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White Rabbit development on Altera platform
No full textInternational audienceIn this presentation, we will showcase the metrological evaluation of a newly developed electronic architecture—a custom carrier board built around the Altera Arria10 FPGA—which integrates White Rabbit technology. This system is an original platform tailored for high-performance frequency and time distribution, as well as precise timing capture for phased-array detectors. We will present detailed performance results, highlighting outstanding short-term jitter and long-term stability of the generated clock and Pulse-Per-Second signals. These results demonstrate cutting-edge timing precision and spectral purity in FPGA-based time transfer systems, with impactful implications for time-frequency metrology, radio astronomy, particle physics, and distributed instrumentation, particularly in systems relying on optical fiber networks
Risk Assessment of the Ground Magnetic Response to the March and April 2023 Geomagnetic Storms Using Geomagnetically Induced Currents Indices
No full textInternational audienceWe analyzed the solar origin and ground response during the severe geomagnetic storms (GSs) of 23–24 March (GS1) and 23–24 April 2023 (GS2) using Geomagnetically Induced Currents Indices (GIC indices) computed from geomagnetic field data. The GSs were initiated by erupting filaments and associated slow (fast) halo coronal mass ejections on 20 March (21 April) 2023. GS1 was also influenced by coronal hole high speed streams (CR HSSs) while substorm onsets drove the most intense GIC X (GIC Y ) of 86 (70) in Abisko, Sweden. GS2 was marked by strong negative Bz in a sheath and magnetic cloud with larger GIC indices of 84 (69) driven by magnetic pulsations, as evident at Abisko. This posed a moderate risk to power networks in Sweden. The threat however, reached only a low/moderate risk level in Boulder during the Sudden Impulse (SI)/main phase of GS1. For GS2, a low risk level was attained in Vernadsky and Eyrewell. As expected, at low latitude, GIC indices constituted a very low risk to ground infrastructures during both storms. The results also revealed longitudinal features with larger GIC indices in Boulder (Vernadsky) during the GS1 (GS2), and a North South Asymmetry characterized by a higher risk level in the northern (southern) hemisphere at the American longitude. Additionally, this study provides evidence that the equatorial electrojet can enhance GIC indices at the magnetic equator in the presence of sufficiently strong dH/dt. Finally, we relate GIC indices at high latitudes to the CR HSS on 23 March, and a magnetic cloud during the recovery phase on 24 April 2023
Orbits of very distant asteroid satellites
No full textInternational audienceContext. The very wide binary asteroid (VWBA) population is a small subset of the population of known binary and multiple asteroids made of systems with very widely orbiting satellites and long orbital periods, on the order of tens to hundreds of days. The origin of these systems is debatable, and most members of this population are poorly characterized.Aims. We aim to develop orbital solutions for some members of the VWBA population, allowing us to constrain possible formation pathways for this unusual population.Methods. We compiled all available high-angular-resolution imaging archival data of VWBA systems from large ground- and space-based telescopes. We measured the astrometric positions of the satellite relative to the primary at each epoch and analyzed the dynamics of the satellites using the Genoid genetic algorithm. Additionally, we used a NEATM thermal model to estimate the diameters of two systems, and we modeled the orbit of Litva’s inner satellite using photometric light curve observations.Results. We determine the effective diameters of binary systems (17246) Christophedumas and (22899) Alconrad to be 4.7 ± 0.4 km and 5.2 ± 0.3 km, respectively. We determine new orbital solutions for five systems, (379) Huenna, (2577) Litva, (3548) Eurybates, (4674) Pauling, and (22899) Alconrad. We find a significantly eccentric (e = 0.30) best-fit orbital solution for the outer satellite of (2577) Litva, moderately eccentric (e = 0.13) solutions for (22899) Alconrad, and a nearly circular solution for (4674) Pauling (e = 0.04). We also confirm previously reported orbital solutions for (379) Huenna and (3548) Eurybates.Conclusions. It is unlikely that BYORP expansion could be solely responsible for the formation of VWBAs, as only (4674) Pauling matches the necessary requirements for active BYORP expansion. It is possible that the satellites of these systems were formed through YORP spin-up and then later scattered onto very wide orbits. Additionally, we find that some members of the population are unlikely to have formed satellites through YORP spin-up, and a collisional formation history is favored. In particular, this applies to VWBAs within large dynamical families, such as (22899) Alconrad and (2577) Litva, or large VWBA systems such as (379) Huenna and NASA’s Lucy mission target (3548) Eurybates
Extended linearity in the high-order wavefront sensor for the Roman Coronagraph
