Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 120-121). Also available via the Internet.

Thesis (M.S.)--California Polytechnic State University, 2010. / Title from PDF title page; viewed on April 21, 2010. Major professor: Franz, Kurfess, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Computer Science." "March 2010." Includes bibliographical references (p. ).

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2010. / Stable and reliable source of electrical energy is a requirement for efficient operation of satellites. Several sources of electrical power for satellites exist such as fuel cells, nuclear or battery stored Direct Current energy but of late concentration has been on solar cells as the advantages compared to the other sources are many. Solar cells are p-n semiconductor devices which convert light energy into electrical energy by photovoltaic effect. The biggest drawback of solar cell energy system is the low light to electricity conversion efficiency. Apart from powering satellites, solar cells and panels have found other numerous applications such as in water pumping systems, rural electrification, street lightning. Photovoltaic principle of solar cells started way back in 1839 when Alexandre Edmund Becquerel observed that electrical currents arose from certain light induced chemical reactions. A comprehensive understanding of this phenomenon became clear when the science of quantum theory was unveiled in the early parts of the 20th century. Most solar cells and panels available today in the market are silicon based made of single junction technology. The disadvantage with single junction technology is that the p-n junction is made of a single type of solar cell material which absorbs a fraction of light wavelengths from the spectrum of light. The disability of the single p-n junction to convert all the light energy to electricity accounts for the low efficiency for the solar cells. One way to go around the problem of efficiency is to use multi-junction solar cells. Multijunction solar cells are designed to absorb a large fraction of the light spectrum and convert them to electrical energy. They are made of multiple p-n junctions made of different solar cell materials which absorb different parts of light spectrum and convert them to electrical energy. In this thesis, a design of a multi-junction solar cell for developing space solar panel is presented. The multi-junction cell has been designed from simulation results of different solar cell materials simulated with space conditions. Ideas and recommendations for future work are also presented.

M.Ing. / This thesis investigates why electromagnetic interference (EMI) and electromagnetic compatibility (EMC) problems exist and how EMI is generated, measured and limited. This investigation is done with reference to power systems and satellite earth stations. To understand the full extend of EMI generation from power systems on satellite earth stations, it was necessary to do a study of EMI, in order to understand EMI in its simplest form. This study consists of the following work: •A background study investigates the components of EMI, how EMI are generated and manifest in electric systems, methods to limit conducted EMI, a theoretical model on how to estimate conducted EMI quantities and EMI measurement techniques. •A conducted EMI model with which the parasitic impedances could be controlled was developed. With this model it could then be determined how conducted EMI would manifest in 3-wire circuit designs and how conducted EMI could be reduced in such circuits. •It was investigated how inductive coupling and capacitive coupling can be reduced. Time and frequency domain measurements were used to investigate the effects of these couplings. It was also of great importance to understand how EMI from measurement set-ups could influence measurements to give inaccurate results. This work investigated how high frequency measurements can be done effectively, how high frequency circuit designs can be improved and how parasitic impedances can be limited in high frequency equipment. •The expected EMI problem at the Klipheuwel wind farm was analysed. Simulations of expected EMI levels, worst case scenarios and measurements taken there showed that no significant EMI are generated from the wind generators and that power systems don’t hold a threat to satellite earth stations, if the necessary precautions are taken.

Modern satellite operations often require a portable ground station capability. However, the traditional large parabolic dish solidly mounted in concrete is not conducive to portable operation. This work offers the helical array as a viable alternative. A critical literature survey shows what work has been performed by others, and what issues must be addressed so that a feasible helical array design may be put forth. Analysis was performed using data from experiments and from a computer simulation. / Master of Science

The design, analysis, and testing of a multi-module, multi-phase (MMMP) battery charger for the NASA Earth Observing System (EOS) is presented. The MMMP converter is comprised of four independent buck converters switched 90° out of phase. The MMMP charger is compared to a single module battery charger, and shown to provide significant performance improvements. The power stage is designed for maximum efficiency and minimum weight. The control loops (Charge Regulation and Bus Voltage Regulation) designs are presented and the small-signal models are verified with experimental results. The charger testing is facilitated by the use of the Space Platform Power System Hardware Testbed. The testbed utilizes battery and solar array simulators which allow for realistic battery charger testing. / Master of Science

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007. / Applications are normally developed with a specific purpose in mind and when new features are needed the source code has to be modified, recompiled and redistributed. It will be more beneficial if new features can be dynamically added during runtime without the need to disrupt execution, especially in the case of ground station software. This thesis is about the implementation of a dynamic development environment within which a modular system can be created from existing components that can be extended with additional components at any time. The interaction between these components can then be specified which can result in a completely automated system. It is concluded that the graphical tools of such an environment can make it easy for people who do not necessarily have programming knowledge to build a system from existing components that can be extended and reconfigured whenever necessary.

