Small satellites increasingly produce more housekeeping telemetry than can be continuously downlinked or inspected, delaying operator awareness of emerging spacecraft-health issues. This thesis develops an explainable on-board thermal anomaly-alerting pipeline for downlink-constrained small-spacecraft missions, using Delfi Twin as a case study. Rather than proposing a stand-alone anomaly-detection algorithm, it defines a deployment pathway linking telemetry scope, anomaly semantics, synthetic event-level evaluation, residual-to-alert decision logic, compact alert packets, and STM32L4-class embedded verification. A lightweight expected-temperature predictor is combined with residual scoring, cumulative evidence, persistence, hysteresis, transient-spike suppression, and explicit gap termination to form bounded detector events. A labelled synthetic benchmark enables quantitative evaluation, while FUNcube-1 telemetry provides qualitative stress evidence on real on-orbit data. Under matched-predictor conditions, all alert-worthy synthetic events were recovered, and STM32L4 replay demonstrated ample timing and memory margins. Flight performance and autonomous operational trust remain future validation tasks. ... Read more

PocketQubes are a young technology that brings with it a vast amount of research opportunities. These pico-satellites consist of standardised units (P) of 5x5x5 cm. Currently, the Delfi team at the Delft University of Technology is developing the next 3P PocketQube mission. One of the goals of this mission is to continue to advance this satellite technology by learning from the challenges encountered in the previous PocketQube.

The focus of this research is on the power generation system of the satellite. In the previous Delfi mission, a Maximum Power Point Tracking (MPPT) technique called Perturb and Observe was used to extract as much power as possible from the small solar cells. However, it did not generate as much power as expected due to the tumbling of the satellite. Therefore, various other MPPT methods were researched and a technique was found that will likely be more suitable for a tumbling PocketQube: temperature-based MPPT. Based on the temperature of the solar cell, this method calculates the voltage at which the cell will generate the most amount of power (V_MPP) using a linear equation. The objective of this research is to design, manufacture and test a prototype circuit that implements this method so that its performance can be investigated. Based on this, the viability of using this method on a PocketQube can be evaluated.

The prototype consists of three separate Printed Circuit Boards (PCBs). One houses the solar cells and temperature sensors and is mounted on a test stand in front of a powerful lamp that mimics the sun. The second PCB is a demo circuit board for a Direct Current to Direct Current converter (DC-DC converter), which is used to convert the power from the solar cells to the correct voltage for the battery. In addition, it can limit the voltage of the solar cells so that they operate at their Maximum Power Point (MPP). The last PCB is the link between the other two and also connects to the load. Furthermore, it houses the control circuit that drives the solar voltage limit set by the DC-DC converter based on the temperature measurement that comes from the PCB with the solar cells.

This prototype was tested with a resistive load while the aforementioned lamp was illuminating the solar cells. By varying the load resistance, the demanded power could be varied. In this way, the performance of the circuit could be measured while operating under, at, and over the MPP. The solar cells could also be cooled down using Peltier modules on the test stand and were heated by the radiation of the lamp, allowing for different temperature environments. The irradiance was also rapidly varied by dropping an opaque plastic sheet between the lamp and the solar cells. Measurements were made with an oscilloscope or using digital multimeters present on the PCB with the control circuit.

In general, the circuit functions as intended and promises to be a viable option for the power generation system of a tumbling PocketQube. It adapts rapidly to changes in irradiance and demanded power from the load, and it keeps up with changes in temperature. It also achieves an overall efficiency of more than 80%, occasionally reaching more than 85%. One major flaw remains: the temperature gradient of the limit set by the DC-DC converter does not exactly match the temperature gradient of the V_MPP of the solar cells. However, this can likely be solved by placing all circuitry on the same PCB. In addition, small tweaks to the design, such as decreasing the volume, and more tests should be performed before this circuit can fly on the next PocketQube. ... Read more

Thermal analysis of CubeSats during early design stages is often limited by lack of time, resources and reliable material property data, which leads to large uncertainties in predicted temperatures and potential thermal risks. Additionally, the use of high-fidelity tools makes iterative analysis difficult, especially for small satellite teams.

To address this, this work develops an integrated approach that combines experimental determination of thermo-optical and thermal properties with reduced-order thermal modeling. A database of material properties for commonly used CubeSat components is generated through laboratory testing. Further, simplified thermal models are created and validated against experimental results to capture the dominant heat transfer behavior with reduced complexity.

