The X-Ray Interferometric Space Telescope (XRIstel) is a proposed single-spacecraft mission designed for high-resolution astrophysics. It targets angular resolutions on the order of 100 μas, representing an O(10^4) spatial resolution improvement over existing X-ray observatories. This capability enables direct imaging and spectro-astrometric observations of compact sources, such as supermassive black holes (SMBHs) and X-ray binaries. Operating in a Lissajous orbit around the Sun-Earth L2 point, the spacecraft undergoes a controlled rolling motion, while its optical payload relies on grazing-incidence and slatted beam combining mirrors operating at wavelengths between 1.24 and 8.68 nm.

Maintaining interference fringe visibility requires optical path length differences between optics and detector to remain within 0.1 to 1.0 nm. Conventional spacecraft structures prioritize strength and stiffness, but lack sub-nanometer thermo-mechanical stability. This study addresses the design and evaluation of an ultra-stable primary structure for XRIstel. The objective is to achieve sub-nanometer stability while satisfying Ariane 6 launch constraints, mass envelopes, and outgassing limitations.

Building on design approaches from heritage missions like LISA and JWST, a Python framework was developed for conceptual structural sizing. The tool evaluated candidate beam geometries, global topologies, and materials, including CFRP laminates, C/C-SiC, Aluminium 7075-T6, and CF/PEEK. Classical Laminate Theory (CLT) was applied to determine the quasi-isotropic properties for composite laminates. Candidate concepts were then modelled in COMSOL Multiphysics using (mostly) shell elements. Finite element simulations evaluated static launch accelerations, linear buckling stability, natural frequencies, thermal environment behaviour, sinusoidal excitation responses, and micrometeoroid impact analyses.

Thin-walled circular beams demonstrated superior behaviour compared to octagonal beam profiles, while a CFRP material consisting of Toray M40J fibres and PMT-F33 cyanate ester resin outperformed other material candidates. A multi-criteria trade-off identified an eight-beam CFRP structure with five support rings as the optimal baseline for detailed design. The concept yielded mass savings while meeting the strict outgassing requirements and launch constraints. A detailed design was developed, including further parameter refinements on wall thicknesses, beam diameters, number of support rings, diagonal beams, cross-volume structures, and the inclusion of multi-layer insulation and solar panels.

Detailed design analyses identify the multi-octagon structural configuration (MO-BR) as the best performing structure, fully satisfying launch survivability with margin and outperforming the single-octagon regarding all metrics. These include the stress levels, eigenfrequencies, total mass, CoG location, and sinusoidal excitation response. Nearly all requirements are satisfied, either fully or marginally, while the spacecraft lid design and the CFRP/aluminium connective joints are identified as a source remaining local stress concentrations and unwanted longitudinal response behaviour.

This study confirms the feasibility of developing a single-spacecraft XRI mission with an ultra-stable spacecraft structure based on CFRP as primary material. The optimized multi-octagon composite structure combines launch survivability with a realistic baseline for further development towards a sub-nanometer thermo-mechanical stable spacecraft.

Future steps of the structural design process are recommended to include the identification and evaluation of the thermal environment and the structure's response during operation. Additionally, the inclusion of optical benches, realistic connective joints, and a detailed spacecraft lid design are recommended in near-future design iterations.
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In the NewSpace era, small satellite missions face increasing pressure to achieve high reliability under tight schedules and limited resources. Model-Based Systems Engineering (MBSE) has demonstrated clear advantages over traditional document-centric workflows, yet its benefits have largely been confined to early design phases, with limited extension into Assembly, Integration, Verification, and Validation (AIV/V) activities. Current AIV/V practice relies on disconnected workflows where requirements, interfaces, test procedures, and verification status are managed across separate tools, introducing inconsistencies and reducing traceability. In collaboration with ISISPACE, this thesis presents the design, implementation, and validation of an integrated Capella-Valispace toolchain establishing a bidirectional digital thread from mission requirement definition to verification close-out. Model artefacts are automatically extracted from Capella and imported into Valispace, while verification outcomes and as built measurements flow back into the Capella model. The framework is evaluated across 26 success factors against document-based and Capella-only reference approaches and demonstrated on a 6UXL CubeSat Earth-observation mission, showing significant improvements in traceability, consistency, flexibility, and stakeholder collaboration. ... Read more

