one of the main limiting factors, special attention is given to strategies which may help to minimize this error source. Therefore, in addition to investigating future instruments, also extended mission constellations containing several satellites/pairs and alternative satellite configurations are examined with respect to their time-variable gravity field retrieval performance. This work is supported by the ESA QSG4EMT study in collaboration with Politecnico di Milano, Delft University of Technology, HafenCity University Hamburg, University of Bonn and University of Trieste.

How to cite: Zingerle, P., Pail, R., Gruber, T., and Abrykosov, P.: Future satellite gravity field missions – Impact of quantum sensors and extended satellite constellations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14264, https://doi.org/10.5194/egusphere-egu23-14264, 2023.

10:05–10:15
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EGU23-12597
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ECS
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On-site presentation
Öykü Koç, Mirko Reguzzoni, Lorenzo Rossi, and Federica Migliaccio

The aliasing problem in gravity field recovery arises from the under-sampling of geophysical signals which have a period less than twice the sampling period of the mission. This temporal aliasing problem matters even more for future gravity missions when assessing the actual improvement provided by using new technologies such as cold atom gradiometers or flying drag-free with a laser interferometer. The level of errors caused by temporal aliasing is significantly higher than these instrument errors. This indicates that to see any sort of improvement in time-variable gravity field recovery from quantum technologies, the aliasing problem must be overcome first.

In this study, we propose a way of mitigating temporal aliasing effects by the space-wise approach. This approach consists of first estimating the very long wavelengths by some global technique (e.g., a least-squares adjustment) and then using this estimation to reduce filtered gravity gradients. A modification considering the short-term variations in the time-variable signal is here introduced into the filtering procedure. Later, the computed residuals are processed by a local collocation gridding procedure with the aim of improving the solution, especially for the shorter wavelengths. The signal covariance function estimation required for the gridding is here modified to account for the time variable signal.


The data analysis based on the newly modified mathematical model is applied for the monthly time-variable gravity field retrieval by performing simulations over half a year time span. This is done along with the static gravity field estimation with the aim of evaluating the possible overall improvement coming from the use of quantum gradiometers.

How to cite: Koç, Ö., Reguzzoni, M., Rossi, L., and Migliaccio, F.: Mitigating Temporal Aliasing Effects by the Space-Wise Approach for Quantum Gravimetry Missions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12597, https://doi.org/10.5194/egusphere-egu23-12597, 2023.

Coffee break
Chairpersons: Daniele Carbone, Marvin Reich, Elske de Zeeuw - van Dalfsen
10:45–10:55
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EGU23-12725
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Highlight
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On-site presentation
Vitali Müller, Malte Misfeldt, Laura Müller, Martin Weberpals, Kai Voss, Kolja Nicklaus, and Gerhard Heinzel

The next generation of gravimetric satellite missions will likely  utilize a single laser-based instrument to track distance variations between the satellites in a pair. These variations are used to derive the monthly average of Earth’s gravity field. Mission studies and technology developments are ongoing at NASA/USA, DLR/Germany and at the European Space Agency (ESA) in order to advance the successful technology demonstrator aboard GRACE-FO, the Laser Ranging Instrument (LRI), to a primary instrument with appropriate redundancy. The new instruments should of course incorporate learned lessons from the development as well as in-orbit operation of the instrument on GRACE-FO.

The new generation of instruments is expected to have similar noise requirements as in GRACE-FO, since laser ranging observations are usually not limiting the monthly gravity field maps. Design changes in the future LRI are carefully assessed in order to ensure that the actual in-flight precision can reach the same level as in the LRI aboard GRACE-FO, which has shown at high frequencies a noise of 200 pm/Hz, i.e. is able to resolve changes in the 200 km distance as small as single atoms over short time scales. Efforts focus in particular on an improved knowledge of the LRI scale factor, i.e. the absolute laser frequency, because the current approach of correlating KBR and LRI range can not be employed in future missions.

In this presentation we address the LRI technology and some of the trade-offs that have been performed in the design of future instruments in the context of the above studies. Moreover, we discuss the limiting performance aspects for tone errors and noise and summarize the learned lessons and their potential relevance for future missions.

How to cite: Müller, V., Misfeldt, M., Müller, L., Weberpals, M., Voss, K., Nicklaus, K., and Heinzel, G.: Towards Laser Ranging in Future Gravimetric Missions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12725, https://doi.org/10.5194/egusphere-egu23-12725, 2023.

Terrestrial Gravimetry - Sensors and Applications
10:55–11:05
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EGU23-16853
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On-site presentation
Felipe Guzman, Adam Hines, Andrea Nelson, Xiangyu Guo, Guillermo Valdes, and Jose Sanjuan

We report on the progress of our novel low-frequency optomechanical accelerometer. This device is designed to be compact and portable, comprised of a monolithically fabricated mechanical resonator and a compact heterodyne laser interferometer. The resonator is made from fused-silica, which is a low-loss material that provides very low mechanical losses near room temperature. The oscillating test mass is read-out with the highly sensitive heterodyne interferometer. With a measured Q of 4.77x105, an mQ-product above 1200 kg, a fundamental mechanical resonance of 4.7 Hz, we can estimated an acceleration noise floor near 1x10-11 m s-2/√Hz, which makes this device a good potential candidate for future applications in gravimetry, geodesy, geophysics, and hydrology.

A prototype packaging has been developed to reduce losses caused by typical mechanical mounts. We have conducted comparison measurements with commercial low-frequency systems to an excellent agreement. Recent measurements taken with the resonator mounted in this packaging atop a vibration isolation platform have indicated that our system is seismically limited above 1 mHz. Noise floors in the order of 82 pico-g/√Hz at 0.4 Hz has been demonstrated in our laboratory.

We will present recent updates on this optomechanical accelerometer, including up to date measurements of the resonator and interferometer sensitivity, as well as that of the combined system.

How to cite: Guzman, F., Hines, A., Nelson, A., Guo, X., Valdes, G., and Sanjuan, J.: Optomechanical accelerometers for geodesy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16853, https://doi.org/10.5194/egusphere-egu23-16853, 2023.

