Researchers Test James Webb Space Telescope’s Gold-Coated Mirrors for NASA Observatory

Six gold-coated mirrors designed for the James Webb Space Telescope (JWST) are to undergo tests under extreme conditions at NASA's Marshall Space Flight Center (MSFC). The conditions simulate deep space and these mirrors form the second set among three sets of mirrors.

Research scientist at the Center for Applied Optics at The University of Alabama in Huntsville, Dr. James Hadaway, leads the team for testing 18 primary mirrors of JWST, which was designed to observe distant stars and galaxies. The telescope is designed to collect infrared radiation from distant galaxies and stars and is over 2.5 times larger than the Hubble telescope.

The testing is to make certain that the gold-coated mirrors stay focused and smooth when they are put into orbit. Tests on the first six mirrors were conducted in April and May. In the X-Ray and Cryogenic Facility (XRCF) at MSFC, a cryogenic chamber as large as a house was adapted for performing the testing. The vacuum chamber was maintained at a temperature of 45 K (-378° F).

MSFC lost electric power due to a tornado outbreak in April, but the team focused and completed the testing. The testing was performed and the data was collected on schedule and as planned. The smooth gold-coated mirrors were initially cooled to the temperature existing in deep space. They were then warmed very slowly to prevent distortion, condensation or damage.

The research team measured the deformation of the mirrors under cold conditions and the data was communicated to Tinsley Laboratories in California. They polished opposite distortions in the mirrors based on the information. The average imperfection that was allowed in the gold-coated mirrors was about the height of 200 hydrogen atoms.

The testing program is expected to be complete by the end of 2011. Hadaway anticipates being involved in the development and preparations for the probable launch in 2015.