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Abstract

The James Webb Space Telescope optical telescope element mirror components, 18 individual primary mirror segment assemblies (PMSA), the secondary mirror (SM), tertiary mirror (TM), and Fine Steering Mirror, have all been fabricated. The performance of the optical telescope (OTE) based on the as-measured optical components is combined with alignment tolerances and the on-orbit alignment process to predict the imaging performance of JWST. The best estimate of the wavefront error, Strehl ratio and Encircled Energy stability is presented.

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... This, 47 in turn, requires the development of reliable methods for mon- 48 itoring the position of the mirror elements. In particular, one 49 of the most advanced tools in this field is the James Webb Space 50 Telescope (JWST) [6,7], which is scheduled to be launched in 51 2021. This telescope has a 6.5-m mirror with 18 segments. ...
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... Development of high-fidelity image simulators has become commonplace in large instrumentation projects in astronomy. [1][2][3][4][5][6][7][8] In addition, a full comprehensive physics-based method capable of simulating images from the source to the readout has been developed. 1,2 For example, galaxy morphology is altered by the atmosphere (for ground-based observatories), geometric aberrations in the optical train, diffraction, mirror micro-roughness, surface misalignments/perturbations, figure errors, and a variety of detector effects. ...
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The James Webb Space Telescope (JWST) is a large aperture (6.6 m primary mirror) cryogenic telescope with active control of the segmented primary and secondary mirror optical elements. The architecture of the telescope makes full end-to-end testing on the ground prohibitive due to both cost and technical considerations. Additionally, because the telescope will be launched in a folded configuration to fit in the Ariane V launch fairing and aligned during flight using image-based Wavefront Sensing and Control (WFS&C), the telescope cannot be tested in the classical "test-as-you-fly" architecture. Due to these considerations, the primary optical performance requirements will be verified through analysis. In order to have high confidence in this approach, a robust analysis validation program has been developed based on testing from the component level through the integrated telescope level. This verification approach focuses on ground testing at the telescope level to ensure there will be adequate range in the adjustable optics for alignment on orbit. In addition to the incremental test program planned for optical verification, a double-pass sampled aperture test of the integrated telescope and instruments is planned at flight-like temperatures as a crosscheck to the analytic verification for flight. Error budgets have been developed to understand the uncertainty propagation through the test and analysis program.
Optical Requirements Allocation for the James Webb Space Telescope
  • P Lightsey
P. Lightsey, et al, " Optical Requirements Allocation for the James Webb Space Telescope ", Proc. SPIE Vol. 5487, (2004).