No full textInternational audienceContext. The aim of the Coronagraphic Instrument (CGI) on board the Roman Space Telescope is to achieve unprecedented levels of contrast for the direct imaging of exoplanets, which will serve as a critical technology demonstrator for future missions such as the Habitable Worlds Observatory (HWO). Achieving these goals requires advanced wavefront sensing and control (WFS&C) strategies, including the use of pair-wise (PW) probing to estimate the electric field in the focal plane. The optimization of PW probe designs is vital in order to enhance performance and reduce operational overhead.Aims. In this study we investigate the performance of different PW probe designs in the context of Roman CGI. Specifically, we compared the classic sinc-sinc-sine probes, previously introduced single-actuator probes, and newly proposed sharp sinc probes in terms of their effectiveness in focal-plane modulation, resilience to nonlinearities at high probe amplitudes, and overall impact on the convergence and contrast levels achieved in laboratory demonstrations.Methods. We conducted experiments on the THD2 testbed, configured to simulate Roman CGI with a custom-made Hybrid Lyot Coronagraph (HLC). We evaluated the three probe designs through closed-loop WFS&C experiments using PW probing for electric field estimation and electric field conjugation (EFC) for wavefront correction. Simulations and hardware tests assessed the contrast convergence and the impact of nonlinear terms at varying probe amplitudes. We also explored low-flux scenarios to demonstrate the effectiveness of high-amplitude probes in reducing exposure times or closing the loop on faint targets.Results. Single-actuator probes emerged as the most effective design, offering faster convergence and reduced susceptibility to nonlinear effects at high amplitudes compared to sinc-sinc-sine probes. Sharp sinc probes perform moderately well, but are less robust than single-actuator probes. High-amplitude single-actuator probes demonstrate advantages in DH digging under low-flux conditions, achieving faster iterations without significant degradation in contrast performance. The THD2 testbed, operating in a contrast regime analogous to Roman CGI, validated these results and underscored its role as a critical platform for advancing WFS&C techniques
Reactive transport models are cornerstone tools for optimizing the phytostabilization management of mining residues
No full textInternational audienceSecuring mining residues represents a major environmental challenge. Most metal mines produce waste containing iron (Fe) and sulfur (S), along with trace elements such as arsenic (As) and lead (Pb). Phytostabilization often appears to be one of the most appropriate options to minimize the aqueous and particulate transport of contaminants-including As-through leaching and erosion, at a moderate cost and with long-term, environmentally friendly benefits. However, the medium-and long-term impacts of phytostabilization on biogeochemical cycles in mine waste and on associated pollutant fluxes still need to be quantified. Furthermore, surface amendments using mineral and organic substances, combined with plant growth, significantly alter the physical, chemical, and biological conditions at the surface of the tailings. Yet, the nature and extent of these modifications remain unclear. Consequently, there is a pressing need to develop a robust understanding and predictive tools that can forecast the consequences of phytostabilization on pollutant migration from mine wastes to surrounding environmental compartments, particularly groundwater. Among the existing predictive tools, reactive transport models (RTMs) appear to be highly effective. These models quantitatively describe and predict the distribution of chemicals across different phases (solid, aqueous, gaseous) over time and space, offering a rigorous framework to test our understanding of observed results, the underlying processes, and the controlling factors
Performance and uses of the Refimeve metrological signal, 1000 km from the source.
No full textInternational audienceWe present a detailed analysis of the end-user performance of the metrological signal at 1542 nm disseminated by the French national fibre network Refimeve, about 1000 km from the source. By the mean of a local ultrastable laser at 729 nm and a frequency comb, we are able to carry out stability and phase noise measurements of the signal with respect to the local laser. With a focus on phase noise analysis we identify different timescales of interest for the use of this signal in optical frequency metrology
Gravimetry platform for evaluation and characterization of quantum technologies
No full textInternational audienceThe Horizon Europe project “Qu-Test” [1] aims to establish a European infrastructure open to industry for the characterization and testing of components, subsystems, and instruments developed from quantum technologies. As part of this project, led by a consortium of Research Technology Institutes and National Metrology Institutes within the European Union, we are developing a platform for the functional and metrological characterization of quantum gravimeters.In my poster, I will present our reference site, which comprises our laboratory, characterized instruments, and models derived from 20 years of measurements.Our laboratory, located in the Paris region, features a 6 m × 5.5 m × 2 m concrete platform supported by 12 m long legs that reach the Fontainebleau sands layer. Initially constructed for the LNE Watt Balance [2], our activities have since expanded to include the use, study, characterization, and calibration of various types of instruments. Relative spring-based gravimeters, such as portable Scintrex CG5 and CG6 models, enable us to map and model gravity differences throughout the laboratory's 40 m³ volume. A superconducting relative gravimeter iGrav, allows continuous monitoring of temporal changes of g. The absolute reference value is provided by the atomic gravimeter CAG [3], which calibrates the iGrav’s scale factor [4] and evaluates its drift.The laboratory's size facilitates the simultaneous accommodation of several gravimeters, enabling regular comparison campaigns. The first comparison in 2006 involved only absolute gravimeters of the FG5 type, while recent comparisons have also included atomic gravimeters like AQGs [5]. The site is routinely used to assess the performance and verify the functionality of the French national gravimeter park (PIN PGravi) [6], particularly before participating in international comparisons with FG5 (#206 and #228) [7] and AQG-B01 [8].This open-access reference site allows users to verify their instruments before field missions, calibrate spring-based relative gravimeters such as the gPhoneX, and test new developments, including quantum gravimeter and dual gravi-gradio-meter systems.