European Space Research and Technology Centre

Aguiar Y., Alía R.G., Kranjčević M., Cecchetto M., Söderström D., Mandal A.R., Gascon J., Trummer J., Vincke H., Alessi A., Cavani O., Constantino A., Lerner G., Sostero L., Girard S., et. al.

Reghenzani F., Baroffio D., Lopez T.A., Fornaciari W., Borel T., Krimmel F.

Polo-López L., Berretti L., Menargues E., Capdevila S., Toso G., Garcia-Vigueras M.

Lyman J.D., Dhillon V.S., Kamann S., Chrimes A.A., Levan A.J., Pelisoli I., Steeghs D.T., Wiersema K.

ABSTRACT GLEAM-X J1627−52 was discovered as a periodic ($\sim$18 min) radio signal over a duration of three months in 2018. It is an enigmatic example of a growing population of ‘long-period radio transients’ consistent with Galactic origins. Their nature is uncertain, and leading models invoke magnetic neutron stars or white dwarfs, potentially in close binary systems, to power them. GLEAM-X J1627−52 resides in the Galactic plane with a comparatively coarse localization ($\simeq$2 arcsec). Here, we study the localization region to search for spectrophotometric signatures of a counterpart using time-domain searches in optical and near-infrared imaging, and MUSE integral field spectroscopy. No sources in the localization display clear white dwarf spectral signatures, although at the expected distance we can only provide modest limits on their presence directly. We rule out the presence of hot subdwarfs in the vicinity. We found no candidate within our search for variability or periodic behaviour in the light curves. Radial velocity curves additionally show only weak evidence of variation, requiring any realistic underlying system to have very low orbital inclination ($i \lesssim 5$ deg). Two Balmer emission line sources are reminiscent of white dwarf pulsar systems, but their characteristics fall within expected M-dwarf chromospheric activity with no signs of being in a close binary. Currently the white dwarf pulsar scenario is not supported, although longer baseline data and data contemporaneous with a radio active epoch are required before stronger statements. Isolated magnetars, or compact binaries remain viable. Our limits highlight the difficulty of these searches in dense environments at the limits of ground-based data.

Luoni F., Weber U., Lang A.K., Westermayer M., Horst F., Baricco M., Bocchini L., Giraudo M., Santin G., Schuy C., Durante M., Boscolo D.

Galactic cosmic rays (GCR) are among the biggest hindrances to crewed space exploration. The ions contributing the most to fluence and absorbed dose in free space are 1H and 4He. In addition, their contribution to dose equivalent increases behind thick shields. In this work, the results of depth-dose measurements performed with high-energy 1H and 4He ions (2 GeV and 480 MeV 1H, and 430 MeV/u 4He) in structural (aluminum alloy), standard (PMMA and high-density polyethylene), innovative (lithium hydride) and in situ (Moon regolith simulant) shielding materials are presented. A strong dose build-up effect, due to target fragments and secondary protons, is observed in the first part of the Bragg curve for all the tested ion beams. The experimental results are compared to the Monte Carlo simulation tools most used for radiation protection in space, i.e., different physics lists of Geant4, PHITS, and FLUKA.

Papadopoulos A., Kyriakou I., Matsuya Y., Cortés-Giraldo M.A., Galocha-Oliva M., Plante I., Stewart R.D., Tran N.H., Li W., Daglis I.A., Santin G., Nieminen P., Incerti S., Emfietzoglou D.

