With the space industry growing, environmental considerations become increasingly important, especially with respect to the propulsion systems used to launch satellites into space and control their position in orbit. Since traditional satellite propellants are highly toxic, there is an increased demand for green, i.e., environmentally friendly, substitutes like hydrogen peroxide.
This work explored the modelling of hypergolic bi-liquid thrusters in the framework of the Greenlam project, which aims to develop a 100N hydrogen peroxide kerosene thruster. While previous works were either experimental or focused on staged H2O2–RP-1 engines with a catalyst bed, this thesis investigated a numerical approach and focused on unstaged engines, aiming to identify and validate models viable to simulate the decomposition of hydrogen peroxide and subsequent combustion with kerosene with the aid of a catalyst.
Transient three-dimensional simulations were performed. k-ω SST, the Peng Robinson real-gas equation of state and Species Transport with Finite Rate chemistry were employed to model turbulence, gas properties and reactions, respectively. The effect of the catalyst was represented by adapting the Arrhenius rate parameters. Propellants were injected using the Discrete Phase Model. The Eulerian model was shown not to be suitable to simulate the propellant injection and atomisation.
A coaxial, an impinging-jet and a pintle injector were considered. Simulations with the coaxial injector showed good agreement with data obtained from CEA and with other rocket engines. Simulations with the impinging-jet and pintle injector failed to capture droplet impingement and consequent atomisation and thus could not be validated.
Both stoichiometric and fuel-rich propellant mixtures and H2O2 concentrations of 95% and 98% were simulated. Thrust was between 62 and 63N under sea-level conditions, equivalent to 103 to 105N in vacuum and hence approximately 3 − 5% higher than anticipated. Chamber temperature reached up to 2763K. Chamber pressure was 7.6bar. The stoichiometric mixtures showed higher thrust output, higher chamber temperature and higher wall temperature than the fuel-rich mixtures. The higher concentrations led to higher chamber and wall temperatures. Analysing the kerosene mass fraction in the exhaust showed that in any case at least 9% of the injected kerosene was ejected unburnt due to a lack of mixing, and most of the additional kerosene in the fuel-rich mixtures was also simply ejected. The chamber walls reached temperatures of up to 3271K, about 500K higher than bearable by the material. While the coaxial injector was shown to be a cause for the high wall temperatures due to unfavourable propellant distribution, an adiabatic wall boundary condition was assumed which likely also led to an overestimation of the temperature.
A set of models applicable for simulating hypergolic bi-liquid rocket engines was found and validated. More work is required in terms of injector design and modelling, confirmation of reaction rate parameters and wall modelling.

Interplanetary missions have relied on Radio Science (RS) for recovering gravity fields via detecting their signature on the spacecraft’s trajectory. Yet the weak gravitational fields of small bodies, coupled with the prominent influence of confounding accelerations, hinder the efficacy of this method. Meanwhile, quantum sensors based on Cold Atom Interferometry (CAI) have demonstrated absolute measurements with an inherent stability and repeatability, reaching the utmost accuracy in microgravity. This work addresses the potential of CAI-based Gradiometry (CG) as a means to strengthen the RS gravity experiment for small-body missions. Phobos represents an ideal science case as astronomic observations and recent flybys have conferred enough information to define a robust orbiting strategy, whilst promoting studies linking its geodesic observables to its origin. A covariance analysis was adopted to evaluate the contribution of RS and CG in the gravity field solution, for a mission duration of one week.

The favourable observational geometry and the small characteristic period of the gravity signal add to the competitiveness of Doppler observables. Provided that empirical accelerations can be modelled below the nm/s2 level, RS is able to infer the 6x6 spherical harmonic spectrum to an accuracy of 0.1-1% w.r.t. the homogeneous interior values. If this correlates to a density anomaly beneath the Stickney crater, RS would suce to constrain Phobos’ origin. Yet, in event of a rubble pile or icy moon interior (or a combination thereof) CG remains imperative, enabling an accuracy below 0.1% for most of the 10x10 spectrum. Nevertheless, technological advancements will be needed to alleviate the current logistical challenges associated with CG operation. This work also reflects on the sensitivity of the candidate orbits with regards to dynamical model uncertainties, which are common in small-body environments. This brings confidence in the applicability of the identified geodetic estimation strategy for missions targeting other moons, particularly those of the Giant planets, which are targets for robotic exploration in the coming decades.

