Primary mirror segment assembly integration and alignment for the James Webb Space Telescope

Wells, Conrad; Mallette, Mark; Fischer, David G.; Coon, Matthew; Amon, John; Kuipers, Les; Spina, John A.

doi:10.1117/12.861871

Cited by 5 publications

(4 citation statements)

References 5 publications

(7 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The optical test equipment used for the cryogenic testing was designed specifically for the measurements needed 13 . The key components included the Center of Curvature Optical Assembly (CoCOA 14 ), which included interferometers to measure the surface figure of the entire PM; a photogrammetry (PG) system of cameras on four rotating booms 15 to measure the relative positions of optical targets over on the flight hardware and test equipment; the AOS Source Plate Assembly, which provided light sources at the intermediate Cassegrain focus of the OTE for use in downward (half-pass) imaging and upward (pass-and-a-half) imaging (in conjunction with three autocollimating flats); and fiducial light strips around the edges of the PM for measuring pupil shear and vignetting.…”

Section: Thermo-mechanical Stabilitymentioning

confidence: 99%

James Webb Space Telescope optical stability lessons learned for future great observatories

Feinberg,

McElwain,

Bowers

et al. 2023

J. Astron. Telesc. Instrum. Syst.

View full text Add to dashboard Cite

The James Webb Space Telescope (JWST) launched on December 25, 2021, and its optical performance in orbit has been even better than predicted pre-flight. The static wavefront error (WFE) is less than half the value specified for the requirement of having diffraction-limited image quality at 2 microns in the NIRCam shortwave channel, enabling the observatory to deliver both sharper images and higher sensitivity than anticipated. In addition to the excellent image quality, the optical stability has also exceeded expectations, both in terms of high-frequency dynamic contributions (which would be perceived as part of "static WFE") and in terms of drifts over minutes, hours, and days. Stability over long timescales is critical for several important science cases, including exoplanet transit spectroscopy and coronagraphy. JWST's stability success was achieved through detailed design and testing, with several important lessons learned for future observatories, especially the Habitable Worlds Observatory that is expected to need even higher levels of stability. We review the stability architecture, how it was technologically demonstrated, the ground test results and improvements, the on-orbit results, and the lessons learned.

show abstract

Section: Thermo-mechanical Stabilitymentioning

confidence: 99%

James Webb Space Telescope optical stability lessons learned for future great observatories

Feinberg,

McElwain,

Bowers

et al. 2023

J. Astron. Telesc. Instrum. Syst.

View full text Add to dashboard Cite

show abstract

“…As the largest aerospace telescope, James Webb Space Telescope, using Leitz CMM to control radius of curvature, conic constant and aspheric figure for primary mirror, secondary mirrors and tertiary mirror during generation and rough polishing. Besides, CMM is also used to assist the alignment of the primary mirror segment assembly (PMSA) to determine its contribution to the shim prescription [7][8] . W.C. Lin and S.T.…”

Section: Introductionmentioning

confidence: 99%

The alignment and isostatic mount bonding technique of the aerospace Cassegrain telescope primary mirror

Lin¹,

Chang²,

Lin³

et al. 2012

SPIE Proceedings

View full text Add to dashboard Cite

In order to meet both optical performance and structural stiffness requirements of the aerospace Cassegrain telescope, iso-static mount is used as the interface between the primary mirror and the main plate. This article describes the alignment and iso-static mount bonding technique of the primary mirror by assistance of CMM. The design and assembly of mechanical ground support equipment (MGSE) which reduces the deformation of primary mirror by the gravity effect is also presented. The primary mirror adjusting MGSE consists of X-Y linear translation stages, rotation stage and kinematic constrain platform which provides the function of decenter, orientation, tilt and height adjustment of the posture sequentially. After CMM measurement, the radius of curvature, conic constant, decenter and tilt, etc. will be calculated. According to these results, the posture of the mirror will be adjusted to reduce the tilt by the designed MGSE within 0.02 degrees and the distance deviation from the best fitted profile of mirror to main plate shall be less than 0.01 mm. After that, EC 2216 adhesive is used to bond mirror and iso-static mount. During iso-static mount bonding process, CMM is selected to monitor the relative position deviation of the iso-static mount until the adhesive completely cured. After that, the wave front sensors and strain gauges are used to monitor the strain variation while the iso-static mount mounted in the main plate with the screws by the torque wrench. This step is to prevent deformation of the mirror caused from force of the iso-static mount during the mounting process. In the end, the interferometer is used for the optical performance test with +1G and -1G to check the alignment and bonding technique is well or not.

show abstract

Section: Introductionmentioning

confidence: 99%

The alignment of the aerospace Cassegrain telescope primary mirror and iso-static mount by using CMM

Lin¹,

Chang²,

Lin³

et al. 2011

SPIE Proceedings

View full text Add to dashboard Cite

In order to meet both optical performance and structural stiffness requirements of the aerospace Cassegrain telescope, the primary mirror shall be mounted with the main plate by iso-static mount. This article describes of the alignment of the aerospace Cassegrain telescope's primary mirror and iso-static mount by using coordinate-measuring machine (CMM), and the design and assembly of mechanical ground support equipment (MGSE). The primary mirror adjusting MGSE consists of three 3-axis linear stages and point contact platforms, which hold the mirror while avoid the rotated movement when adjusting the stage. This MGSE provide the adjustment of tilt and height for the mirror. After the CMM measurement, the coordinates of measured point on the mirror will be analyzed by the software based on least square fitting to find the radius of curvature, conic constant, de-center and tilt, etc. According to these results, the mirror posture will be adjusted to reduce de-center and tilt by the designed MGSE. The tilt in x and y direction are reduced within 0.001 degrees and the distance deviation from the best fitted profile of the mirror to the main plate shall be less than 0.008mm.

show abstract

Primary mirror segment assembly integration and alignment for the James Webb Space Telescope

Cited by 5 publications

References 5 publications

James Webb Space Telescope optical stability lessons learned for future great observatories

James Webb Space Telescope optical stability lessons learned for future great observatories

The alignment and isostatic mount bonding technique of the aerospace Cassegrain telescope primary mirror

The alignment of the aerospace Cassegrain telescope primary mirror and iso-static mount by using CMM

Contact Info

Product

Resources

About