Browsing by Author "Van Der Stokker, Luke"

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    An investigation into the imager pointing accuracy and stability for a CubeSat Using a CubeADCS in sun-synchronous low earth orbits
    (Stellenbosch : Stellenbosch University, 2021-12) Van Der Stokker, Luke; Steyn, Herman; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: The past decade has seen a rapid increase in investment and interest into the CubeSatellite industry, with a particular rise in interest seen from the commercial sector. The demand for miniaturised satellite technology has further fuelled the need for miniaturised attitude determination and control systems, without which, most mission objectives would be unattainable. Few companies exist whose sole purpose is to provide CubeSatellite mission designers with the control system they need to achieve their mission objectives. One such company which has emerged, is the South African born CubeSpace Satellite Systems RF (Pty) Ltd. whose CubeADCS does exactly this. This thesis sought to investigate the imager pointing accuracy that can be achieved by a CubeSatellite in a sun-synchronous low Earth orbit, equipped with a CubeADCS. An initial investigation found that components such as star trackers and reaction-wheels are critical to high accuracy pointing, and that other systems in industry have been able to achieve arcsecond pointing accuracies. An in-depth investigation was conducted into the underlying components of the CubeADCS, consisting of both a theoretical study and practical hardware investigation, which aimed to understand the inner workings of each component, in addition to identifying and characterising their primary sources of error. An accurate simulation space environment reflective of that experienced by a CubeSatellite in low Earth orbit was constructed. A model of the CubeADCS model was additionally developed from the results of the subcomponent investigation to be tested by means of comprehensive simulations. The CubeADCS was investigated in its ability to track a constant reference, in addition to its ability to perform an accurate target tracking manoeuvre in an attempt to image a location on Earth’s surface. Several scenarios were investigated, which aimed to observe the effects of changing various size, orientation, star tracker placements, and attitude estimator parameters. Simulation results revealed that the CubeADCS is capable of achieve pointing accuracies of within 32′′ when following a constant reference, and within 31′′ during target tracking manoeuvres in Sun-synchronous orbits. A stability analysis revealed that the CubeADCS would be acceptable for the likes of stellar observation missions, making it more than adequate to satisfy Earth observation stability requirements.