Planetary observational accuracy increases and the dynamical modeling of tidal behaviour has to follow. In this thesis, a newly developed method (Correia et al. 2014; Boue et al. 2016) to deal with tidal interactions in a 2D two body problem is validated and for the first time applied to Solar system dynamics on a short time-scale. This method uses a Maxwell rheology for the tidally perturbed body, to calculate the instantaneous deformation of the body with a differential equation at the same time as its position, spin vector and orientation. The coupling between the translational, rotational, and tidal dynamics is incorporated in a consistent way, taking into account the frequency dependency of classical tidal parameters. The coupled model is more general and is in contrast to currently used models valid for every eccentricity, spin rate and orientation. The model is applied to the Mars-Phobos and Earth-Moon systems and the tides are determined separately on both the central as the satellite body in various propagations. Several parameters of tidal effects of these systems are obtained and compared with currently available literature approximations and currently used tidal models. The instantaneous deformation of the tidal body and the evolution of the system's orbit for the tides on the primary compare to the literature approximations and currently used direct tidal force model (Lainey et al. 2007). However, the coupled model displays behaviour of the tidal time lag and angle, which are accompanied with the deformation, that cannot be captured by the classical method. Small differences between final states of the coupled model and the direct tidal force model are obtained that could potentially be important in future space missions and ephemeris determination. The tides on the locked secondary show a larger difference between the coupled model and the current tidal direct force models (Lainey et al. 2007; Lari et al. 2018) in the case of an existing libration. Phobos has such a libration and huge differences in evolution of the states and orbit are found. The coupled model's evolution values can be partly justified by the theoretical work of Efroimsky et al. (2018) that states the additional dissipation in these bodies with large librations. Altogether, currently used methods or literature approximations can still be used for inaccurate propagations. However, for more accurate propagations, and for bodies with large physical librations, it rewards to switch to a coupled method. Especially when regarding the tides on the satellite body a coupled model is beneficial.

Aims: Analysing historical disk-integrated polarization data of Venus with the help of numerical simulations to learn about the time variability in cloud and haze properties, the position of the UV-absorber and the polar cap regions.
Method: With numerical simulations, polarization curves will be calculated for specific input conditions. We compare numerically computed polarization curves to the historical polarization data to derive the microphysical properties of Venus's cloud and haze particles. Results: From our research we obtain values for the imaginary part of the refractive index of the cloud particles of the order 10^(-4). It is most likely that the absorber is mainly located at the equator or in patchy clouds covering 80% of the planet. It is found that in the presence of precise disk-integrated polarization data, it is possible to detect variations in the polar regions. For Venus we found that it is likely that there exist larger particles at higher altitudes at the Venus poles. Unfortunately, it is very hard to say something about the long term variations on the planet. For the Venus case, it can be roughly stated that: the polarization was higher in 1975/1976 than in 1965/1968; the polarization was also higher in 1968/1970 than 1965/1968 but not higher than in 1976; there was a decrease in the polarization of the ultraviolet region in the years 1964/1965. Conclusions: Future observations should be made in a broad range of wavelengths, at as many phase angles as possible and in time frames similar to the orbital period of the (exo)planet. Since Venus can be observed as if it were an exoplanet (broad range of observable phase angles and disk-integrated data), we applied this research to exoplanets as well. We concluded with the help of the Venus data and simple models that it is possible to obtain cloud properties, such as the refractive index and the optical thickness of the cloud, of exoplanets using polarization observations. It was found that those properties are harder to distinguish using flux measurements since the geometric albedo and the distance to the planet are unknown.