Abstract Radiation quality for determining biological effects is commonly linked to the microdosimetric quantity lineal energy ( $$y$$ y ) and to the dose-mean lineal energy ( $${y}_{\text{D}}$$ y D ). Calculations of $${y}_{\text{D}}$$ y D are typically performed by specialised Monte Carlo track-structure (MCTS) codes, which can be time-intensive. Thus, microdosimetry-based analytic models are potentially useful for practical calculations. Analytic model calculations of proton $${y}_{\text{D}}$$ y D and radiation protection quality factor ( $$Q$$ Q ) values in sub-micron liquid water spheres (diameter 10–1000 nm) over a broad energy range (1 MeV–1 GeV) are compared against MCTS simulations by PHITS, RITRACKS, and Geant4-DNA. Additionally, an improved analytic microdosimetry model is proposed. The original analytic model of Xapsos is refined and model parameters are updated based on Geant4-DNA physics model. Direct proton energy deposition is described by an alternative energy-loss straggling distribution and the contribution of secondary electrons is calculated using the dielectric formulation of the relativistic Born approximation. MCTS simulations of proton $${y}_{\text{D}}$$ y D values using the latest versions of the PHITS, RITRACKS, and Geant4-DNA are reported along with the Monte Carlo Damage Simulation (MCDS) algorithm. The $${y}_{\text{D}}$$ y D datasets are then used within the Theory of Dual Radiation Action (TDRA) to illustrate variations in $$Q$$ Q with proton energy. By a careful selection of parameters, overall differences at the ~ 10% level between the proposed analytic model and the MCTS codes can be attained, significantly improving upon existing models. MCDS estimates of $${y}_{\text{D}}$$ y D are generally much lower than estimates from MCTS simulations. The differences of $$Q$$ Q among the examined methods are somewhat smaller than those of $${y}_{\text{D}}$$ y D . Still, estimates of proton $$Q$$ Q values by the present model are in better agreement with MCTS-based estimates than the existing analytic models. An improved microdosimetry-based analytic model is presented for calculating proton $${y}_{\text{D}}$$ y D values over a broad range of proton energies (1 MeV–1 GeV) and target sizes (10–1000 nm) in very good agreement with state-of-the-art MCTS simulations. It is envisioned that the proposed model might be used as an alternative to CPU-intensive MCTS simulations and advance practical microdosimetry and quality factor calculations in medical, accelerator, and space radiation applications.

Haworth T.J., McCaughrean M.J., Pearson S.G., Booth R.A.

ABSTRACT We present the JWST discovery of a highly extincted ($A_V\sim 52$) candidate brown dwarf (${\sim} 0.018$ M$_\odot$) in the outskirts of the Trapezium Cluster that appears to be coincident with the end of a ${\sim} 1700$ au long, remarkably uniformly wide, dark trail that broadens only slightly at the end opposite the point source. We examine whether a dusty trail associated with a highly extincted brown dwarf could plausibly be detected with JWST and explore possible origins. We show that a dusty trail associated with the brown dwarf could be observable if dust within it is larger than that in the ambient molecular cloud. For example, if the ambient cloud has a standard ${\sim} 0.25$ $\mu$m maximum grain size and the trail contains micron-sized grains, then the trail will have a scattering opacity over an order of magnitude larger compared to the surroundings in NIRCam short-wavelength filters. We use a simple model to show that a change in maximum grain size can reproduce the high $A_V$ and the multifilter NIRCam contrast seen between the trail and its surroundings. We propose and explore two possible mechanisms that could be responsible for the trail: (i) a weak far ultraviolet radiation-driven wind from the circum-brown dwarf disc due to the O stars in the region and (ii) a Bondi–Hoyle–Lyttleton accretion wake. The former would be the most distant known case of the Trapezium stars’ radiation driving winds from a disc, and the latter would be the first known example of ‘late’ infall from the interstellar medium on to a low-mass object in a high-mass star-forming region.

Monopoli M., Biondi M., Nannipieri P., Moranti S., Fanucci L.

Bartsch A., Gay B.A., Schüttemeyer D., Malina E., Miner K., Grosse G., Fix A., Tamminen J., Bösch H., Parker R.J., Rautiainen K., Hashemi J., Miller C.E.

Arnold E., Spilger P., Straub J.V., Müller E., Dold D., Meoni G., Schemmel J.

We present a novel software feature for the BrainScaleS-2 accelerated neuromorphic platform that facilitates the partitioned emulation of large-scale spiking neural networks. This approach is well suited for deep spiking neural networks and allows for sequential model emulation on undersized neuromorphic resources if the largest recurrent subnetwork and the required neuron fan-in fit on the substrate. We demonstrate the training of two deep spiking neural network models—using the MNIST and EuroSAT datasets—that exceed the physical size constraints of a single-chip BrainScaleS-2 system. The ability to emulate and train networks larger than the substrate provides a pathway for accurate performance evaluation in planned or scaled systems, ultimately advancing the development and understanding of large-scale models and neuromorphic computing architectures.

