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Pinelands, South Africa

Sharpe C.,SKA South Africa
Proceedings of the International Astronautical Congress, IAC | Year: 2014

The scope of this paper investigates the socio economic and political issues that enhance and inhibit technological, space and general scientic advancement in African nations. In addition to high-level political factors, within Africa there are unique social, traditional and psychological factors, which come into play at a business and even political level. This paper presents research into the economic, legal and policy issues and benefits relating to space projects and collaboration within the African context, as well as identifying and assessing the major risks and changes underway. In addition, a commentary on the African Union and its strategies moving forward as they relate to space. Socio economic factors can drive, enhance or inhibit development in space, technology and science in African nations. Some important considerations include the level to which technology can be adopted, human capital development capacity, security requirements, available investment and political stability. Equally, political agendas and motivations can grow or stunt technological, space and scientific advancement. Political agends include the pursuit of programmes for national pride, regional dominance and defense, science and academic advancement, development of a private and sustainable commercial industry or the development of national space infrastructure for national social benefit, for example, remote sensing capability and communications. Funding and Sustainability are largely dependent on the motivational push factors. Copyright ©2014 by the International Astronautical Federation. All rights reserved.

De Witt A.,Hartebeesthoek Radio Astronomy Observatory | Bietenholz M.,Hartebeesthoek Radio Astronomy Observatory | Bietenholz M.,York University | Booth R.,SKA South Africa | Gaylard M.,Hartebeesthoek Radio Astronomy Observatory
Monthly Notices of the Royal Astronomical Society | Year: 2014

Herbig-Haro objects are regions of shocked gas and dust which are produced when collimated outflows from a protostar interact with the surrounding dense gas. They have many similarities to supernova remnants which are interacting with molecular clouds. 1720-MHz OH masers have been identified towards a number of interacting supernova remnants. Observations and models indicate that these masers are shock excited and are produced behind C-type shocks. If conditions behind the shock fronts of Herbig-Haro objects are similarly able to support 1720-MHz OH masers they could be a useful diagnostic tool for star formation. We therefore searched for 1720-MHz OH maser emission towards a sample of 97 Herbig-Haro objects using the Green Bank Radio Telescope.We detected 1720-MHz OH lines in emission in 17 of them, but neither their spectral signature nor follow-up observations with the Very Large Array showed any conclusive evidence of maser emission. We conclude that the emission detected from our single-dish observations must be extended and most likely originates from thermal or quasi-thermal excitation processes. We also investigated the properties of Herbig-Haro shocks more closely and conclude that despite the overall similarities to supernova remnants, the conditions required for maser emission, in particular a sufficient velocity-coherent column density, are not likely to occur in Herbig-Haro objects © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Merry B.,SKA South Africa
Astronomy and Computing | Year: 2016

Convolutional gridding is a processor-intensive step in interferometric imaging. While it is possible to use graphics processing units (GPUs) to accelerate this operation, existing methods use only a fraction of the available flops. We apply thread coarsening to improve the efficiency of an existing algorithm, and observe performance gains of up to 3.2× for single-polarization gridding and 1.9× for quad-polarization gridding on a GeForce GTX 980, and smaller but still significant gains on a Radeon R9 290X. © 2016 Elsevier B.V.

Schwardt L.C.,SKA South Africa
Proceedings of the 2012 International Conference on Electromagnetics in Advanced Applications, ICEAA'12 | Year: 2012

Compressed sensing (CS) provides the theory behind the CLEAN deconvolution step found in aperture synthesis imaging in radio astronomy and suggests many new algorithms for it. A few CS algorithms, including greedy methods such as Orthogonal Matching Pursuit (OMP) and convex relaxation methods based on Basis Pursuit (BP), are evaluated on a small dataset produced by the KAT-7 array. The new algorithms outperform a standard CLEAN algorithm on this snapshot imaging task. © 2012 IEEE.

Merry B.,SKA South Africa
Monthly Notices of the Royal Astronomical Society | Year: 2015

Wprojection is a commonly used approach to allow interferometric imaging to be accelerated by fast Fourier transforms, but it can require a huge amount of storage for convolution kernels. The kernels are not separable, but we show that they can be closely approximated by separable kernels. The error scales with the fourth power of the field of view, and so is small enough to be ignored at mid- to high frequencies. We also show that hybrid imaging algorithms combining Wprojection with either faceting, snapshotting, or Wstacking allow the error to be made arbitrarily small, making the approximation suitable even for high-resolution wide-field instruments. © 2015 The Authors. Published by Oxford University Press.

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