The JUICE (JUpiter ICy moons Explorer) mission by ESA aims to explore the emergence of habitable worlds around gas giants and the Jupiter system as an archetype for gas giants. MAJIS (Moons and Jupiter Imaging Spectrometer) is the visible to near-infrared imaging spectrometer onboard JUICE which will characterize the surfaces and exospheres of the icy moons and perform monitoring of the Jupiter atmosphere. The launch is scheduled for June 2022 with the first MAJIS observations inside the Jovian system occurring more than 7.5 years later. MAJIS will use two Teledyne H1RG detectors for both spectrometer channels (VIS-NIR and IR). For this mission, they will be operated in a non-standard way. The detectors will allow near/full-frame retrieval over short integration times (<< 1 sec) while maintaining good noise performance. This is due to the relatively high levels of irradiance of the targets compared to the detector well depths, and to mitigate the high rate of radiation spikes from the Jovian environment. Additionally, the detectors will operate at higher temperatures than previous space missions due to stringent resources constraints, impacting the dark current levels. We will present the characterization strategy suitable for evaluating the performances of the VIS-NIR and MW-IR channel according to the MAJIS operational specifications. This methodology was tested during two characterization campaigns using two MAJIS Engineering Grade detectors. The first campaign was performed at the Institut d'Astrophysique Spatiale for the MW-IR detector. The second campaign was performed at the Institut royal d'Aeronomie Spatiale de Belgique for the VIS-NIR detector. This MSc thesis will describe the analyses and results of both campaigns. Based on these results, the capacity of MAJIS to reach its scientific objectives will be discussed.

This thesis work has been motivated by the growing interest in small-spacecraft small-body missions and more specifically inspired by a proposed mission to the largest Martian Trojan (5261) Eureka. This binary asteroid represents a promising target for a planetary mission, as a better understanding of its formation and evolution would provide valuable insights into the history of both the Martian system and binary asteroids. This work has focused on identifying orbital designs which would optimise the geodetic parameters estimate, and thus best help characterise the asteroid's internal structure. The orbit determination solutions have been computed from simulated tracking data in various orbital configurations. To compensate the highly perturbed nature of the binary asteroid's environment, pseudo-periodic solutions identified around Eureka have been used as stable initial conditions for the spacecraft orbits. As Eureka's shape, gravity field and rotational state are not well characterised yet, large resulting uncertainties have been accounted for. They have been propagated to assess the robustness of the spacecraft orbits and subsequent orbit determination solutions to dynamical mismodelling, in order to eventually limit the science risk of the mission. For single CubeSat configurations, an optimal semi-major axis has been identified, being the one closest to the asteroid before orbital instability would start deteriorating the orbit determination solution. Non-equatorial retrograde orbits have been found to provide the lowest formal errors for geodetic parameters. Moreover, the benefit of simultaneously deploying two or even three CubeSats around the asteroid has been demonstrated. In both the two and three CubeSats configurations, promising orbital designs have been identified. They provide an estimation of the geodetic parameters which is accurate enough to bring insights into Eureka’s internal structure, and has been proven to be robust to dynamical mismodelling.
The methodology developed in this work is of interest to design other small-spacecraft small-body missions, and optimise their achievable geodetic parameters estimate. Additionally, Eureka's dynamical model and the large uncertainties assigned to it have been mostly based on models available for other binary asteroids. This brings confidence in the possible applicability of the identified optimal orbital designs to CubeSats missions targeting other binary asteroids.

We present an analysis of the temporal evolution of hazes on Neptune between 1994 and 2018, using HST archival data at visible wavelengths from theWFPC2 and WFC3 cameras. We assess the changes over time of the global reflectivity in the F850LP/F845M (methane) and F467M (blue) filters, adding more than 10 years of data to previous analyses. We see an increase in brightness in the methane filter from at least 1996 until 2009, followed by a decrease until today, as seen from cloud-free regions only. A similar behavior is observed in the blue filter, which reaches a maximum disk-averaged I/F value in 2002 and stays nearly constant until 2015, when the planet starts to darken. We also evaluate variations in individual latitudinal bands between 90°S and 50°N. We note the largest increases for southern mid-latitudes (65°S-30°S) for both filters, and the northernmost band (20°N-50°N) for the methane filter. The largest decreases are seen in the northernmost band for the blue filter and for southern near-polar (90°S-65°S) and mid- to low latitudes (50°S-5°N) in the methane filter. We perform radiative transfer modeling to assess the latitudinal variability in the hazes altitudes and to identify changes in the atmospheric vertical structure that may give rise to the observed trends. Adopting the SUNBEAR code and assuming a two-haze-layer model, we find an optically thin (τ α Æ 0.03) upper haze layer placed around 0.6 bar and an optically thicker (τ ß 2.2) lower cloud based at 4.1 bar. This model describes the observed I/F values of the atmosphere in 2009 as well as for 2015 for latitudes north of 30°S, but does not agree with southern latitudes, where the best fitting model demands a shallower pressure base (3.4 bar) and methane depletion (methane mixing ratio lowered from 0.05 to 0.03) for the lower haze. The parameters retrieved for 2002 hint at a higher altitude (2.6-3.0 bar) lower haze layer compared to both 2009 and 1996, with the largest difference occurring in relatively cloud-free latitudes (65°S-50°S and 30°S-5°N). The upheaval of the lower haze might be related to the strong cloud activity seen in 2002. Today, southern latitudes’ lower hazes have descended to deeper pressure levels (3.6-4.1 bar) with respect to 2009, and different scattering properties are seen for them at southern mid-latitudes and northern regions.

