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.

Thesis presented in ful lment of the requirements for the degree of Magister Technologiae in Electrical Engineering at the Cape Peninsula University of Technology, 2013 / The power system is essentially one of the most critical subsystems to any satellite, without some form of power system a satellite would simply cease to function. The research within these pages investigates the areas pertaining to satellite power systems with the main focus towards the CubeSat platform. The end objective of this research was the development of a reliable analogue based switch-mode power system for a CubeSat. The research began with an investigation into the CubeSat platform, the space environment and a basic overview of a satellite and its systems. The research then focussed on satellite power systems, focussing primarily on satellite power system topologies and switch-mode power systems. Various components and concepts surrounding the satellite power system were investigate and included the photovoltaic (PV) solar cell, batteries, satellite power system topologies, protection concepts and typical CubeSat power systems. The nal part of the literature review included research into typical CubeSat power systems. The space environment complicates the design of satellite systems. The developed electrical power system harnessed electrical power from a PV solar panel by means of a fractional opencircuit voltage (FOCV) based maximum power point tracker (MPPT) with the use of a SEPIC DC-DC converter. The use of a SEPIC DC-DC converter allowed the system to operate at a greater e ciency than could be expected from linear designs. The requirement for an e cient system was important as the heat generated by the power system could bring rise to dissipation issues, resulting in over-heating of various components. The design took into account component sizing, as larger components would be more prone to damage during the high accelerations and vibrations associated with being launched into space. The use of a MPPT allowed the power system to better utilise the available PV solar panel power, by maintaining the PV solar panel near its optimum operating voltage. The design slid between MPPT and voltage regulation to harness as much power as possible while not over-charging the Lithium polymer battery. The power system consisted of battery under-voltage protection as well as over-current protection for the attached payloads and satellite subsystems. The SEPIC DC-DC converter was selected over other SMPS topologies, as this topology could be used in a 1U and 3U CubeSat with a wide variety of PV solar panel cell con gurations. The bene ts of this SMPS topology are due to the SEPIC DC-DC converter's ability to produce an output voltage greater than, less than or equal to the input voltage (National Semiconductor, 2008; Texas Instruments, 2008a). This, along with the operation of the FOCV based MPPT, allowed the power system to be very exible. The designed FOCV based MPPT could be pre-set to di ering PV solar cell technologies due to the adjustable ratio between the maximum power point voltage, Vmpp, and the open-circuit voltage, Voc of the PV solar panel. It was decided not to select a Buck or Boost DC-DC converter based power system as this would limit the exibility of the system. Additionally, the SEPIC DC-DC converter brings with it the ability to isolate the input and output voltage upon shut down. This isolation is due to the SEPIC DC-DC converter's coupling capacitor and this topologies operation as described by National Semiconductor (2008) and Texas Instruments (2008a). The prototype was versatile allowing a wide variety of PV solar cell technologies to be used. The wide operating voltage of the prototype allowed the design to be connected to a series or parallel combination of solar cells with an operating voltage of 3 V to 20 V. The power handling capability of the prototype per solar panel channel allows the design to be applied to a 1 U or 3 U CubeSat given that the channel did not exceed 10 W. All components of the prototype operated without fault, e ectively charging the Li-poly battery safely while protecting payloads and subsystems. The SEPIC DC-DC converter utilised by the MPPT achieved an e ciency of 71 % under full load and with an input voltage of 10 V.