Primary mirror with Φ 1m and f 3.5m is the most important optical part in the space Main Optical Telescope (MOT).
Since its required surface error is less than λ/40(rms.), where λ is about 0.6μm, the mirror deformation induced by space
heat and gravity must be within 0.015μm, it's necessary to make thermal calculation and structural analysis to improve
its structure. In this paper, the MOT structure and its finite element model is described. The mechanical properties are
then analyzed in order to verify whether this structure can meet the optical requirements of sufficient strength, stiffness,
and thermal stability. Mechanical analysis is carried out with MSC.Nastran software under 3 different load cases: gravity
influence on-ground, dynamic impact during launching, weightlessness and heat environment in-orbit. Space thermal
analyses are also done to simulate the space environment. The coupled deformation of heat and structure is finally
analyzed. Calculation results show that different support ways and support forces will be the keys to determine the
surface precision of primary mirror. The structure can meet the optical demands, but the thermal deformation can not,
especially in an asymmetric temperature distribution, which should be tested and controlled by some strict methods.