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Proceedings Paper

Externally occulted terrestrial planet finder coronagraph: simulations and sensitivities
Author(s): Richard G. Lyon; Sally Heap; Amy Lo; Webster Cash; Glenn D. Starkman; Robert J. Vanderbei; N. Jeremy Kasdin; Craig J. Copi
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Paper Abstract

A multitude of coronagraphic techniques for the space-based direct detection and characterization of exo-solar terrestrial planets are actively being pursued by the astronomical community. Typical coronagraphs have internal shaped focal plane and/or pupil plane occulting masks which block and/or diffract starlight thereby increasing the planet's contrast with respect to its parent star. Past studies have shown that any internal technique is limited by the ability to sense and control amplitude, phase (wavefront) and polarization to exquisite levels - necessitating stressing optical requirements. An alternative and promising technique is to place a starshade, i.e. external occulter, at some distance in front of the telescope. This starshade suppresses most of the starlight before entering the telescope - relaxing optical requirements to that of a more conventional telescope. While an old technique it has been recently been advanced by the recognition that circularly symmetric graded apodizers can be well approximated by shaped binary occulting masks. Indeed optimal shapes have been designed that can achieve smaller inner working angles than conventional coronagraphs and yet have high effective throughput allowing smaller aperture telescopes to achieve the same coronagraphic resolution and similar sensitivity as larger ones. Herein we report on our ongoing modeling, simulation and optimization of external occulters and show sensitivity results with respect to number and shape errors of petals, spectral passband, accuracy of Fresnel propagation, and show results for both filled and segmented aperture telescopes and discuss acquisition and sensing of the occulter's location relative to the telescope.

Paper Details

Date Published: 21 September 2007
PDF: 12 pages
Proc. SPIE 6687, UV/Optical/IR Space Telescopes: Innovative Technologies and Concepts III, 668719 (21 September 2007); doi: 10.1117/12.731755
Show Author Affiliations
Richard G. Lyon, NASA Goddard Space Flight Ctr. (United States)
Sally Heap, NASA Goddard Space Flight Ctr. (United States)
Amy Lo, Northrop Grumman (United States)
Webster Cash, Univ. of Colorado, Boulder (United States)
Glenn D. Starkman, Case Western Reserve Univ. (United States)
Robert J. Vanderbei, Princeton Univ. (United States)
N. Jeremy Kasdin, Princeton Univ. (United States)
Craig J. Copi, Case Western Reserve Univ. (United States)

Published in SPIE Proceedings Vol. 6687:
UV/Optical/IR Space Telescopes: Innovative Technologies and Concepts III
Howard A. MacEwen; James B. Breckinridge, Editor(s)

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