Satellite networks provide an alternative to terrestrial networks where cost and lack of infrastructure are driving parameters. For a satellite network to be cost effective one needs to be able to increase the efficiency of the network: this is accomplished by focusing on the parameters that affect the performance of the system and improving on them where possible. The factors affecting the network performance include the capacity, the propagation delay, the protocol used, and the channel error rate, among others. There are various ways to implement a satellite network depending on the satellite orbit, the architecture used, the access technique used, the radio interfaces used, etc. This thesis work describes the chosen satellite standard, Digital Video Broadcasting – Return Channel via Satellite (DVB-RCS) and the associated Medium Access Control (MAC) protocols. Two protocols were designed and investigated under ideal channel conditions, these being the Combined Free/Demand Assigned Multiple Access with Piggy Backing – Packet Dropping (CF/DAMA-PB-PD) protocol; and the Combined Free/Demand Assigned Multiple Access with Piggy Backing – Prioritised Earliest Deadline First (CF/DAMA-PB-PEDF) protocol, both derived from the Combined Free/Demand Assigned Multiple Access with Piggy Backing (CF/DAMA-PB) protocol. The multimedia traffic models for voice, video and web classes are described, validated through simulations and presented; these provide the heterogeneous vi traffic required for evaluating the performance of the satellite system implemented and the designed protocols. Under the multimedia traffic, CF/DAMA-PB-PD was shown to excel in average packet delay reduction while reducing the overall system throughput. The CF/DAMA-PB-PEDF does not contribute to an improvement over the CF/DAMA-PB-PD protocol. The effects of a non-ideal channel on the CF/DAMA-PB-PD protocol was investigated and presented along with the design of three MAC protocols that take the channel characteristics into account to improve on the system performance. The cross-layer interactions, more specifically the interaction between the physical and data–link layers, were used, investigated and presented. The channel state information in terms of signal-to-noise ratio (SNR) was used to improve the system performance. The five protocols evaluated under non-ideal channel conditions were the CF/DAMA-PB, CF/DAMA-PB-PD, CF/DAMA-PB-BSNRF, CF/DAMA-PB-DD and the CF/DAMA-PB-BSNRF+DD. The best overall performance, both in average packet delay while maintaining good QoS levels and throughput was shown to be that of the CF/DAMA-PB-DD protocol. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: This thesis describes the development of a distributed ground support system to be used in the small satellite program at the University of Stellenbosch. A literature study was done to determine the current trends in ground support design. These trends are presented together with an analysis of the SUNSAT groundstation software. New technologies in the field of distributed systems are discussed and used in the design of a distributed ground support system. The design centres around a servicesbased architecture where services are distributed on the network. The design is evaluated according to attributes exhibited by effective distributed systems. Certain services were implemented to demonstrate the feasibility of the design. The implementations are discussed and suggestions are made for future improvements and fields of possible further study. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die ontwikkeling van 'n verspreide-grondstasie-sisteem vir gebruik in die Universiteit van Stellenbosch se satelliet-program. Eerstens is 'n literatuurstudie gedoen om die huidige verwikkelinge in die veld van satellietondersteuning-ontwikkeling vas te stel. Hierdie verwikkelinge word bespreek en gebruik om die SUNSAT-grondstasie sagteware te evalueer. Nuwe tegnologieë in die veld van verspreide stelsels word ondersoek en bespreek. Die ontwerp van die grondstasie is gebaseer op 'n verspreide dienste argitektuur. Die ontwerp word beskryf en geëvalueer aan die hand van kenmerke tipies van 'n effektiewe verspreide stelsel. Om die werkbaarheid van die ontwerp te toon, is sekere van die dienste geïmplimenteer, en die funksionering daarvan word bespreek. Voorstelle word ook gemaak oor moontlike toekomstige navorsing wat gedoen kan word.