LAMOST子镜镀膜研究进展

对大口径光学/红外天文望远镜而言,为保障其稳定高效运行,镜面镀膜是重要的维护环节之一.镀膜质量的好坏直接影响镜面光学反射率的高低,也严重影响到天文望远镜的成像质量、观测效率.国家重大科技基础设施—大天区面积多目标光纤光谱天文望远镜(Large Sky Area Multi-Object Fiber Spectroscopic Telescope, LAMOST,又名郭守敬望远镜)自2009年6月通过国家竣工验收并逐步投入巡天观测,目前已进入第2个5 yr巡天计划阶段,取得近两千万的光谱产出和大批高显示度的科学成果. LAMOST共拥有24块施密特改正镜子镜和37块球面主镜子镜,为了确保在野外恶劣观测环境下镜面反射率维持在较高水平,每年要对大批子镜进行镀膜.主要介绍了镀膜需求、镀膜设备,并基于大量实验和多年的完善探索出一套可行的镀膜工艺流程,确保了LAMOST子镜极高的镀膜质量.镀膜后子镜平均反射率高达90%以上,满足了LAMOST光谱巡天的镜面反射率要求.

Research Progress of LAMOST Sub-mirror Coating

For large-aperture optical/infrared astronomical telescopes, mirror coating is one of the most important maintenance technologies to ensure their stable and efficient operation. The quality of the coating directly affects the optical reflectivity of the mirror, and further the imaging quality and observation efficiency (throughput) of the astronomical telescope. LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope), the first astronomical national major scientific and technological infrastructure, has passed the national completion acceptance and gradually put into survey observation since June 2009. At present, it has entered the second five-year regular sky survey stage, and already acquired about twenty million spectral products and achieved a lot of important scientific discoveries. LAMOST has 24 Schmidt corrector (MA) sub-mirrors and 37 spherical primary (MB) sub-mirrors. In order to maintain LAMOST mirror reflectivity and further LAMOST spectral efficiency at the highest level in the wild observatory environment, all sub-mirrors are re-coated every year or every two years. This paper mainly introduces the LAMOST coating requirements and actual implementation progress of the latest coating technology optimization. Based on a lot of experiments and improvements, a set of feasible coating process is finally explored and mastered during the past ten years with the optimal quality of the LAMOST sub-mirror coating. The average reflectivity of all the sub-mirrors over the visible waveband after coating is more than 90%, which satisfies the requirements of the mirror reflectivity of LAMOST spectroscopic survey.