We propose the establishment of an observational network comprising micro gravitometers across East Asia including, but not limited to Republic of Korea, Japan, Taiwan, and the Chinese mainland. The network will generate a parallel observation belt within the seismogenic zone that connects the Japan Trench, Ryuku Trenches, and Nankai Through, both constituent components of the Ring of Fire, for the detection of slight changes in micro-gravity for analyzing earthquakes of different magnitudes with different sources and depths. We will establish a data hub for sharing data, managing combined data format, and distributing computing resources for conducting collaborative research. In addition, the network measurement of micro-gravity can be used for searching the dark matter candidate inside Earth. The presentation demonstrates various science cases that could be undertaken by implementing a network of GWR Instruments Inc.’s superconducting gravimeters and a data hub within the East Asian region.

How to cite: Son, E. J., Kim, J. W., Oh, J. J., Kim, H., Hwang, C., Cheng, C.-C., Ito, Y., Tanaka, Y., Shen, W., Luan, W., Hu, M., Liu, Z., Sun, H., Chen, X., Bae, S., and Yoon, H.: ENIGMA: East-Asian Network Initiative for Gravity Measurement Alliance: A Proposal and Science Cases, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3305, https://doi.org/10.5194/egusphere-egu24-3305, 2024.

We present the status of the Yemi micro-gravity observatory (YeMiGO), including the installation, operation, and initial analysis of the gravity data. In October 2022, we installed GWR Instruments Inc,’s iGrav (serial #001) superconducting gravimeter (SG) at Yemi underground laboratory (YemiLab) in South Korea. YemiLab is located approximately 1,008 and 118 meters below the Earth's surface and mean sea level, respectively. The noise characteristics were assessed using one month of raw data collected in September 2023 and compared to those of other seismometer stations. The results show the noise level at the SG station, especially in the seismic band, is significantly low and proves the stability of the Lab.  The research findings also indicate that blasting during mining operations at a distance between ~700 and ~900 meters (please confirm this) from the SG impacted the dewar and barometer pressures as well as the tilt balance data. However, no discernible effects were observed in the raw SG data, leading to the hypothesis that the SG tilt system was able to compensate for the resulting vibrations. After 6 months of continuous data recording from 16th November 2022 to 18th May 2023, a calibration factor of -92.17 μGal∙V^-1 was estimated using tidal analysis. In November 2023, a new calibration factor of -94.15 μGal∙V^-1 was estimated using parallel measurements with FG5-231 provided by the Ministry of Interior, R.O.C. (Taiwan). Having accounted for various environmental effects, including Earth tide, atmospheric pressure, groundwater level, and polar motion, during the initial six months of data, the residual gravity was obtained. Spectral analysis revealed several unidentified residual gravity power spectrum density frequencies, necessitating further investigation. Co-seismic gravity changes resulting from four earthquakes in May 2023 with different magnitudes and within various distances from the SG station were examined. The M6.2 earthquake that occurred 765 km away was linked to the most notable co-seismic gravity alteration, which recorded a value of 0.561 μGal. The mentioned changes decreased gradually and faded away entirely within half an hour after the SG's first arrival.

How to cite: Oh, J. J., Dehghan, M. J., Woo, I., Kim, H., Son, E. J., You, S., and Kim, J. W.: YeMiGO: Data Processing and Analysis of Underground Superconducting Gravity Data in South Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2746, https://doi.org/10.5194/egusphere-egu24-2746, 2024.

Subsidence poses a significant global threat to the viability and economic development of approximately one-fifth of the world's population, especially in coastal or heavily urbanized regions experiencing ground settlements ranging from centimeters per month to meters per decade. This phenomenon, driven by natural or anthropogenic factors, is intricately linked to hydrology, geology, tectonics, and the geotechnical properties of underlying formations. Multiple triggers, including underground cave collapses, organic soil oxidation, natural gas and oil extraction, and aquifer consolidation, contribute to subsidence, disrupting vital water reserves crucial for societal needs. Spatial and temporal limitations of conventional techniques like gravimetry, positioning, and spatial imaging in resolving the effects of extreme weather events and resource exploitation on subsidence prompt an exploration of their complementarity and the emergence of quantum sensors—specifically, atomic clocks sensitive to gravitational potential variations.
Since 2021, the SYRTE, IPGP, IGN, and SHOM participate in the ANR ROYMAGE project (Optical Ytterbium Mobile Atomic Clock Applied to Geodetic Exploration). The project aims to develop a transportable atomic clock prototype with sufficient performance to determine altitude differences within the T-REFIMEVE fiber network, achieving a centimeter-level uncertainty in just a few hours across points separated by hundreds of kilometers for geodetic applications. As optical atomic clocks become integral to fieldwork, their sensitivity to mass anomalies and vertical displacement becomes a crucial consideration.