11:05–11:15
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EGU23-12432
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ECS
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On-site presentation
Anthony Amorosi, Mayana Teloi, Loïc Amez-Droz, Laura Faure, Vincent Ménoret, Peter Rosenbusch, Brieux Thibaut, and Christophe Collette

Over the past decades, gravimeters based on different working principles have been developed, such as superconducting gravimeters, spring gravimeters or interferometric gravimeters. Their ability to measure local changes in gravitational acceleration with a very high level of sensitivity makes these instruments widely used in fundamental physics, inertial navigation and geophysics. Recently, quantum gravimeters based on cold atom interferometry have demonstrated some of the best resolution and stability. The atomic quantum gravimeter (AQG) from iXblue is a drift-free absolute gravimeter with a sensitivity of 750 nm/s^2 at 1 sec and a long-term stability that reaches 10 nm/s^2, currently standing as a top-class industry-standard instrument [1]. However, due to its cyclic operation principle, the sensor is subject to dead times and concentrates on low-frequency variations (DC – 1 Hz). In addition, ground vibrations often overshoot the atom interferometer dynamic range. These issues have been demonstrated to be overcome by combining the quantum gravimeter with a classical accelerometer that senses ground accelerations and decouples the atom interferometer from them, so creating a hybrid quantum-classical sensor [2]. We present the hybridization of an Atomic Quantum Gravimeter with a custom-made optical accelerometer. The accelerometer has been specifically designed to optimally reject ground vibrations in the sensitivity range of the atom interferometer in real time. It consists of a force-feedback interferometric inertial sensor with a bandwidth from 10 s to 100 Hz and sub-picometer resolution. The accelerometer mechanics features fused-silica flexures, allowing to reach a 2.8 Hz natural frequency and a mQ-product of 1100 kg in a compact, 10x10x10 cm3, design. The hybridization of the quantum gravimeter with the optical accelerometer is expected to push down the noise floor of both sensors, ultimately hitting the quantum projection noise of the Absolute Quantum Gravimeter, being 350 nm/s2 at 1 sec. This improvement would therefore open new perspectives for applications of the quantum gravimeter, such as Newtonian-Noise estimation or seismic isolation.

[1] Ménoret et al, Gravity measurements below 10-9g with a transportable absolute quantum gravimeter, Scientific Reports 8, 12300 (2018)

[2] Merlet et al, Operating an atom interferometer beyond its linear range, Mtrologia 46, 87 (2009)

[3] Lautier et al, Hybridizing matter-wave and classical accelerometers, Applied Physics Letters 105, 144102 (2014)

How to cite: Amorosi, A., Teloi, M., Amez-Droz, L., Faure, L., Ménoret, V., Rosenbusch, P., Thibaut, B., and Collette, C.: High-resolution hybrid atomic quantum gravimeter with real-time vibration compensation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12432, https://doi.org/10.5194/egusphere-egu23-12432, 2023.

11:15–11:25
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EGU23-5171
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ECS
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On-site presentation
Camille Janvier, Sebastien Merlet, Peter Rosenbusch, Vincent Ménoret, Arnaud Landragin, Franck Pereira dos Santos, and Bruno Desruelle

We report on the recent progress on exail’s Differential Quantum Gravimeter (DQG). Developed by exail quantum sensors (formerly known as muquans). The DQG  measures the acceleration due to gravity and the vertical gravity gradient simultaneously. It is an industry-grade demonstrator that has been operational for three years now and has achieved state-of-the-art sensitivity mainly limited by Quantum Projection Noise down to a noise floor at about 40E/sqrt(tau) and a long-term stability better than 1E [1]. For gravity measurements the performances are on par or better than exail’s AQG with a sensitivity of 600nm/s²/sqrt(tau) and a stability down to 5nm/s². Measuring the acceleration of the Earth gravity g and the gravity gradient simultaneously and at the same location promises enhanced information on the distribution of underground masses, especially at shallow depths [2].

In addition to survey measurements, we report on the DQG evaluation at the the LNE-Trappes characterized gravimetry laboratory near Paris [3]. A comparison to the gravity reference value has shown good agreement. The vertical gravity gradient measurement also compared favorably to the determinations obtained using a spring relative gravimeter both in terms of performance and in terms of ease-of-use.

Finally, we present on-going instrumental developments that will be key to the design of more compact instruments. Such instruments will be the basis for the Horizon Europe project FIQUgS which aims at realizing field compatible commercial gravimeters as well as data processing tools.

 

[1] C. Janvier, et al., “A compact differential gravimeter at the quantum projection noise limit”, Phys. Rev. A 105, 022801 (2022)

[2] G. Pajot, O. de Viron, M. M. Diament, M. F. Lequentrec-Lalancette, V. Mikhailov, Geo-Physics 73, 123 (2008).

[3] S. Merlet, et al., “Micro-gravity investigations for the LNE watt balance project” Metrologia vol 45 265 (2008)

 

How to cite: 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, 23–28 Apr 2023, EGU23-5171, https://doi.org/10.5194/egusphere-egu23-5171, 2023.

11:25–11:35
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EGU23-14404
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ECS
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On-site presentation
Pablo Nuñez von Voigt, Nina Heine, Waldemar Herr, Christian Schubert, Ludger Timmen, Jürgen Müller, and Ernst M. Rasel

The transportable Quantum Gravimeter QG-1 is based on the principle of atom interferometry with collimated Bose-Einstein condensates (BEC) to determine the absolute value of the local gravitational acceleration g, aiming for an unprecedented level of accuracy < 3 nm s−2. The QG-1 uses an atom-chip to produce well-defined magnetic fields, allowing high controllability of the atomic cloud and creating a BEC. After release from the magnetic trap into free fall, using well-controlled laser pulses the BEC is split, each part accumulating phase on its trajectory during free fall, and thereafter recombined, leading to self-interference. From the phase difference of the two parts of the BEC, the local gravitational acceleration g can be determined. Environmental vibrations contribute to the accumulating phase during free fall, leading to a disturbing phase shift of the interfering BEC. By measuring the high-frequency environmental noise with a classical accelerometer, this additional phase shift can be infered and corrected for in the determination of g.
In this contribution tide-resolving results of the latest measurement campaign with implemented classical sensors to correct for high-frequency vibrations with an accelerometer and drifts with a tiltmeter will be presented, rendering an important milestone for the development of our QG-1.
We acknowledge financial funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Project-ID 434617780 - SFB 1464 TerraQ and under Germany’s Excellence Strategy - EXC 2123 QuantumFrontiers, Project-ID 390837967.

How to cite: Nuñez von Voigt, P., Heine, N., Herr, W., Schubert, C., Timmen, L., Müller, J., and Rasel, E. M.: Atom interferometry in the transportable Quantum Gravimeter QG-1, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14404, https://doi.org/10.5194/egusphere-egu23-14404, 2023.