This research focuses on GNSS users interested in a faster position fix in a situation where the receiver holds limited data. This occurs when turning on a mobile phone or sport watch to use a location-based service, driving out of a parking garage with a navigational device or activating a search & rescue beacon. In these cases, users care more about directly setting a certain action into motion, than waiting until a sub-meter level of accuracy is acquired. For this purpose, we aim to decrease the time to first fix (TTFF) of a receiver at the expense of position accuracy by focusing on its most dominant component: the time to read the first fix data, i.e. the TTFFD. In turn, the TTFFD is decreased by reducing the size of the clock correction and ephemeris data (CED) and integrating this reduced set into the existing Galileo I/NAV message while maintaining backward compatibility. Three reduction strategies are presented to reduce the size of the CED. First, the expression of the CED parameters relative to the matching almanac parameters, which requires downloading the most recent almanac. Second, the absorption of the clock and ephemeris time reference into related parameters by leveraging redundancies in the user algorithm. Third, the truncation of the CED parameters, where the optimal parameter bit allocation per CED size is determined by means of a Monte Carlo simulation. Subsequently, the optimal reduced set is integrated in the existing Galileo I/NAV message, since it is not only size but also the location and repetition rate of the reduced CED in the navigation message that determine the final decrease in TTFFD. A simulation is developed where the three reduction strategies are combined and applied to one year of Galileo navigation messages and almanacs starting from October 2017. The current I/NAV message has a size of 428 bits and an average TTFFD of 25.4 seconds. The relative expression of the CED parameters, the absorption of the clock time reference and ephemeris time reference yield a 76, 15 and 10 bit reduction respectively, without a significant decrease in position accuracy expressed as the signal-in-space ranging error (SISRE). The reduction in size that can be realized by truncation results from a trade-off with the maximum acceptable level of SISRE. When combining all three reduction strategies a 296 bit, i.e. 69%, size reduction can be realized at a SISRE level of 10.04 meters, yielding a 132 bit CED. 66% of the size reduction is in this case achieved by parameter truncation. To maintain backward compatibility, the spare and reserved bits of the I/NAV message are used to integrate the reduced set. This finally results in an average TTFFD of 6 seconds, which is a decrease of almost 20 seconds. With the reduced CED the user gains full independence of out-of-band channels for the computation of a fast position fix. In addition, it decreases the impact of bit errors on the TTFF and increases the chance of receiving an error free set of first fix data. Moreover, the reduced CED is not only of interest to fast fix applications that desire a decrease in waiting time. Positioning based on the reduced set also decreases the time the receiver has to be "on" to read the navigation data and consequently the receiver's power usage. This leads to a second type of applications that benefits from the reduced CED: low-power applications that do not require a high accuracy, such as freight management, wildlife tracking and stolen goods trackers. To conclude, the constructed reduced CED provides multiple advantages for a wide range of GNSS users and should therefore be considered as a purpose for the spare and reserved bits of the Galileo I/NAV message.