The combined framework allows faster and more reliable preliminary thermal analysis, helping identify thermal issues early in the design process and improving overall confidence in thermal design. ... Read more

Infrared imaging for simultaneous Earth horizon and Sun detection provides a compact solution for spacecraft attitude determination, particularly for small satellites with strict resource constraints. This thesis investigates the use of low-resolution infrared cameras for three-axis attitude estimation in low Earth orbit, with application to the Delfi-Twin satellite platform.

A simulation framework was developed to generate realistic synthetic horizon images incorporating orbital geometry and sensor characteristics. Classical image-processing methods were implemented to extract horizon and Sun vectors and reconstruct attitude from geometric observations. Performance was assessed through extensive simulations and Monte Carlo analyses to quantify accuracy and robustness.

Results show that accurate horizon and Sun vector measurements can be obtained from low-resolution imagery, enabling stable attitude estimation over a wide range of viewing geometries. Monte Carlo simulations indicate robust performance under realistic sensor noise and partial Earth visibility conditions. These findings demonstrate that reliable attitude estimates can be achieved using only low-resolution infrared imaging combined with gyros. ... Read more

CubeSats enable affordable access to space, making them popular with universities, research institutes, and hobbyists. However, CubeSats still have a relatively high failure rate, particularly for missions with a small budget. In this thesis, we show evidence that insufficient testing is one of the root causes for this. This insufficiency is often caused by a lack of availability, budget, and time for the necessary testing. It would appear that the success chance of similar future missions could be improved by offering more affordable and accessible testing for all.

This thesis presents an open-source, end-to-end design for a magnetic testing system. This system facilitates important validation testing of nanosatellites for less than €12,500. The accompanying Helmholtz Cage Toolkit software allows for the simulation of magnetic field envelopes experienced by a satellite in orbit, which can then be reproduced by the hardware with an average pointing error of a few degrees. ... Read more

Several satellite engineering domains already adopt a standardised digital format, however the communication subsystem still uses and outdated approach, namely link budget tables. Because of this, the concept of the Link Budget Data Format (LBDF) is introduced which is a standardised, digital format to share link budget data. This thesis presents a conversion tool to convert the satellite link budget data from Redwire Space’s calculation tool to the LBDF standard. The impact of this approach is studied by taking interviews of both Redwire Space and European Space Agency (ESA) employees. These interviews show that the LBDF tool has a great impact on the time consumption of the data exchange and verification process, the error reduction due to the elimination of the manual copy-paste process and finally, cost savings. On top of this, the newly created tool provides opportunities within the company to automate their own processes such as the verification and optimisation of the link budget. A new verification tool shows a fully verified link budget of the Analysis of Resolved Remnants of Accreted galaxies as a Key Instrument for Halo Surveys (ARRAKIHS) mission, while a new optimisation tool calculates the maximum achievable data rate for different modulation and coding schemes considered for the ARRAKIHS mission. The theoretical optimal solution deemed to be 8 Phase Shift Keying (PSK) modulation with concatenated coding of Reed-Solomon and convolutional coding. Both tools use the new LBDF file as input and greatly improve the speed of these processes. ... Read more

Sloshing in liquid-filled tanks remains a critical challenge for spacecraft attitude control due to its strong coupling with rotational dynamics. As modern missions demand increased agility, larger propellant volumes, longer lifetimes, and compliance with ESA debris mitigation requirements through guaranteed deorbiting, sloshing-induced forces and torques become increasingly significant. These disturbances can degrade pointing performance, increase actuator usage, and, in extreme cases, lead to mission failure. Both historical anomalies and more recent incidents demonstrate that sloshing continues to pose a tangible risk to guidance and control systems.
This thesis investigates the extent to which a ground-based experimental platform can replicate and characterize sloshing behavior relevant to spacecraft applications, with particular emphasis on the validity limits of linear sloshing models. While sloshing is inherently nonlinear, linear representations are widely used for control-oriented analysis and stability assessment, making identification of their applicable excitation range essential.
The experimental campaign was conducted at GMV Portugal using the TRACTOR platform, a rotational testbed providing near-free motion about a single vertical axis. A rigidly mounted sloshing tank was excited using a reaction wheel, and inertial sensors recorded the dynamic response. Sloshing dynamics were identified using frequency domain system identification, and experimental results were compared against synthetic responses generated from a strictly linear model.
The results reveal clear indicators of nonlinear sloshing beyond a threshold excitation amplitude, including amplitude dependent frequency shifts and reduced coherence. The achieved Bond number regime is representative of operational spacecraft tanks, demonstrating the platform’s capability to investigate space relevant sloshing phenomena in a laboratory environment. ... Read more

