What is the current status of the telescope?
(Status as of December 2009) There are 18 flight JWST primary mirror segments plus 3 spares including the pathfinder Engineering Demonstration Unit (EDU). The segment blanks were all machined out of beryllium and light-weighted. Most of the segments have completed fine polishing and are ready for the measurement of their cryogenic figure at Marshall Space Flight Center (MSFC), in preparation for the final stage, known as cryo-polishing. Upon completion of the initial polishing, the segments are built up into a primary mirror segment assembly, with the attachment of the mirror actuators onto the back. The mirrors are tested cryogenically at the X-ray & Cryogenic Facility (XRCF) that was built at MSFC to test and calibrate Chandra. The EDU has just completed it final cryo-polish and is about to begin cryo-testing at the XRCF to verify its final performance at cryogenic temperatures. The EDU will then be ready for its gold coating. • What is the performance of the JWST detectors? The HgCd
