Dish Verification Antenna – 1 Project NRC - Herzberg Gary Hovey 18 November 2013

2 SKA Precursor Antennas Allan Telescope ArrayMeerKat ASKAP Dish Verification Antenna 1

3 Why Composites Superior performance and cost competitive with metal Low thermal expansion materials. Evolving material and manufacturing technologies Large membrane surfaces possible. Can tailor material to cost or performance requirement. Highly accurate precision surface - Stable over gravity, wind, and temperature. A stable and predictable radiation pattern - Needed to ensure dynamic range goal of 1 part in 10 million are met.

4 History 2005 Began investigation composites reflectors Built two 10m symmetric dishes

5 MK 1 Surface Accuracy Max. Deviations + 4mm - 3mm RMS 1.2 mm

6 Max. Deviations + 2.5mm - 1.7mm RMS 0.54 mm MK 2 Surface Accuracy

7 Dish Verification Antenna Objectives Demonstrate performance and manufacturing advantages of composites. Maintain a cost competitive design that can be mass produced. Demonstrate mechanical structural innovations yield high performance at competitive cost. 7 of 13

8 The main design elements are: 15m Gregorian offset feed-high optics Unblocked aperture Large space for feeds Stiffer, lower cost than feed-low DVA-1 Antenna Design Description Molded single piece rim- supported composite reflectors Tubular backup structure Tubular composite feedlegs Pedestal-type mount allows small offset to elevation axis Deep truss backup structure with central pocket for pedestal mount Central compliant connector allows movement in wind without distortion

9 DVA-1 Mount Components

10 DVA-1 Features Gregorian Shaped Optics - maximize area and minimize noise, (A eff /T sys ) Cost effective but robust mount design - Optimized feed support that is stiff, light, and low cost - Simple and stiff back support structure Rim supported composite reflectors - Carbon fibre low thermal expansion materials, 1/8 of aluminium - Large shaped membrane surfaces possible - Can tailor material to cost or performance requirement - Highly accurate precision surface, stable over gravity, wind, and temperature - A stable and predictable radiation pattern, necessary to ensuring dynamic range goal of 1 part in 10 million Secondary focus provides large space for receivers

11 DVA-1 Construction

12 Pedestal and Reflector on Site

13 DVA-1 Status and Future Work Status Critical Design Review completed June 2012 Construction underway, completion June 2013 Testing to begin in Mechanical verification, static and dynamic - On-sky RF characterization - Feed testbed; EMSS SPF, NRC & CSIRO PAFs, others Future work Investigate design and cost/performance improvements Optimize design for cost and mass production Update mass production study, memo 116