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Proceedings Paper

Analysis of a conical and a hexapod secondary mirror support tower for the Next-Generation Space Telescope (NGST)
Author(s): Gary W. Wilkerson; Stephen Kenneth Pitalo
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Paper Abstract

Different secondary mirror support towers (pedestals) were modeled for the NGST Optical Telescope Assembly (OTA) B. Transmittance analyses at two levels were performed on the secondary mirror support towers. Detailed transmittances were accomplished by the use of the CODE V optical design/analysis program and were compared to a quick approximation method that required only tracing four rays. A way to obtain simple, very quick approximate transmittances without raytrace also developed by the same author, is laid out. Point spread function (PSF) calculations, including both diffraction and aberration effects, were performed on CODE V. PSF contours can be delineated on CODE V down to about 10-8 times the peak intensity, fine detailing the differences in the wings of the PSF. As one goes out from the center of the blur (for a point source), two types of support towers showed little difference between their PSF intensities until one reaches about the 3% level. Between the first type of tower and the hexapod tower below 3% of the peak intensity, the PSF contour maps well delineated significant differences in the outer portions of the PSFs. The hexapod tower provided the best PSF. Such differences in the wings of the PSF significantly impact the resolution of brown dwarfs or extra solar planets from their star.

Paper Details

Date Published: 29 October 1999
PDF: 12 pages
Proc. SPIE 3785, Advanced Telescope Design, Fabrication, and Control, (29 October 1999); doi: 10.1117/12.367618
Show Author Affiliations
Gary W. Wilkerson, Micro Craft, Inc. (United States)
Stephen Kenneth Pitalo, NASA Marshall Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 3785:
Advanced Telescope Design, Fabrication, and Control
William Roybal, Editor(s)

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