SiC in Space is one of the experiments on KTH’s miniature satellite, MIST. The experiment carries out tests on bipolar junction transistors of silicon and silicon carbide. This thesis describes how the characteristics of a transistor can be measured using analog circuits. The presented circuit design will work as a prototype for the SiC in Space experiment. The prototype measures the base current, the collector current, the base-emitter voltage as well as the temperature of the transistor. This thesis describes how a test circuit may be designed. The selected design has been constructed in incremental steps, with each design choice explained. Different designs have been developed. The designs have been verified with simulations. We have also constructed and tested three different prototypes on breadboards and printed circuit boards. / SiC in Space är ett av experimenten på KTHs miniatyrsatellit, MIST. Experimentet utför test på bipolära transistorer av kisel och kiselkarbid. Detta examensarbete förklarar hur transistorns karakteristik kan mätas med analoga kretsar. Den framtagna kretsdesignen kommer att fungera som en prototyp till SiC in Space-experimentet. Prototypen mäter basströmmen, kollektorströmmen, bas-emitter-spänningen samt temperaturen för transistorn. Detta examensarbete förklarar hur en testkrets kan designas. Den valda designen byggs i inkrementella steg, där varje designval förklaras. Olika designer har utvecklats. Designerna har verifierats genom simuleringar. Vi har också konstruerat och testat tre olika prototyper på kopplingsdäck och kretskort.

Space industry has been booming in the recent times, investments have not justbeen made on satellites and launch vehicles but also on space sustainability. Spaceindustry has its users in national agencies, private commercial agencies, academia andexperimental organisations. Smallsats and cubesats are one of the most interestingdomains in space industry today. This has led to pure research and astonishinginnovations in this domain to enable lower costs, lower mass, increased orbital period,better accessibility and global impact. Development of sustainable products requiresthe system to qualify a certain standard set up in the industry. This standard ensuresthat the system safely completes its mission up in space. The problem described byGomSpace Sweden concerns one of their ongoing products, a cold gas propulsionunit which is suitable for a typical 6U cubesat called ESA6DOF. In large, the productconsists of a structure, two propellant tanks, one plenum tank, piping, electronics andsix thrusters. Qualification of this propulsion system module involves the system toundergo a random vibration test according to ECSS standards. This thesis work shallbe focused on setting up the structure needed to perform random vibration simulationsin COMSOL. This step is done to primarily iterate the design to make it robust enoughto sustain loads during flight and also to avoid any physical damages during testingcampaign. Followed by performing the actual random vibration test at a facility usingthe assembled ESA6DOF propulsion module. Finally, this ends with validating thesimulation results with that of testing. / Rymdindustrin har blomstrat den senaste tiden. Investeringar har inte bara gjortspå satelliter och bärraketer utan också på hållbarhet i rymden. Rymdindustrinhar sina användare i nationella organisationer, privata kommersiella organisationer,universitetsvärlden och forsknings organisationer. Smallsats och cubesats är tvåav de mest intressanta domänerna inom rymdindustrin idag. Detta har letttill grundforskning och häpnadsväckande innovationer inom detta område för attmöjliggöra lägre kostnader, lägre massa, ökad omloppstid, bättre tillgänglighetoch global påverkan. Utveckling av hållbara produkter kräver att systemet möteren viss standard uppsatt i branschen. Denna standard säkerställer att systemetsäkert slutför sitt uppdrag uppe i rymden. Problemet som beskrivs av GomSpaceSweden gäller en av deras pågående produkter, en kallgasdrivenhet lämplig för entypisk 6U cubesat kallad ESA6DOF. I stort består produkten av en struktur, tvådrivmedelstankar, en plenumtank, rörledningar, elektronik och sex finjusterarraketer.Kvalificeringen av denna framdrivningssystemmodul innebär att systemet genomgåren slumpmässig vibration enligt ECSS-standarder. Detta examensarbete harfokuserat på att sätta upp den struktur som behövs för att utföra slumpmässigavibrationssimuleringar i COMSOL. Detta steg gjordes för att i första hand itereradesignen för att göra den robust nog att tåla belastningar under flygning och ävenför att undvika fysiska skador under testkampanjen. Efter detta utfördes det faktiskaslumpmässiga vibrationstestet på en anläggning med den sammansatta ESA6DOF-framdrivningsmodulen. Avslutningsvis utfördes validering av simuleringsresultatenmot testresultaten.