Within the ANR framework, we have initiated digital tool implementation to model the signal generated by remote clock comparisons, mainly gravitationally and geometrically influenced by mass and altitude variations. The challenge lies in identifying and decorrelating signal sources to reveal the studied phenomenon. Geopotential differences, a novel geodetic observable, necessitate modeling considering gravitational signatures at the Earth's surface from buried mass anomalies (e.g., aquifers), the (in)elastic medium response to pressure changes causing vertical crust displacement, and other effects like solid Earth tides, ocean tide loading, polar motion, etc. Preliminary results suggest that clock comparisons with centimeter-level uncertainties could detect variations in regional groundwater levels.

This work proposes to assess whether chronometric leveling, in France, can complement gravimetric, spatial imaging and levelling techniques to study vertical soil displacements resulting from disturbances in underground water resources due to climatic or anthropogenic origins.

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., chanard, K., Pajot, G., Diament, M., and Jamet, O.: Monitoring aquifers and subsidence with the chronometric leveling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6235, https://doi.org/10.5194/egusphere-egu24-6235, 2024.

The 2017-2027 Decadal Survey for Earth Science and Applications from Space has identified the Targeted Mass Change Observable as one of 5 Designated Mission. In Europe, ESA has confirmed at Ministerial Counsel of November 2022 to continue the development on the Next Generation Gravity Mission with a Phase B.

These missions will continue the observation provided by GRACE and GRACE-FO. In these missions and the future concepts, the accelerometer provides either the gravity signal in a gradiometer configuration (GOCE type mission), or the non-gravitational acceleration to be suppressed to the ranging measurement between two satellites (GRACE-type mission).

ONERA has procured the accelerometer for all the previous gravity missions (GRACE, GOCE, GRACE-FO) and works to improve the scientific return of the instruments for the future missions.

In a frame of a contract with ESA, ONERA is developing its new accelerometer MicroSTAR, a high accuracy accelerometer with 3 sensitive linear acceleration measurements as well as 3 angular acceleration measurements for the attitude control or reconstruction.

In parallel, a miniaturized version of MicroSTAR with low accuracy, CubeSTAR accelerometer, is developed with internal funding. CubeSTAR is adapted for constellation or nanosat.

Another way is to improve the low-frequency noise of the accelerometer, by hybridization of electrostatic accelerometer with cold atom interferometer.

The presentation will detail these developments.

How to cite: Dalin, M., Christophe, B., Lebat, V., Boulanger, D., Liorzou, F., Rodrigues, M., Zahzam, N., Bidel, Y., and Bresson, A.: ONERA accelerometers for future gravity mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11059, https://doi.org/10.5194/egusphere-egu24-11059, 2024.

Since 2002, the GRACE and GRACE-FO satellite gravity missions have been observing changes in the Earth’s gravity field. ESA and NASA are currently planning a double-pair satellite constellation MAGIC, which promises an enhanced spatial and temporal resolution compared to GRACE/-FO. After MAGIC, in the long-term post-2040-time frame, a gravity mission constellation with multiple satellite pairs equipped with novel quantum sensor instrumentation is considered as a promising candidate concept to improve the observation time series even further. It has the potential to acquire unprecedented data on key Earth processes and is expected to significantly expand the potential range of applications.

