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Proceedings Paper

Advanced mirror technology development (AMTD) II modal test of a 1.5-m ultra-low expansion slumped mirror
Author(s): J. Brent Knight; H. Philip Stahl; Frank Tsai; Adam Burt; Andy Singleton; Ron Hunt; Rusty Parks; Alex McCool IV; Brendan Sontag
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Paper Abstract

The Advanced Mirror Technology Development (AMTD) project is in Phase 2 of a multiyear effort initiated in Fiscal Year 2012 to mature toward the next technology readiness level critical technologies required to enable 4-m-or-larger monolithic or segmented ultraviolet, optical, and infrared (UVOIR) space telescope primarymirror assemblies for general astrophysics and ultra-high-contrast observations of exoplanets. As part of AMTD II, a free-free modal test was performed of a light weighted slumped 1.5 m mirror made of Corning Ultra Low Expansion (ULE®) material. The test article and support structure were suspended via bungee to simulate a free-free environment. Modes were excited by roaming an instrumented modal test hammer and responses were measured. Predicted and measured frequencies are presented as well as Modal Assurance Criteria (MAC) results to compare the mode shapes. The finite element mirror model used for pre-test predictions and posttest comparisons was provided by the mirror vendor, Harris Corporation. The mirror FEM included deformations of the ribs that were a result of the slumping process. Modal test frequencies matched predictions within the 5% target with the exception of one mode and that pair differed by 5.2%. Of the seven modes measured and predicted, four had MAC values meeting the target of ≥ 0.90, one was just under and two were notably below the target.

Paper Details

Date Published: 14 September 2018
PDF: 7 pages
Proc. SPIE 10742, Optical Manufacturing and Testing XII, 1074203 (14 September 2018); doi: 10.1117/12.2320334
Show Author Affiliations
J. Brent Knight, NASA Marshall Space Flight Ctr. (United States)
H. Philip Stahl, NASA Marshall Space Flight Ctr. (United States)
Frank Tsai, NASA Marshall Space Flight Ctr. (United States)
Adam Burt, NASA Marshall Space Flight Ctr. (United States)
Andy Singleton, NASA Marshall Space Flight Ctr. (United States)
Ron Hunt, NASA Marshall Space Flight Ctr. (United States)
Rusty Parks, NASA Marshall Space Flight Ctr. (United States)
Alex McCool IV, NASA Marshall Space Flight Ctr. (United States)
Brendan Sontag, NASA Marshall Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 10742:
Optical Manufacturing and Testing XII
Ray Williamson; Dae Wook Kim; Rolf Rascher, Editor(s)

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