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 on the 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.
PR 1578 adhesive is often used for bonding a glass mirror to its mounting flexures (Invar or Aluminum) when the mirror assembly is designed to operate in a low temperature environment PR 1578 is used because it has high strength and remains elastic at low temperature. Several tests conducted at Itek, however, show that the thermal stress induced in the bond may cause fracture of the glass near the bond at cryogenic temperawre. This paper examines the reason of fracture and the effects of flexure material, adhesive thickness, and size of bonding. A finite element model is developed for simulating the bonding of flexure, adhesive, and glass. Temperature dependent material properties are used in the analysis. Good correlation between the analysis and the test is obtained.
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