11:35–11:45
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EGU23-8681
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On-site presentation
Integrated system development of a MEMS Pendulum Gravimeter
(withdrawn)
Phoebe Utting, Abhinav Prasad, Richard Middlemiss, and Giles Hammond
11:45–11:55
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EGU23-4856
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On-site presentation
Henrietta Rakoczi, Giles Hammond, Christopher Messenger, and Abhinav Prasad

This work is concerned with applying machine learning to Bayesian gravity inversion. While various Bayesian frameworks have been explored for this application, these methods are not ideal due to the associated long computation time and can become intractable for a high-dimensional parameter space. For many applications, machine learning can offer a faster approach to obtaining posterior approximations, while not sacrificing accuracy. Normalising flows, which are based on the simple principles of the change of variables formula, recently have become a focus of development for a wide variety of applications. They are a popular alternative to other generative Bayesian frameworks due to their relative ease to train and their simple principles and architecture, making them more transparent and trustworthy for researchers. This work explores how this type of architecture can be applied to the common inverse problem in gravimetry and how it can improve on traditional methods. As a first application, results are shown for the inverse modelling of cuboid underground objects from a variety of gravimetry survey configurations. These simple shapes are not defined by a small number of parameters, rather the model is kept as a 3-dimensional density map defined by a grid of single-density voxels. This decision results in a more difficult problem with a high dimensional posterior space, however, it allows the approach to be more flexible and be directly applicable to the modelling of irregular bodies. Finally, it is discussed how the method performs compared to other traditional and Bayesian inversion methods.

How to cite: Rakoczi, H., Hammond, G., Messenger, C., and Prasad, A.: Normalising Flows for Bayesian Gravity Inversion, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4856, https://doi.org/10.5194/egusphere-egu23-4856, 2023.

11:55–12:05
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EGU23-8358
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On-site presentation
Beatrice Giuliante, Philippe Jousset, Charlotte Krawczyk, Jacques Hinderer, Umberto Riccardi, Tania Toledo, Florian Forster, and Anette Mortensen

The sustainable exploitation of a geothermal reservoir is usually assessed through continuous field monitoring and structural exploration of the hydrothermal reservoir. However, accurate subsurface mass and fluid displacement as well as energy transfer model of the hydrothermal reservoir is most of the time not resolved enough both in space and time. Since 2017, both at Krafla and Theistareykir powerplants (northern Iceland), we use several multi-parameter stations each equipped with a gravity meter (superconducting or spring relative meter), a broad band seismometer, a GNSS receiver and other meteorological and hydrological sensors. With this set-up, we aim to model mass and stress transfer through the combination of absolute and micro gravity measurements, continuous signals measured at the multi-parameter stations and seismic measurements.

We present results from the 2022 micro gravity and absolute gravity campaigns conducted at Theistareykir geothermal field. Through inversion and interpretation of such results, as well as the analysis of the continuous measurements, and injection and production data, we aim to assess the anthropogenic contribution in the mass and energy transfer models of the investigated area.  Furthermore, we show the first continuous measurements and accurate Earth tide model for the Krafla area. The final goal of this study is to verify the conditions of sustainable exploitation of the reservoirs, and establish reservoir parameters, such as permeability, that regulate the response of the geothermal system to changes in production and injection rates.

How to cite: Giuliante, B., Jousset, P., Krawczyk, C., Hinderer, J., Riccardi, U., Toledo, T., Forster, F., and Mortensen, A.: Modelling mass balance and stress transfer at Krafla and Theistareykir geothermal systems, Iceland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8358, https://doi.org/10.5194/egusphere-egu23-8358, 2023.

12:05–12:15
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EGU23-12533
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ECS
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On-site presentation
Martina Capponi, Daniele Sampietro, Thomas Jacob, and Camille Janvier

The measurement of gravity acceleration and of its variations are commonly used by geophysicists in many Earth sciences applications. It is quite well known that gravity at the surface of the Earth is influenced by the masses surrounding the instrument, so its measurement can be exploited to characterize subsurface mass density distribution and to investigate many phenomena related to the Earth lithosphere. Gravity measurements also contribute to the exploration of underground resources (mining, hydrology, oil & gas) as well as to civil engineering activities with the detection of voids and cavities. Quantum gravity sensors have already demonstrated interesting competitive advantages with respect to classical gravimeters since they can measure the field with a higher accuracy and they allow to perform absolute measurements. In the framework of FIQUgS project, funded by the European commission in 2022, a new generation of quantum gravity sensors (QGs) is under development to overcome the barriers limiting the first-generation sensors operational usage (e.g. the transportability and robustness not suitable for outdoor operations). Within the project, a new Absolute Quantum Gravimeter (AQGs) and a Differential Quantum Gravimeter (DQGs) are foreseen to allow not only on field absolute gravity measurements but also measures of the vertical derivative.

In the context of the FIQUgS project a wide review of potential use cases for quantum gravity sensors has been performed. Applications, which benefits from the advantages of the next generation QGs, have been identified, within different market sectors. Different scenarios have been considered and by means of specific synthetic simulations the capabilities of this technology have been assessed.

The potential applications for QGs investigated can be divided in two macro-sectors: the first one includes all the static applications that aim at retrieving the density distribution within a certain area to distinguish any kind of target (e.g. geological models for mining exploration, voids and cavities detection, archeological applications…). The second sector includes dynamic, or the so-called time variable applications which are instead focused on analyzing the temporal variability of potential field signals linked to mass changes (e.g. monitoring of CCS, hydrology variations etc.). For each of the identified scenarios a simulation has been set, which means to build a synthetic model of the study area and analyze its effect in terms of gravity supposing different hypothesis and background information.

The results of this analysis will be here presented showing potentialities of quantum sensors and advantages of this next generation of instruments for geophysics applications.

How to cite: Capponi, M., Sampietro, D., Jacob, T., and Janvier, C.: Gravity applications enabled by quantum sensors. Perspectives for the FIQUgS project., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12533, https://doi.org/10.5194/egusphere-egu23-12533, 2023.

12:15–12:25
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EGU23-4459
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Virtual presentation
Filippo Greco, Alessandro Bonforte, and Daniele Carbone

We present results of repeated absolute gravity and GPS measurements, carried out at Mt. Etna volcano between 2009 and 2018. Absolute gravity measurements are rarely performed along arrays of stations on active volcanoes and, through our unprecedented dataset, we highlight the possibilities of this method to track underground mass changes over long time-scales.

Analysis of the residual absolute gravity data and ground deformation reveals a cycle of gravity increase and uplift during 2009 to 2011, followed by gravity decrease and subsidence during 2011 to 2014.

Data inversion points to a common mass and pressure source, lying beneath the summit area of the volcano, at depth of ~5 km b.s.l. The bulk volume change inferred by the inversion of the deformation data can account for only a small portion of the mass change needed to explain the correspondent gravity variations. We propose that the observed relationship between gravity and vertical deformation was mostly due to the compressibility of the magma in the inferred reservoir, which, in turn, was enhanced by the presence of exsolved gas.

Overall, the gravity and deformation data we present reveal a cycle of magma recharge (2009 – 2011) and discharge (2011 – 2014) to/from the inferred storage zone. During the recharge phase only degassing occurred from the summit craters of Mt. Etna. During the following phase of discharge, the magma lost from the reservoir at ~5 km b.s.l. fed the exceptional phase of volcanic activity during 2011 to 2014, when tens of lava fountaining episodes took place.

