For spacecraft development, realizing strong supporting ground segment software is as important as designing the actual hardware component of the spacecraft. This thesis describes the author’s contributions to the ground segment software design and development for nanosatellite space missions at the UTIAS Space Flight Laboratory. Particular emphasis is given to the ground segment software for the CanX-3 and CanX-4/-5 missions. For the CanX-3 mission, several software applications are explored, specifically ground control software for the payload on-board computer and star tracker, and mission planning software. For the CanX-4/-5 mission, its mission monitor and control software, and whole orbit data parser are discussed. For each software application, design considerations and decisions made during the development are explained. Furthermore, detailed discussions on their architectural and graphical user interface design and implementation are presented.

This thesis describes the assembly and integration procedures, methods and strategies used for the Generic Nanosatellite Bus (GNB) developed at the Space Flight Laboratory. The design of the interconnection medium routing will be presented and aspects of thermal testing such as thermal shock procedures and the satellite support structure design for the thermal vacuum testing. The compliance of the assembly, integration and testing requirements is demonstrated through validation and implementation. Step by step procedures are presented for GNB assembly, solar cell bonding and thermal tape application. The evolution of the integration design is described based on optimizing efforts and GNB design changes. Flexible circuits are presented as an alternative to the conventional harness for future missions. Finally, general assembly, integration and thermal testing recommendations are offered to add to the wealth of knowledge acquired by SFL in the proper design of nanosatellites.

This thesis describes technologies developed for nanosatellites at the Space Flight Laboratory. A critical ground station component, the Terminal Node Controller, was upgraded in order to support Generic Nanosatellite Bus and future missions. Sun sensor requirements and operation were reviewed, followed by details of the author's work in executing the acceptance testing on these parts, including thermal shock testing, thermal functional testing, calibration, system level testing and on orbit commissioning. A new calibration test process was developed, along with supporting structure and software to ease the testing process, producing accurate calibration parameters and expected performance results for the sensors. A thermal qualification campaign was completed, demonstrating that sun sensors are capable of functioning with negligible performance degradation after exposure to extreme temperatures. A process for installing the sun sensor pin hole was developed using photolithography. Finally, power subsystem analysis for the NEMO-AM mission is presented.

The CanX-4/-5 mission currently under development at the Space Flight Laboratory will demonstrate sub-metre formation control in four separate formations consisting of two nanosatellites. Formation maintenance is performed using a propulsion payload providing one axis of thrust, resulting in frequent slewing to meet thrust targets. Navigation is GPS dependent, with both satellites equipped with a receiver and antenna pair. Presented is a mission simulation developed for evaluating formation flying algorithm performance and the effects of frequent slewing on GPS coverage. CanX-4 and CanX-5 will be joined for commissioning prior to commencing formation flying via a mechanism, the Intersatellite Separation System. Details regarding the performance testing and troubleshooting of the system are described. Integration and testing of CanX-4/-5 flight hardware into a functional “FlatSat” is presented. Additionally, a description of satellite operations for two nanosatellites is given, with an emphasis on the relevance to the work performed for the CanX-4/-5 mission.

For spacecraft development, realizing strong supporting ground segment software is as important as designing the actual hardware component of the spacecraft. This thesis describes the author’s contributions to the ground segment software design and development for nanosatellite space missions at the UTIAS Space Flight Laboratory. Particular emphasis is given to the ground segment software for the CanX-3 and CanX-4/-5 missions. For the CanX-3 mission, several software applications are explored, specifically ground control software for the payload on-board computer and star tracker, and mission planning software. For the CanX-4/-5 mission, its mission monitor and control software, and whole orbit data parser are discussed. For each software application, design considerations and decisions made during the development are explained. Furthermore, detailed discussions on their architectural and graphical user interface design and implementation are presented.

Microsystem interfaces to the macroscopic surroundings and within the microsystems themselves are formidable challenges that this thesis makes an effort to overcome, specifically for enabling a spacecraft based entirely on microsystems. The NanoSpace-1 nanospacecraft is a full-fledged satellite design with mass below 10 kg. The high performance with respect to mass is enabled by a massive implementation of microsystem technology – the entire spacecraft structure is built from square silicon panels that allow for efficient microsystem integration. The panels comprise bonded silicon wafers, fitted with silicone rubber gaskets into aluminium frames. Each module of the spacecraft is added in a way that strengthens and stiffens the overall spacecraft structure. The structural integrity of the silicon module as a generic building block has been successfully proven. The basic design (silicon, silicone, aluminium) survived considerable mechanical loads, where the silicon material contributed significantly to the strength of the structural element. Structural modeling of the silicon building blocks enables rapid iterative design of e.g. spacecraft structures by the use of pertinent model simplifications. Other microsystem interfaces treats fluidic, thermal, and mechanical functions. First, solder sealing of microsystem cavities was demonstrated, using screen-printed solder and localized resistive heating in the microsystem interface. Second, a dismountable fluidic microsystem connector, using a ridged silicon membrane, intended for monopropellant thruster systems, was developed. Third, a thermally regulated microvalve for minute flows, made by a silicon ridge imprint in a stainless steel nipple, was investigated. Finally, particle filters for gas interfaces to microsystems, or between parts of fluidic microsystems, were made from sets of crossed v-grooves in the interface of a bonded silicon wafer stack. Filter manufacture, mass flow and pressure drop characterization, together with numeric modeling for filter design, was performed. All in all this reduces the weight and volume when microsystems are interfaced in their applications.

