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The 3D Energetic Electron Spectrometer (3DEES) onboard PROBA-3: Geant4-simulations and calibration
No full textThe 3D Energetic Electron Spectrometer (3DEES) is conceived as a compact and modular science-class spectrometer optimized for measurements of angle-resolved high-energy electron fluxes in the heart of the radiation belts. The covered electron energy range extends from about 0.14–10 MeV, with an adjustable number of measurement channels between 16 and 32 (set to 24 bins). It also allows for the quantification of proton fluxes in the energy range 2.5–50 MeV (number of channels set to 10), while performing absolute electron-proton discrimination for protons up to 200 MeV. In its baseline design, the 3DEES has the capability to measure angular distributions at 12 angles spanning over 180° in two planes. However, for the in-orbit technology demonstration on board PROBA-3, 3DEES is equipped with only one detector head consisting of 6 apertures in one plane. Each aperture has a field of view of ~15°, and the looking directions of any two apertures are separated by 30°. The satellite was launched on 5th December 2024 into a highly elliptical orbit: 60,530 km apogee, 600 km perigee, 59° inclination, 19.5 h orbital period. With these orbital parameters, the satellite will cover parts of the inner belt, outer belt, and mostly the border of the magnetosphere. At the time of writing, the commissioning phase of the spacecraft is ending. This paper presents a description of the 3DEES design and demonstrates the importance of extensive Geant4-based simulations to support the design and characterization of the instrument. To assess the performance of the instrument in orbit, the instrument’s response functions are folded with differential energy spectra obtained from radiation belt models. In addition, the calibration of the instrument in a proton beam, as well as its verification with a 90Sr/90Y source, is presented. Those measurements validate the Geant4 simulations and verify the expected functioning of the instrument
Upper limits of CH4 and OCS in the Martian atmosphere from NOMAD/TGO solar occultation: A study of vertical averaging and systematic uncertainties
Full text linkHere we update the search for two trace species of high interest in the Martian atmosphere, methane (CH4) and carbonyl sulfide (OCS), using solar occultation (SO) measurements from the NOMAD spectrometer on board the Trace Gas Orbiter (TGO). Neither species has been detected in previous analyses of TGO’s dedicated SO instruments, ACS and NOMAD. Our approach focused on NOMAD-SO data, assessing in detail the calibration uncertainties to quantify systematic error components, and investigating if vertical averaging of spectra to reduce random noise would enhance the signal-to-noise ratio (SNR). The latter step required careful data cleaning with precise radiative transfer modeling and should improve upon earlier searches that analyzed spectra individually. We examined 19,330 NOMAD SO spectra targeting CH4 and OCS, from diffraction orders 134 and 129, corresponding to 76 and 142 vertical scans, respectively. These scans span a wide range of latitudes and seasons over three Martian years (April 2018 to November 2022, MY34-MY36). No CH4 or OCS absorption features were detected and our composite vertical profiles (5–50 km tangent altitude) yielded stringent upper limits. For methane, the 1-σ upper limits typically lie around 0.5 ppbv, reaching 0.2 ppbv at some altitudes and locations. Our methane limits were primarily constrained by systematic uncertainties, particularly the residual baseline shape, and are therefore relatively higher than those previously reported in Knutsen et al. (2021), who processed the spectra differently to remove this effect. For OCS, our composite profiles indicate concentrations below 5 ppbv at low altitudes and below 2 ppbv in some cases, also at the 1-σ significance level. Further improvements will require additional calibration refinements, ideally through better characterization of instrument behavior under thermal variations. As a practical step, narrowing the analyzed spectral intervals can reduce continuum uncertainties, provided contaminating features are absent. For methane features in diffraction order 134, such narrowing lowers uncertainties by a factor of three, getting closer to the most stringent limits previously reported (Knutsen et al., 2021)
Archives du Service Public Fédéral Intérieur : DG Budget et Contrôle de la gestion : Tableau de tri : Septembre 2025
No full textThis retention schedule was officially published for the first time on 31 December 2025. The latest version is available for download below. Licensed under CC BY-NC. Use permitted for non-commercial purposes with attribution.(Excel) Tableau de tri. SPF Intérieur. DG Budget et Contrôle de gestion. Septembre 2025(PDF) Tableau de tri. SPF Intérieur. DG Budget et Contrôle de gestion. Septembre 2025Gestion des versionsVersion 01 : Septembre 2025 : Philippe Wery (published 2025-12-31
Interstellar Comet 3I/ATLAS: Evidence for Galactic Cosmic-Ray Processing
No full textSpectral observations of 3I/ATLAS (C/2025 N1) with JWST/NIRSpec and SPHEREx reveal an extreme CO2 enrichment (CO2/H2O = 7.6 ± 0.3) that is 4.5σ above solar system comet trends and among the highest ever recorded. This unprecedented composition, combined with substantial absolute CO levels (CO/H2O = 1.65 ± 0.09) and red spectral slopes, provides direct evidence for galactic cosmic-ray (GCR) processing of the outer layers of the interstellar comet nucleus. Laboratory experiments demonstrate that GCR irradiation efficiently converts CO to CO2 while synthesizing organic-rich crusts, suggesting that the outer layers of 3I/ATLAS consist of irradiated material whose properties are consistent with the observed composition of the 3I/ATLAS coma and with its observed spectral reddening. Estimates of the erosion rate of 3I/ATLAS indicate that current outgassing samples the GCR-processed zone only (depth ∼15–20 m), never reaching pristine interior material. Outgassing of pristine material after perihelion remains possible, though it is considered unlikely. This points to a paradigm shift: long-residence interstellar objects likely reveal primarily GCR-processed material rather than pristine material representative of their primordial formation environments. With 3I/ATLAS approaching perihelion in 2025 October, immediate follow-up observations are critical to confirm this interpretation and establish GCR processing as a fundamental evolutionary pathway for interstellar objects
