Developement of Metal Mirror Telescope Technology

Research Project

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
Project Status	Completed (Fiscal Year 2018)
Budget Amount *help	¥3,900,000 (Direct Cost: ¥3,000,000、Indirect Cost: ¥900,000) Fiscal Year 2017: ¥260,000 (Direct Cost: ¥200,000、Indirect Cost: ¥60,000) Fiscal Year 2016: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000) Fiscal Year 2015: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
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.
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。