How to cite: Greco, F., Bonforte, A., and Carbone, D.: A long-term charge/discharge cycle at Mt. Etna volcano revealed through absolute gravity and GPS measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4459, https://doi.org/10.5194/egusphere-egu23-4459, 2023.

12:25–12:30

Posters on site: Wed, 26 Apr, 16:15–18:00 | Hall X2

Chairpersons: Sébastien Merlet, Marvin Reich, Daniele Carbone
Chronometric Geodesy
X2.44
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EGU23-2482
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Highlight
Yoshiyuki Tanaka, Hiromu Sakaue, Yoshiaki Tamura, and Yosuke Aoki

Advances in the developments of optical clocks have enabled 10-18-level frequency comparisons between fibre-linked clocks. This leads to chronometric leveling on the Earth’s surface with an uncertainty on the order of 1 cm, based on the observation of the gravitational red shift. Since measurement uncertainty does not deteriorate with increasing fibre length, applications of chronometric leveling in geodesy, particularly unification of height reference systems, have been actively studied. When the uncertainty of chronometric leveling reaches a few cm in height, uncertainties in the verification by geodetic survey must be carefully evaluated. In a previous study, we determined the height difference between two clock sites approximately 100 km apart in the Tokyo area, based on geometric leveling and estimated its uncertainty to be roughly 2 cm. Comparison with chronometric leveling using optical lattice clocks is currently underway. In addition to this, frequency comparison between the clock sites in Tokyo and the Mizusawa VLBI observatory 400 km apart is under preparation. In this study, we will report preliminary results on the geodetic determination of the height difference between the latter two sites. Due to the long distance, we combine so called GNSS-geoid method and local geometric leveling. In this approach, the largest uncertainty comes from the error of the geoid model, precluding a few cm-level verification. Confirmation by geometric leveling over 400 km distance should be considered. Uncertainties in the determination of not only static but also dynamic height difference due to tides etc. are discussed, for future repeated frequency comparison experiments to detect tectonic gravitational potential change due to the postseismic relaxation caused by the M9 Tohoku earthquake in 2011.

How to cite: Tanaka, Y., Sakaue, H., Tamura, Y., and Aoki, Y.: Geodetic measurements of the gravity potential difference to validate a 1000-km scale optical lattice clock comparison in Japan - preliminary result, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2482, https://doi.org/10.5194/egusphere-egu23-2482, 2023.

X2.45
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EGU23-4316
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ECS
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Asha Vincent, Juergen Mueller, and Akbar Shabanloui

The high accuracy of optical atomic clocks can be well utilized in geodetic applications. When clocks are placed on the ground, their position and mass distribution decide their ticking rates due to the relativistic phenomena of gravitational redshift. Hence, the fractional frequency difference between two terrestrial atomic clocks provides the gravitational potential difference or the corresponding height difference between them. This novel method of relative height measurement can be used in estimating the discrepancies between local and regional height systems to an accuracy of 1 cm with high-performance clocks achieving a fractional frequency uncertainty of about 10-18. In our simulation, more realistic errors in the local height values are assumed by considering different scenarios like systematic tilts that can accumulate with the distance from the tide gauges, effects due to the elevation of the leveling points, the presence of noisy leveling lines, etc. As a test case, a known a priori height system was split into local systems affected by various errors, and the reunification was carried out using simulated clock measurements. External tidal effects at each clock site have also been considered for a more realistic comparison. The accuracy in the estimation of specific height errors in the involved systems highly depends upon the number of clocks and their spatial distribution in each local system and hence, they have to be optimized in each test case. The error accumulation during height measurements over long distances does not play a role for clock measurements, in contrast to classical spirit leveling. Thus, chronometric leveling proved to be a promising technique that can complement and partly replace the traditional methods in geodesy.

How to cite: Vincent, A., Mueller, J., and Shabanloui, A.: Unification of height systems using chronometric geodesy – A more realistic scenario, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4316, https://doi.org/10.5194/egusphere-egu23-4316, 2023.

X2.46
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EGU23-3646
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ECS
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Highlight
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Guillaume Lion, Gwendoline Pajot-Métivier, and Michel Diament

350 years ago, the pendulum clock for astronomical observations was diverted to become an instrument for measuring gravity. The measurement of the parallax of Mars by Richer and Cassini from Cayenne and Paris showed that the period of a periodic oscillator depends on the gravity field. A link was thus established between the improvement of time measurement and the knowledge of the phenomena that govern it. Since then, the performance and nature of clocks have evolved considerably. Today, atomic clocks are used in various fields that are essential to modern society, such as the realisation of international atomic time (TAI), satellite navigation (GNSS), geodesy, the traceability of trading events, etc.

In the framework of the french ANR ROYMAGE, we are interested in the contribution of a transportable optical field clock for geoscience applications by using the principle of chronometric geodesy. The idea is based on the gravitational redshift, a relativistic effect that predicts that the beat of a clock depends on the speed at which it is moving and the strength of the surrounding gravitational potential. In practice, this means that if we compare the beat of two clocks, then it is possible to directly measure a difference in gravitational potential (or a change in height) between these two clocks. This type of measurement is original because classical geodetic techniques only allow to determine the potential indirectly from gravimetric and classical levelling data.

In this work, we model the gravitational signature (potential, acceleration and tensor) of a mass anomaly as a function of its geometry, depth, size and density contrast. These synthetic simulations allow us to identify which types of structures can be detected by clock comparison measurements with a relative frequency uncertainty fixed at 10-17-18-19 (i.e. a vertical sensitivity of less than 10 cm - 1 cm - 1 mm respectively). We are also interested in the spatial resolution required for a clock measurement to detect two mass anomalies depending on its orientation. Finally, we show that this new chronometric observable combined with gravimetry and gradiometry data could allow a better separation of the sources by adding an additional constraint thanks to the medium and long wavelength gravitational information it provides.

The authors acknowledge the support of the French Agence Nationale de la Recherche (ANR) under reference ANR-20-CE47-0006.

How to cite: Lion, G., Pajot-Métivier, G., and Diament, M.: Field optical clocks and sensitivity to mass anomalies for geoscience applications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3646, https://doi.org/10.5194/egusphere-egu23-3646, 2023.

