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Pupil Alignment Considerations for Large, Deployable Space TelescopesFor many optical systems the properties and alignment of the internal apertures and pupils are not critical or controlled with high precision during optical system design, fabrication or assembly. In wide angle imaging systems, for instance, the entrance pupil position and orientation is typically unconstrained and varies over the system s field of view in order to optimize image quality. Aperture tolerances usually do not receive the same amount of scrutiny as optical surface aberrations or throughput characteristics because performance degradation is typically graceful with misalignment, generally only causing a slight reduction in system sensitivity due to vignetting. But for a large deployable space-based observatory like the James Webb Space Telescope (JWST), we have found that pupil alignment is a key parameter. For in addition to vignetting, JWST pupil errors cause uncertainty in the wavefront sensing process that is used to construct the observatory on-orbit. Furthermore they also open stray light paths that degrade the science return from some of the telescope s instrument channels. In response to these consequences, we have developed several pupil measurement techniques for the cryogenic vacuum test where JWST science instrument pupil alignment is verified. These approaches use pupil alignment references within the JWST science instruments; pupil imaging lenses in three science instrument channels; and unique pupil characterization features in the optical test equipment. This will allow us to verify and crosscheck the lateral pupil alignment of the JWST science instruments to approximately 1-2% of their pupil diameters.
Document ID
20110015430
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Bos, Brent J. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Ohl, Raymond G. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Kubalak, Daivd A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 25, 2013
Publication Date
August 21, 2011
Subject Category
Optics
Report/Patent Number
GSFC.CP.5027.2011
GSFC.CPR.5026.2011
Meeting Information
Meeting: 2011 SPIE Optics and Photonics
Location: Sand Diego, CA
Country: United States
Start Date: August 21, 2011
End Date: August 25, 2011
Sponsors: International Society for Optical Engineering
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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