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27-07-2007
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Prototype composite dishes at HartRAO, South Africa (left) and HIA, Canada (right) .

Submitter: Colin Greenwood
Description: One of the ‘Grand Challenges’ facing the radio astronomy community is to build large collecting areas with low cost, high performance reflectors. A number of SKA Pathfinder Telescopes are applying innovative materials and fabrication techniques to address this challenge, for example: (left) the 15m prototype dish newly erected at Hartebeesthoek Radio Astronomy Observatory (HartRAO), South Africa, and (right) the 10m prototype dish under construction at The Herzberg Institute of Astrophysics (HIA), Canada.

Reduction of the per-unit-area cost of dish antennas for SKA and other applications is a primary goal of the South African MeerKAT project. The prototype 15-metre dish at HartRAO has been fabricated using composite materials to calibrate the cost function for this fabrication technique, and test its performance. The dish and its supporting foundations and pedestal, dubbed the XDM (eXperimental Design Model), were constructed in five months by the contractor IST Dynamics in conjunction with composite specialist company MMS. Innovations in this design include the one-piece dish moulding, minimal backing structure, and an embedded reflective surface. An illustrated chronology of the project can be viewed at www.hartrao.ac.za/xdm. People in the picture (L to R): Justin Jonas (Project Scientist), Roy Booth (Director, HartRAO), George Nicolson (SKA-SA), Mike Gaylard (HartRAO).

The Composite Applications to Radio Telescopes (CART) 10m prototype composite reflector under construction at HIA is pictured on the mould prior to vacuum bagging for infusion. The dish surface, rim and support structure are to be moulded in one piece. The goal of the prototype is to prove the concept of on-site construction of composite reflectors for the SKA. Mechanical, and radio frequency performance, will be measured to validate computer models and manufacturing costs tracked to verify cost projections. The reflector has been successfully infused and is scheduled to be mounted on a refurbished ex-VLBI pedestal in late August 2007.
Copyright: Richard Schilizzi (right) and Peter Dewdney (left).
 
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