A computational and experimental study of the thermal and thermally induced deformation of a plano mirror undergoing mW heat loading was performed to verify the capability to model the response of a representative imaging optic on the Space Interferometry Mission (SIM) spacecraft. Novel state of the art experimental and computational techniques provided milliKelvin and picometer precision in temperature and deformation prediction and experimental measurement. Mirrors of two different substrates, initially at ambient temperature under vacuum, were subjected to a thermal loading profile representing flight-like and overdrive thermal disturbance conditions. The experimental setup measured milliKelvin level temperature changes and picometer level deformation responses. I-deas / TMG was used to generate an integrated model to predict milliKelvin level changes in temperature of the mirror and picometer level deformation responses of the mirror surface. This paper focuses on the thermally induced deformation modeling and correlation to experimental data for the optical system. Comparison between experimental results and computational models for the deformation aspects of the test agreed well for the fused silica test mirror. In particular for the flight-like regime of primary interest, agreement between the experimental deformations and computational deformation results was within 18%. However the experimental results for the deformation of the Zerodur mirror presented challenges in prediction by the computational models. This is partly attributed to the low value of Zerodur CTE which affects numerical precision and partly due to non-homogeneity of the CTE which is neither modeled nor measured. Bi-material affect of coating was also investigated and found to be a potential source of discrepancy. Further studies regarding computational methods for Zerodur deformation are planned.
Thermal Deformation Prediction and Measurement of Space Optical Systems
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Scott, MI, Sexton, MN, Stubbs, DM, & Hashemi, A. "Thermal Deformation Prediction and Measurement of Space Optical Systems." Proceedings of the ASME 2005 International Mechanical Engineering Congress and Exposition. Heat Transfer, Part B. Orlando, Florida, USA. November 5–11, 2005. pp. 39-47. ASME. https://doi.org/10.1115/IMECE2005-80174
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