Header for SPIE use The Large Adaptive Reflector: A 200-m diameter, wideband, cm-m wave radio telescope Brent Carlson a , Luc Bauwens b , Leonid Belostotski c , Elizabeth Cannon d , Ya-Ying Chang e , Xiaohui Deng b , Peter Dewdney a , Joeleff Fitzsimmons f , David Halliday g , Kai Kürschner e , Gerard Lachapelle d , David Lo g , Pedram Mousavi h , Meyer Nahon i , Lot Shafai h , Sigfried F. Stiemer e , Russell Taylor j , Bruce Veidt a a National Research Council Canada, Herzberg Institute of Astrophysics, P.O. Box 248, Penticton, B.C. Canada V2A 6K3 b Dept. of Mech. Eng., Univ. of Calgary, 2500 University Dr. NW, Calgary, Alberta, Canada, T2N 1N4 c Dept. of Electrical & Computer Eng., Univ. of Alberta, Edmonton, Alberta, Canada, T6G 2G7 d Dept. of Geomatics, Univ. of Calgary, 2500 University Dr. NW, Calgary, Alberta, Canada, T2N 1N4 e Dept. of Civil Engineering, Faculty of Applied Science, Univ. of British Columbia, 2053-2324 Main Mall, Vancouver, B.C. Canada V6T 1Z4 f National Research Council Canada, Herzberg Institute of Astrophysics, 5071 Saanich Road West, Victoria, B.C. Canada V8X 4M6 g AGRA Coast Limited, 1515 Kingsway Ave. Port Coquitlam, B.C. Canada V3C 1S2 h Dept. of Electrical & Computer Eng., Univ. of Manitoba, Winnipeg, Man., Canada, R3T 5V6 i Dept. of Mech. Engineering, Univ. of Victoria, P.O. Box 3055, Victoria, B.C. Canada V8W 3P6 j Dept. of Phys. & Astr., Univ. of Calgary, 2500 University Dr. NW, Calgary, Alberta, Canada, T2N 1N4 ABSTRACT The Large Adaptive Reflector (LAR) is a concept for a low-cost, large aperture, wideband, radio telescope, designed to operate over the wavelength range from 2 m to 1.4 cm. It consists of a 200-m diameter actuated-surface parabolic reflector with a focal length of 500 m, mounted flat on the ground. The feed is held in place by a tension-structure, consisting of three or more tethers tensioned by the lift of a large, helium-filled aerostata stiff structure that effectively resists wind forces. The telescope is steered by simultaneously changing the lengths of the tethers with winches (thus the position of the feed) and by modifying the shape of the reflector. At all times the reflector configuration is that of an offset parabolic antenna, with the capability to point anywhere in the sky above ~15º Elevation Angle. At mid-range wavelengths, the feed is a multi-beam prime-focus phased array, about 5 m diameter; at meter wavelengths, it is a single-beam phased array of up to 10 m diameter. Simulations have shown that in operating wind conditions (10 m / s average speed with 2.5 m / s gusts), the position of the feed platform can be stabilized to within a few cm over time scales of ~20 s. Research indicates that the telescope concept is feasible and that an order of magnitude improvement in cost per m 2 of collecting area over traditional designs of large parabolic antennas can be achieved. Keywords: radio telescope, phased array, reflector panel, space frame, actuator, aerostat, tether, parabolic, SKA. 1. INTRODUCTION An international consortium of radio astronomers and engineers have agreed to investigate technologies to build the Square Kilometer Array (SKA), a cm-to-m wave radio telescope for the next generation of investigation into cosmic phenomena. A looming “sensitivity barrier” will prevent current telescopes from making much deeper inroads at these wavelengths, particularly in studies of the early universe. The aim of the SKA project is to increase the collecting area, the fundamental factor governing sensitivity, over existing telescopes by two orders of magnitude. The Large Adaptive Reflector (LAR) is a concept put forward by a group led by the National Research Council of Canada and supported by university and industry collaborators. 1.,2.,3. The LAR concept is well suited to meeting the key SKA requirements of 150 MHz to 22 GHz operation, one square degree field of view at mid-range wavelengths, and sky coverage of about half the sky. So far, the LAR is the only future radio telescope concept that is being designed to operate from wavelengths of several meters to 1.4 cm.