61-element adaptive optical system for 1.2-m telescope of Yunnan Observatory

Abstract

A 61-element adaptive optical system is being built for the 1.2m telescope of Yannan Observatory for astronomical observation in visible range. It consists of a 61-element deformable mirror, a fast steering mirror, a Hartmann-Shack wavefront sensor with 8 by 8 subapertures, a parallel digital processor and control electronics. The arrangement of subapertures is square matched with triable arrangement of actuators. The detector of H-S sensor is intensified CCD with frame rate of 838 Hz. The effective bandwidth is about 50 Hz for the DM control loop. A quadrant tracking detector consisting of 4 photon counting PMT detectors is used in the control loop of fast steering mirror. This system has been tested. The basic configuration and the preliminary results of the test are reported in this paper. This system will be integrated with a laser guide star system, in which a frequency doubling Nd:YAG pumped by laser diode array is used for producing a Rayleigh guide star. The pulse energy is 100 mJ with frequency of 838 Hz. A separated optics will be used to project the laser beam. The estimated specifications of this Rayleigh guide star system will be described in this paper too.