Using a Laser Tracker System to Align and Position LAMOST

Publication Details

Abstract

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) project is an innovative scientific project being undertaken by the Chinese Academy of Science. LAMOST is a quasimeridian-reflecting Schmidt telescope that has been laid down on the ground with its optical axis fixed in the meridian plane. The aperture of LAMOST is 4 m, enabling it to capture the spectra of objects as faint as 20m.5 (with F = 5) using an exposure of 1.5 hours. Its focal plane is 1.75 m in diameter (a 5° field of view) that accommodates as many as 4,000 optical fibers. Light from 4,000 celestial objects is simultaneously fed into a number of spectrographs. The telescope possesses one of the highest spectrum acquiring rates in the world. FARO’s Laser Tracker system was utilized to ensure installation alignment for each of the three key subsystems of LAMOST, first, reflecting Schmidt plate MA, second, fixed spherical mirror MB, and third, focal plane. Each subsystem is supported by a similar movable and complex supporting structure, which allows each subsystem to align itself in the correct position to collect the best set of data for analysis. The Laser Tracker system was used to align the supporting structure with the mirror plane to achieve the best optimal installation results. For this project, the FARO team used a package of SpatialAnalyzer measurement planes together with the FARO Si Laser Tracker system. Utilizing FARO’s metrology solution, the LAMOST team was able to collect solid measurement data to achieve optimal alignment results for this complex optical system. Optimized metrology measurement accuracy increased the overall performance of the LAMOST telescope, a significant milestone for this very important project.