Solar flares are sudden releases of energy from the Sun that can produce intense electromagnetic radiation and energetic particles, with the potential to disrupt satellite systems, radio communications, and other space-based and technological infrastructure. Accurate solar flare prediction is therefore important for providing timely warnings, while interpretable models are needed to understand the physical information driving predictions and to assess their reliability in operational settings. This study investigates a neural-network-based solar flare prediction model using SHARP magnetic-field parameters and flare-history information, with particular emphasis on model performance, interpretability, and the effects of incorporating physical constraints. The baseline model achieves competitive predictive performance, while temporal deployment on new data results in a small performance decrease. Physics-informed loss functions are shown to alter the model’s classification behavior without substantially reducing overall performance, although the effect depends strongly on the physical relationship imposed. The Pearson MEANGBZ constraint reduces false negatives at the cost of more false positives, whereas the Kendall MEANGAM constraint produces the opposite behavior and substantially more missed flares. These results demonstrate that TSS alone is insufficient to characterize the operational behavior of flare prediction models and that threshold selection and the balance between false positives and false negatives are important considerations. Finally, a parameter study shows substantial redundancy among the input features: a reduced model using only 11 features achieves a TSS of 0.7152, close to the approximately 0.72 of the full baseline. Overall, the results indicate that accurate, interpretable, and operational solar flare prediction can be achieved with fewer input parameters, while physics-informed learning can be used as a constraint to modify model behavior without necessarily compromising predictive performance. ... Read more

This thesis presents a model-based methodology for Assembly, Integration, and Verification (AIV) of space systems, targeting post-Critical Design Review (post-CDR) project phases. While Model-Based Systems Engineering (MBSE) is increasingly adopted in early life cycle stages, its application to AIV remains limited and largely document-driven. The proposed methodology formalizes AIV through a structured ontology and process model, capturing relationships between requirements, verification activities, criteria, and evidence. Implemented in SysML v1, it enables end-to-end traceability and supports consistent AIV planning, execution, and reporting. Alignment with ECSS verification documentation requirements is demonstrated through model-based artifact generation. The approach is applied to a CubeSat payload qualification campaign. Results indicate improved transparency, consistency, and traceability compared to traditional practices, highlighting the potential of MBSE to support digital continuity beyond early space system life cycle phases. ... Read more

The NEBULA-Xplorer Mission (Netherlands Educational Satellite for Exploration of Binary-Linked Astrophysics) is a space mission initiated by Space Research Organization Netherlands (SRON) and carried out by students from Dutch educational institutes with the support of other industrial partners from the Netherlands. The scientific goal of the project is to observe X-ray binaries to better understand the universe and gather information that can help solve the mysteries of one of the most controversial topics in the history of science: black holes. X-Ray binaries are combinations of an extremely compact object, such as a black hole or a neutron star, and a companion star. The compact object extracts matter from the companion star, which releases great amounts of energy that can be observed using X-ray sensors. SRON has intentionally assigned the conceptual mission design to a student team as part of its objective to support the development of future space engineers and strengthen the Dutch space engineering ecosystem. This provides students with the opportunity to contribute to a mission with real scientific relevance while working within a professionally guided environment. As a result, the project has both scientific and educational purposes, which frame the scope and risk exposure in this early design phase.
Observational satellites currently observing X-ray binaries are approaching their End-Of-Life (EOL), with the final mission estimated to last until 2028. The planned future missions will only launch in the second half of the 2030s, creating a scientific gap in the observation of X-ray binaries. This critical gap can be filled with the NEBULA-XPlorer Mission with a 2030 launch date. The lack of other missions adds significant scientific value to the NEBULA-XPlorer. The mission is categorised as an European Space Agency (ESA) Mini-F Rideshare Mission. The Mini-F class encompasses small satellites with a mass range of 200-400 kg, and spacecraft mass is directly proportional to Mission and Launch Costs. As the spacecraft is a mini-satellite with very high scientific value, the mission’s total value is magnified enormously. It is also worth noting that ESA is increasingly interested in low-cost, high-return scientific missions, which align well with the NEBULA-Xplorer mission.
Another critical aspect of the mission is its aim to support and contribute to the independence of Europe’s Space Industry. While outlining the mission, the launch vehicle chosen was specifically a European launch vehicle. The Vega-C launch vehicle was selected as suitable for this mission after research into the options. Currently, Vega-C is launched only from the Guiana Space Centre in French Guiana. Therefore, this is assumed to be the only option for the NEBULA-Xplorer Mission, because a European launch site will be used. Furthermore, during the design process, European Cooperation for Space Standardization (ECSS) standards have been used to comply with the regulations for European space missions. These requirements have been extensively studied and implemented during the early design stages to prevent any complications that can occur during the adoption of the NEBULA-Xplorer Mission by ESA. ... Read more