Fresnel reflection of starlight in the oceans of exoplanets results in two main phenomena: (1) a glint in the exoplanetary ocean, whose size increases with wind speed, and (2) a maximum degree of polarization at the Brewster angle. The corresponding features in the planetary phase curve, i.e. the flux and degree of polarization of the reflected light by the exoplanet orbiting its parent star, have been studied before. However, these studies did not use (1) horizontally inhomogeneous models, allowing the analysis of the glint appearing and hiding behind patchy clouds and (2) a set of consecutive wavelengths together with (3) a gas layer on top of the clouds. We present the phase curves of the (polarized) flux and degree of polarization of oceanic exoplanets with patchy cloud covers and a substellar cloud for tidally-locked planets. We discuss the spectropolarimetric signatures that could potentially be observed in the near future or that may be considered in the design of future telescopes. We show that (1) a previously suggested method to detect an ocean on an exoplanet, based on the shift of the peak value of the degree of polarization towards the Brewster angle, is sensitive to atmospheric surface pressure, (2) the clouds are not necessarily a limiting factor for detecting an ocean when a gas layer on top of the cloud is considered and a set of wavelengths is used, (3) the phase curves of the different wavelengths intersect in one point whose location could help estimating the cloud fraction and that (4) such an intersection in the polarized flux could be observed in the presence of an ocean for surface pressures up to 10 bar and cloud fractions up to 95%, while it never occurs in the absence of an ocean. We conclude that this color reversal in the polarized flux could potentially be used for detecting oceans on exoplanets.

In recent years, private entities have joined the race to send humans to the Red Planet. While Mars is well defined as the next frontier for human space flight, little work has been done towards identifying possible settlement sites on its surface. The current site proposals use a bottom-up approach, that is focusing on one settlement site and then investigating if and why this site fulfils all requirements considered relevant to a human outpost. Here, the Expert System: Settlement (ESS) is presented, a tool that follows the inverse, top-down approach in which initially the entire Martian surface is considered. From there, the set of possible settlement sites is reduced stepwise for various criteria, discharging those sites not fulfilling the specified criteria. Examples of these site requirement are the max. MOLA elevation, the solar power available on the surface, and the water concentration in the subsurface. To cover the different criteria included in this work, the ESS was assembled of the three sub-expert systems Expert System: Engineering Constraints (ESE), Expert System: Climate (ESC), and Expert System: Resources (ESR). The ESS was successfully verified using the engineering constraints defined for the landing site selection of the NASA InSight mission, returning, inter alia, the mission's selected landing site. With view on manned missions, settlement selection constraints were derived from literature to provide input to the ESS. The ESS identified possible settlement sites fulfilling the requirements in Xante Terra/Lunae Planum and West of Elysium Planitia. Other qualifying sites were located in the Northernmost part of Noachis Terra, in Vastitas Borealis between 40°N and 50°N latitude and in Arcadia Planitia, Northwest of Olympus Mons. The ESS is built completely generic, allowing to run the expert system for a variety of possible and diverse mission architectures. Moreover, the code architecture allows to simply add further selection constraints and corresponding planetary data sets required for future selection processes. The ESS is capable of investigating both landing ellipses (as has been done for the NASA InSight mission) and circular exploration zones around a nominal site. Next to settlement site selection, the code developed is therefore also suitable for landing site selection. With suitable data available, the code can be adapted to any celestial body. The current application of the tool regarding site analysis is directly dependent on the available data sets' coverage and maximum resolution; where the latter controls the computation time of the ESS.

The investigation of small bodies in the Solar System such as asteroids and comets is of increasing interest to the space exploration community for scientific and security reasons. A key enabling technology is the availability to control position and attitude of spacecraft for asteroid close-proximity operations. Dynamics and control issues related to these operations have been investigated addressing the orbital and attitude motion of the spacecraft with no coupling between them assumed. In reality however, the translational and rotational dynamics of spacecraft are generally coupled. It is therefore desirable to simultaneously take into account the full six degrees of freedom problem when developing pose (position and orientation) control laws for practical applications. One way of doing that is by expressing the state variables with dual quaternions, a mathematical formulation that naturally couples both motions in an efficient and compact way.
The goal of this thesis is to determine what advantages and disadvantages can a six degrees of freedom controller based on dual quaternions bring over classical methods regarding asteroid close-proximity operations. To do so, a simulator was developed in Matlab R2016b with the two different representations: the dual quaternion one and the classical one using vectors for position, velocity and angular velocity, and quaternions for the attitude. Then, a controller was designed and optimized for each representation to follow a reference trajectory in three different scenarios, such as orbiting, hovering and landing on the asteroid Bennu. The dual quaternion representation has only two equations of motion instead of the four required for the classical one because of its compactness and natural way of coupling rotational and translational motions. However, results show that the dual quaternion controller takes 15% more computational time to achieve the same level of accuracy and energy consumption as the classical controller for the nominal scenarios. The reason for that is because the total number of operations involved in the integration of the equations of motions is higher. Moreover, a stability analysis was carried out and showed that controllers based on dual quaternions can handle much larger perturbations than the classical ones. Specifically, between 23 and 227 times larger perturbations depending on the scenario. Apart from that, results also proved that dual quaternion controllers can correct trajectory perturbations in a much faster and efficient way than the classical ones. Specifically, they have a settling time between 29% and 92% shorter, accumulate between 2.6 and 19 times less error and consume between 3.2 and 9.3 times less energy, depending on the scenario.

