Modeling temperature-induced surface distortions in the MMTO 6.5 meter primary mirror

T. E. Pickering

doi:10.1117/12.788581

11 July 2008 Modeling temperature-induced surface distortions in the MMTO 6.5 meter primary mirror

T. E. Pickering

Proceedings Volume 7017, Modeling, Systems Engineering, and Project Management for Astronomy III; 701718 (2008) https://doi.org/10.1117/12.788581
Event: SPIE Astronomical Telescopes + Instrumentation, 2008, Marseille, France

Abstract

We have performed finite element thermal analysis of our 6.5 meter primary mirror in the hopes of improving the accuracy of our open loop models and reducing the need to interrupt science observations to tune our optics. In the analysis we apply temperature variations to the front, back, and middle of the mirror to correspond to the locations of installed thermocouples. The input temperature variations and the predicted steady-state surface distortions are modeled as Zernike polynomials. The most significant effect we find is the focus error generated by a temperature gradient between the front and back of the mirror. Comparison with wavefront sensor data shows that we can get reasonably good agreement between predicted and measured focus errors. However, we do not yet get good agreement for other, higher order terms. There is also poorer agreement when conditions are changing rapidly.

Citation Download Citation

T. E. Pickering "Modeling temperature-induced surface distortions in the MMTO 6.5 meter primary mirror", Proc. SPIE 7017, Modeling, Systems Engineering, and Project Management for Astronomy III, 701718 (11 July 2008); https://doi.org/10.1117/12.788581

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