Within the ongoing ESA project “Quantum Space Gravimetry for monitoring Earth’s Mass Transport Processes” (QSG4EMT) an online questionnaire was created to assess user requirements for such a future quantum mission concept. We will present the results of this community assessment based on 135 answers from various user groups (hydrology, oceanography, glaciology, atmospheric and climate sciences, solid earth sciences, and geodesy). In addition to application-driven demands of the different disciplines regarding the required spatial and temporal resolution, accuracy, and latency, we discuss the expected added benefits of hypothetical future mission scenarios and outline possible new application fields.

How to cite: Eicker, A., Strohmenger, C., Braitenberg, C., Kusche, J., Pail, R., and Daras, I.: Community assessment on user requirements for future satellite gravity missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14722, https://doi.org/10.5194/egusphere-egu24-14722, 2024.

Satellite gravimetry missions have been providing a global measure of Earth's mass transport for more than 20 years. This provides insights into the solid Earth, cryosphere, ocean dynamics and hydrology. Planned NASA and ESA missions will continue this observation well into the 2030s. They are likely to be based on the technology currently used on the GRACE-FO mission, with some further developments, e.g. in laser ranging technology. A higher temporal and spatial resolution of these gravity field products, currently limited to a few hundred km for 1 cm equivalent water height, is required to meet future user need.

One of the limitations is related to instrumental effects, of which the accelerometer is a major aspect. Quantum-based accelerometers are a potential improvement for future missions, but the required technology readiness level (TRL) for key technologies currently precludes deployment. A European pathfinder mission is planned to increase the TRL and demonstrate the technology in space.

Under the Horizon Europe funding programme, technology development and maturation are being promoted and "the [Quantum Space Gravimetry] Pathfinder mission shall be launched within this decade, paving the way for the deployment of an EU [Quantum Space Gravimetry] mission within the next decade". Within this framework, the Cold Atom Rubidium Interferometer in Orbit for Quantum Accelerometer - Pathfinder Mission Preparation (CARIOQA-PMP) project is the first step in the design and preparation of the Pathfinder mission. It identifies user needs, prepares simulation tools and develops an engineering model of the quantum accelerometer.

This presentation will give an overview of the scientific activities within CARIOQA-PMP, including the link between hardware design and specification, as well as the planning for the Pathfinder mission and a future gravimetry mission. The focus will be on the elements and workflow of the simulation of the quantum sensor on a satellite platform, combining the efforts of the physics and geodesy partners.

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. Funded by the European Union

How to cite: Schilling, M., Forsberg, R., Gaaloul, N., Gruber, T., Lévèque, T., Migliaccio, F., Müller, J., Pereira Dos Santos, F., and Zahzam, N. and the CARIOQA-PMP Consortium: CARIOQA-PMP quantum accelerometer simulation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14996, https://doi.org/10.5194/egusphere-egu24-14996, 2024.

The ESA Earth System Model (ESA ESM) provides a synthetic data-set of the time-variable global gravity field that includes realistic mass variations in atmosphere, oceans, terrestrial water storage, continental ice-sheets, and the solid Earth on a wide set of spatial and temporal frequencies. It was widely applied as a source model in simulations of for gravity missions, but has been also applied to study novel gravity observing concepts on the ground. For that purpose, the ESM needs to include a wide range of signals even at very small spatial scales which might not yet have been reliably observed by any active mission.

In this contribution, we present first steps towards an update to the current ESA ESM. We focus in particular on an evolved oceanic component which will newly include (a) deep oceanic transport variations in the Atlantic Overturning Circulation and the associated variation in oceanic bottom pressure along the shelf slope of the Western boundary; (b) an update to the realistically perturbed de-aliasing model and (c) the inclusion of the Sea-Level Equation for spatially variable barystatic sea-level variations and global mass conservation.

How to cite: Shihora, L., Balidakis, K., Dill, R., and Dobslaw, H.: Updating the ESA Earth System Model for Future Gravity Missions Simulation Studies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17336, https://doi.org/10.5194/egusphere-egu24-17336, 2024.

In order to meet the objectives of the Next Generation Gravity Mission (NGGM), the French Aerospace Lab ONERA is developing a new accelerometer concept MicroSTAR with three sensitive linear and three true angular acceleration measurements (Dalin et al., session G4). This instrument benefits from previous developed accelerometers which flew in the well-known gravity space missions: CHAMP, GRACE, GOCE, GRACE-FO.

