Browsing by Subject "SKA"

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    A new systemic model for the implementation of sustainable space science and technology investment for Sub-Saharan African economies: an implementation process derived from a case study of MeerKAT and the Square Kilometre Array projects
    (2025) Mitchell, Carla; Nicolls, Frederick; Martinez, Peter
    This research develops a sustainable implementation model for African developing nations undertaking space science and technology (SST) programmes, using the MeerKAT project and the forthcoming Square Kilometre Array (SKA) as central case studies. Econometric analysis of Sub Saharan African (SSA) economies reveals that standard economic inputs namely labour, capital, and technology, are insufficient to plan for or predict growth in this context. Instead, a broader set of socio-economic variables, often overlooked in conventional models, must be considered. Panel data from 48 SSA countries informed the construction of four composite variables—access to finance, employment, education, and technology efficiency—which more accurately reflect the region's structural and cultural conditions. Findings indicate that SST investments have an inconsistent impact on labour productivity, largely due to inefficiencies in technology absorption and local capacity utilisation. In response, this research proposes a three-phase Space Science and Technology Framework (SSTIF) made up of the Impact Causality Cycle (ICC) which establishes causal links between SST investments and socio-economic outcomes, emphasising effective technology deployment. The Political Decision Matrix (PDM) which guides sustainability-oriented investment planning by evaluating socio economic benefits, as demonstrated through the MeerKAT project. A result of the PDM case study is that socio economic investment reduces project risk and improves sustainability. The Science-Driven Economic Benefit (SDEB) which model translates these insights into a practical implementation cycle, tested through a detailed application to the MeerKAT case. Together, these phases form an integrated pathway from theory to decision-making to implementation. The SKA project, as an expansion of MeerKAT, validates the framework's scalability and relevance, reinforcing the case for strategic SST investment in SSA. Ultimately, this thesis contributes a practical roadmap for policymakers—linking science infrastructure to inclusive economic development and long-term investment sustainability.
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    Assessing GridSim for modeling the global distribution of next-generation astronomy data
    (2025) Tunbridge, James K; Simmonds, Robert
    The transfer of big data between geographic locations incurs various costs that are better managed when computing resources are used efficiently. Measuring the energy used by a computing facility is a mechanism for managing computational efficiency because the energy provided to the facility can be measured and managed. The Square Kilometer Array (SKA) radio telescope will share large volumes of science-ready astronomical data with the project collaborating partners. This dissertation attempts to address the weaknesses of the GridSim simulation toolkit for the configuration of the SKA data grid. Some of the GridSim features suited for the simulation project are: a) a network extension claiming realistic network communication; b) an extendable application programming interface because of the Java programming language; c) a datagrid extension that simulates distributed data storage, and tasks for managing the distributed files; d) packet- and flow-level network extensions and e) GridSim is used in simulations of similar real-world networks e.g., the Australian GrangeNet Gigabit network. GridSim was built primarily for modeling resources and application scheduling of parallel computing and distributed computation grids, and to assess different job scheduling policies. The SKA wide area collaborative network will send data to its distributed partners who have their own network and energy-related policies. This work proposes a design to implement, in GridSim, a prototype of the end-to-end energy cost model for large scale networks, ECOFEN (Orgerie, 2015). The purpose of this work being to demonstrate the utility of the GridSim toolkit in spite of a few known problems with the software. Invalidation exercises were performed to determine the cause of lost events in a network extension simulation, and to assess the implementation of the Routing Information Protocol, in GridSim, in multiple executions of the same simulation and configuration. In this work, GridSim simulations lose events for which a solution is suggested. In addition, the work found that routing tables do not always contain matching shortest path information for multiple executions of a simulation. The implementation of the proposed design for an ECOFEN model extension in GridSim is a project for future work after one unsuccessful attempt to implement the model in GridSim. This work considered other simulation tools as potential alternatives to the GridSim toolkit, finding SimGrid to be a likely candidate. Modern computational systems are just too complex for popular software simulation tools to copy dependably which has supported a return to live network emulation testbeds for the accurate and scalable modeling of real-world systems.
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    Big Science: SKA and the next phase of astronomy in Africa
    (2013) Horrell, Jasper
    In 2012 the country celebrated the news that South Africa had won a substantial part of the bid to build the most ambitious radio astronomy array in the world - the Square Kilometer Array. This audio lecture explains the purpose and function of this massive investment in international astronomy, and its implications for the future of astronomy in South Africa. This resource is useful for anyone interested in the Square Kilometer Array and astronomy in general.
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    SKA and Meerkat: major milestones in radio astronomy
    (2012) Van der Heyden, Kurt
    Presented by: Dr Kurt van der Heyden, Department of Astronomy, University of Cape Town. This audio lecture will be of interest to astronomy enthusiasts and the general public who wish to learn more about radio astronomy and the topical issue of SKA and Meerkat.
