Innovations in science and technology with the LAMOST

Abstract

<p indent=0mm>The LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) is a special reflecting Schmidt telescope with an effective aperture of <sc>3.6–4.9 m,</sc> a focal length of <sc>20 m</sc> and a field of view (FOV) of 5 degrees. Its optical system is designed with three major components, namely Ma, Mb, and a focal surface. The correcting mirror Ma <sc>(5.72 m</sc>×<sc>4.40 m)</sc> is made up of 24 hexagonal plane sub-mirrors; the primary mirror Mb <sc>(6.67 m</sc>×<sc>6.05 m)</sc> has 37 hexagonal spherical sub-mirrors. In the process of observation, Ma is capable of synchronously changing its specific aspherical figure to give excellent optical quality. The focal surface has 4000 precisely positioned fibers connected to 16 spectrographs with a distributive parallel-controllable fiber positioning system, thus LAMOST can observe up to 4000 objects simultaneously. LAMOST adopts an innovative active optics technique, achieved by changing its mirror surface continuously to achieve a series different reflecting Schmidt systems. This novel concept and unique design broke through the bottleneck of former astronomical instruments that could not combine a large clear aperture with a wide FOV. The new active optics system creatively developed in LAMOST is used for correcting Ma, which is a combination of the thin deformable mirror active and segmented active optics. The distributive parallel-controllable fiber positioning technique is also an advanced technology which solved the problem of simultaneously and accurately locating 4000 astronomical objects. LAMOST opened up the ability to have a large scale optical fiber spectroscopic sky survey with as many as 4000 optical fibers. The LAMOST project was approved as a national major science project by the Chinese government in April 1997. LAMOST started to be constructed in August 2001. The installation of all LAMOST systems was completed on time in August 2008. The telescope is located at the Xinglong Station of National Astronomical Observatories, Chinese Academy of Sciences (NAOC). After the two years commissioning period starting in 2009, a pilot spectroscopic survey was performed using LAMOST from October 2011 to June 2012. The regular survey of LAMOST began in September 2012. Up to June 2020, LAMOST has obtained more than 17 million spectra of celestial objects, in which the stellar parameters of 7.7 million stars were obtained. The data archive of LAMOST would be an exceedingly valuable resource for a variety of astronomical fields. It would be used as a “digital Galaxy” to understand our Galaxy. As the telescope of the highest spectrum acquiring rate, LAMOST breaks through the “bottleneck” of spectroscopic observation in astronomy, becoming the most powerful spectroscopic survey telescope for researches of wide field and large sample astronomy. LAMOST yields a unique data set of more than 10 million stellar spectra and makes a substantial contribution to the study of stellar astrophysics and the research of the Galaxy, such as stellar populations, chemical composition, kinematics and structure of the disk and the halo, gravitational potential and dark matter distribution in the Galaxy, interstellar dust extinction, extremely metal-poor and hyper-velocity stars, and to ultimately advance our understanding of the assemblage of the Milky Way and other galaxies and the origin of regularity and diversity of their properties.