X2.47
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EGU23-17126
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ECS
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Constantin Nauk, Benjamin Kraus, Jost Hinrichs, Simone Callegari, Stephan Hannig, and Piet Schmidt

Optical atomic clocks achieve fractional systematic and statistical frequency uncertainties on the order of 10−18. This enables novel applications, such as height measurements in relativistic geodesy with ∼ 1 cm resolution for earth monitoring. Towards this goal, we set up a transportable clock based on the 1S03P0 transition in 27Al+. A co-trapped 40Ca+ ion allows state detection and cooling via quantum logic spectroscopy and sympathetic cooling.
We unveil the design and the current status of the transportable apparatus and review the recent development of the laser systems. In particular, we present the clock laser setup emitting at 267.4 nm based on single-pass frequency-quadrupling which allows phase stabilization of the complete path. Furthermore, we show the performance of the fundamental frequency to reach a fractional frequency uncertainty of ~ 10−16 at 1 s.

How to cite: Nauk, C., Kraus, B., Hinrichs, J., Callegari, S., Hannig, S., and Schmidt, P.: Progress on PTB’s transportable Al+ ion clock, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17126, https://doi.org/10.5194/egusphere-egu23-17126, 2023.

X2.48
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EGU23-8745
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ECS
Fatima Rahmouni, Jesús Romero González, Benjamin Pointard, Paul-Eric Pottie, Guillaume Lion, Olivier Jamet, Marie-Francoise Lalancette, William Moreno, Jérôme Lodewyck, and Rodolphe Le Targat

As a direct consequence of the gravitational time dilation predicted by Einstein, atomic clock frequencies depend on the local gravitational potential. Several groups in the world have developed the capacity to control the frequency of a new generation of optical clocks at the 18 digits level, which corresponds to the ability to detect 1 cm height changes. Therefore, it raises the perspective of contributing to a refined definition of the geoid by rivaling traditional geodesy techniques, based either on satellites or on spirit leveling.

 

Transportable optical clocks have drawn considerable interest in the last years [1-3], as they are the only ground-based instruments able to perform a mapping of geopotential variations [4]. In this context, SYRTE has started the development of a new optical lattice clock based on neutral Ytterbium, on top of 3 stationary optical clocks (neutral strontium or mercury) already operational in the lab. It is designed to be transportable and aims at an uncertainty in the 10-18 range. This new optical frequency standard will exploit the research infrastructure REFIMEVE, a metrological fiber network disseminating throughout the French territory a 1542 nm ultrastable frequency reference [5]. The ~60 outputs spread along the link will allow us to remotely compare it to the ~12 stationary European optical clocks that are already connected to the network.

 

We will present a description of the clock design, stressing the technological and conceptual choices that we did in prevision for the field conditions outside of a well-controlled lab. We will notably discuss the strategy we follow to reduce the deadtime in order to adapt to the reduced stability of the clock. It allows us to adapt to the spectral degradation of the narrow laser probing the metrological transition due to field conditions (vibrations, temperature gradients …). Thanks to the operational capacity of the REFIMEVE infrastructure to deliver not only a stable but also accurate optical signal, we will have the possibility to generate locally, with a transportable optical frequency comb, an accurate RF signal able to reference all the instruments attached to the transportable clock. We will therefore conclude by showing how the device under development can be operated exclusively by optical referencing to the REFIMEVE signal.

This work has received support from: Agence Nationale de la Recherche (ANR) with project ROYMAGE (ANR-20-CE47-0006), DIM SIRTEQ, and Labex First-TF with project PATHYNAGE.

[1] M. Takamoto et al., "Test of general relativity by a pair of transportable optical lattice clocks", Nature Photonics 14.7, 411-415 (2020)

[2] J. Grotti et al., "Geodesy and metrology with a transportable optical clock", Nature Physics 14.5, 437-441 (2018)

[3] J. Cao et al., "A compact, transportable single-ion optical clock with 7.8×10−17 systematic uncertainty", Applied Physics B 123.4, 1-9 (2017)

[4] G.Lion, I.Panet, P.Wolf, C.Guerlin, S.Bize and P.Delva, "Determination of a high spatial resolution geopotential model using atomic clock comparisons", Journal of Geodesy91(6), 597-611 (2017)

[5] E. Cantin, M. Tønnes, R. Le Targat, A. Amy-Klein, O. Lopez and P.-E. Pottie, “An accurate and robust metrological network for coherent optical frequency dissemination”, New Journal of Physics, vol. 23, p. 053027 (2021)

How to cite: Rahmouni, F., Romero González, J., Pointard, B., Pottie, P.-E., Lion, G., Jamet, O., Lalancette, M.-F., Moreno, W., Lodewyck, J., and Le Targat, R.: An Yb transportable clock connected to the REFIMEVE fiber network for chronometric geodesy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8745, https://doi.org/10.5194/egusphere-egu23-8745, 2023.

Gravimetry in Space and on Ground
X2.49
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EGU23-2224
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ECS
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Alexey Kupriyanov, Arthur Reis, Manuel Schilling, Vitali Müller, and Jürgen Müller

Twenty years of gravity observations from the satellite missions GRACE, GOCE, GRACE-FO have provided unique data about mass redistribution processes in the Earth system, such as melting of Greenland’s ice shields, sea level changes, underground water depletion, droughts, floods, etc. Ongoing climate change underlines the urgent need to continue this kind of observations utilizing Next Generation Gravimetry Missions (NGGM) with enhanced instruments. Here, we focus on accelerometers (ACC).

Drifts of the electrostatic accelerometers (EA) are one of the limiting factors in the current space gravimetry missions dominating the error contribution at low frequencies (<10−3 Hz). The focus of this study is on the modelling of enhanced EAs with laser-interferometric readout, so called ‘optical accelerometers’ and evaluating their performance at Low Earth Orbits (LEO). Contrary to GRACE(-FO) or GOCE capacitive accelerometers, optical ones sense the motion of the test mass (TM) in one or more axes by applying laser interferometry. Combination of sensing in multiple directions and of several test masses would lead to enhanced gradiometry which would improve the determination of the static gravity field to a higher spatial resolution and may even enable to observe time-variable gravity changes.

Our research is based on very promising results of the mission LISA-Pathfinder which has demonstrated the benefit of using a drag-free system in combination with optical accelerometry and UV TM discharge which allowed sensing of non-gravitational accelerations several orders of magnitude more accurate than it is realized in current gravity missions like GRACE-FO. This research project is carried out in close collaboration with the IGP and the DLR-SI, to provide - on the long run - a roadmap for improved angular and linear accelerometry for NGGM.

In this presentation, we now introduce a framework for modeling enhanced EA with laser-interferometric readout mainly developed by IGP including major noise sources, like actuation noise, capacitive sensing, stiffness and thermal bias. Also, parametrization of the developed ACC model will be discussed including different TM weights and TM-electrode housing gaps. Finally, improved results of the recovered gravity field will be shown based on various mission scenarios applying optical accelerometry and gradiometry.

This project is funded by: Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 434617780 – SFB 1464.

