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Proceedings Paper

Measuring the cryogenic optical alignment between the telescope element and the instruments module of the James Webb Space Telescope
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Paper Abstract

The alignment between the Aft Optical Subsystem (AOS) and the Integrated Science Instruments Module (ISIM) is non-adjustable in orbit, so the alignment must be carefully verified in a cryogenic vacuum environment prior to launch. Optical point source locations calibrated by optical metrology instruments are imaged through the AOS onto the Science Instruments to determine focal, lateral, and clock angle alignment. The pupil image of the AOS is overlaid onto the pupil image of the NIRCam to determine the tip and tilt alignment. In addition, an image from fiducial lights at the Primary Mirror checks the pupil alignment between the telescope entrance pupil, the telescope pupil mask, and the NIRCam aperture stop. The image positions are combined to determine the relative alignment between the Optical Telescope Element (OTE) and the ISIM in all six degrees of freedom with corresponding alignment uncertainties. Uncertainties in the position of focused images of the test sources and images from the pupils are derived from sensitivities of an optical model of the system and the Science Instrument sensing capability. Additional uncertainty in the pupil alignment measurement is due to uncertainty in the analytical removal of gravity effects that simulate the on-orbit alignment environment.

Paper Details

Date Published: 14 September 2011
PDF: 7 pages
Proc. SPIE 8146, UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts V, 814609 (14 September 2011); doi: 10.1117/12.894634
Show Author Affiliations
Tony Whitman, ITT Corp. Geospatial Systems (United States)
Eugene Olczak, ITT Corp. Geospatial Systems (United States)

Published in SPIE Proceedings Vol. 8146:
UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts V
Howard A. MacEwen; James B. Breckinridge, Editor(s)

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