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Exoplanet characterization across the mass-radius space using machine learning
No full textCharacterizing the internal composition of exoplanets is an essential part in understanding the diversity of observed exoplanets and the processes that govern their formation and evolution. However, the interior of an exoplanet is inaccessible to observations, and can only be investigated via numerical structure models. Furthermore, interior models are inherently non-unique, because the large number of unknown parameters outweigh the limited amount of observables. One set of observable parameters can correspond to a multitude of possible planet interiors.
Probabilistic inference methods, such as Markov chain Monte Carlo sampling, are a common, but computationally intensive and time-consuming tool to solve this inverse problem and obtain a comprehensive picture of possible planetary interiors, while also taking into account observational uncertainties. This prohibits large-scale characterization of exoplanet populations.
We explore here an alternative approach to interior characterization utilizing ExoMDN, a stand-alone machine-learning model based on mixture density networks (MDNs) that is capable of providing a full probabilistic inference of exoplanet interiors in under a second, without the need for extensive modeling of each exoplanet's interior or even a dedicated interior model. ExoMDN is trained on a large database of 5.6 million precomputed, synthetic interior structures of low mass exoplanets.
The fast prediction times allow investigations into planetary interiors which were not feasible before. We demonstrate how ExoMDN can be leveraged to perform large-scale interior characterizations across the entire population of low-mass exoplanets. We can show how ExoMDN can be used to comprehensively quantify the effect of measurement uncertainties on the ability to constrain the interior of a planet, and to which accuracy these parameters need to be measured to well characterize a planet’s interior
Zero emission heating with calcium oxide and water: development and demonstration of first pilot scale thermochemical heating system for buildings
No full textFastCAV: Efficient Computation of Concept Activation Vectors for Explaining Deep Neural Networks
No full textConcepts such as objects, patterns, and shapes are how humans understand the world. Building on this intuition, concept-based explainability methods aim to study representations learned by deep neural networks in relation to human-understandable concepts. Here, Concept Activation Vectors (CAVs) are an important tool and can identify whether a model learned a concept or not. However, the computational cost and time requirements of existing CAV computation pose a significant challenge, particularly in large-scale, high-dimensional architectures. To address this limitation, we introduce FastCAV, a novel approach that accelerates the extraction of CAVs by up to 63.6x (on average 46.4x). We provide a theoretical foundation for our approach and give concrete assumptions under which it is equivalent to established SVM-based methods. Our empirical results demonstrate that CAVs calculated with FastCAV maintain similar performance while being more efficient and stable. In downstream applications, i.e., concept-based explanation methods, we show that FastCAV can act as a replacement leading to equivalent insights. Hence, our approach enables previously infeasible investigations of deep models, which we demonstrate by tracking the evolution of concepts during model training
High strength Al recycling alloys for additive manufacturing
No full textThe recycling of aerospace scraps is challenging, as it is composed of different grades of Al alloys, where sorting is laborious and often not economical feasible. One promising strategy for achieving high recycling rates, potentially up to 100 %, is cross-alloying of the two Al grades (2xxx and 7xxx alloys) mainly used in modern airframes. In this way, the formation of the intermetallic T-phase is promoted in a eutectic reaction, which opens up the potential for the creation of fine structures that contribute to high mechanical properties. To explore this approach, thermodynamic calculations were carried out to identify suitable compositions with high recycling potential. Selected compositions where then cast into cylindrical samples, and laser treatments simulating laser powder bed fusion (LPBF) were performed to assess the suitability for additive manufacturing.
The microstructure of the laser treated samples showed columnar Al grains oriented along the solidification direction, featuring a very fine dendritic substructure. T-phase forming interconnected networks was observed in the interdendritic regions and at the Al dendrite colony boundaries. It can be anticipated that similar microstructures, which may be detrimental for the mechanical properties, will also be formed during LPBF. To mitigate this, spheroidization heat treatments were carried out, breaking up the interconnected T-phase networks.
Furthermore, the laser treatment experiments revealed distinct cracking phenomena. In the almost fully eutectic model alloy, large cracks perpendicular to the scan vector direction were observed, indicating a cold cracking mechanism and a very brittle material behavior. Interestingly, the alloy that allows a 100% recycling rate performed better than alloys with reduced amounts of T-phase, which appeared more prone to hot cracking.