In recent years the space industry has seen significant growth in numbers of sub 10kg satellite platforms now known more broadly in the industry as nanosatellites. Nanosatellites potential applicability is driven by flourishing technologies miniaturisation in the consumer electronics market and commercialisation of space. Currently nanosatellite mission operations are limited in both lifetime and manoeuvrability due to limitations in on board propulsion technologies. Further enhancement of mission operations relies on more effective integration of current reaction-mass-based propulsion technologies and further development of miniaturised propulsion systems. Paradoxically, the compact spacecraft size and mass that facilitate nanosatellite access to space is presently a drawback in terms of acceptable systems performance and propulsion systems capacity. Moreover characteristic power density and vulnerability to the space environment is already high in nanosatellites in contrast to major satellites, rendering the design, inclusion, and optimisation of propulsion technologies a challenging task. This thesis focuses on techniques to support mission planning and characterisation of propulsion technologies for nanosatellites. Acknowledging the outweighing significance of solar activity modulating space environment perturbations and particularly atmospheric drag, a robust solar forecast method is proposed to support lifetime estimations. Complementing the pivotal framework information for propulsion system design and management, the vulnerability to atmospheric drag is assessed to identify the profile of the current vaguely defined drag coefficient of standard nanosatellites. Finally, addressing a crucial task on emerging propulsion technologies for nanosatellite systems, a method to improve low thrust characterisation via in-orbit manoeuvres using standard elementary attitude determination resources is devised. The robust solar activity forecast is carried out using observed historic and reconstructed Sun’s polar magnetic field, to define the initial state of an up-to-date solar magnetohydrodynamics computational model; the method successfully reproduces recent solar cycles activity, anticipating moderate-to-low activity during the next 25th cycle. The identification of the drag coefficient profile in standard nanosatellites is enabled by the statistical assessment of observed orbital decay through an iterative fitting process of propagated orbits; the profile is physically consistent and descriptive mostly in orbits below 350km during moderate-to-high solar activity. Finally, the devised thrust characterisation method exploits the regular geometry and mass distribution of standard nanosatellites to identify low thrust actuation via actuated body angular rotation rates in an intermediate axis spinner; precise computer simulations show that it is possible to improve low thrust estimations from weak and noisy sensor signals using the proposed method against typical methods using body angular acceleration.

Thesis submitted in fulfillment of the requirements for the degree Master of Technology: Electrical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology / Small satellites, such as CubeSats are mainly utilized for space and earth imaging missions. Imaging CubeSats are equipped with high resolution cameras for the capturing of digital images, as well as mass storage devices for storing the images. The captured images are transmitted to the ground station and subsequently stored in a database. The main problem with stored images in a large image database, identified by researchers and developers within the last number of years, is the retrieval of precise, clear images and overcoming the semantic gap. The semantic gap relates to the lack of correlation between the semantic categories the user requires and the low level features that a content-based image retrieval system offers. Clear images are needed to be usable for applications such as mapping, disaster monitoring and town planning. The main objective of this thesis is the design and development of an image classification, storage and retrieval system for a CubeSat. This system enables efficient classification, storing and retrieval of images that are received on a daily basis from an in-orbit CubeSat. In order to propose such a system, a specific research methodology was chosen and adopted. This entails extensive literature reviews on image classification techniques and image feature extraction techniques, to extract content embedded within an image, and include studies on image database systems, data mining techniques and image retrieval techniques. The literature study led to a requirement analysis followed by the analyses of software development models in order to design the system. The proposed design entails classifying images using content embedded in the image and also extracting image metadata such as date and time. Specific features extraction techniques are needed to extract required content and metadata. In order to achieve extraction of information embedded in the image, colour feature (colour histogram), shape feature (Mathematical Morphology) and texture feature (GLCM) techniques were used. Other major contributions of this project include a graphical user interface which enables users to search for similar images against those stored in the database. An automatic image extractor algorithm was also designed to classify images according to date and time, and colour, texture and shape features extractor techniques were proposed. These ensured that when a user wishes to query the database, the shape objects, colour quantities and contrast contained in an image are extracted and compared to those stored in the database. Implementation and test results concluded that the designed system is able to categorize images automatically and at the same time provide efficient and accurate results. The features extracted for each image depend on colour, shape and texture methods. Optimal values were also incorporated in order to reduce retrieval times. The mathematical morphological technique was used to compute shape objects using erosion and dilation operators, and the co-occurrence matrix was used to compute the texture feature of the image.