A finite element model of the CubeSat MIST was created, in order to assess the stresses that occur in the satellite in response to loads during its launch. Due to size limits of thesoftware used, simplifications had to be made to the geometry of the model. The loads assessed were quasi-static accelerations, random vibrations, shock loads, as well as a combined quasi-static acceleration and random vibration case. The study assumed the worst possible loads from a list of different potential launch vehicles for the satellite. Non-linear boundary conditions could not be modelled, and instead different linear boundary condition combinations were assessed. The results showed that the satellite showed positive margins of safety for the quasi-static loads. The lowest natural frequency for the satellite was above 130 Hz. For the random vibration loads, positive margins of safety could be shown if adverse stresses attributed to the boundary conditions inthe worst case were ignored. The model proved too conservative to qualify the satellite for the shock loads. Shock testing is therefore recommended for future work, unless requirements for waiving the shock testing can be met. The random vibration and combined loads analysis showed that the −X shear panel experienced high stresses in the corners of its windows, and the part should be inspected once environmental tests are conducted. The −X shear panel only showed adverse stresses in the most extreme boundary condition case, where its deformation was deemed unrealistic. / En finit elementmodell av nanosatelliten MIST skapades for att undersöka dess respons till lasterna under uppskjutning. På grund av storleksbegränsningar i programvaran behövde modellens geometri förenklas. Lasterna som undersöktes var kvasistatiska accelerationer, stokastiska vibrationer, chocklaster samt ett kombinerat kvasistatiskt accelerations- och stokastiskt vibrationsfall. Studien använde de värsta tänkbara lasterna från en lista över olika potentiella bärraketer för satelliten. Icke-linjära gränsvillkor kunde inte modelleras och istället utvärderades olika kombinationer av linjära gränsvillkor. Resultaten visade positiva säkerhetsmarginaler för kvasistatiska belastningar. Den lägsta naturliga frekvensen för satelliten var över 130 Hz. För de stokastiska vibrationsbelastningarna kunde positiva säkerhetsmarginaler motiveras om hänsyn togs till oegentligheter orsakade av gränsvillkoren i det extremaste fallet. Chocklastanalysen visade på begränsningar i modellen. Mekaniska chocktester kommer därmed behövas för att undersöka chocklasterna, om inte kraven for att hoppa över chocktestning uppfylls. Analyserna av de stokastiska vibrationerna och det kombinerade lastfallet visade att skjuvpanelen på −X-sidan upplever höga spänningar i hörnen på sina fönster, och bör inspekteras när experimentella tester genomförs. Skjuvpanelen på −X-sidan upplevde enbart för höga spänningar i fallet med mest extrema gröäsvillkor, där deformationerna bedömdes vara orealistiska.

