Memo 106 Composite Applications for Radio Telescopes ( CART ) : The Mk 2 Reflector Results

This document describes the design, fabrication and measurement results of the CART Mk2 10 m radio reflector prototype constructed at the Dominion Radio Astrophysical Observatory. Introduction The Composite Applications for Radio Telescopes (CART) project at the Herzberg Institute of Astrophysics’ (HIA) Dominion Radio Astrophysical Observatory (DRAO) in Penticton Canada is an ongoing effort to investigate the application of composite materials to radio telescope structures to provide cost effective collecting area for the Square Kilometer Array (SKA). The first phase of the project is focused on reflectors as they are seen to have the highest potential for cost/performance gains from the application of composite materials. The first 10-m prototype reflector was completed in the summer of 2007. The result was a light (~1000 kg), stiff reflector with a surface accuracy of 1.2 mm RMS. While the RMS value of the surface was low the deviations were not uniformly distributed and some large scale deviations existed. In addition many lessons were learned during the construction process and there were seen to be opportunities for improvement. The design of a second reflector, dubbed the Mk2, was initiated immediately after completion of the first with the focus on improvements in surface accuracy, structural design and manufacturability. The Mk1 prototype proved the feasibility of the concept. On the Mk2, design and process were further optimized, which will enable designers to develop SKA specific reflectors with a high degree of confidence. The CART Mk 2 reflector is an improvement on the Mk1 in all aspects. The change of design approach to separately fabricated beams and hub bonded to a monolithic surface and rim improved manufacturability and yielded a more accurate surface.