The domain gap challenges artificial intelligence models in Earth Observation, degrading performance when patterns shift between the data encountered during training and deployment. Although the existence of the gap is acknowledged, predicting this performance degradation is challenging, especially for tasks such as ship segmentation in satellite imagery, which are inherently imbalanced. This thesis demonstrates that traditional domain gap metrics are inadequate for this task due to their inability to handle class imbalance.

To overcome this, a new metric is proposed: the positive difference of confidences. By focusing only on the model's confidence in the positive (ship) class, it ignores insignificant background changes. Tested across 22 source-target domain combinations, the metric​ proved a powerful predictor of target performance, with a correlation of 0.78 and a mean absolute error of 0.06, significantly outperforming existing metrics. The positive difference of confidences​ offers an accurate method for ensuring performance of ship segmentation models. ... Read more

To ensure the safety of a spacecraft, operators collect thousands of telemetry signals and monitor them for anomalies, which is both expensive and time-consuming. Space agencies have been researching Machine Learning (ML)-based Time Series Anomaly Detection (TSAD) methods to improve automation, but this is hindered by a lack of high-quality benchmarks. This thesis explores the application of ML-based TSAD on instrument telemetry data for the XMM-Newton space telescope. The data was explored to find several unique challenges, such as recurring eclipses and a high volume of missing data. A methodology was then developed to pre-process the raw data into an ML-compatible format, detect anomalies using a semi-supervised forecasting approach and post-process the detections into a benchmark-suitable format. The method yielded over 40 detections, which were partially validated in discussion with instrument engineers. A refined methodology, incorporating areas for improvement, is presented to proceed with an eventual XMM-Newton anomaly benchmark. ... Read more

The design of an optimized retroreflector array for satellite laser ranging (SLR) is critical for enhancing satellite tracking accuracy and providing a passive space segment backup for conventional attitude determination systems. This thesis documents the research aimed at developing an effective retroreflector array for the new TU Delft platforms: Delfi-Twin and the Da Vinci satellite. The goal is to enable SLR measurements via both the International Laser Ranging Service (ILRS) network and the laser communication terminal at Delft University. Following a structured approach, the most suitable array configurations were identified through a Probability of Visibility (PoV) simulation. Consequently, a link budget analysis was performed, coupling the selected arrays with the considered ground stations to define the required retroreflector size to enable SLR measurements. Improvements to the Delft laser communication terminal have also been proposed to enhance its SLR capabilities. Future work will focus on qualifying the acquired retroreflectors and finalising the holder structure for satellite integration. ... Read more

With the projected expansion of the small satellite market and the rise of the lunar economy, the development of cost efficient and reliable navigation in cislunar space—defined as the region of space between Earth and Moon including the region around the surface of the Moon—has become increasingly important. However, the increase in the number of satellites strain existing communication networks in terms of availability, which exerts pressure on orbit determination quality and the financial budgets. One way to release the pressure from the existing ground station communications is through the concept of Autonomous Orbit Determination (AOD) by using inter-satellite radio two-way range between at least two satellites. The three-body problem of cislunar space-the most common region for small satellite deep space missions-makes it an ideal environment to perform AOD due to strong third body perturbations. Previous literature also has not clearly linked AOD with mission and spacecraft design related parameters, and is primarily focused on the orbit estimation aspect rather than including navigation as well.

The analysis of this work is based on a case study in which an L2 Lagrange point orbiter (LPO), called LUMIO, and an elliptical lunar orbiter (ELO), called LPF (based on the SSTL Lunar Pathfinder), perform AOD based on two-way inter-satellite ranging with a Gaussian noise level of 2.98m1σ, observed at a 300 s interval. This thesis aims to research the strategic adjustment of the timing of inter-satellite tracking sessions while optimizing for 1 year of station keeping cost for LUMIO, defined in ∆V.  Since the accuracy of the maneuvers relies on the magnitude of estimation errors from the OD process, which in turn depends on the state observability and thus relative satellite geometry during a tracking arc, solving for lowest ∆V is a complex optimization problem. Three different timing strategy categories were set up in which tracking is performed with varying levels of complexity: tracking based on constant tracking duration and interval, tracking around the perilune or apolune of the LPF satellite, and tracking based on the solution of a heuristic optimization routine that adjusts each tracking arc individually.