Missions to Near-Earth Objects (NEOs) are a growing trend in spaceflight. The interest for such bodies is not only justified by the threat that they represent for the Earth, but also because they are potential sources of extra-terrestrial materials, provide windows to the past of the Solar System and to planetary formation, and offer a good opportunity to demonstrate deep-space mission technologies.

The Asteroid Impact Mission (AIM) is the next European Space Agency mission to a NEO, which has among its main objectives the deployment of the Asteroid Spectral Imaging Mission Cubesat (ASPECT) in the vicinity of the binary asteroid Didymos during the Payload Delivery Phase (PDP). However, this deployment is affected by the uncertainties and errors coming from the strongly perturbed environment, the previous phase dispersions, and the navigation and command inaccuracies.

The objective of this thesis is therefore to assess the viability of the cubesat deployment in terms of the safety of the reference trajectories and the accuracy of the deployment conditions achieved.

The reference trajectories that target the cubesat’s commissioning orbit injection point were designed by implementing a two-arc hyperbolic trajectory design problem in a direct-shooting optimisation architecture in the commercial heuristics optimisation software known as Mixed Integer Distributed Ant Colony Optimization (MIDACO). These trajectories were obtained in an ideal, unperturbed scenario. The safety and accuracy of the trajectories obtained were tested in a series of Monte Carlo campaigns in which the uncertainties, errors and dispersions present in the system were used as Monte Carlo variables in a high-level Guidance, Navigation and Control (GNC) simulator implemented in Simulink 2016b.

After identifying the pericentre of the target Self-Stabilised Terminator Orbit (SSTO) as the best point to carry out the deployment, five different families of trajectories that bring the spacecraft within the safety deployment margins were found. The total velocity increment required for these trajectories were found to vary from 1.2 to 3.4 m/s. These relatively high velocity increments are caused by the combination of the constraints imposed in the design process that emanate from the mission operational requirements.

The first Monte Carlo set of simulations showed that the optimum number of guidance correction manoeuvres is assessed to be three. The timing of these manoeuvres is case dependent, but one correction must take place in the first arc flown, and the other two during the second arc and before the deployment.
Results of the second Monte Carlo campaign showed that the trajectories were unsafe according to the mission safety requirements on the minimum distance to the main asteroid and on the margin to the escape velocity. Of these two requirements, the escape velocity margin was the main cause of these safety violations, with several trajectories falling below the margin of 2 cm/s at certain epochs. This was due to the initial state vector dispersion coming from the previous phase and, to a lesser extent, due to the potential thrust failures.

In the final Monte Carlo campaign, the ASPECT injection success rates reached a maximum value of 75% for the trajectory that targets the SSTO with a semi-major axis equal to 5 km. The cause of this low success rate was attributed to a combination of high initial position dispersions and velocity navigation errors. Due to this velocity navigation inaccuracies, the corrections made by the guidance subsystem are not capable of compensating the dispersions in initial position. These corrections further deteriorate the final deployment conditions, since their calculation only takes into account deviations in position, and not in velocity.

The results of this study highlight the need of finding ways of reducing the position dispersion with respect to the nominal trajectory prior to the autonomous PDP. Furthermore, they indicate that the prediction of success rates can be improved by refining the navigation performance models, since these are considered conservative when compared to the real scenario.

