Understanding the role of ocean swell, monitoring and modelling it is critical for a diverse range of oceanographic research, coastal management initiatives and for better weather forecasting and climate modelling.
Currently, swell measurements are obtained through in-situ measurements, wave models, and satellite measurements. So far, swell wave parameters have been retrieved from orbit using optical instruments, imaging radars and wave spectrometers. The potential to retrieve swell wave spectra from radar altimeters was recently demonstrated using fully focused synthetic aperture radar (FFSAR) signal processing.
Sentinel-6 (S6) would be a good candidate for investigating the potential of swell parameter retrieval, however, no study has been performed regarding the impact that the on- board data compression/ waveform truncation mode of S6 could have on the retrieval of swell parameters. Swell wave period estimates were thus derived from the raw and compressed S6 FFSAR waveforms collected over a study area in the Channel Islands of California during a 22 month- period. A performance analysis was carried out comparing the period estimate pairs from a given timestamp with the records obtained by a buoy in the study area at the same time.
The study demonstrated the presence of differences in the performance of swell period retrieval for the different operating modes of S6. It was found that swell period estimates can be derived also from the compressed waveform signal, obtaining however a lower accuracy compared to raw waveforms.

An array of BlackGEM telescopes is currently being constructed in Chile. The Royal Netherlands Air Force wants to assess the suitability of the BlackGEM telescopes for initial orbit determination of unknown objects in high orbits around Earth. A set of short arc observations of geostationary satellites of no more than 5 minutes is available from a prototype of the BlackGEM telescope called MeerLICHT, which is located in South Africa. Using the classical initial orbit determination methods of Gauss and Gooding and a newly developed circular orbit method, orbit estimates are calculated based on the short arcs. In addition, two methods to reduce measurement error that are specific to the observation system are developed and tested. As a final outcome, recommendations for observation strategies and orbit determination methods are formulated to optimise BlackGEM telescopes for satellite orbit determination.

Accurately tracking the trajectory of launching vehicles during the boost phase is crucial for a variety of reasons. First, an accurate burnout point location and  velocity of the launch vehicle will facilitate the estimation of its trajectory during the following phases of ballistic flight and the impact location. This has important implications for safety purposes. The first stage of many launcher systems such as the Russian Soyuz or the Chinese Long March rockets commonly impact on land, sometimes on populated areas. Furthermore, the proliferation of suborbital rocket launches presents a hazard if regulations are not properly followed. Therefore, it becomes critical to estimate the impact point of any vehicle that reenters the lower layers of the atmosphere beforehand, during the boost phase, in order to prevent personal and material damage. Second, a critical aspect in any space mission is to insert the payload into the required orbit. An accurate tracking of the launcher system during the boost phase allows carrying out early orbit determination in order to successfully complete the payload insertion. In this Master Thesis, an analysis and performance comparison of different tracking algorithms for launching vehicles during boost (e.g. launcher systems or suborbital rockets) has been carried out. This type of tracking problem has several difficulties that must be overcome. First, the unknown thrust profile – thrust magnitude and orientation – of a launching vehicle makes difficult to develop motion models that can accurately describe its behavior. Second, the observations of the plume of the launching vehicle obtained from two line-of-sight passive sensors located in geostationary satellites are used. The way these observations are obtained does not allow to accurately measuring the initial state and trajectory of the vehicle, complicating the initialization and the trajectory estimation processes of the tracking filters. Finally, the nonlinearities present in the system and measurements models of the tracking filters compel us to devise linearization schemes or the implementation of alternative filtering methods.The work presented in this document has been developed at the Military and  Security department of Airbus Defense and Space, as a continuation of an ongoing project. To solve the aforementioned difficulties of the tracking problem, a tracking system – EKF-Tool – was developed at ADS previous to the start of this Thesis. Nevertheless, this tool shows several limitations that hinder its performance, even preventing from successful tracking. In this Thesis, the limitations and potential areas of improvement of the EKF-Tool have been analyzed. Based on the results of this analysis, an alternative tracking algorithm – PKF-Tool – is introduced with the aim of overcoming the limitations of the EKF-Tool. The tracking performance of both tools has been tested using several indicators: stability, consistency, credibility, accuracy, precision, and versatility. 

