Performance of the center-of-curvature optical assembly during cryogenic testing of the James Webb Space Telescope

James B. Hadaway; Conrad Wells; Gene A. Olczak; Mark Waldman; Tony L. Whitman; Joseph Cosentino; Michael Zarella; Mark Connolly; David M. Chaney; Randal Telfer

doi:10.1117/12.2315762

6 July 2018 Performance of the center-of-curvature optical assembly during cryogenic testing of the James Webb Space Telescope

James B. Hadaway, Conrad Wells, Gene A. Olczak, Mark Waldman, Tony L. Whitman, Joseph Cosentino, Michael Zarella, Mark Connolly, David M. Chaney, Randal Telfer

Author Affiliations +

Proceedings Volume 10698, Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave; 1069803 (2018) https://doi.org/10.1117/12.2315762
Event: SPIE Astronomical Telescopes + Instrumentation, 2018, Austin, Texas, United States

Abstract

The James Webb Space Telescope (JWST) primary mirror (PM) is 6.6 m in diameter and consists of 18 hexagonal segments, each 1.5 m point-to-point. Each segment has a 6 degree-of-freedom hexapod actuation system and a radius-of-curvature (ROC) actuation system. The full telescope was tested at its cryogenic operating temperature at Johnson Space Center (JSC) in 2017. This testing included center-of-curvature measurements of the PM wavefront error using the Center-of-Curvature Optical Assembly (COCOA), along with the Absolute Distance Meter Assembly (ADMA). The COCOA included an interferometer, a reflective null, an interferometer-null calibration system, coarse and fine alignment systems, and two displacement measuring interferometer systems. A multiple-wavelength interferometer was used to enable alignment and phasing of the PM segments. By combining measurements at two laser wavelengths, synthetic wavelengths up to 15 mm could be achieved, allowing mirror segments with millimeter-level piston errors to be phased to the nanometer level. The ADMA was used to measure and set the spacing between the PM and the focus of the COCOA null (i.e., the PM center-of-curvature) for determination of the ROC. This paper describes the COCOA, the PM test setup, the testing performed, the test results, and the performance of the COCOA in aligning and phasing the PM segments and measuring the final PM wavefront error.

Conference Presentation

Citation Download Citation

James B. Hadaway, Conrad Wells, Gene A. Olczak, Mark Waldman, Tony L. Whitman, Joseph Cosentino, Michael Zarella, Mark Connolly, David M. Chaney, and Randal Telfer "Performance of the center-of-curvature optical assembly during cryogenic testing of the James Webb Space Telescope", Proc. SPIE 10698, Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave, 1069803 (6 July 2018); https://doi.org/10.1117/12.2315762

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