Successful production of the engineering development unit (EDU) primary mirror segment and flight unit tertiary mirror for JWST

During 2009, Tinsley finished most of the Configuration 1 pre-cryo test Computer Controlled Optical Surfacing (CCOS) operations on the James Webb Space Telescope primary mirror segments and in mid-2009 we began the Configuration 2 post-cryo test CCOS operations. After completing the grinding and polishing operations, including final figuring to a cryo-null target, we delivered the finished Engineering Development Unit (EDU) to Ball Aerospace Technology Corporation on 4 December 2009. Achieving fabrication and metrology conditions to meet the specifications for this off-axis ~1.5 m hexagonal point-to-point segmented mirror required special methods. Achieving repeatable and accurate interferometric alignment of the off-axis aspherical mirror surface and stable thermal gradient control of the beryllium substructure during tests required rigorous component and system-level validation. Final optical wavefront measurements over the various spatial frequency ranges have demonstrated that all of the requirements are met. This success has validated our processes of fabrication and metrology and allows us to proceed with the production of the 18 flight mirror segments. The first finished flight mirror, the Tertiary Mirror, was shipped to BATC on 24 February, 2010. Performance of that mirror is reported here also.