How to cite: Kupriyanov, A., Reis, A., Schilling, M., Müller, V., and Müller, J.: Evaluation of optical accelerometry for next generation gravimetry missions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2224, https://doi.org/10.5194/egusphere-egu23-2224, 2023.

X2.50
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EGU23-7997
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Mohsen Romeshkani, Jürgen Müller, Annike Knabe, and Manuel Schilling

A big interest exists in geoscience disciplines to know the mass variations of the Earth with high resolution and accuracy. For monitoring climate change processes at the required level, it is essential to select the appropriate sensor technology and satellite missions. Future satellite missions will strongly depend on the advancement of novel technology and dedicated observation concepts of the Earth's gravitational field.

The first objective of this study is to characterize various quantum and hybrid gradiometer concepts and to describe their respective error properties. As a result of their white noise behavior at low frequencies, Cold Atom Interferometry (CAI) accelerometers and gradiometers are perfectly suited as complementary methods to classical electrostatic concepts. Future gravity satellite missions could greatly benefit from accelerometers and gradiometers applying atom interferometry, alone or in some hybrid constellation. The comparison will demonstrate the differences in the spectral behavior as well as the mutual benefit of CAI-based and classical electrostatic gradiometers (as used in GOCE).

Using simulated atom-interferometric and hybrid gradient measurements along one or more gradiometer axes in GOCE-like orbits, we determine the gravity field in spherical harmonics coefficients for the various cases and discuss the pros and cons of the selected concepts.

We acknowledge the financial support by the DLR project Q-BAGS, ID 50WM2181 and DLR project QUANTGRAV, ID 50EE2220B.

How to cite: Romeshkani, M., Müller, J., Knabe, A., and Schilling, M.: Benefit of Quantum technology for future earth observation from space – gradiometry case, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7997, https://doi.org/10.5194/egusphere-egu23-7997, 2023.

X2.51
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EGU23-13152
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ECS
Vishu Gupta, Dorothee Tell, Ali Lezeik, Mario Montero, Constantin Stojkovic, Jonas Klussmeyer, Klaus Zipfel, Sebastian Bode, Henning Albers, Christian Schubert, Ernst M. Rasel, and Dennis Schlippert

Quantum sensors based on atom interferometry allow the high-precision measurement of fundamental physical properties. The Very Long Baseline Atom Interferometry (VLBAI) facility in the Hannover Institute of Technology is working towards the measurement of inertial effects, which can be used for tests of fundamental physics and metrology. The sensitivity of atom interferometers depends on several factors one of which being the interferometer time and the large base- line of VLBAI facility provides longer interferometer time which leads to higher sensitivity.
Here we present the current status of the 15 m high VLBAI facility which aims for sub nm/s2 gravity measurement sensitivity. It includes a 10 m high magnetically shielded baseline to reach gradients below 1.5nT/m and a seismic attenuation system for inertial referencing which allows for excellent control over external perturbations of the inertial reference mirror. The long baseline at the VLBAI facility uses rubidium and ytterbium BEC source based atom interferometers with possible interferometer time of 2.8s. After the demonstration of small-scale interferometer, the rubidium BEC source is currently being inserted as fountain source on long baseline.

This work is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation): Project-ID 274200144 - SFB 1227 DQ-mat (projects B07 and B09), Project-ID 434617780 - SFB 1464 TerraQ (project A02), and Germany’s Excellence Strategy - EXC-2123 QuantumFrontiers - Project-ID 390837967.

How to cite: Gupta, V., Tell, D., Lezeik, A., Montero, M., Stojkovic, C., Klussmeyer, J., Zipfel, K., Bode, S., Albers, H., Schubert, C., Rasel, E. M., and Schlippert, D.: Inertial sensing using Very Long Baseline Atom Interferometry, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13152, https://doi.org/10.5194/egusphere-egu23-13152, 2023.

X2.52
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EGU23-3266
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ECS
Nolwenn Portier, Françoise Liorzou, Vincent Lebat, Bruno Christophe, Marine Dalin, and Andreas Gierse

Based on the strong experience acquired through the development of ultra-sensitive electrostatic accelerometers for the GRACE, GOCE and GRACE FOLLOW-ON satellite gravity missions, ONERA is developing a new concept of gravity gradiometer (GREMLIT) for airborne survey. Using a control loop, four proof masses are maintained motionless with respect to the surrounding electrodes. The applied electrostatic forces needed for this control, are linked to the accelerations suffered by each proof mass. Observation of differences in the four proof-mass acceleration outputs inform on the horizontal gravity gradient with an expect accuracy of one Eötvös (10-9 s-2) in laboratory. The adaptation of GREMLIT to airborne conditions requires the cancellation of the acceleration gradiometer common-mode, which is done by integrating GREMLIT on a controlled platform. The operability of GREMLIT in aircraft therefore depends on the stabilizer platform ability to retrieve the parasitic aircraft accelerations, which constitutes a real technical challenge. The presentation will emphasize the conception and development of this stabilizer system and the next steps of the project with hopefully, a first mobile acquisition performed by the end of 2023.

How to cite: Portier, N., Liorzou, F., Lebat, V., Christophe, B., Dalin, M., and Gierse, A.: Planar Electrostatic Gravity Gradiometer GREMLIT, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3266, https://doi.org/10.5194/egusphere-egu23-3266, 2023.

X2.53
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EGU23-3446
André Gebauer, Alfredo Pasquaré, Alexander Lothhammer, Axel Rülke, Mirko Scheinert, Andreas Richter, Thorben Döhne, Eric Marderwald, Abelardo Romero, Claudio Brunini, Mauricio Gende, Reinhard Falk, Gerardo Connon, Sergio Cimbaro, Diego Piñón, and Hernán Guagni

The project “Gravimetric determination of the solid earth reaction due to mass changes in south Patagonia”, funded by the German Research Foundation (DFG), focuses on the viscoelastic characteristics of the upper mantle and its ongoing response to past and present changes in stress caused by the surface loading of the changing ice masses of the Patagonian ice fields. Such in-situ data form an important pre-requisite to constrain the information on present-day ice mass balance obtained by the GRACE and GRACE-Follow On satellite missions.

The GNSS observations carried out by the TU Dresden group in southern Patagonia in the recent decade have shown high uplift rates but at a relatively small spatial scale. These uplift rates are mainly due to glacial mass loss for the time period from the little ice age to present. However, the GNSS data used to determine the surface deformation cannot unambiguously separate elastic and viscoelastic processes. This project seeks to add absolute gravimetry at selected locations which are both situated close to the southern Patagonian ice field and further radiate from the maximum observed uplift. Due to the east-west asymmetry of the observed uplift rates, the measurement range has been extended by stations up to the coast of the Atlantic Ocean. It is well established but little applied in practice, that using GNSS together with absolute gravity time series allows these two processes to be separated. Combining the gravimetric and GNSS observations with seismic measurements and with modelling we hope to improve the observational evidence in this region undergoing rapid viscoelastic deformation. Thus, we aim to yield new insights into the physical properties of the Earth’s interior, especially of the rheology of the mantle, to be later combined with GIA modelling.