New Space is a phrase used to describe the expanding commercialization into the areas of space, for instance the Low Earth Orbit at approximately 500 km altitude. This is due to the decrease in cost as the satellites are becoming smaller and the transport vehicles cheaper. This reduction of cost provide the opportunity for industry and researchers tosend up customized equipment to orbit with standardized smaller satellites, such as the nanosatellites. Many parts of the nanosatellites system are commercially available but some subsystems are dependent on the situation. One of which is the satellite to satellite communication, referred to as Inter-Satellite Link (ISL). This thesis aims To evaluate the feasibility of asystem that allow for ISL capability and the basic operations of a satellite. Two hypothetical mission designs, Earth Observation and Global Coverage, were used to simulate the restrictions and requirements of the subsystems together with Commercial Of the Shelf (COTS) equipment to consider the satellite system as a whole. The major principles of the Radio Frequency (RF) communication system and their low level components are investigated and discussed. The scope of this thesis were to present and evaluate the high system level of the satellite. Thus the results and discussion describe a theoretical system performance that could be achieved with suggestions of low level components and system configuration. Besides from the communication subsystem this thesis also includes theory of mission design, the satellite subsystems and external interactions to describe how it all affects the design work of the communication system. Conclusion of this work offers a versatile preliminary system design that is theoretically capable of limited ISL communications. Furthermore this thesis include the fundamental principles of the satellite system that can be used for further work or alternative mission designs.

Dans cette thèse, le problème du contrôle d’attitude de satellites agiles à l’aide de grappes d’actionneurs gyroscopiques (AGs) est considéré et plus particulièrement son application au contrôle de micro/nanosatellites (10-100 kg). Des outils d’analyse topologique sont tout d'abord développés. La comparaison de différentes configurations de grappes justifie le choix d'une géométrie pyramidale à six actionneurs gyroscopiques. Des analyses plus approfondies de cette grappe, avec et sans cas de panne, permettent de déduire des contraintes que la loi de pilotage doit vérifier pour être adaptée à ce système. Pour y répondre, après analyse de la littérature, une nouvelle structure de loi de pilotage ainsi qu’une formulation différente des équations cinématiques sont développées. Cette structure est basée sur l’algorithme du filtre de Kalman étendu. Elle a pour avantages de répondre aux exigences en termes de calcul temps réel au bord des satellites, de flexibilité sur la gestion des contraintes et de facilité d’adaptation en cas de pannes. En outre, une procédure de génération de boucle de commande, englobant la loi de pilotage et un contrôleur robuste du système, est proposée. La généralisation de cette boucle de commande est illustrée sur des bras manipulateurs à base fixe et spatiaux.En parallèle, l’étude du passage des singularités internes intraversables mène à une nouvelle stratégie d’évitement de ces singularités. Des simulations sur des modèles de satellites représentatifs illustrent les résultats. La grappe d’actionneurs et la boucle de commande développées seront testées dans le cadre d’une expérimentation en microgravité. / In this thesis, the attitude control problem for agile satellites with control moment gyro (CMG) clusters is studied. In particular, the problem applies to micro/nanosatellites (10-100kg). First, numerical tools are developed to analyse the compatibility of various cluster configurations with the nanosatellite constraints. The pyramidal six-CMG cluster is then selected. This cluster topology is analysed in depth, with and without actuator failures. Constraints on the development of a steering law adapted to our system are deduced. Among them, the singularity avoidance issue is emphasised. To meet the requirements, an analysis of the literature is carried out. Then, a new steering law structure and a different formulation of the kinematic equations are developed. This structure is based on the extended Kalman filter algorithm. It meets the requirements because it can be calculated in real-time onboard satellites, constraints imposed on the system are handled with flexibility and it is easily adaptable in case of actuator failures. In addition, a procedure to generate the control loop is proposed, containing a robust controller. The generalisation of this control loop is shown on space and fixed-base manipulator arms. Furthermore, the study of the internal elliptic singularities in CMG clusters leads to a new singularity avoidance strategy. Software simulations on highly representative simulators show the results of the steering law in various actuator failure cases. The CMG cluster and the control loop will be tested in a parabolic flight campaign, and the development of this experiment is detailed in this thesis.