Abstract
The James Webb Space Telescope (JWST) primary mirror is 6.6 m in diameter and consists of 18 hexagonal mirror segments each approximately 1.5 m point-to-point. Each primary mirror segment assembly (PMSA) is constructed from a lightweight beryllium substrate with both a radius-of-curvature actuation system and a six degree-of-freedom hexapod actuation system. With the JWST being a near to mid-infrared observatory, the nominal operational temperature of a PMSA is 45 K. Each PMSA must be optically tested at 45 K twice, first to measure the change in the surface figure & radius-of-curvature between ambient & cryogenic temperatures and then to verify performance at cryo following final polishing. This testing is conducted at Marshall Space Flight Center's (MSFC's) X-Ray & Cryogenic Facility (XRCF). The chamber & metrology system can accommodate up to six PMSAs per cryo test. This paper will describe the optical metrology system used during PMSA cryogenic testing. This system evolved from systems used during the JWST mirror technology development program. The main components include a high-speed interferometer, a computer-generated holographic null, an absolute distance meter, a tiltable window, and an imaging system for alignment. The optical metrology system is used to measure surface figure error, radius-of-curvature, conic constant, prescription alignment, clear aperture, and the range & resolution of the PMSA actuation systems.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.