Cryogenic radius of curvature matching for the JWST primary mirror segments

David M Chaney; James B. Hadaway; Jackson A. Lewis

doi:10.1117/12.845115

17 September 2009 Cryogenic radius of curvature matching for the JWST primary mirror segments

David M Chaney, James B. Hadaway, Jackson A. Lewis

Proceedings Volume 7439, Astronomical and Space Optical Systems; 743916 (2009) https://doi.org/10.1117/12.845115
Event: SPIE Optical Engineering + Applications, 2009, San Diego, California, United States

Abstract

The JWST (James Webb Space Telescope) primary mirror consists of 18 hexagonal mirror segments. Each segment is approximately 1.5 meters point to point and is constructed from a lightweight beryllium substrate. In order for the 18 segments to act as a single 6.5 meter diameter mirror each one must be capable of 6 degrees of freedom motion relative to the mirror backplane and be able to change its radius of curvature to closely match those of the other segments. As it would be nearly impossible to manufacture the 18 individual segments with the same radius, a RoC (radius of curvature) actuation mechanism is attached to each mirror allowing RoC fine tuning post manufacturing. The RoC actuation system consists of a single actuator and six struts attached to the back of the mirror. The radius of curvature is matched by closely manufacturing the radius of each segment relative to the nominal value and then, during cryogenic testing, actuating the RoC of each mirror. This cryogenic actuation reduces polishing times and allows for compensation of radius changes measured during other manufacturing steps. Presented here is a high-level overview of the method used to set the mirror's radius of curvature at cryogenic temperature, disassemble the mirror system for additional polishing and processing, and perform final cryogenic verification.

Citation Download Citation

David M Chaney, James B. Hadaway, and Jackson A. Lewis "Cryogenic radius of curvature matching for the JWST primary mirror segments", Proc. SPIE 7439, Astronomical and Space Optical Systems, 743916 (17 September 2009); https://doi.org/10.1117/12.845115

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available