Thesis (MscEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The Cape Peninsula University of Technology, in collaboration with Stellenbosch University, is developing a 3-unit CubeSat for a low earth polar orbit. The two main payloads are a camera and a radio frequency beacon. This beacon will be used to calibrate the radar antenna patterns of an antenna of the Hermanus Magnetic Observatory at their base in Antarctica. This thesis describes the development of an aerodynamic attitude determination and control system needed to achieve three-axis stabilisation of the satellite and to perform accurate pointing of the camera. The satellite structure is designed to utilise aerodynamic means of control. It includes four feather antennae for passive pitch-yaw stabilisation and two active aerodynamic roll control paddles. The sensors used are a three-axis magnetometer, ne sun sensor and nadir sensor. Three attitude determination methods are investigated, namely the Triad, Rate Kalman Filter and Extended Kalman Filter algorithm. Apart from the aerodynamic control elements of the satellite, three magnetic torque rods and three nano-reaction wheels are also included in the design. Three control modes for the satellite are identi ed and various control methods are investigated for these control modes. The various attitude determination and control methods are evaluated through simulations and the results are compared to determine the nal methods to be used by the satellite. The magnetic Rate Kalman Filter is chosen as attitude determination method to be used when the satellite is tumbling and a combination of the sun Rate Kalman Filter and the Triad algorithm is to be used when the satellite experiences low angular rates. The B-dot and Y-spin controller is chosen for the detumbling control mode, the aerodynamic and cross-product control method for the three-axis stabilisation control mode and the quaternion feedback control method for the pointing control mode of the satellite. The combination of magnetic and aerodynamic control proved to be su cient for the initial stabilisation of the satellite, but the three nano-reaction wheels are required for the pointing control of the imaging process. / AFRIKAANSE OPSOMMING: Die Kaapse Skiereiland Universiteit van Tegnologie, in samewerking met die Universiteit van Stellenbosch, is tans besig met die ontwikkeling van 'n 3-eenheid CubeSat vir 'n pol^ere, lae aard-wentelbaan. Die twee loonvragte van die satelliet bestaan uit 'n kamera en 'n radiofrekwensie-baken. Die radiofrekwensie-baken sal gebruik word om 'n antenna van die Hermanus Magnetiese Observatorium, by hul basis in Antarktika, se radar antenna patrone te kalibreer. Hierdie tesis beskryf die ontwikkeling van 'n aerodinamiese ori entasiebepaling en -beheerstelsel wat benodig word om die satelliet in drie asse te stabiliseer en om die kamera noukeurig te rig. Die satelliet se struktuur word ontwerp vir aerodinamiese beheer. Dit sluit vier veerantennas in vir passiewe duik-gier beheer, asook twee aerodynamiese rolbeheer appies vir aktiewe beheer. Die sensors wat gebruik word sluit 'n drie-as magnetometer, fyn sonsensor en nadirsensor in. Drie ori entasiebepalingsmetodes word ondersoek, naamlik die Drietal, Tempo Kalman lter en die Uitgebreide Kalman lter algoritmes. Buiten die aerodinamiese beheerelemente van die satelliet, word daar ook drie magneetstange en drie nano-reaksiewiele ingesluit in die ontwerp. Daar word onderskeid getref tussen drie beheermodusse en verskeie beheermetodes word ondersoek vir hierdie beheermodusse. Die verskeie ori entasiebepalings- en ori entasiebeheermetodes word ge evalueer deur middel van simulasies en die resultate word vergelyk om die beste metodes vir die satelliet se gebruik te bepaal. Die magnetiese Tempo Kalman lter word gekies as ori entasiebepalingsmetode vir 'n tuimelende satelliet en die kombinasie van die son Tempo Kalman lter en Drietal algoritme word gebruik vir 'n satelliet met lae hoektempos. Die B-dot en Y-spin beheerder word gekies vir die tuimelbeheermodus, die aerodinamiese en kruisproduk beheermetode vir die drie-as-stabilisasie-beheermodus en die kwaternioon terugvoer beheermetode vir die rigbeheermodus van die satelliet. Daar word bepaal dat die samespanning van magnetiese en aerodinamiese beheer voldoende is vir die aanvanklike stabilisering van die satelliet, maar dat die drie nano-reaksiewiele benodig word om die kamera te rig tydens die beeldvormingproses.

A three-rotational degree of freedom attitude control system has been developed for the NASA Jet Propulsion Laboratory’s INSPIRE Project by the Texas Spacecraft Laboratory at The University of Texas at Austin. Using 3D plastic printing manufacturing techniques, a cold gas thruster system was created in order to detumble and maintain the attitude of two 3U CubeSats traveling through interplanetary space. A total of four thruster units were produced, including two engineering designs and two flight units. The units feature embedded sensors and millisecond level thrust control while using an inert, commercially-available refrigerant as a propellant. The thrust, minimum impulse bit, and specific impulse performance of the cold gas units was characterized using a ballistic pendulum test stand within a microtorr vacuum chamber. A heating element was used to change the temperature conditions of the propellant and determine the relationship between temperature and performance. The flight units were delivered in January of 2014 and the INSPIRE satellites are expected to launch in the upcoming year. / text