The Jupiter Icy moons Explorer (JUICE) will generate ephemerides of the Galilean moons to assess their ability to sustain live. However, determining the ephemerides only using radiometric tracking (acquired using PRIDE and 3GM) results in an unstable solution which is related to the absence of flybys of especially Io, such that its dynamics can only be estimated indirectly (through the Laplace resonance). This problem is partially mitigated in this thesis by optimizing the observation schedule for optical astrometry of Io (provided by JANUS) using the NSGA-II algorithm. The optimal epochs for space-based astrometry are found to be preferentially distributed around the closest approaches of JUICE with respect to Io. During these events, the observations show a high sensitivity with respect to the dynamics of Io and have a low positional uncertainty. Using the optimized astrometry, both the condition number and formal errors can be substantially reduced.

The objective of this MSc thesis was to design a miniaturised Raman spectrometer that can be used in terrestrial deep ice applications of the IceMole probe. This probe is a manoeuvrable subsurface system for clean in situ analysis and sampling, developed at FH Aachen University of Applied Sciences since 2008, that is now part of a bigger DLR collaborative initiative, called Enceladus Explorer (EnEx). It combines melting with a hollow rotating ice screw and it now presents a cross sectional area of 80mm x 80mm.

A Raman spectrometer is a promising non-destructive technique that allows to identify both mineral and biological compounds with a minimum amount of sample, by measuring the inelastic scattering of light. In order to achieve an appropriate design for the instrument, the project followed a systems engineering approach.
The first step was the derivation of the requirements related to the technical constraints dictated by the miniaturised design of the probe and to the performances that allow the spectrometer to detect potential biosignatures.

The design process was carried out by successive choices so as to propose a final configuration, developed as a CAD model in the software CATIA™. The instrument performs its measurements through a sapphire window in the IceMole probe, looking directly into the ice. It excites the sample with a laser wavelength of 532nm transmitted via a dichroic beamsplitter. The scattered light is collected by a long-pass edge filter and a 30° off-axis parabolic mirror that focuses the light into a collimator. The light is then delivered to a CCD spectrometer via an optical fibre. The spectrometer is able to measure a spectral range of 546.9-700nm with an accuracy of at least 0.4nm, combination of the characteristics of the optical components. The final result is a Raman spectrometer design modelled by the use of off-the-shelf components, selected through systems engineering trade-offs. The final dimensions of the instrument are 65mm x 65mm x 150mm, with a mass of about 1.1kg.

The outcome of this thesis will have to be verified and validated in order to ensure the correct working of the system, the compliance with the derived requirements and the validity of the use of this instrument to satisfy the customers’ needs and expectations. Therefore, a preliminary verification plan was proposed in accordance to systems engineering.

Eventually, the future of such a Raman spectrometer will be space exploration and life detection missions as payload of the subsurface probe. The space targets for those missions are the ones identified as most promising for harbouring potential living micro-organisms: the polar caps of Mars, Jupiter’s moon Europa and Saturn’s moon Enceladus.

Glacial isostatic adjustment is the viscoelastic response of the earth to ice sheet loading. Ice dynamic models employ glacial isostatic adjustment to accurately simulate bedrock uplift. In previous studies, ice dynamic models use only a constant relaxation time to predict bedrock uplift. In this study, the aim is to improve an ice dynamic model by using a laterally varying bedrock relaxation time.

Shear wave velocity data suggest a sharp increase in relaxation time between West and East Antarctica. Viscosity fields based on shear wave velocity data were converted to a set of relaxation time fields that are compatible with the ice dynamic model. These relaxation time fields were used in an ice dynamic simulation for the Antarctic Ice Sheet.

It was found that largest differences between the different relaxation time models occur from 20 000 years ago up to PD. The model with a high relaxation time average showed a decrease in ice volume of 22.0%, whereas the model with a low relaxation time average, decreased by 17.4%. It was found that the largest differences between the models occurred at the WAIS due to the strong interaction of sea level and bedrock uplift. Furthermore, it was found that a reduction of ice sheet wavelength led to relaxation time decrease, locally up to 50%. This appeared to be a stabilising mechanism for decreasing ice sheets, but the effective retained ice volume by this mechanism remains unknown.