The principle of operation of these accelerometers is to maintain motionless a proof-mass with respect to the surrounding electrodes using a control loop. The applied electrostatic forces needed for this control, are proportional to the accelerations suffered by the proof-mass. The proof-mass is polarized with a very thin (few micrometer) wire in order to measure precisely its position by capacitive detection with the electrodes and to avoid charging in orbit. The stiffness and damping induced by the polarization wire impact the performance of the accelerometer at low frequencies. To quantify on-ground the performance limitation due to the wire, an electrostatically suspended torsion pendulum (PTSE) is used (Willemenot 1997, Willemenot and Touboul 2000).

The PTSE is a six-axes servo-controlled accelerometer, optimized for the measurement of angular accelerations about the vertical axis. The torque noise spectral density is 1.3 10^-14 Nm/√Hz  around 0.05 Hz with a 1/√f increase at lower frequency, corresponding to 10^-8 rad/s²/√Hz , and 2 10^-10 ms^-2/√Hz with a lever arm of 2cm. For instance, regarding a gold wire of 7.5µm diameter and 1.7cm length, we use it to measure theoretical stiffness of 2.5 10^-5 N/m i.e. a torsion of 10^-8 Nm/rad. In our presentation, this instrument will be described before sharing ideas for its improvement.

Willemenot, P. Touboul; Electrostatically suspended torsion pendulum. Rev Sci Instrum 1 January 2000a; 71 (1): 310–314. https://doi.org/10.1063/1.1150198

Willemenot, P. Touboul; On-ground investigation of space accelerometers noise with an electrostatic torsion pendulum. Rev Sci Instrum 1 January 2000b ; 71 (1): 302–309. https://doi.org/10.1063/1.1150197

Willemenot, Pendule de torsion à suspension électrostatique, très hautes résolutions des accéléromètres spatiaux pour la physique fondamentale. Ph.D. thesis, Université Paris 11, France, 1997

How to cite: Portier, N., Christophe, B., Dalin, M., Lebat, V., Liorzou, F., and Rodrigues, M.: Improvement of ONERA Electrostatically suspended torsion pendulum, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8931, https://doi.org/10.5194/egusphere-egu24-8931, 2024.

The Laser Ranging Interferometer (LRI) on board the GRACE Follow-On spacecraft has successfully demonstrated for the first time interferometric laser ranging between satellites with a noise level below 1 nm/rtHz. In addition, the LRI’s steering mirror information provides attitude information that enable inter-comparisons with the conventional star cameras. Two new twin-satellite missions are now under development: the Next Generation Gravity Mission (NGGM) by ESA and the GRACE-C mission by a US-German partnership. Both missions rely on laser interferometry as the primary and only means of measuring the distance variations between the spacecraft.

In this presentation, we introduce the measurement concept and design principles, report on the current status of the ranging instruments and explain the changes to be implemented with respect to GRACE-FO, mainly related to redundancy and lessons learned.

How to cite: Müller, V., Bekal, P., Misfeldt, M., Müller, L., Sudha, R., Weberpals, M., Nicklaus, K., Voss, K., and Heinzel, G.: Laser Ranging Interferometry for the next gravity missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8912, https://doi.org/10.5194/egusphere-egu24-8912, 2024.

Geodesy's primary objective lies in the determination of Earth's gravity field through ground and space-based measurements. General relativity and, thus, relativistic geodesy, introduce a novel perspective, leveraging high-precision clock comparisons to potentially unveil a new tool for globally determining Earth's gravito-electric potential based on the gravitational redshift.

In the pursuit of clock-based gravimetry, which involves chronometry in stationary spacetimes, precise expressions for the relativistic redshift and timing among observers in different configurations are presented. These observers, equipped with standard clocks, move on arbitrary worldlines. The analysis reveals how redshift measurements, employing clocks on the ground and/or in space, can be harnessed to deduce the (mass) multipole moments of the underlying spacetime geometry. Importantly, our findings align with the Newtonian potential determination via conventional methods such as the energy approach.