This thesis presents the design, simulation and analysis of a new network based on the Automatic Packet Reporting System (APRS) concept to enhance communications of CubeSat. Created in the 1980s, APRS is arguably one of the world’s largest Radio Frequency (RF) networks maintained by a community of licensed amateur radio volunteers for a variety of terrestrial purposes. Using these established nodes we can create a virtualized ground station network for satellite downlinks. Based on literature reviews of CubeSat communications systems and their orbital elements, as well as direct surveys of the amateur radio community, comprehensive far-field antenna models were created in 4nec2 for both the ground and space sections of the CubeSat downlink. The ground station antenna models include: a directional AMSAT/OSCAR Yagi-Uda, an omnidirectional J-pole, ground plane, and a whip antenna. The CubeSat antenna models used include dipoles, monopoles, and turnstiles. These models were evaluated and then imported into the Analytical Graphics Inc (AGI) Systems Tool Kit (STK) to form a discrete event simulation based on nonhomogeneous WGS84 location data extracted from real world APRS Internet Gateway (I-Gate) packets. All objects within the simulation use realistic antenna models, node locations, propagation models and satellite orbital mechanics. This simulation can act as a suite of generally applicable example satellites models (ExampleSat) for analytical comparisons that include link budgets, access times, differing data rates, antenna designs, orbital altitudes and ground station locations. Furthermore, it represents a North American continental scale RF satellite communications downlink network model. Using the virtual ground station network alters the net probability distribution of the received signal from the spacecraft. Specifically, the thesis compares non-stationary time series analysis methods upon the net received signal. The virtualized ground station network enables the aggregated received signal to appear stationary. This in turn may allow for alternative signals analysis techniques to improve a CubeSat’s downlink performance. The simulation allows us to generate representative received signals from ExampleSat to the ground station nodes for exploratory analysis, utilizing less arbitrary assumptions. This simulation and the set of models enable a more rapid start to trade-off studies for link budget design. This set of ExampleSat downlink models can be used by new designers of small-satellite communications systems. / February 2017

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: CubeSats are small, lightweight satellites which are often used by academic institutions due to their application potential and low cost. Because of their size and weight, less powerful attitude controllers, such as solar sails, can be used. In 2010, the Japanese satellite, Ikaros, was launched to illustrate the usage of solar sails as a propulsion system. Similarly, by exploiting the solar radiation pressure, it is possible to use a solar sail, together with three magnetorquers, to achieve 3-axis attitude control of a 3-unit CubeSat. Simulations are required to demonstrate the attitude control of a sun-synchronous, low Earth orbit CubeSat using a solar sail. To allow the adjustment of the solar sail, and its resulting torque, a mechanical structure is required which can be used to position the sail within two orthogonal axes. Although the magnetorquers and solar sail are sufficient to achieve 3-axis attitude control, the addition of a reaction wheel can be implemented in an attempt to improve this control. / AFRIKAANSE OPSOMMING: CubeSats is klein, ligte satelliete wat dikwels deur universiteite gebruik word weens hul lae koste en groot toepassings potensiaal. As gevolg van hulle gewig en grootte, kan minder kragtige posisie beheerders, soos byvoorbeeld sonseile, gebruik word. Die Japannese satelliet, Ikaros, was in 2010 gelanseer om die gebruik van ’n sonseil as aandrywingstelsel te illustreer. Net so is dit moontlik om die bestraling van die son te gebruik, met behulp van ’n sonseil, en drie magneetstange om 3-as posisiebeheer op ’n 3-eenheid CubeSat te bekom. Simulasies word benodig om die posisie beheer van ’n sonsinkrone, lae-aard wentelbaan CubeSat met ’n sonseil te demonstreer. ’n Meganiese struktuur word benodig vir die posisionering van die sonseil in twee ortogonale asse sodat die sonseil, en dus die geassosieerde draaimoment, verskuif kan word. Alhoewel die magneetstange en sonseil voldoende is om 3-as posisiebeheer te bekom, kan ’n reaksiewiel bygevoeg word om hierdie beheer te probeer verbeter.

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: With CubeSats becoming popular as a cheap alternative to larger satellites, the need for advanced miniature attitude determination and control systems (ADCS) arises to meet the pointing requirements of satellite operations such as earth imaging and orbit maintenance. This thesis describes the design of a complete ADCS for use on CubeSats. A previously designed CubeSat on-board-computer, CubeComputer, and ne sun and nadir sensor, CubeSense, is incorporated in the design. The remaining requirements with regard to sensors and actuators were met by CubeControl, an additional module, the design, manufacturing and testing of which are described. CubeControl can implement magnetic control with the use of a magnetometer and three magnetorquers. It is also capable of driving three reaction wheels for accurate active 3-axis stabilization. / AFRIKAANSE OPSOMMING: Met CubeSats wat gewild raak as 'n goedkoop alternatief tot groter satelliete ontstaan die behoefte vir gevorderde miniatuur ori entasiebepaling en -beheerstelsels wat satelliet operasies soos aardwaarneming en wentelbaan korreksies moontlik maak. Hierdie tesis beskryf die ontwerp van 'n volledige ori entasiebepaling en -beheerstelsel vir CubeSats. 'n Voorheen ontwikkelde CubeSat aanboordrekenaar, CubeComputer, en 'n fyn sonsensor en nadirsensor, CubeSense, is ingesluit in die ontwerp. Die orige benodighede met verband tot sensors en aktueerders word vervul deur CubeControl, 'n addisionele module waarvan die ontwerp, vervaardiging en toetsing beskyf word. CubeControl kan magnetiese beheer implementeer deur gebruik te maak van 'n magnetometer en drie magneetstange. Dit kan ook drie reaksiewiele aandryf vir akkurate aktiewe 3-as stabilisering.

