Support structure of LAMOST Schmidt plate MA,

摘要

Abstract: The Large Sky Area Multiobject Fiber Spectroscopic Telescope (LAMOST) is a very special designed reflecting Schmidt telescope. It will have both the large field of view (5 degrees) and the large aperture (4 meters). The reflecting Schmidt plate M$-A$/ will not only serve as the correcting plate for eliminating the spherical aberration of the primary mirror M$-B$/, but also will serve as the tracking mirror simultaneously during the observation with an alt- azimuth mounting. The support structure of M$-A$/, corresponding to its 24 hexagonal submirrors, is composed of 24 hexagonal submirror cells and a M$-A$/ primary cell which is a space truss structure. This paper presents the design and the analysis for the M$-A$/ support structure which mainly aided by the finite element method. It includes analyses of gravitational influence, the thermal deformation and the wind load influence. The dimension of the whole support structure is about 6 $MUL 5 $MUL 3 meters. The total mass of the structure is about 2 tons and the lowest natural frequency is 27.3 Hz. During 1.5 hours observation, the maximum image spread due to the gravitational deflection is less than 0.13 arcseconds. While the temperature gradient along the structure in vertical direction is 1$DGR@C, the image spread due to the thermal deformation of the structure is less than 0.06 arcseconds.!5