Opto-mechanical design, analysis and economical manufacture of a large aperture LIDAR receiver telescope

Abstract

Aryabhatta Research Institute of Observational Sciences (ARIES) at Nainital (29° 22’ N, 79° 27’ E, 1950 m amsl) is located in the central Himalayan region. Taking benefit of its pristine geographical location away from major urban pollution a LIDAR system was planned at this location to study the dynamics of atmosphere. Optical design analysis of LIDAR receiver telescope with backend detection optics was carried out in ZEMAX - EE simulation package to optimize system parameters. A concave mirror of 840 mm diameter was used as primary mirror to develop a large aperture LIDAR receiver telescope for receiving back-scattered photons from atmosphere. Mirror was housed in a simple three piece mirror cell manufactured precisely and economically from cast aluminium alloy 535.0 by Lost - Foam casting process. Mirror was kept floating at 18 points on axial supports designed, analyzed and manufactured for maintaining the optical quality of telescope. Solid modeling and deflection analysis of the axial supports confirmed that deflection due to mirror weight was within 10 µ whose effect on degradation of optical parameters was analyzed and found quite negligible. Key words: Telescope, LIDAR, lost - foam casting (LFC), axial supports.