Meteors have been observed by accident from geostationary orbit (GEO). It is of interest for surveillance, meteor science and the updating of empirical models to know what instruments are needed on a GEO satellite to observe meteors and re-entering capsules in Earth ‘s atmosphere. A re-entry simulation code is written to fill the gap of missing observation data of meteors and re-entry capsules. The simulated re-entry data is used to determine what optical instrument is needed to track or detect these objects. The calculations take into account the reflected sunlight, Earth’s thermal irradiance and atmospheric transparency, and the requirement of a sufficient signal-to-noise ratio and signal-to-background ratio. The investigated meteors, with a minimal absolute magnitude of -2.9, and the two investigated Hayabusa and Stardust re-entry capsules can be tracked from GEO for at least 3 consecutive observations with a sub 1 meter aperture diameter optical instrument. A 2 to 5 second tracking time of the investigated meteors requires aperture diameters between 0.1 m and 0.87 m. For 20 second tracking of the re-entry capsules a 0.1 m aperture diameter is needed, which increases to 0.27 m when tracking for 50 seconds. To observe the whole Earth multiple optical instruments would be needed on one GEO satellite. This requires in most cases less than 1 cubic meter of space on the satellite.

The military use of space brings interesting challenges for both technology and operational aspects. The Netherlands armed forces are a small player within the military world. However, in 2013 the beginning of a space program was started by the Royal Netherlands Air Force (RNLAF). One of the key mission statements
stated: “show the military relevance of Nano Satellites". A feasibility study was conducted and the realisation of the first satellite, the BRIK-II,was started. One of the payloads of this satellite is a store and forward system. In this thesis work a systems engineering approach towards, requirements definition, design, verification and testing is provided.

This thesis shows the mass reduction of a mechanical bracket, without compromising on thermal, EMC and structural aspects. The focus was on analysing thermal aspects related to bracket design. Models were made to show the deflection and solder layer stresses due to CTE mismatches between the bracket and PCB. A thermal heat transfer model was built to analyse the temperature distribution over the bracket and PCB. Using these models, the performance of different materials can be analysed. The most promising candidate for bracket design was aluminum silicon. This material was used in the design of a new bracket. The resulting bracket has a mass of 74 g, which is only 8 % of the mass of the original copper bracket.

Electric low-thrust propulsion has nowadays found wide application in space dynamics as it entails considerable savings in spacecraft propellant mass, thanks to the very high specific impulse that this kind of engine is able to generate. However, continuous thrust opens new extensive sets of feasible trajectories, and optimization algorithms are needed to mine the admissible search space and find optimal transfers. Practical methods to solve complex optimal control problems as low-thrust trajectory optimization typically involve high computational times, the major bottleneck of these techniques. The objective of this work is the development of a novel multiple-shooting optimization tool, employing a variational approach for quick derivative computation, and the assessment of its performance against a variety of test cases. Indeed, after a first analysis of practical optimization methods, the derivative estimation by finite-difference approximations has been found as the major contributor to the computational burden, and the propagation of the variational dynamics has been selected as an accurate approach to speed-up their computation. The theory of variational dynamics for multiple-shooting application has been analyzed in detail, and further developed for what concerns the second-order equations. After practical considerations on the method implementation (scaling procedures, sparsity patterns, et cetera) and its interface with WORHP, the selected non-linear programming solver, the tool has been applied to a broad range of test cases, spanning from elementary problems to practical applications. For what concerns the latter cases, two complex problems were analyzed and optimized: a CubeSat rendezvous departing from Earth-Moon L2 and arriving at asteroid 2000SG334, resulting in a propellant mass convenient trajectory suitable for asteroid reconnaissance well before a proposed NASA manned mission in 2069; The Kessler Run, i.e. the 9th Global Trajectory Optimization Competition (GTOC9), in which the developed tool, employed as last step of the optimization cascade of Strathclyde++ team, managed to make the solution constraint-feasible, valid and further mass-optimal.