Observational Requirements for Quantifying the Diurnal Cycle of XCO2 From Space
No full textSpatiotemporal variations in atmospheric carbon dioxide (CO2) provide a means to quantify surface fluxes of carbon over a range of space and timescales. NASA's Orbiting Carbon Observatory-3 (OCO-3), aboard the International Space Station, is the first CO2-monitoring mission to observe the sunlit portion of the diurnal cycle of total column-averaged CO2 (XCO2) from space, since OCO-3 collects data at various times of the day. Previous analysis of the climatological diurnal cycle in XCO2 measured from a ground-based spectrometer in the Total Carbon Column Observing Network (TCCON) suggests that the XCO2 diurnal cycle provides information about local fluxes. Here, we examine the diurnal signal at four TCCON sites spanning the tropics through midlatitudes. The signal is typically less than 1 ppm even at the peak of the growing season. Because relatively sparse OCO-3 data observes a diurnal cycle at a given location only across multiple days, mesoscale transport variations complicate detection of the diurnal signal from the space-based record. We bootstrap the long-term records of TCCON XCO2 to quantify the minimum number of OCO-3 observations necessary to infer the climatological diurnal cycle of XCO2, and find that even during the peak growing season, of order 10 observations per daylight hour for each month are required for robust detection. The number of required observations increases outside the growing season when fluxes are weaker. Our results show that dense and long-term observation are required to infer the diurnal cycle from OCO-3 or future CO2-monitoring satellite missions
The Light Ion Analyzer (LIA) for the SMILE Mission
No full textThe Light Ion Analyzer (LIA) instrument, part of the Solar-wind-Magnetosphere–Ionosphere-link- Explorer (SMILE) mission, is designed to measure the ion velocity distribution function within an energy range of 5 eV up to 25 keV. LIA provides in-situ measurements of the ion velocity distribution functions of the solar wind and magnetosheath, from which the moments can be derived on the ground, serving as an upstream input for the magnetosphere-ionosphere downstream responses. Two identical 2π sr field-of-view LIA instruments are mounted on two opposite sides of the spacecraft platform, offering a combined 4π sr instantaneous field-of-view. Each LIA consists of a top-hat electrostatic analyzer, electrostatic aperture deflectors, and a microchannel plate detector for analyzing the energy, direction, and flux of ions. Depending on the operation mode, the angular resolution ranges from 5.625° to 22.5° in elevation and from 7.5° to 30° in azimuth, and the time resolution spans from 0.25 to 2 seconds. This paper describes the design of the LIA, its performance, ground calibration, operation procedures, and resultant data products
Atmospheric lifetime of sulphur hexafluoride (SF6) and five other trace gases in the BASCOE model driven by three reanalyses
No full textIn this work, sulphur hexafluoride (SF6), which is often used as a tracer for stratospheric transport due to its inertness in the stratosphere and nearly linear growth rate in the troposphere, is included in the chemistry transport model (CTM) of the Belgian Assimilation System for Chemical ObsErvations (BASCOE). Sink and recovery reactions for this species are implemented in the model, which has a top in the mesosphere at 0.01 hPa. The simulated SF6 distributions are compared with MIPAS and ACE-FTS observations and the global atmospheric lifetime is computed from CTM runs driven by three recent meteorological reanalyses: ERA5, MERRA2 and JRA-3Q. The results show that BASCOE SF6 profiles are generally within 10 % of the satellite observations below 10 hPa, although discrepancies increase at higher altitudes. The global atmospheric lifetime is used as an additional diagnostic for the implementation of the chemistry in the mesosphere, where satellite measurements are unavailable. The derived SF6 lifetimes are 2646 years with ERA5, 1909 years with MERRA2 and 2147 years with JRA-3Q, in accordance with recent literature. Due to the large spread of published lifetimes for SF6, the study is extended to N2O, CH4, CFC-11, CFC-12 and HCFC-22, to validate the SF6 results. The lifetimes for these species are in agreement with previously reported values, and their spread between simulations is smaller compared to SF6. This analysis highlights the sensitivity of SF6 to the input reanalysis data sets and thus to differences in dynamics
Energetic spectra from semi-implicit particle-in-cell simulations of magnetic reconnection
No full textAstrophysical observations suggest that magnetic reconnection in relativistic plasmas plays an important role in the acceleration of energetic particles. Modeling this accurately requires numerical schemes capable of addressing large scales and realistic magnetic field configurations without sacrificing the kinetic description needed to model particle acceleration self-consistently. We demonstrate the computational advantage of the relativistic semi-implicit method (RelSIM), which allows for reduced resolution while avoiding the numerical instabilities typically affecting standard explicit methods, helping to bridge the gap between macroscopic and kinetic scales. Two- and three-dimensional semi-implicit particle-in-cell simulations explore the linear tearing instability and the nonlinear development of reconnection and subsequent particle acceleration starting from a relativistic Harris equilibrium with no guide field. The simulations show that particle acceleration in the context of magnetic reconnection leads to energetic power-law spectra with cutoff energies, consistent with previous work done using explicit methods, but are obtained with a considerably reduced resolution
BELTRANS status report first year
No full textThis report details the status of the BELTRANS project after 7 months of collaborative work to inform the follow-up committee. The BELTRANS project is a KBR coordinated, BRAIN research project funded by the Belgian Science Policy Office (BELSPO) with the following partners: KU Leuven and UCLouvain. The aim of the project is to analyse intra-Belgian book translations, with specific attention to the fields of literature and history, from French to Dutch and Dutch to French in the period of 1970 to 2020