Dieball A., Kordulla W., Steelant J.

Berretti L., Loison R., Menargues E., Polo-LÓPez L., Toso G., GarcÍA-Vigueras M.

Ramella C., Florian C., Garcìa M.D., Davies I., Pirola M., Colantonio P.

Somers F., Roos C., Biannic J.‐., Sanfedino F., Preda V., Bennani S., Evain H.

ABSTRACTMonte Carlo simulations have long been a widely used method in the industry for control system validation. They provide an accurate probability measure for sufficiently frequent phenomena but are often time‐consuming and may fail to detect very rare events. Conversely, deterministic techniques such as or IQC‐based analysis allow fast calculation of worst‐case stability margins and performance levels, but in the absence of a probabilistic framework, a control system may be invalidated on the basis of extremely rare events. Probabilistic ‐analysis has therefore been studied since the 1990s to bridge this analysis gap by focusing on rare but nonetheless possible situations that may threaten system integrity. The solution adopted in this paper implements a branch‐and‐bound algorithm to explore the whole uncertainty domain by dividing it into smaller and smaller subsets. At each step, sufficient conditions involving upper bound computations are used to check whether a given requirement–related to the delay margin in the present case–is satisfied or violated on the whole considered subset. Guaranteed bounds on the exact probability of delay margin satisfaction or violation are then obtained, based on the probability distributions of the uncertain parameters. The difficulty here arises from the exponential term classically used to represent a delay , which cannot be directly translated into the Linear Fractional Representation (LFR) framework imposed by ‐analysis. Two different approaches are proposed and compared in this paper to replace the set of delays . First, an equivalent representation using a rational function with unit gain and phase variations that exactly cover those of the original delays, resulting in an LFR with frequency‐dependent uncertainty bounds. Then, Padé approximations, whose order is chosen to handle the trade‐off between conservatism and complexity. A constructive way to derive minimal LFR from Padé approximations of any order is also provided as an additional contribution. The whole method is first assessed on a simple benchmark, and its applicability to realistic problems with a larger number of states and uncertainties is then demonstrated.

Sabatini M., Pisano A., Fanelli C., Buongiorno Nardelli B., Liberti G.L., Santoleri R., Donlon C., Ciani D.

This study evaluates the potential impact of the Copernicus Imaging Microwave Radiometer (CIMR) mission on the sea surface temperature (SST) products of the Mediterranean Sea. Currently, infrared (IR) radiometers provide accurate, high-resolution SST measurements, but they are limited by their inability to see through clouds. Passive microwave (PMW) radiometers, on the other hand, offer monitoring capabilities in almost all weather conditions but typically at lower spatial resolutions. The CIMR mission represents a notable advance in microwave remote sensing of SSTs, as it will ensure a ≤15 km spatial resolution in the recovered SST field. Using an observing system simulation experiment (OSSE), this study evaluates the effect of inserting synthetic CIMR observations into the Copernicus Mediterranean SST analysis system, which is based on an optimal interpolation (OI) algorithm. The OSSE was conducted using data for the year 2017, including daily SST and salinity outputs from a Mediterranean Sea model, hourly precipitation rates from the IMERG, and wind and cloud cover data from ERA5. The results suggest that the improved spatial resolution and accuracy of the CIMR could potentially improve SST retrievals in the Mediterranean Sea, offering better insights for climate and environmental monitoring in semi-closed basins. Including CIMR data in the OI algorithm reduced the mean error and root mean square error (RMSE) of the SST analysis, especially under conditions of low IR coverage. The greatest improvements were found to occur in July, corresponding to coastal upwelling and Atlantic inflow into the Alboran Sea. Improvements ranged from 16% to 29%, with an overall improvement of 26% for the full year of 2017. In conclusion, this preliminary study indicates that Copernicus Mediterranean Sea HR SST products could benefit from the inclusion of the CIMR in the current IR sensor constellation.