JWST's cryogenic position metrology system

Tony L. Whitman; Randolph P. Hammond; Joe Orndorff; Stephen Hope; Stephen A. Smee; Thomas Scorse; Keith A. Havey Jr.

doi:10.1117/12.926565

21 September 2012 JWST's cryogenic position metrology system

Tony L. Whitman, Randolph P. Hammond, Joe Orndorff, Stephen Hope, Stephen A. Smee, Thomas Scorse, Keith A. Havey Jr.

Proceedings Volume 8442, Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave; 84422L (2012) https://doi.org/10.1117/12.926565
Event: SPIE Astronomical Telescopes + Instrumentation, 2012, Amsterdam, Netherlands

Abstract

The James Webb Space Telescope will undergo a full system test in the cryogenic vacuum chamber A at the Johnson Spaceflight Center in order to verify the overall performance of the combined telescope and instrument suite. This will be the largest and most extensive cryogenic test ever undertaken. Early in the test system development, it was determined that precise position measurements of the overall hardware would enhance the test results. Various concepts were considered before selecting photogrammetry for this metrology. Photogrammetry has been used in space systems for decades, however cryogenic use combined with the size and the optical/thermal sensitivity of JWST creates a unique set of implementation challenges. This paper provides an overview of the JWST photogrammetric system and mitigation strategies for three key engineering design challenges: 1) the thermal design of the viewing windows to prevent excessive heat leak and stray light to the test article 2) cost effective motors and mechanisms to provide the angle diversity required, and 3) camera-flash life and reliability sufficient for inaccessible use during the number and duration of the cryogenic tests.

Citation Download Citation

Tony L. Whitman, Randolph P. Hammond, Joe Orndorff, Stephen Hope, Stephen A. Smee, Thomas Scorse, and Keith A. Havey Jr. "JWST's cryogenic position metrology system", Proc. SPIE 8442, Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave, 84422L (21 September 2012); https://doi.org/10.1117/12.926565

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