The overarching conclusion of this work is that improvements can be made compared to this value in each of the three strategy categories but with varying levels of ∆V. Initial observation windows were defined as a set of tracking arcs of1.0 day with a 3.0-day interval between each arc, where the predicted annual cost equated to 0.613±0.0066 1σ m/s, serving as the baseline value. The best of the constant tracking category showed an an annual ∆V of 0.375±0.0020 m/s, but this comes at the cost of large relative tracking time with a length-interval combination of 0.5-0.5 days. The best of orbit-based solutions reduce cost to an annual mean of 0.5 m/s and have relatively short tracking arcs, which makes it possible to spend more time on collecting scientific data. The Particle Swarm Optimization (PSO) algorithm shows that a reduction to 0.280±0.0134 1σ m/s can be made. All in all, from a mission design perspective, it means that it pays to adapt to a more complex tracking scheme, but employing a constant-type tracking arc timing scheme can also already yield ∆V improvements.  Advances in reducing power and fuel budgets can extend mission duration by lowering fuel consumption. Optimized tracking reduces total tracking time, requiring less power for signal transmission and freeing more power for payloads or other subsystems. This allows more time for scientific observations, increasing the mission's output. ... Read more

Multiple in-space experiments with deep learning have shown promising results in applying deep neural networks for automation of satellite fault detection tasks. However, the deployment of such neural networks on small satellites with low-power onboard computers is hindered by the highly limited computational resources of these devices. In this thesis, an effort has been made to create a lightweight neural network solution for satellite temperature monitoring, to explore whether such networks can improve the quality of fault detection even when deployed on low-power devices. The designed neural network solution tested on the MSP432P401R microcontroller uses only 29.5 kB of RAM and 65.2 kB of flash memory and can detect small-sized deviations in the satellite temperature sensor readings long before they grow into anomalies that exceed the safe operating range. ... Read more

The first mission proposals to visit the Alpha Centauri system use photon-sail acceleration as a mode of propulsion to reach this stellar system closest to our own Solar System. To prepare for a future mission, the photon-sail dynamics in the system is investigated. Planar Lyapunov orbits around the colinear classical Lagrange points are designed to explore the Alpha Centauri system. This has been done before in other systems like the Earth-moon and Sun-Earth systems, but not yet in an elliptical binary star system. Starting with an initial guess in the circular restricted three-body problem without photon-sail acceleration, a Multiple Shooting Differential Correction (MSDC) algorithm changes the trajectory to a periodic orbit. A continuation method increases the eccentricity to match e = 0.5208, which is the eccentricity of the inner binary system of Alpha Centauri. The lightness number of the photon sail is increased to add photon-sail acceleration to the model up to a defined maximum of ?ZNe = 2. A set of five constant steering laws is chosen to investigate its effect. Next to that, the moment at which the periodic orbit starts in terms of the true anomaly is varied as well. This results in a set of 40 families of periodic orbits with increasing lightness numbers. Depending on the orientation, the augmented Lyapunov orbit either shrinks into smaller orbits or expands into larger orbits when increasing the lightness number. If the orbit shrinks, it can either converge into an artificial equilibrium point or the photon-radiation pressure on the sail can become minimal. In that case, the Lyapunov orbit becomes (almost) independent on the lightness number and reaches ?ZNe = 2. If the orbit expands, the maximum velocity will eventually go to infinity. At this vertical asymptote, the maximum lightness number is found. The initial true anomaly of Alpha Centauri 0 has a great effect on the Lyapunov orbits around L2 and L3 in the classical ER3BP. For 0 = 0, the orbit either converges to an AEP or the maximum velocity goes to infinity. For 0 = , a few orientations can reach ?ZNe = 2. To further explore Alpha Centauri, an adaptive differential evolution algorithm is used to design trajectories between the Lyapunov orbits. The performance of the algorithm is expressed as the Euclidean difference between the states at the end of the departure leg and the beginning of the arrival leg. Three different lightness number of ? = 0.1, 0.5 and 2 are used for these trajectories. With a lightness number of 0.1, the dimensionless Euclidean error is in the range of 1E-1 to 1E-3, depending on the Lyapunov orbits. With this lightness number, the stars are also used as a gravity assist. For larger lightness numbers, the Euclidean error becomes negligible in the range 1E-7. With a lightness number of 2, the time of flight during the trajectory is significantly lower. In future research, this can be further decreased using an MSDC algorithm. ... Read more

