On May 11, 2017, the large telescope design team of the Photoelectric Detection Research Department in CIOMP accomplished the 2m SiC adaptive telescope’s integrated testing. Two months later, the telescope had been mounted onto the test tower to align with the Coude optical system and cooperated with the adaptive optics system. Then, the telescope got its first light on July 16. Although the telescope worked in a bright background influenced by the city lights, and suffered from strong atmospheric turbulence, the observation result showed that the performance of the telescope is better than two times of the diffraction limit. It was helpful for the future telescope installation and test outdoor.

                                                                               2M telescope(Photo by CIOMP)

                                            Solar image corrected by adaptive optical system (Photo by CIOMP)

SiC ceramic is applied as the primary mirror of 2m telescope, which possesses high specific stiffness and thermal conductivity. The CAS Key Laboratory of Optics System Advanced Manufacturing Technology of CIOMP have made significant breakthrough in some core technologies, such as high-precision gel-casting, drying without cracks, stress-less reaction joining and vaccum sintering. And 2m diameter SiC primary mirror have been prepared, which is the maximum aperture SiC mirror via integral forming currently in China. By taking advanced multi-mold manufacturing technique which combined with Stress Lap and MRF (magnetorheological finishing), the final surface figure of the 2m SiC primary mirror can achieve less than λ/42. To accommodate the high stiffness and high thermal expansion coefficient of the primary mirror, the Kinematic principle of flexible support system was developed, which can ensure the stability the supporting force, and reduce the effects of temperature. The mirror surface figure under support is better than λ / 40. Furthermore, in order to enlarge the bandwidth in precision tracking control, the mount adopts the self-developed large double rows contact angular ball bearing. And use of the advanced control strategy based on adaptive structure filtering and acceleration feedback combined with vector control technology is used to achieve the tracking accuracy of 0.04 ″(RMS) of solar tracking. The self-developed 349 unit deformation mirror adaptive optical system adopts multi-input and multi-output real-time parallel data processing technology, and the system correction frequency reaches 2000Hz, which has obtained a good correction effect. It is the largest adaptive optical system in china.

The successful development and observation of 2m SiC adaptive telescope is the result of years of technical innovation supported by CIOMP, and it is also the result of years of efforts of the "large telescope" team and the material and manufacturing team of the CAS Key Laboratory of Optics System Advanced Manufacturing Technology of CIOMP. For the subsequent 4m or larger telescope, it verifies the key technologies, cultivates young talents, and accumulates experience.