We will present the observations covering the working area between the Atlantic coast in the east and the southern Patagonian ice field in the west. In 2020 and 2022 two observation campaigns were performed including absolute gravimetry, relative gravimetry, GNSS, precise leveling and particular water level observations. In this presentation we will focus on the absolute gravity measurements which have been performed at eight locations in southern Patagonia using a micro-g LaCoste FG5 absolute gravimeter. We will discuss the observational setup, the instrumental performance and the results obtained so far together with the uncertainties of the observations.

How to cite: Gebauer, A., Pasquaré, A., Lothhammer, A., Rülke, A., Scheinert, M., Richter, A., Döhne, T., Marderwald, E., Romero, A., Brunini, C., Gende, M., Falk, R., Connon, G., Cimbaro, S., Piñón, D., and Guagni, H.: Absolute gravimetry in South Patagonia for geodynamic applications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3446, https://doi.org/10.5194/egusphere-egu23-3446, 2023.

X2.54
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EGU23-5267
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ECS
Mathijs Koymans, Elske de Zeeuw-van Dalfsen, Läslo Evers, Josefa Sepulveda Araya, Andy Hooper, Ronni Grapenthin, Benedikt Ófeigsson, Freysteinn Sigmundsson, and Yilin Yang

In August 2021, Askja volcano in Iceland experienced  a sudden onset of rapid uplift that followed decades of continuous subsidence. We review the extensive microgravity record from Askja, revisiting data recorded between 1988 and 2017, and presenting new microgravity data from 2021 and 2022 that were collected after the uplift had started. Based on our findings, we provide a comprehensive set of recommendations that should be followed for optimal microgravity data collection and treatment in volcano monitoring. Without such standards, it becomes increasingly challenging to interpret the microgravity results in terms of volcanic processes. At Askja, from 1988 – 2016, exponentially decaying surface subsidence was accompanied by a microgravity decrease, potentially signaling the contraction of its magma chamber, eviction of magma to deeper levels, or other density-decreasing processes. Following this, between 2016 and 2021, a gravity increase occurred in the center of the caldera which effectively annuls the microgravity decrease detected between 1988 and 2016. This increase took place either during subsidence or leading up to and during the uplift, and may potentially be explained by mass accumulation below the caldera. After August 2021, gravity changes follow the free-air gradient, despite continuing deformation with a total uplift of up to 40 cm, suggesting subsurface density decreases as a driving process. Such a process could be envisaged as the previously emplaced intrusion before 2021 that is now undergoing magma vesiculation, is causing a change in the hydrothermal system, or represents the replacement of dense basaltic magma with less dense rhyolitic magma. However, uncertainties for these data are large (50μGal) and small mass intrusions contributing to the uplift may remain undetected. The driving mechanism for the uplift remains enigmatic and future microgravity campaigns will help shed light on its nature.

How to cite: Koymans, M., de Zeeuw-van Dalfsen, E., Evers, L., Sepulveda Araya, J., Hooper, A., Grapenthin, R., Ófeigsson, B., Sigmundsson, F., and Yang, Y.: Recommendations for microgravity campaigns and insight into volcanic subsidence and uplift gained from microgravity data at Askja, Iceland between 1988 - 2022, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5267, https://doi.org/10.5194/egusphere-egu23-5267, 2023.

X2.55
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EGU23-10359
John J. Oh, Ik Woo, Hwansun Kim, Edwin J. Son, SeungMi You, Javad Dehghan, and Jeong Woo Kim

We introduce the recent construction and current status of a deep underground microgravity laboratory, YeMiGO (Yemi Micro-Gravity Observatory), in South Korea. On October 2022, YeMiGO was built at the YemiLab in Jeongseon-gun, Gangwon-do Province, eastern mountain region of the Korean Peninsula. YemiLab is the underground experiment laboratory constructed and operated by the Institute of Basic Science (IBS) in South Korea, designed for a dark matter search project. Through a collaboration between the National Institute for Mathematical Sciences (NIMS) of IBS and the University of Calgary in Canada, GWR Instruments Inc.’s superconducting gravimeter, iGravTM (serial #001) was installed in the joint lab, YeMiGO. YeMiGO‘s surface coordinates are (37.190656N, 128.658326E, and 885m above the mean sea level (MSL)), and the gravimeter was installed at about 1,003m and 118m below the surface and MSL, respectively. In this paper, the construction of the lab, installation, and operation of iGravTM, and its current status are presented. Detailed information on calibration, environmental noise characteristics, and its geophysical application will be also presented. 

How to cite: Oh, J. J., Woo, I., Kim, H., Son, E. J., You, S., Dehghan, J., and Kim, J. W.: New Deep Underground Microgravity Laboratory in South Korea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10359, https://doi.org/10.5194/egusphere-egu23-10359, 2023.

X2.56
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EGU23-9502
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Highlight
Daniele Carbone, Flavio Cannavò, Chiara Montagna, and Filippo Greco

The gravity time series from two iGrav superconducting gravimeters and an AQG-B absolute quantum gravimeter, installed at Mt. Etna volcano, reveal a marked gravity decrease during early-June to late-July 2021, a period when more than 20 short-lasting and strongly explosive eruptions (the so-called lava fountain events) took place from one of the summit craters of the volcano. GNSS data indicate that this phase of gravity decrease was associated to deflation of the volcano edifice. 
We performed a joint inversion of the gravity data and deformation field to define the parameters of the common mass/pressure source. The optimal source is located beneath the summit crater area of Mt. Etna, at a depth between 2 and 3 km below the sea level. Results of the joint modeling also point to a residual mass change that is largely in excess of the corresponding volume change, for any reasonable density of the material extracted from the source. 
We propose that the observed gravity decrease was mostly driven by a decompression-related density change, i.e., an increase in the proportion of exsolved gas to magma in the source reservoir. This hypothesis is checked through comparing the results of the geophysical data inversion with independent estimates of the change in exsolved gas content due to pressure decrease in the source reservoir.

How to cite: Carbone, D., Cannavò, F., Montagna, C., and Greco, F.: Continuous gravity measurements across the June – July 2021 series of lava fountains at Mt. Etna volcano, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9502, https://doi.org/10.5194/egusphere-egu23-9502, 2023.