The use of small satellites, enabled by the standardization of the CubeSat specifications and miniaturization in electronics, has seen a rapid increase in the past decades. The low-cost and short development time of these satellites has made them an attractive option for both commercial and academic applications, making space exploration more accessible. However, these small satellites are prone to failures, leading to lost scientific potential. Mitigation of these failures forms the motivation for this thesis. Recent advances in neural networks have shown promise in the field of anomaly detection. The black-box nature of such models, however, makes it challenging to understand the reasoning behind their predictions.

Constraining the data-driven models with known physics can not only help us understand the reasoning behind their predictions, but also ensuring the model is consistent with the real-world behavior of the system. The work presented in this Master's thesis aims to demonstrate the advantages of such first-principles neural networks over purely data-driven models in thermal behavior modeling of small satellites. Baseline performance of data-driven Long Short-Term Memory (LSTM) networks is established using FUNCube-1 telemetry data, quantifying the temperature prediction accuracy of the models under ideal conditions. The limitations of these models, especially with sparse data, are then investigated, to highlight the need for more robust models.

First-principles models, based on a physics-informed curve-fit and simplified thermal network models, are then developed to constrain the data-driven model predictions. The first-principles models are shown to be more robust to sparse data, with the predictions on data not seen during training being more consistent with the real-world thermal behavior of the satellite. Methods to relate the first-principles model parameters to the physical properties of the satellite are also proposed and explored, to help extract the evolution of the thermal behavior of the satellite over time. ... Read more

As space technology continues to advance, the landscape of telecommunication is witnessing a transition from traditional radio frequency to laser communication technology, driven by its enhanced efficiency. Notably, laser communication offers the potential for achieving millimeter-level ranging accuracy, thanks to its significantly higher data rates. This thesis presents the design of a system utilizing a field-programmable gate array (FPGA) and commercial off-the-shelf (COTS) multi-gigabit optical transceivers. The system tests laser communication ranging through time-of-flight measurements, leveraging the inherent structure of optical data. Through extensive testing, the thesis aims to characterize the system's maximum achievable accuracy, identifying constraints in the avenues of improvement. The use of COTS components ensures scalability and facilitates seamless integration into future test setups. ... Read more

Small satellite systems such as CubeSats and PocketQubes have strict requirements in terms of size, weight, and power available onboard. In light of these constraints, small satellite systems typically omit the inclusion of a ranging system due to its power and specialized hardware requirements. However, new research in satellite ranging invented the telemetry ranging class of techniques which do not place any such requirements on the satellite. The thesis explores the possibility of implementing a telemetry ranging technique on the Delfi-PQ satellite, which is already in orbit using only software modifications. The working and performance of the technique in determining the position of the satellite were explored using its engineering model and have positive implications for small satellite navigation and science.
... Read more

This thesis report has explored the complex field of satellite formation flying, focusing on Guidance, Navigation and Control (GNC) strategies for maintaining formations of multiple satellites. The research has been guided by a series of research questions aimed at improving the understanding and implementation of GNC systems for satellite formations. The report begins by providing an overview of the background and context of satellite formation flying, highlighting its significance in modern space missions. It emphasizes the need for precise control systems to maintain formations and addresses the challenges posed by various disturbances and constraints. To address these challenges, the report presents a detailed methodology for developing an end-to-end GNC system. This methodology involves the use of nonlinear dynamics models, including considerations for Earth’s oblateness and drag effects, to describe the motion of satellites within the formation. Additionally, the report explores the use of both absolute and relative dynamics models to enable the control of large satellite formations. Throughout the report, the performance of the GNC system is analyzed through various simulations and experiments. Different thruster models, including variable and fixed thrusters, are evaluated, shedding light on their effectiveness in maintaining formations. The analysis also considers the impact of energymatching conditions on reducing the frequency of maneuvers. The results of the simulations demonstrate the challenges and limitations of the Sliding Mode Controller (SMC) based control system, particularly in the context of real-world thruster implementations. Tracking errors and drift in formations are observed, necessitating further research into mitigating these issues. In the final chapters, the report explores potential areas for future research and improvements. These include investigating alternative thruster models, optimizing control algorithms, and developing strategies for reducing drift in formations. In conclusion, this thesis report provides valuable insights into the complexities of satellite formation flying, and the challenges faced by GNC systems. It offers a comprehensive methodology for developing
and analyzing these systems and highlights areas for future research. Ultimately, the report contributes to the ongoing advancements in satellite formation flying, paving the way for more precise and efficient space-based operations. ... Read more

