The James Webb Space Telescope (JWST) main mirror seen here during recent ‘centre of curvature’ test. The test was conducted by a team from NASA Goddard, Ball Aerospace and the Space Telescope Science Institute. Engineers made detailed measurements of the mirror segments’ shape and position by looking how light is reflected from them. Then they compare it with a reference that represents what the mirrors ideally should be.
JWST is a joint project of NASA, ESA and the Canadian Space Agency, scheduled for launch in October 2018 on an Ariane 5 rocket from Europe’s Spaceport in Kourou. http://www.esa.int/spaceinimages/Images/2016/11/Inspecting_JWST_s_primary_mirror
