Cryogenic testing complete for NASA's Webb telescope mirrors

Cryogenic testing is complete for the final six primary mirror segments and a secondary mirror that will fly on NASA's James Webb Space Telescope. The milestone represents the successful culmination of a multi-year process that broke new ground in manufacturing and testing large mirrors. The Webb telescope will have 21 mirrors, with 18 mirror segments working together as a large 21.3-foot (6.5-meter) primary mirror. Each individual mirror segment has been successfully tested to operate at -387 Fahrenheit (or -233 Celsius). The Webb telescope is the world's next-generation space observatory and successor to the famed Hubble Space Telescope. It will be the most powerful space telescope ever built, providing images of the earliest galaxies ever formed and exploring planets around distant stars. It is a joint project of NASA, the European Space Agency and the Canadian Space Agency.