[1] https://qu-test.eu[2] M. Thomas et al (2017) metrologia 54[3] R. Karcher et al (2018) New J. Phys 20[4] S. Merlet et al (2021) J Geod 95[5] V. Ménoret et al (2018) Sci Rep 8[6] S. Merlet et al (2024) IEEE Instrum Meas Mag 27[7] H. Wziontek et al (2025) G4.2 EGU[8] S. Merlet et al (2025) G4.2 EG
First results from the comparison of absolute gravimeters WETCAG-2024 at the Geodetic Observatory Wettzell, Germany
No full textInternational audienceThe validation of compatibility and long-term stability of absolute gravimeters is a key component for the realization of the International Terrestrial Gravity Reference Frame (ITGRF) of IAG and is relevant for metrology, in particular for the realization of the kilogram. Because a natural reference for the absolute value of gravity acceleration is not accessible, international comparisons of absolute gravimeters are well established. The gravity reference is realized based on a set of accurate absolute measurements and the functional model for their processing. After the CCM.G-K2.2023 key comparison supplemented by additional comparison ICAG-2023 held in September 2023 at Table Mountain Geophysical Observatory (TMGO) Boulder, Colorado, USA, there was a need to distribute the gravity reference further to institutions in Europe. Therefore, the EURAMET key comparison of absolute gravimeters EURAMET.M.G-K2.2023 and additional comparison WETCAG-2024 was organized at the Geodetic Observatory Wettzell, Germany, in May and June 2024, where 15 institutions participated with 17 absolute gravimeters. The link to CCM.G-K2.2023 is provided by three gravimeters that took part in both comparisons. Additionally, deviations from the verticality and Eötvös/Coriolis accelerations during the free fall were determined for most of the gravimeters. We present first results for the equivalence of the participating gravimeters as well as for the verticality and Eötvös effects. Further, we evaluate and discuss the stability of the reference values over decades, based on a reference function deduced from the registration of the superconducting gravimeter GWR SG030, repeated absolute gravity observations since 2010 and several regional comparisons performed at this station, in particular with the comparison EURAMET.M.G-K3 held at Wettzell in 2018. Quantum gravimeters are represented in WETCAG-2024 with two instruments. This allows to compare the new technology with the reference established at the Wettzell station over 15 years, specifically in the context of stability of gravimeters and the upcoming realization of the ITGRF.
Results and Findings from the Worldwide First Joint Measurements with 5 Absolute Quantum Gravimeters
No full textInternational audienceQuantum gravimeters have been in use as laboratory instruments by various research groups for some time and have been available as user-friendly commercial devices since 2014. In contrast to traditional absolute gravimeters such as the FG5, which employ corner cubes as a falling test mass, these devices utilise laser-cooled cold-atom clouds. The Absolute Quantum Gravimeter (AQG) produced by the French company Exail is available in two model series: indoor observatory devices (A-series) and outdoor capable devices (B-series).In this contribution, we present the results of the world's first AQG comparison, conducted in January 2024 at Leibniz University Hanover (Germany) in the gravimetric laboratory of the HiTec building.Five AQG units (B-series) participated in the comparison, operated by teams from France, Poland and Germany. The measurement activities were conducted over a five-day period, comprising 12-hour tracking series conducted both during the day and night. In contrast with traditional gravity comparisons, the primary objective of these joint measurements was to enhance the understanding of the operational principles of AQGs. In addition to the long measurements each device carried out on 3 out of 5 available pillars, dedicated tests were conducted jointly on all instruments, including tiltmeter calibrations and accelerometer response. The data processing and evaluation focused on device characteristics, stability over time, individual noise levels, and statistical uncertainties of individual measurements.The joint AQG measurements were independently supported by classical relative and absolute gravity measurements with CG6 and FG5 gravimeters
Emissions de signaux horaires et de fréquence étalon
No full textInternational audienceThe activities of the Working Party 7A concerning time signals and frequency standard emissions, in relation to the Radio Regulations and the 2027 World Radiocommunication Conference, are being developed. In particular, the future of Coordinated Universal Time and Resolution 655 (Rev.WRC-23), implicitly included on the agenda of WRC-27 under item 9 concerning the report of the Director of the Radiocommunication Bureau, are being addressed