1 October 2007 Photogrammetric metrology for the James Webb Space Telescope integrated science instrument module
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The James Webb Space Telescope (JWST) is a 6.6m diameter, segmented, deployable telescope for cryogenic IR space astronomy (~40K). The JWST Observatory architecture includes the Optical Telescope Element and the Integrated Science Instrument Module (ISIM) element that contains four science instruments (SI) including a Guider. The ISIM structure must meet its requirements at the ~40K cryogenic operating temperature. The SIs are aligned to the structure's coordinate system under ambient, clean room conditions using laser tracker and theodolite metrology. The ISIM structure is thermally cycled for stress relief and in order to measure temperature-induced mechanical, structural changes. These ambient-to-cryogenic changes in the alignment of SI and OTE-related interfaces are an important component in the JWST Observatory alignment plan and must be verified. We report on the planning for and preliminary testing of a cryogenic metrology system for ISIM based on photogrammetry. Photogrammetry is the measurement of the location of custom targets via triangulation using images obtained at a suite of digital camera locations and orientations. We describe metrology system requirements, plans, and ambient photogrammetric measurements of a mock-up of the ISIM structure to design targeting and obtain resolution estimates. We compare these measurements with those taken from a well known ambient metrology system, namely, the Leica laser tracker system.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Maria Nowak, Allen Crane, Pamela Davila, William Eichhorn, James Gill, Acey Herrera, Michael Hill, Jason Hylan, Mark Jetten, James Marsh, Raymond Ohl, Robert Quigley, Kevin Redman, Henry Sampler, Geraldine Wright, and Philip Young "Photogrammetric metrology for the James Webb Space Telescope integrated science instrument module", Proc. SPIE 6692, Cryogenic Optical Systems and Instruments XII, 66920P (1 October 2007); doi: 10.1117/12.733896; https://doi.org/10.1117/12.733896

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