Design and simulation of 6.2m wide-field telescope for spectroscopic survey

A wide-field optical IR spectroscopic survey telescope is designed to deliver spectra of several millions of astronomical sources. The baseline design of the telescope is a 6.2m segmented primary mirror with 19 hexagonal segments, 84 edge sensors, & 57 soft actuators. The telescope is designed to provide a 2.5deg FOV achieved through a system of wide field corrector lenses with a design residual <0.2". Also, it delivers an f/3.6 beam suitable for directly feeding optical fibres. A mechanical concept of the telescope is designed with a truss-based mirror cell to support the segmented primary mirror and keep deformation to a minimum. As the primary mirror is segmented, the deformation due to different disturbances like wind, vibration and thermal effects must be corrected to a nanometer accuracy to make it act like a monolithic primary mirror. A simulation tool, codeSMT, is built using the state-space model to incorporate dynamic wind disturbance from the IAO Hanle site and vibration effects. A detailed parameter sensitivity & error multiplier analysis is performed numerically using this tool. This paper presents an Optical, Mechanical and Active Control system design of telescope.