The framework of chronometric geodesy is introduced and demonstrated across various exact vacuum spacetimes for clarity. The study extends to gravity degrees of freedom, encompassing gravito-magnetic contributions, with investigations into potential experiments for their determination. Looking ahead, upcoming gravity field recovery missions might incorporate clock comparisons as an additional resource for advanced data fusion.

How to cite: Philipp, D., Hackmann, E., Hackstein, J., and Laemmerzahl, C.: General Relativistic Chronometry from Ground and in Space, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10007, https://doi.org/10.5194/egusphere-egu24-10007, 2024.

Satellite gravity missions are a powerful tool to measure the global Earth’s gravity field and consequently provide important information for geosciences. However, improvements in spatial and temporal resolution are required for many applications. Simulation studies are performed to quantify the influence of improved sensors, orbit parameters and measurement concepts on the recovered gravity field solution. The investigations focus primarily on accelerometers by evaluating the concept of Cold Atom Interferometry (CAI) accelerometers and their combination with electrostatic accelerometers for future satellite gravity missions.

The CAI noise behavior is mainly estimated based on the quantum projection noise, but also challenges due to the longer duration of the measurement cycle are investigated. The results of the low-low Satellite-to-Satellite Tracking (ll-SST) closed-loop simulations indicate, on the one hand, benefits from the addition of CAI and reveal, on the other hand, the dominance of background modeling errors. Furthermore, the combination of ll-SST and cross-track gradiometry is studied. In order to significantly benefit from an additional cross-track gradiometer, it has to achieve a low noise level of 1 mE and the angular velocity measurements have to ensure high accuracies.

We acknowledge the support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 434617780 – SFB 1464 and under Germany’s Excellence Strategy – EXC-2123 Quantum-Frontiers – 390837967, the support by Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR) for the project Q-BAGS and the European Union for the project CARIOQA-PMP (Project-ID 101081775).

How to cite: Knabe, A., Schilling, M., Romeshkani, M., HosseiniArani, A., Fletling, N., Kupriyanov, A., Müller, J., Beaufils, Q., and Pereira dos Santos, F.: Cold Atom Interferometry Accelerometers for Future Satellite Gravity Missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7350, https://doi.org/10.5194/egusphere-egu24-7350, 2024.

Cold Atom Interferometry (CAI) stands poised as a groundbreaking technique in satellite gravimetry, offering unparalleled precision and unbiased measurements. Despite the numerous studies on CAI's conceptual measurement techniques, attitude reconstruction accuracy poses a critical challenge. This submission seeks to bridge this gap by conducting an analysis of state-of-the-art attitude sensors and their suitability for upcoming quantum low-low satellite-to-satellite and gravity gradiometry missions utilizing CAI instruments.

Acknowledging the immense promise of Cold Atom Interferometry, we emphasise the need to put this conceptual potential in the context of the accuracy of attitude reconstruction, a factor that significantly influences the feasibility of Quantum Space Gravimetric (QSG) missions. We examine the specifications, strengths, and limitations of attitude, acceleration, position and inter-satellite distance sensors to combine them realistically in scenarios specific to quantum low-low satellite-to-satellite and gravity gradiometry missions relying on CAI instruments. We also analyse the classic counterparts, offering valuable insights into the conceptual mission configurations that benefit the most from CAI-based observations. Our findings contribute not only to the advancement of the use of CAI technology in future graviemtric missions but also to the broader understanding of the intricate interplay between cutting-edge measurement techniques and the supporting instrumentation required for their successful implementation.

This work is supported by the European Space Agency, under the project Quantum Space Gravimetry for monitoring Earth’s Mass Transport Processes (QSG4EMT), which has the general objectives to analyse future QSG mission architectures with ultimate goal to optimally exploit the performance of quantum sensors for retrieving temporal variations of Earth’s gravity field, evaluate the impact of mission configurations on the quality of the retrieved gravity field models and support the evolution of user requirements for future QSG missions.

How to cite: de Teixeira da Encarnacao, J., Siemes, C., Daras, I., Strangfeld, A., Zingerle, P., and Pail, R.: Towards a realistic modelling of gravimetric errors in future missions equipped with quantum sensors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16325, https://doi.org/10.5194/egusphere-egu24-16325, 2024.