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    The faint low-frequency radio universe in continuum: exploitation of the pre-SKA deepest survey
    (2020) Ocran, Emmanuel; Taylor, Andrew Russell
    This thesis presents a thorough and significant work on the properties of radio sources as derived from deep 610-MHz GMRT data and ancillary multi-wavelength data. The faint radio sources at 610-MHz are found out to distances such that the objects are seen as they were when the universe was less than half its current age. These data provide a first look at the faint radio sky at sensitivities that will soon be achieved by key programs on the South African MeerKAT radio telescope, and thus take a first step in the exploration of the radio universe that will be made by the Square Kilometre Array. I report deep 610-MHz GMRT observations of the EN1 field, a region of 1.86 deg2 . We achieve a nominal sensitivity of 7.1µ Jy beam−1 . From our 610 MHz mosaic image, we recover 4290 sources after accounting for multiple component sources down to a 5σ flux density limit of 35.5 µ Jy. From this data, I derive the 610 MHz source counts applying corrections for completeness, resolution bias and Eddington bias. The 610- MHz source counts show a flattening at flux densities below 1 mJy. The source counts are higher than previous observations at this frequency below this break. However, they are generally consistent with recent models of the low-frequency source population. Using ancillary multi-wavelength data in the field, I investigate the key issue of source population classification using the deepest data at an intermediate-low frequency (higher than LOFAR and lower than JVLA), where previous work has not been sensitive enough to reach the µJy population. By cross-matching against the multi-wavelength data, I identify 72% of the radio sample having reliable redshifts, of which 19% of the redshifts are based on spectroscopy. From the classification, I obtain 1685 sources as Star-Forming Galaxies (SFGs), 281 sources Radio-Quiet (RQ) and 339 sources Radio-Loud (RL) Active Galactic Nuclei (AGN) for the sub-sample with redshifts and at least one multi-wavelength AGN diagnostic. SFGs are mostly low-power radio sources, i.e L610 MHz < 1025 W Hz−1 while RQ AGN and RL AGN have radio powers L610 MHz > 1025 W Hz−1 . From cross-matching my sample with other radio surveys (GMRT at 325-MHz, FIRST at 1.4-GHz and JVLA at 5-GHz), I obtain the median spectral index from 325-MHz to 610-MHz to be −0.80 ± 0.29, 610-MHz to 1.4-GHz to be −0.83 ± 0.31 and 1.4-GHz to 5-GHz to be −1.12 ± 0.15. The main result is that the median spectral index appears to steepen at the highest frequency. With the above catalogue in hand, I use the non-parametric V/Vmax test and the radio luminosity function to investigate the cosmic evolution of different source populations. I study SFGs and derive their IR-radio correlation and luminosity function as a function of redshift. By integrating the evolving SFG luminosity functions I also derive the cosmic star formation rate density out to z = 1.5. I address the long standing question about the origin of radio emission in RQ AGN. I compare the star formation rate (SFR) derived from their far-infrared luminosity, as traced by Herschel, with the SFR computed from their radio emission. I find evidence that the main contribution to the radio emission of RQ AGN is the star formation activity in their host galaxies. At high luminosities, however, both SFGs and 1 RQ AGN display a radio excess when comparing radio and infrared star formation rates. The vast majority of our sample lie along the SFR − M? ”main sequence” at all redshifts when using infrared star formation rates. This result opens the possibility of using the radio band to estimate the SFR even in the hosts of bright AGN where the optical-to-mid-infrared emission can be dominated by the AGN. I investigate the evolution of radio AGN out to z ∼ 1.5 with continuous models of pure density and pure luminosity evolution with Φ? ∝ ( 1 + z)(2.25±0.38)−(0.63±0.35)z and L610 MHz ∝ ( 1 + z)(3.45±0.53)−(0.55±0.29)z respectively. I also constrain the evolution of RQ AGN and RL AGN separately with a continuous model of pure luminosity evolution. For the RQ and RL AGN, we find a fairly mild evolution with redshift best fitted by pure luminosity evolution with L610 MHz ∝ ( 1 + z)(2.81±0.43)−(0.57±0.30)z for RQ AGN and L610 MHz ∝ ( 1 + z)(3.58±0.54)−(0.56±0.29)z for RL AGN. The results reveal that the 610 MHz radio AGN population thus comprises two differently evolving populations whose radio emission is mostly SF-driven or AGN-driven respectively. Finally, I probe the infrared-radio correlation and radio spectral indices of the faint radio population using stacking. I stack infrared sources in the EN1 field using the MIPS 24 micron mid-infrared survey and radio surveys created at 325 MHz, 610 MHz and 1.4 GHz. The stacking experiment shows a variation in the absolute strength of the infrared-radio correlation between these three different frequencies and the MIPS 24 micron band. I find tentative evidence of a small deviation from the correlation at the faintest infrared flux densities. The stacked radio spectral index analyses reveal that the majority of the median stacked sources exhibit steep spectra, with a spectral index that steepens with frequency between α 325 610 and α 610 1400. This work is particularly useful to pave the way for upcoming radio surveys with SKA pathfinders and precursors.