The correct lens mount lightweighting design of thermal cycle stress in Cassegrain telescope

M. Y. Hsu; S. T. Chang; T. M. Huang; Ming-Ying Hsu

doi:10.1117/12.892064

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5 October 2011 The correct lens mount lightweighting design of thermal cycle stress in Cassegrain telescope

M. Y. Hsu, S. T. Chang, T. M. Huang, Ming-Ying Hsu

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Proceedings Volume 8127, Optical Modeling and Performance Predictions V; 81270B (2011) https://doi.org/10.1117/12.892064
Event: SPIE Optical Engineering + Applications, 2011, San Diego, California, United States

Abstract

The Cassegrain telescope system was design for space environment. The correct lens mount assembly is included as correct lens, lens mount, spacer, mount barrel and retainer. The system mass budget allocated to correct lens assembly was 5 Kg. Meanwhile, according to optical design the correct lens is made from fused silica, the lens diameter is 130 mm, and the mass is 2.3 Kg. Therefore, remain mass budget is 2.7 Kg; including the lens mount, spacer, mount barrel and retainer. The telescope system deformation is mainly caused by thermal deformation on space orbit. The correct lens mount was made from invar material in initial design. The CTE (Coefficient of Thermal Expansion) of invar is only 1* 10^-6/°C, low CTE would be resistant to thermal deformation, but invar density is 8* 10^-6 kg/mm³. If all components were made from invar, the total mass was over 2.7 kg. Thus, the components material would consider titanium alloy (CTE is 8.6* 10^-6/°C, density is 4.43* 10^-6 kg/mm³) or aluminum alloy (CTE is 23.6* 10^-6/°C, density is 2.81* 10^-6 kg/mm³). The titanium alloy density is 1.83 times lighter than invar, but CTE is 8.6 times higher. The aluminum alloy density is 2.84 times lighter then invar, but CTE is 23.6 times higher. The lens mount thermal deformation would effect correct lens surface wavefront error and introduce optical aberration. This article analyzes the correct lens assembly thermal deformation and optical performance in different lens mount material. From above conditions, using FEM (Finite Element Method) and optical software, simulation and optimization on the lens mount design have been performed to achieve system mass requirement.

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M. Y. Hsu, S. T. Chang, T. M. Huang, and Ming-Ying Hsu "The correct lens mount lightweighting design of thermal cycle stress in Cassegrain telescope", Proc. SPIE 8127, Optical Modeling and Performance Predictions V, 81270B (5 October 2011); https://doi.org/10.1117/12.892064

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