Thesis submitted in partial fulfilment of the requirements for the degree of Master of Technology: Electrical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2013 / Earth observation satellites utilise sensors or cameras to capture data or images that are relayed to the ground station(s). The ZACUBE-02 CubeSat currently in development at the French South African Institute of Technology (F’SATI) contains a high resolution 5 megapixel on-board camera. The purpose of the camera is to capture images of Earth and relay them to the ground station once communication is established. The captured images, which can amount to a large volume of data, have to be stored on-board as the CubeSat awaits the next cycle of transmission to the ground station. This mode of operation introduces a number of problems, as the CubeSat has limited storage and memory capacity and is not able to store large amounts of data. This, together with the limitation of the downlink capacity, has set the need for the design and development of an image compression system suitable for the CubeSat environment. Image compression focuses on reducing the size of images to be stored as well as reducing the size of the images to be transmitted to the ground station. The purpose of the study is to propose a compression system to be implemented on ZACUBE-02. An intensive study of current, proposed and implemented compression methods, algorithms and techniques as well as the CubeSat specification, served as input for defining the requirements for such a system. The proposed design is a combination of image segmentation, image linearization and image entropy coding (run-length coding). This combination technique is implemented in order to achieve lossless image compression. For the proposed design, a compression ratio of 10:1 was obtained without negatively affecting image quality.The on-board storage memory constraints, the power constraints and the bandwidth constraints are met with the implementation of the proposed design, resulting in the downlink transmission time being minimised. Within the study a number of objectives were met in order to design, implement and test the compression system. These included a detailed study of image compression techniques; a look into techniques for improving the compression ratio; and a study of industrial hardware components suitable for the space environment. Keywords: CubeSat, hardware, compression, satellite image compression, Gumstix Overo Water, ZACUBE-02.

The I2T5, an iodine-propelled, cold gas thruster, developed by ThrustMe, France, is the first of its kind to make it successfully to space. Due to its simple, reliable and cost-effective design, it is a suitable propulsion system for CubeSat missions with low delta-V (ΔV) requirements. To ensure that the I2T5 performs at its peak, it is crucial to maintain good thermal control of the thruster, to keep it within the operational temperature range. The first flight measurements of the I2T5 provided insight into its thermal performance. It was observed that the required temperature to sublimate the iodine propellant was not reached within the expected time frame, which led to a longer warm-up period, and a reduction in thrust. The problem arose due to an unforeseen conductive thermal contact between the tank and the thruster walls. This thesis delves deeper into this issue, and focuses on alleviating the total conductive heat loss from the tank to the satellite frame, where the I2T5 is integrated. The insulating washer-bolt configuration of the I2T5 side panels is observed to be responsible for the conductive heat transfer. A preliminary analysis is performed to obtain an initial maximum for the conductive heat flux lost to the satellite frame. A plan of action is then determined to optimise the geometry, material or configuration of the insulating washers to lower the maximum heat flux value. Following this, an experiment was conducted with a new washer-bolt configuration to determine the heat flux values. A case study is performed for the orbital environment heat fluxes that the I2T5 would receive if it were integrated to a CubeSat in sun-synchronous orbit. An overview of results shows that, for the thermal simulations, all the methods employed to reduce the conductive heat loss at the frame were effective. The experiment provided neutral results, and would need to be repeated with different experimental parameters to have a clear perspective of the heat losses. In reality, the satellite frame receives radiative fluxes in addition to conductive heat fluxes, but radiation is not considered for this thesis, and is suggested as a prospective study.