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Proceedings Paper

Testing and calibration of phase plates for JWST optical simulator
Author(s): Qian Gong; Jenny Chu; Severine Tournois; William Eichhorn; David Kubalak
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Paper Abstract

Three phase plates were designed to simulate the JWST segmented primary mirror wavefront at three on-orbit alignment stages: coarse phasing, intermediate phasing, and fine phasing. The purpose is to verify JWST's on-orbit wavefront sensing capability. Amongst the three stages, coarse alignment is defined to have piston error between adjacent segments being 30 μm to 300 μm, intermediate being 0.4 μm to 10 μm, and fine being below 0.4 μm. The phase plates were made of fused silica, and were assembled in JWST Optical Simulator (OSIM). The piston difference was realized by the thickness difference of two adjacent segments. The two important parameters to phase plates are piston and wavefront errors. Dispersed Fringe Sensor (DFS) method was used for initial coarse piston evaluation, which is the emphasis of this paper. Point Diffraction Interferometer (PDI) is used for fine piston and wavefront error. In order to remove piston's 2π uncertainty with PDI, three laser wavelengths, 640nm, 660nm, and 780nm, are used for the measurement. The DHS test setup, analysis algorithm and results are presented. The phase plate design concept and its application (i.e. verifying the JWST on-orbit alignment algorithm) are described. The layout of JWST OSIM and the function of phase plates in OSIM are also addressed briefly.

Paper Details

Date Published: 30 September 2011
PDF: 14 pages
Proc. SPIE 8150, Cryogenic Optical Systems and Instruments XIII, 81500M (30 September 2011); doi: 10.1117/12.892125
Show Author Affiliations
Qian Gong, NASA Goddard Space Flight Ctr. (United States)
Jenny Chu, Orbital Sciences Corp. (United States)
Severine Tournois, Stinger Ghaffarian Technologies, Inc. (United States)
William Eichhorn, NASA Goddard Space Flight Ctr. (United States)
David Kubalak, NASA Goddard Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 8150:
Cryogenic Optical Systems and Instruments XIII
James B. Heaney; E. Todd Kvamme, Editor(s)

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