Browsing by Author "Lombard, Francois"

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    Remote vessel detection using an optical imager and an AIS receiver combination for a CubeSat constellation
    (Stellenbosch : Stellenbosch University, 2020-03) Lombard, Francois; Steyn, H. W.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: This thesis investigates illegal shing activities on the coast of South Africa. It was concluded that a constellation of 10 6U satellites orbiting in a specialised orbit, with repeating ground tracks, is best for surveying South Africa's coast. This orbit will require an orbital inclination angle of 48° at an altitude of 493:2 km. It can survey the coast with passive imagers up to 35 times a day, with a 10-day eclipse period in a solar year. Furthermore, it can send and receive radio signals in the South African region for 112 solar days with a maximum revisit time of 10 hours. Lastly, a comprehensive communication link analysis was conducted, and it is concluded that 95% of the vessels in the South African coast can be intercepted. Three orbits were compared using a simulation environment developed in MATLAB using a simplified general perturbation model. Additionally, the link analysis was performed by sampling the vessels from a realistic distribution and simulating the vessel and satellite antennas. It was found that 85% of the vessels lie on the satellite's radio horizon and it is recommended to have an antenna configuration with a stronger gain towards this region. Thereafter, classical image processing techniques, that can function on board a satellite, were investigated. Images were successfully pre-processed to extract regions of interests containing vessels. These regions were refined and classi ed using a linear support vector machine that extracts eight features from candidate regions. These were combined into six new features with less interclass variance, resulting in a classification score of 71%. To conclude, this thesis presents a successful feasibility study whether vessels can be detected in the South African coast using a 6U satellite constellation. It includes a comprehensive list of recommendations on which this thesis can be improved upon.