Dynamic Optical Deformations Of A Chopping Secondary Mirror

Daniel Vukobratovich; Robert DiTolla; Ralph M. Richard

doi:10.1117/12.950688

23 February 1985 Dynamic Optical Deformations Of A Chopping Secondary Mirror

Daniel Vukobratovich, Robert DiTolla, Ralph M. Richard

Proceedings Volume 0572, Infrared Technology XI; (1985) https://doi.org/10.1117/12.950688
Event: 29th Annual Technical Symposium, 1985, San Diego, United States

Abstract

The finite element method was used to analyze the optical performance of the Space Infrared Telescope Facility (SIRTF) fused-silica secondary mirror as it is subjected to a dynamic chopping motion. The chopping motion was assumed to be of quasi-square wave form with the mirror stationary during a dwell period following the actual chop rotation. The primary optical deformation was "ringing" during the dwell period; damping during the dwell time (20 ms) was not effective. For a given chopping motion, the magnitude of the optical deflections could be reduced by proper choice of the support points, by increasing the stiffness of the mirror, reducing the magnitude of the chop angle, and/or increasing the chop period. Prescribed acceleration versus time during the chop motion affects the optical deformations as well. There are optimum support-point locations for each type of motion. Tapering the back of the secondary mirror does not significantly affect optical deformation provided that supports are located at the optimum points. For the best trade of mass moment of inertia against deformation, lightweight mirror geometries should be used.

Citation Download Citation

Daniel Vukobratovich, Robert DiTolla, and Ralph M. Richard "Dynamic Optical Deformations Of A Chopping Secondary Mirror", Proc. SPIE 0572, Infrared Technology XI, (23 February 1985); https://doi.org/10.1117/12.950688

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