Gemini Preprint #10

Gemini Primary Mirror Cell Design

E. Huang
Gemini 8m Telescopes Project, 950 N. Cherry Ave., Tucson AZ 85719


To minimize the wind buffeting effect on the primary mirror figure, the Gemini primary mirror cell is designed to provide additional mirror stiffness by coupling the mirror to the cell structure through a six-zone hydraulic support system. Therefore the cell structure is designed as though it were a light weight mirror for minimum top surface distortion. This paper describes the design requirements, the design features, and the detail predicted performance of this cell structure, particularly the effects on the primary mirror figure.

As the cell structure supports the primary mirror with a six-zone hydraulic system, the mirror is coupled to the cell structure with three degree of freedom overconstraints. These overconstraints induces the possible distortion onthe mirror figure due to the cell deformation. This paper presents a solution to eliminate this effect by supporting the mirror cell on the telescope structure through four bipods. The locations of the bipods are so arranged that the cell deformation will not distort the mirror figure as the telescope rotates from zenith to horizon pointing.

Appears in Proc. SPIE 2871, "Optical Telescopes of Today and Tomorrow".

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Ruth A. Kneale / / November 15, 1996