CubeSats have risen in popularity since its first launch in the year 2003. The low mass, lower launch cost, lower development cost, possibility for piggyback with larger satellites and lower development time involved compared to larger satellites have opened them to be commercialised by private companies. In contrast to being used for educational, research and technology demonstration purposes in their early years, they are now used for varied applications such as communications, Earth observation, military surveillance, in-orbit manufacturing, asteroid exploration, Internet-of-things and interplanetary exploration missions. Their lucrative features make them favourable over their larger counterparts. As a result, they are predicted to launch in higher numbers in the coming years, considering their preference for missions involving constellations or distributed space systems. This trend of increasing demand for CubeSats and their application in advanced missions requires more electrical power for their operation. The increased electrical power demand can be solved using a Solar Array Drive Mechanism. The SADM allows relative rotary motion of the solar arrays with respect to the satellite structure so that the solar panels are always perpendicularly positioned to the Sun independent of the payload pointing requirements. They can produce up to 185% more power than the panels just deployed in the case of a 3U CubeSat. Only a handful of six such SADM products were found in the commercial market, and four of them had a very similar design that drove two solar arrays and could be used in limited panel mounting configurations. A need in the commercial market for a SADM system that is modular and scalable was identified. Space mechanisms such as the SADM were found to be one of the major causes of mission failure after communications and unknown causes. It was found that tribological elements were the prominent root cause of such space mechanism failure. A research gap was identified to find the root causes of tribological failure in space mechanisms and design a SADM system that minimises failure caused due to tribological elements. This thesis has succeeded in designing a SADM that is scalable to multiple sizes of CubeSats (3U to 12U), applicable to more than three panel mounting configurations that were possible with the existing SADM and minimising failure chances due to tribological elements. The current SADM has minimised the chances of failure due to common tribological elements such as roller bearings and sliprings by eliminating the cause of failure. This includes eliminating rolling elements, liquid lubricants and metals in the case of bearings and a novel power and data transfer mechanism alternative to sliprings called "Flex-wrap" has been designed in this project. The current SADM is the smallest in the market in dimensions (70x50x6.9 mm) and applies to 5 different solar array mounting configurations. ... Read more

The optimization of interplanetary, low-­thrust trajectories is a computationally expensive aspect of preliminary mission design. To reduce the computational burden associated with it, surrogate models can be used as cheap approximations of the original fitness function. Training the surrogate models in a fully online manner can be done to remove the need of having previously generated datasets, which is another source of computational cost. The Sims­-Flanagan transcription is used to model an Earth-Mars transfer which is optimized through different optimization routines. The development of a C++ library with machine learning tooling was initiated, containing implementations for Generalized Regression Neural Networks (GRNNs) and Radial Basis Function Networks (RBFNs) that are used in global and local surrogates, respectively, having their hyperparameters tuned through cross-­validation. A surrogate model was constructed using Differential Evolution (DE) operators and an uncertainty-based infill criterion for the global search phase, and approximation of the derivative of the original fitness function which is provided to SNOPT (Sparse Nonlinear Optimizer), in the local search phase. An ablation study was performed to assess how each of the components of the surrogate model contribute to the results. It was verified that neither the derivative information nor the local search as a whole led to better results. The surrogate model was also outperformed by the standard optimization strategy found in literature, Monotonic Basin Hopping (MBH). Two new surrogate models incorporating ideas of this strategy were created, with one of them outperforming every other model that was tested. Despite not having performed a full study of the computational effort due to the simulations having been run in a server with a variable load, the new models present better results for similar amounts of fitness function evaluations. A Wilcoxon rank-­sum test was performed to assess whether the results have statistical significance, leading to the conclusion that a surrogate model can be used to improve the optimization of low-­thrust trajectories modeled with the Sims­-Flanagan transcription when inserted in a monotonic basin hopping optimization scheme. ... Read more