X2.57
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EGU23-14115
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ECS
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Marvin Reich, Adam Novak, Heiko Thoss, Viviana Wöhnke, Annette Eicker, Matthias Weigelt, and Andreas Güntner

Regularly updated information about states, trends and dynamics of water storage in different spatio-temporal scales has gained increasing importance, especially with a perspective on hydrological extreme events as well as water management issues. Monitoring these storage dynamics is challenging due to the spatial heterogeneity and the contribution of different storage compartments (e.g., near-surface soil moisture, deep unsaturated zone, groundwater). A promising monitoring technique is gravimetry, well suited for the integral observation of different storage compartments. While satellite gravimetry (GRACE, GRACE-FO) provides information on storage variations at a spatially large scale with low spatial and temporal resolution, the opposite is true for terrestrial gravimetry. Ways to combine both satellite and terrestrial gravimetry are addressed and evaluated within the German Collaborative Research Centre TerraQ. For the terrestrial approach, several gravimeters were deployed for continuous monitoring at different locations within Germany. The work presented here takes as an example a forest site within the TERENO observatory of north-eastern Germany, with continuous observations  of a superconducting gravimeter (iGrav 033) since 2017.
The signal footprint of such a gravimeter typically covers a radius of 0.5 to 2 km, depending on local topography, although most of the signal originates from the direct vicinity of the instrument. Also, the device can sense mass changes beyond this distance, depending on their magnitude (e.g., tides, atmosphere or global hydrological effects). In hydro-gravimetric studies, all non-desired signals are typically removed, resulting in residuals that are representative for the local hydrological effects only. Towards comparing and combining these terrestrial measurements with satellite products, one open question is how representative the terrestrial gravity residuals are in a regional context. With the goal to assess this spatial representativeness, we conducted seasonal relative gravity surveys with 2 CG-6 gravimeters in an extent of roughly 25 by 30 km around the iGrav installation. The survey data were combined with spatial information about topography and land-use. Water storage changes could thus be attributed to each survey point. A joint analysis with the continuous measurements of the superconducting gravimeter at the permanent installation site allowed for mapping the spatial patterns and similarities among all sites.

This study is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 434617780 – SFB 1464

How to cite: Reich, M., Novak, A., Thoss, H., Wöhnke, V., Eicker, A., Weigelt, M., and Güntner, A.: Assessing the spatial representativeness of water storage variations from superconducting gravimeter residuals by regional CG-6 surveys, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14115, https://doi.org/10.5194/egusphere-egu23-14115, 2023.

X2.58
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EGU23-1730
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ECS
Estimation of Groundwater Storage Variations in African River Basins: Response to Global Climate Change Using GRACE and GRACE-FO among Past Two Decades
(withdrawn)
Hussein Mohasseb, Wenbin Shen, Jiashuang Jiao, Yuanjin Pan, and Mohamed Freeshah
X2.59
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EGU23-17003
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ECS
Comparison of GRACE and GNSS Seasonal Load Displacements Considering Regional Averages and Discrete Points
(withdrawn)
Lan Zhang, He Tang, and Wenke Sun

Posters virtual: Wed, 26 Apr, 16:15–18:00 | vHall GMPV/G/GD/SM

Chairpersons: Jürgen Müller, Elske de Zeeuw - van Dalfsen
Novel Gravimetric Concepts
vGGGS.2
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EGU23-5134
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ECS
Kuangchao Wu, Wen-Bin Shen, Xiao Sun, Chenghui Cai, and Ziyu Shen

Based on the gravity frequency shift equation, by comparing the frequencies between two precise clocks at two different stations at the 203 Institute Laboratory (in Beijing) and the Luojia Time-Frequency Station (in Wuhan), respectively, the geopotential difference between the two stations is determined. Here, we conduct a clock-transportation experiment for measuring the geopotential difference between the two stations by comparing two remote hydrogen atomic clocks’ frequencies via satellite links. Based on the gravity frequency shift measured between the two remote clocks at Beijing and Wuhan, the geopotential difference between the two stations was determined. Comparisons show that the experimental result deviates from the EGM2008 result by 38.5(45.7) meters in orthometric height. The results are consistent with the frequency stabilities of the hydrogen clocks (at the level of 10−15@day) used in the experiment. With the rapid development of time and frequency science and technology, the approach discussed in this study for measuring the geopotential is prospective and thus, could have broad applications. This study is supported by the National Natural Science Foundations of China (Nos. 42030105, 41721003, 41804012, 41631072, and 41874023), Space Station Project (No.2020-228), and the Natural Science Foundation of Hubei Province of China (No. 2019CFB611).

 

How to cite: Wu, K., Shen, W.-B., Sun, X., Cai, C., and Shen, Z.: Measurement of the geopotential difference between two sites at Beijing and Wuhan using two hydrogen clocks via CVSTT technique, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5134, https://doi.org/10.5194/egusphere-egu23-5134, 2023.

vGGGS.3
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EGU23-3079
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ECS
Fangzheng Li, Le Gao, Bingyang Cai, Wenjie Wu, and Liang-Cheng Tu

The measurements of gravity have been widely applied to earthquake monitoring, resource exploration and identification of natural voids. Traditional gravimeters, restricted by the exorbitant price and bulk, are hardly to be utilized in newly developed applications such as AUV-borne gravimetry and the multi-pixels gravimetry. Fortunately, this is changing with the development of portable MEMS gravimeters.

Here, we have already developed a relative MEMS gravimeter with a quasi-zero stiffness spring-mass system and an arrayed area-changed capacitor for displacement transducing and actuating. This quasi-zero stiffness spring-mass system transfers the acceleration variation to the displacement of the proof-mass with high sensitivity. The displacement is then detected by the arrayed area-changed capacitor. The spring-mass system was installed inside a vacuum chamber for reducing the thermal noise and environmental disturbances. However, the response time of the gravimeter was enlarged when operating in open-loop mode dues to the decreased air damping. Therefore, a force-balance system is utilized in a MEMS gravimeter to improve the response time and the measurement range. This paper proposes an area-changed capacitors for transducing the displacement and balancing the inertial force on the proof-mass. As no additional structures are required on the MEMS chip, the design of the force-balance system is beneficial to simplifying the fabricating process and avoiding additional noise sources.

We calibrated our MEMS gravimeter statically in our cave lab. After linear correction of the drift, the output of the MEMS agrees well with the theoretical earth tide with a coefficient of association of 0.92. The self-noise is evaluated to be 1 μGal/√Hz, which is one of the most sensitive MEMS-based gravimeter reported. In addition, the response time of the MEMS gravimeter was calibrated to be 0.2 s in close-loop mode, which is 2000 times faster than that in open-loop mode. This will promote improved accessibility of mobile gravity measurements at an affordable cost.

How to cite: Li, F., Gao, L., Cai, B., Wu, W., and Tu, L.-C.: A force-balance MEMS gravimeter with area-changed capacitors for transducing and actuating, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3079, https://doi.org/10.5194/egusphere-egu23-3079, 2023.