Share Email Print

Proceedings Paper

Response Of Large Optical Mirrors To Thermal Distributions
Author(s): E. Pearson; L. Stepp
Format Member Price Non-Member Price
PDF $14.40 $18.00
cover GOOD NEWS! Your organization subscribes to the SPIE Digital Library. You may be able to download this paper for free. Check Access

Paper Abstract

The National New Technology Telescope program at NOAO is developing technology to be used in the design of a 15-meter multiple-mirror telescope. One configuration being considered for the primary mirrors is a lightweight honeycomb sandwich structure cast from borosilicate glass. This material has a relatively large coefficient of thermal expansion (about 3 parts per million per degree C) which can produce optically-significant distortions when the mirror is exposed to a typical observatory thermal environment. To study this problem we have tested a prototype borosilicate glass mirror, 1.8 meters in diameter, in various thermal environments. Finite-element modeling was used to predict the thermal distortions of the optical surface. This led to an analysis in which temperature patterns were described by a least-squares fit to a polynomial expression, and the polynomial was then used to predict nodal temperatures of the model. The individual terms of the polynomial describe patterns of temperature such as linear-diametral gradients, radial gradients, etc. The optical distortions resulting from these cases are described in this paper. An analytical solution for a 3-dimensional linear temperature gradient was developed to check the finite-element results, and is also presented.

Paper Details

Date Published: 3 June 1987
PDF: 14 pages
Proc. SPIE 0748, Structural Mechanics of Optical Systems II, (3 June 1987); doi: 10.1117/12.939833
Show Author Affiliations
E. Pearson, National Optical Astronomy Observatories (United States)
L. Stepp, National Optical Astronomy Observatories (United States)

Published in SPIE Proceedings Vol. 0748:
Structural Mechanics of Optical Systems II
Alson E. Hatheway, Editor(s)

© SPIE. Terms of Use
Back to Top