The Hydrogen and Real-time Analysis eXperiment (HIRAX), led from UKZN, has deployed two new prototype telescope dish designs, one aluminium and the other fibreglass, at the South African Radio Astronomy Observatory (SARAO) Hartebeesthoek site near Johannesburg.
The fibreglass dish was designed and manufactured by MMS Technology in Pretoria, and the aluminium one through a partnership between NJV Consulting and Rebcon in Durban. Funding for the prototype dishes was provided by UKZN and the Department of Science and Innovation through the National Research Foundation.
This milestone marks the successful completion of months of collaboration between the HIRAX project, and local engineering and manufacturing firms, and brings HIRAX one step closer to the installation of the full 1 024-dish array in a compact configuration on the HIRAX main site in the Karoo. This telescope will enable research on the evolution of dark energy through hydrogen intensity mapping, and on transient radio sources such as fast radio bursts (FRBs) and pulsars. Dark energy is a mysterious force that scientists believe is acting against gravity to cause accelerated expansion of the universe. FRBs are millisecond extragalactic flashes in the sky of unknown origin.
Collaboration on the dish design started at the beginning of 2018 with the aim of defining final dish requirements for the project. The design of these 6-metre dishes has strict tolerances on the shape, surface accuracy, and receiver position. The mechanical design also allows for the manual repointing of the dishes every few months, enabling the instrument to map about a third of the sky over a five-year period while minimising costs by eliminating the need for active drive mechanisms.
HIRAX will instrument and analyse the two new prototype dishes over the next few months to develop the final requirements for an open tender for the first 256 dishes to be installed at the main site in the Karoo. SARAO Managing Director Rob Adam said: ‘After the successful testing at our Hartebeesthoek site we are looking forward to hosting HIRAX at our site in the Karoo. We always had the idea that the SKA site would prove to be an attractor for other leading-edge global astronomy projects and this is turning out to be the case.’
This installation could not have been achieved without the support of the professional staff at the SARAO Hartebeesthoek site. Their experience and domain knowledge have been harnessed to provide support and technical assistance for various aspects of the HIRAX project. All of the current antenna prototyping work is being conducted at the SARAO Hartebeesthoek observatory site, and SARAO staff at the site have assisted with the installation and testing of the dishes, and the execution of the associated civil infrastructure work.
Professor Cynthia Chiang, HIRAX Instrumentation Lead, Professor at McGill University and Fractional Professor at UKZN, said: ‘In order to deliver high-precision science, HIRAX has stringent specifications that require custom-built telescope dishes. The two new dishes from MMS and Rebcon represent a significant milestone toward achieving HIRAX’s goals, and they will be crucial for informing the final instrument design.’ Both MMS and the NJV/Rebcon collaboration worked hand-in-hand with the HIRAX project to produce prototype designs that will inform final dish requirements for the HIRAX project.
The MMS dish was installed in August 2019 by their team led by director Heinrich Bauermeister and consists of a fine aluminium mesh embedded in fibreglass. The MMS dish can tilt in elevation 30 degrees either side of zenith. Bauermeister said: ‘Designing and manufacturing this dish was a serious trade-off between performance and cost. For this reason, the mount was kept as low and simple as possible and the dish itself as thin as possible without compromising too much on performance. The single piece composite material dish does not need any post-manufacturing setup, and the mount is low enough to facilitate easy adjustment of the dish elevation by one person.’
The NJV/Rebcon dish was installed in October 2019 by their team, led by Warren Butler, who indicated that, ‘team input of the design development was dynamic to incorporate practical solutions regarding assembly/disassembly, transportation, ease of installation on site in a remote location and serviceability of the prototype once installed.
‘The design intent was realised by a form of laser-cut profiled aluminium elements which provided the parabolic accuracy the project required. Appropriate skills and collaboration have resulted in a practical buildable and easily erectable structure, that is fully recyclable,’ he added.
The dish is made of aluminium mesh with an aluminium backing structure. Furthermore, it is fixed in azimuth and can tilt in elevation down to the horizon. Linda Ness, Director of NJV Consulting (Pty) Ltd remarked, ‘Collaboration between designer and fabricator on unusual engineering fabrications at conceptual stage is invaluable, and this was one of those great opportunities. Early interaction like this allows cross-over of skills between the two companies, who have worked together for many years. With multiple units in mind, material optimisation, repeat fabrication and erection are key. Detailed structural modelling analyses and finer stress design work could then be downstream from wholly considered upfront thinking, sketching and deliberation together with the scientists.’
The HIRAX team hopes that these partnerships are the first of many to come between the project and South African industry. In addition to collaborating on HIRAX dish hardware, the project hopes to manufacture some of its subsystems in South Africa, work with local technology companies to develop big data analysis tools, and hire local labour for the deployment of the instrument in the Karoo. Principal Investigator of the project, UKZN’s Professor Kavilan Moodley noted, ‘Through these and future collaborations with industry and the scientific community, the project endeavours to build technical capacity nationally as South Africa increases its radio astronomy portfolio through MeerKAT and the development towards the Square Kilometre Array (SKA).’
HIRAX is led by UKZN and hosted as a guest instrument by SARAO, the national facility mandated to support the development and operation of radio astronomy instruments in South Africa. It is managed by a consortium which includes five additional South African institutions: the African Institute for Mathematical Sciences, Durban University of Technology, Rhodes University, and the Universities of Cape Town and the Western Cape.
Seventeen international partners currently provide significant financial and in-kind contributions to the project. They include: AIMS-Rwanda, Botswana International University of Science and Technology, Carnegie Mellon University, École Polytechnique Fédérale de Lausanne, ETH-Zurich, Inter-University Centre for Astronomy and Astrophysics, McGill University, NASA Jet Propulsion Laboratory, Oxford University, Perimeter Institute for Theoretical Physics, University of British Columbia, University of Geneva, Universite Paris Diderot – Paris 7, University of Toronto, University of Wisconsin-Madison, West Virginia University and Yale University.
Words: Malishca Perumal