The backplane will carry the giant space telescope's 21-foot-diameter primary mirror, as well as a total of 7,500 pounds of telescope optics and instruments, in orbit 990,000 miles (1,584,000 kilometers) from Earth.
"The Webb telescope's ultimate ability to discover the first stars and galaxies is critically dependent on the mirror backplane performing to fantastically demanding standards," said Eric Smith, NASA's Webb Telescope program scientist.
The backplane is designed to provide unprecedented thermal stability at temperatures lower than minus 400F (minus 240C) -- conditions far colder than encountered by any prior space telescopes, NASA said.
The backplane is to be completed by late 2010 for integration into the Webb telescope, which is expected to be launched during 2013.
NASA's Goddard Space Flight Center in Greenbelt, Md., is managing the overall development of the Webb telescope -- a joint project of NASA and the European and Canadian space agencies.