According to a NASA statement, on July 8, the agency’s long-gestating James Webb Space Telescope succeeded in another evaluation. This was a static load test for the telescope’s primary mirror backbone support structure (PMBSS), the strong framework that will cradle the science instruments and the 18 beryllium mirror-segments that comprise the 21-foot-wide primary mirror. The PMBSS will need to keep the mirror perfectly motionless as it scans space.
The test confirmed that the PMBSS can endure the vibration of launch. The PMBSS is exceedingly strong, but very lightweight. By itself, the PMBSS is 24 feet tall, 19.5 feet wide, and weighs 2,180 pounds. However, it will be able to support 12 times its own weight in hardware. The PMBSS is also designed to minimally deform in the extreme temperatures of space, between minus 406 and -343 degrees Fahrenheit; the structure must not shift more than 38 nanometers, about one one-thousandth the width of a human hair.
“This is the largest, most complex cryogenically stable structure humans have ever built,” said Scott Texter, Optical Telescope Element manager at Northrop Grumman, which is under contract to develop optics and other hardware. “Completion of the static testing verifies it can hold the weight it is designed to hold. Now the structural backbone of the observatory is officially verified and ready for integration.”
The next hurdle the Webb must clear is the integration of its composite structures with its deployment mechanisms. Once finished, this will constitute the Optical Telescope Element structure, which will then be transported to Goddard Space Flight Center for the installation of the mirrors.
The Webb is due to launch in 2018. A joint venture of NASA, ESA, and the Canadian Space Agency, the Webb will be the most powerful space telescope in history, able to gather information on the farthest objects in the universe, peer back to the formation of the first galaxies, and examine exoplanets around other stars.