Servo System for GMRT Antennas

Introduction

The Giant Meterwave Radio Telescope, an aperture synthesis array consisting of 30 fully steerable parabolic dishes of 45-metre diameter each. The motion of these giant antennas needs to be controlled by a precession control system. Pointing of the antennas should be accurate i.e. the radio source, antenna focused and the antenna center should be aligned. The GMRT servo system has designed with three nested control loops to achieve the pointing accuracy of (1 or 2) arc minutes RMS for wind speed less than 20 km/ph. Because of high weight alt-azimuth mount is the most favourable approach for positioning the dish antenna. Here the elevation axis sits on the azimuth drive. The elevation drive moves antenna up and down directions while azimuth drives moves antenna in clockwise & counter-clockwise direction. Hence enabling the antenna to point anywhere in the sky.