Developement of Metal Mirror Telescope Technology

2018 Fiscal Year Final Research Report

• Project/Area Number: 15K13467
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Astronomy
• Research Institution: National Astronomical Observatory of Japan
• Principal Investigator: UKITA Nobuharu 国立天文台, ハワイ観測所, 特別客員研究員 (20184989)
• Research Collaborator: MATSUNAGA Noriyuki ; IZUMIURA Hideyuki ; KAMBE Eiji ; YANAGISAWA Kenshi ; KURODA Daisuke ; TSUTSUI Hironori
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: 天体望遠鏡 / 金属鏡 / 金属研磨

Outline of Final Research Achievements

Key technologies to realize a metal mirror telescope system for astronomical spectroscopy observations have been studied and developed. High precision(2μm rms) and lightweight(17 kg) aluminum panels made with an NC machine for a 8-segmented primary mirror(a diameter of 2.1 m and focal length of 3.5 m) have polished manually using a polishing-pad, water-resistant sandpaper(＃2000-5000), and abrasive(3μm). A mirror surface accuracy of 0.5 μm rms (an image size of 10 arcseconds ) was obtained. It is about three times worse than an original target value of 3 arcseconds, which shall be challenged in the future. In the final stage, buffing was performed to obtain a reflectance of 60 %. Test observations were successfully made with a low dispersion spectrometer, using an optical fiber link to feed light from the prime focus.

Free Research Field

天文学

Academic Significance and Societal Importance of the Research Achievements

地上から天体観測をする限り望遠鏡の分解能は大気の揺らぎで制限されるので、シャープな星像や上質な金属光沢の反射面にこだわらない望遠鏡システムを検討した。これまであまり試みられてこなかった金属鏡を用いた分光観測専用の天体望遠鏡システム構築のための要素技術を開発した。これらの開発研究により大学の研究室規模でも軽量&低価格&低運用負荷の口径2mクラスの分光専用望遠鏡を短工期で実現する技術的見通しが得られた。