Sep 2 2010
A primary mirror segment of NASA's James Webb Space Telescope has completed the final step in the manufacturing process. It is the first of the telescope's primary mirror segments to achieve this milestone. Northrop Grumman Corporation (NYSE:NOC) is leading the telescope's design and development effort for the space agency's Goddard Space Flight Center.
The mirror segment, an engineering development unit and flight spare, has been coated with an ultra-thin layer of evaporated gold to ensure that infrared light is properly reflected from the primary mirror into the observatory's science instruments. The next step is a trip to Ball Aerospace in Boulder, Colo., where the support and actuation structures will be attached. The entire assembly will then undergo a final cryotest in September and October at NASA's Marshall Space Flight Center in Huntsville, Ala. The primary mirror engineering development unit will be closely followed by the other 18 primary mirror flight segments in the coating process. Mirror manufacturing began seven years ago with beryllium blanks.
"This is the first primary mirror segment to have reached this level of completion and we have every confidence it is flightworthy," said Scott Willoughby, Webb Telescope program manager for Northrop Grumman Aerospace Systems sector. "On the heels of a successful Mission Design Review, we continue to make significant progress with flight hardware components."
Teammate Quantum Coatings, Inc. built an 80-inch square chamber at its Moorestown, N.J. facility to perform the thermal evaporative gold coating process for the Webb mirrors. Each 4-ft.diameter primary mirror segment is suspended face down in the chamber. Gold is heated to its liquid point, over 2500 degrees Fahrenheit, and evaporates onto the mirror's optical surface. Several layers of material are applied to the beryllium mirrors: binder coatings between the gold coat and the mirror surface and between the gold and a final protective coat of silicon dioxide (glass). The coatings are 120 nanometers, a thickness of about a millionth of an inch or 200 times thinner than a human hair.
In addition, the Webb telescope's much smaller tertiary and fine steering mirrors have also been successfully coated. The 30 x18-inch tertiary mirror position is fixed – the only mirror that is not adjustable – so the rest of the telescope is aligned to this mirror. The 8 inch diameter fine steering mirror is used for accurate optical pointing and image stabilization. The smaller mirrors will be cryotested at Ball Aerospace and then integrated into the Aft Optics Subsystem during the telescope's integration and assembly phase.
The James Webb Space Telescope is the world's next-generation space observatory and successor to the Hubble Space Telescope. The most powerful space telescope ever built, Webb will observe the most distant objects in the universe, provide images of the very first galaxies ever formed and see unexplored planets around distant stars. Scheduled for launch in 2014, the Webb Telescope is a joint project of NASA, the European Space Agency and the Canadian Space Agency.