Most mission costs and risks are determined early, but risk assessments are performed late when design freedom is low. Traditional document-based dependability methods fail to inform early design choices. This research explored how Model-Based Systems Engineering (MBSE) can embed risk management within system architecture to shift dependability analysis earlier in the lifecycle.
The objective was to develop a fault-detection and risk-assessment framework integrated with MBSE to improve early-phase design evaluation for the NEBULA-Xplorer mission. The study addressed how MBSE models can represent fault-critical information, what early fault patterns can be detected, how external analysis can be integrated, and how effective the resulting framework is in identifying system-level risks. A layered, tool-agnostic framework was developed that combined four layers: requirements traceability, rule-based fault detection, graph-based failure analysis, and severity-driven risk assessment. Functional, structural, and parametric model views were enhanced with design and failure attributes such as redundancy, power, and radiation tolerance.
Failure propagation was analysed using graph-theory metrics (connectivity, min-cut, and centrality) to identify single points of failure and structural bottlenecks. Results were then translated into an ECSS-aligned Functional FMEA, producing a structured risk assessment directly from the MBSE model. The framework was applied and demonstrated in the Capella environment for the NEBULA-Xplorer, a student X-ray observation mission developed at SRON. The mission’s resource constraints and educational nature made it ideal for demonstrating a lightweight, explainable MBSE-based dependability process. Analyses highlighted key functions acting as system-level bottlenecks, validating the framework’s ability to expose early architectural vulnerabilities.
The framework satisfied all functional and non-functional requirements and aligned with ECSS dependability standards. Validation against FEMMP criteria confirmed strengths in methodological rigour, traceability, and automation, while identifying improvement in scalability and GUI maturity. The approach enabled traceable, modeldriven fault detection and risk assessment during Phases A–B, reducing manual analysis effort.
This work demonstrates that MBSE can evolve from a descriptive modelling tool into a driver of early, actionable, model-based risk management. Future extensions should incorporate multi-failure scenarios, degradation states, time-dependent behaviours, and improved usability to further strengthen risk management within MBSE. ... Read more

The Earth’s lunar-distance magnetopause is a highly dynamic boundary. Its position plays a key role in shaping weather events within the magnetotail and other space-weather phenom- ena. Statistical studies of the magnetotail require the identification of magnetopause crossings from spacecraft observations to study its dynamics. However, current detections have some shortcomings. Detecting magnetopause crossings can be time-consuming with rule-based methods and manual inspection, especially at the lunar distance due to its variability. Recent automated classifiers do cover larger datasets, but often miss the dynamic nature of the mag- netopause, due to their coarse timing and limited number of detected events. This limits the usability of these datasets for detailed studies of magnetotail dynamics. This thesis addresses these challenges by developing and evaluating machine learning ap- proaches for detecting magnetopause crossings in the lunar-distance magnetotail using AR- TEMIS mission data. First, a gradient-boosted decision tree is used as a baseline, trained to classify magnetosheath and magnetotail samples. Afterwards, a double masked autoen- coder (MAE) Transformer is introduced. This model uses a reconstruction-based method to detect changes in plasma regimes and shifts from the magnetotail to the magnetosheath and vice versa. Both models are trained and validated using a labelled dataset, combining ion spectrograms, plasma moments, and a list of known magnetopause crossings. The results show that the MAE Transformer achieves higher precision with similar recall, and improves timing accuracy compared to the baseline. The MAE transformer is applied to twelve years of ARTEMIS P1 and P2 data, detecting around 3000 magnetopause crossings. The spatial distribution of these crossings matches well with empirical magnetopause models, and a clear correlation to the solar cycle is observed. Outliers in the detected crossings are linked to solar and geomagnetic activity. ... Read more

In the history of humankind only three spacecraft have ever ventured into interstellar space [2]. How- ever, none of them have been equipped for proper exploration of interstellar space, all of these five spacecraft were equipped for exploring the outer planets and objects of the solar system but not for interstellar space and/or the heliosphere. In part due to this lack of in-situ measurements of the inter- stellar medium and the heliosphere, not a lot is known of these areas. This report aims to provide a detailed overview of the concept of an interstellar heliosphere probe to investigate the heliosphere and the interstellar medium. This report will examine the requirements that are needed for such a spacecraft and explain why these requirements exist. Moreover, a component level description of the various subsystems typically involved in spacecraft manufacturing will be provided. With these subsystems, estimations of the mass, cost, power and data will be given when appropriate in an overview of all the subsystems. ... Read more

The goal of project Altus is to do an in-situ investigation of Polar Mesospheric Clouds (PMCs). These clouds form around an altitude of 84 km, and only for 60 to 80 days per year, during the summer. Normally, these clouds only form in the polar regions, from around 50◦ latitude north and south. Recently, however, PMCs have been observed as low as 40◦ north. There are theories linking this change in location, and other unexpected behaviours of PMCs, to climate change. However, further research is still required to confirm these theories. As these changes are happening at a slow rate, a database of PMC measurements would be extremely beneficial to track indicator values over time. Project Altus sets out to bridge this knowledge gap by taking regular measurements of PMCs over an extended period of time. ... Read more