28 August 2014 Mirror placement optimization for the multi-segmented James Webb Space Telescope primary mirror
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Abstract
The Primary Mirror (PM) of NASA’s James Webb Space Telescope (JWST) consists of 18 segment assemblies that are aligned on-orbit using hexapod actuators to function as a single monolithic optic. The individual segment assemblies are polished into one of three different prescriptions. Each segment of a given prescription may be placed in one of six different locations for that prescription, resulting in tens of millions of possible placement combinations of the 18 segments on the backplane of the telescope. A method is proposed to optimize the placement based on minimizing the known alignment offsets of as-built mirrors in combination with the predicted shifts of each attachment point on the telescope backplane due to material creep, cool down shifts, launch shifts, and gravity release. The optimization routine can be configured to allow for minimization of errors in any of the six rigid-body degrees of freedom and can further reduce selection options based on defined hardware constraints. Such a routine can be utilized to minimize initial misalignments of the PM on-orbit, reducing the need to exercise mirror actuators to achieve an aligned state. The end result is reduced commissioning time and increased probability of success of the mission.
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D. Porpora, J. Wachs, A. Barto, J. S. Knight, "Mirror placement optimization for the multi-segmented James Webb Space Telescope primary mirror", Proc. SPIE 9143, Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave, 91433O (28 August 2014); doi: 10.1117/12.2054806; https://doi.org/10.1117/12.2054806
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