Based on these findings, a candidate for a high strength AM alloy was selected. In the next step, pre-alloyed powder will be produced for the validation of the processability by LPBF
Remote Sensing Technologies and Applications in Urban Environments X
No full textPROCEEDINGS OF SPIE, Remote Sensing Technologies and Applications in Urban Environments X, Volume 13672, Proceedings of SPIE 0277-786X, V. 13672
Die Durchführung einer LEOP ist Teamwork: Hausweite LEOP Simulation
No full textAn der Durchführung einer LEOP (Launch and Early Orbit Phase) sind alle GSOC-Abteilungen beteiligt. Sie sind miteinander komplex vernetzt und arbeiten im Schnitt 3-5 Jahre an der Erstellung des Bodensegments und der Validierung und Qualifikation aller notwendigen Flugprodukte und Prozesse. Momentan werden 10
Satelliten in der Routinephase am GSOC betreut, daher können die LEOP-spezifischen Prozesse und Arbeitspakete kaum trainiert werden. Diese Erfahrungslücke wird durch eine mehrwöchige Schulung
(„Hausweite LEOP-Simulation“) während des laufenden Routinebetriebs vor allem bei den neu eingestellten Mitarbeitenden geschlossen. Dabei werden das Schulungskonzept, die herausfordernde Planungsarbeit und die erzielten Ergebnisse detailliert vorgestellt
Porosity and hydrous alteration of the Martian crust from InSight seismic data
No full textThe composition and layering of the Martian crust provide important constraints on planetary crustal evolution as well as on present-day conditions, e.g., with regard to the presence of liquid water or ice. The seismic data of the InSight mission yielded new and critical information on crustal structure at several locations on Mars. Here, we use rock physical models to investigate the range of lithologies, porosities and alteration scenarios compatible with seismic P- and S-wave velocities as well as vP/vS ratios from InSight. We find that present-day crustal porosity extends to 20–25 km depth at all sampled locations, with large Noachian impacts as main drivers for the creation of porosity, and viscous pore closure as likely agent of removal of porosity at depth, resulting in a discontinuous increase in seismic velocities. Spatially heterogeneous seismic velocities can be related to differences in porosity that could be caused by subsequent localized magmatic activity. At the InSight landing site, where seismic data indicate a four-layered crust, hydrated minerals as traces of aqueous alteration are present throughout the crust, though the water within these minerals could be fairly limited at 0.3 wt% or less. The most likely types of hydrated minerals are also consistent with a post-depositional environment that was limited in water. The velocity increase at about 10 km depth beneath InSight can either be attributed to a change in composition from felsic to basaltic, or to a change in porosity by the deposition of Utopia ejecta. A felsic component to the crust, e.g. due to impact-generated buoyant partial melts, can accordingly not be excluded, but would not be present globally. Seismic and geological constraints for the layer at approximately 200 m to 2000 m depth beneath the lander strongly favor basaltic Noachian sediments saturated with a mixture of up to 10 % ice and brine. However, the lateral extent of this present day aquifer is not constrained by the available data
Ca1− xSrxMnO3− δ granules, pellets, foams: Influence of fabrication conditions and microstructure on oxidation kinetics
No full textMicrostructure and oxidation kinetics are closely intertwined factors that significantly influence the behavior of materials in oxidative environments. This relationship is of particular importance for redox materials such as CaSrMnO, where reversible oxygen ions exchange and oxidation state shifts are key to their functionality. In the first study, scanning electron microscope (SEM) was used to examine how varying Sr content affects the morphology and microstructure of CaSrMnO powder compositions. The results indicate that increasing Sr content leads to smaller particle sizes and improved particle size homogeneity. Granules with Sr concentrations ranging from 0 % to 40 % exhibit notable changes in morphology. However, the microporosity and d50 vary slightly across the samples in a non-monotonic manner, with no clear trend emerging with respect to Sr concentration. The second study investigates how macrostructural forms, such as foams and pellets, impact oxidation kinetics in Ca0.8Sr0.2MnO3. Parameters including particle size distribution of the raw material, overall microporosity, and structural characteristics of these macrostructures were analyzed for their effect on oxidation rates. Findings reveal that macrostructural configuration, alongside microstructural features like microporosity, significantly impacts oxidation kinetics. These studies collectively underscore the critical relationship between dopant concentration, microstructural characteristics, and structural morphology in determining the oxidative behavior of CaSrMnO, providing key insights into optimizing material performance in redox environments
To the Moon: DAS measurements of anthropogenic signals in LUNA
No full textThe LUNA Moon analogue facility, jointly operated by DLR and ESA in Cologne, Germany, provides a simulated lunar environment for instrument and experiment tests and operations training for both robotic and crewed missions. At the heart of LUNA is a 700 m2 regolith testbed, filled to 60 cm depth with EAC-1A Mare simulant, which also contains a deep-floor area with of to 3 m depth. Before filling the hall with the regolith simulant, a 500 m long fiber-optic cable containing single- and multi-mode fibers, as well as an engineered fiber, was deployed in a spatial grid to support future tests of DAS and DTS applications for the Moon. The first user campaign after inauguration of LUNA collected 4 days of DAS data in November 2024, partly overlapping with a test of vertical-component geophones for a possible Artemis IV deployed instrument. Besides, a preliminary set-up of the LUNA broad-band station (Trillium Compact 120 s) was recording continuously at the same time. In this presentation, we show results for geolocating and mapping the fiber in LUNA (using tap test, weight drops, and QGIS) and compare the characteristics of signals recorded by the different instruments. We investigated and describe hammer shots for geophone-based refraction seismics, signals from cars, airplane take-offs (from nearby CGN airport), a helicopter overfly (with characteristic Doppler shift), the crane within LUNA, and a small, 3U-cubesat sized rover driving in LUNA. We also recorded a teleseismic earthquake with the DAS. Our results provide a comprehensive baseline characterization of anthropogenic noise at our facility, offering a valuable reference for identifying external events at LUNA during future user campaigns and mission preparations