Today, an important milestone will be achieved in the construction phase of the enormous James Webb Space Telescope (JWST). Mission planners say that about six of the observatory's 18 mirror segments will be delivered to the NASA Marshall Space Flight Center, in Huntsville, Alabama, where they will undergo testing in the X-ray and Cryogenic Facility (XRCF). The purpose of these experiments is to ensure that the high-tech mirrors are able to withstand the harsh temperatures of outer space, where they will need to operate flawlessly.

According to official documents, the segments will be placed in an environment featuring a temperature of about minus 414 degrees Fahrenheit, or minus 247.7 degrees Celsius. These conditions will closely mimic those the JWST will be subjected to upon orbital deployment. Due to its incredibly large size, the telescope will not be launched in its open configuration, but in a tighter form. Once it reaches its destination, it will essentially “bloom” and assemble itself into the final configuration. As this is done, the JWST will dwarf Hubble and its large lens.

“By the time testing in the XRCF concludes in 2011, all 18 flight segments will have been through multiple measurements while experiencing the extreme temperatures of space. This process has been six years in the making and we're excited that we can support the Webb telescope development with our world class cryogenic test facility,” Marshall James Webb Space Telescope Activities Project Manager Helen J. Cole says.

“This is a tremendously important milestone to the Webb Telescope project that bodes well for both our future mirror manufacturing schedule and for the potential performance capabilities of the telescope,” JWST Optical Telescope Element Manager Lee Feinberg, also an expert at the NASA Goddard Space Flight Center (GSFC), in Greenbelt, Maryland, adds. In the XRCF, experts will survey how the shape and form of the mirrors change in the five days it takes the test chamber to reach cryogenic temperatures. This type of information will allow the engineers working on JWST to redesign the mirrors, if need be, in such a way that would ensure they survive their environment.