Department of Computer Science

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Browsing Department of Computer Science by Subject "Astronomy -- Observations"

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    Solidifying what is known about calibration artefacts and the development of an educational tool to assist in the teaching of interferometric imaging
    (Stellenbosch : Stellenbosch University, 2023-03) Jackson, Jason Peter; Grobler, Trienko; Ludick, Danie; Stellenbosch University. Faculty of Science. Dept. of Computer Science.
    ENGLISH ABSTRACT: Radio interferometers are arrays of radio antennas that work together to capture celestial radio emission. Imaging involves transforming the raw measurements made by these so-called interferometers into images of the radio sky. The first contribution of this thesis is the creation of an educational tool that utilizes the Transient Array Radio Telescope (TART). This tool can be used to teach radio interferometric imaging to undergraduate and postgraduate students. Calibration is the act of trying to correct for the effects that may have interfered with the celestial radio emission that an interferometer receives. Calibration artefacts or systematics are inadvertently created when we calibrate our instrument. Calibrating with an incomplete sky model in particular can create artefacts called ghosts. Ghosts are spurious sources that do not truly exist. A second contribution of the thesis is the creation of a scientific tool with which calibration artefacts can be studied. This tool is then used to investigate what artefacts form when a single extended source is only partially modelled (with a point source model). The results of this study show that for the aforementioned extended use-case ghosts become extended sources themselves. They also alter the original extended source in various ways. The original source takes on the same flux scale as the source in the calibration model and its profile changes; it becomes more point-like. The shorter baselines are also more severely affected than the longer baselines are and in contrast to previous studies for this particular setup the number of antennas does not impact the severity of the artefacts which are created.