The first mirror segment for the James Webb Space Telescope (JWST) pass its initial series of cryogenic, or super-cold, tests at Marshall Space Flight Center, Northrop Grumman Corp. [NOC] announced.
JWST will be launched in 2013 to replace the Hubble Space Telescope, which is about to receive a major overhaul.
That mirror segment was tested in the X-ray and Cryogenic Facility at Marshall. To give engineers the absolute certainty that the mirrors can withstand the rigors of space, they will be polished more and tested again.
“We’ve had to invent entire manufacturing and measurement processes because no one has ever built a telescope this large that has to operate at temperatures this extreme,” said Martin Mohan, Northrop JWST program manager.
The mirror segment is the first of 18 flight mirror segments that will be joined to make a giant, 6.5-meter diameter (21.3 feet) hexagonal mirror. The segments will be subject to temperatures of -414 degrees Fahrenheit in a 7,600 cubic-foot helium-cooled vacuum chamber at the Marshall Center.
Engineers will measure in extreme detail how the shape of the mirror changes as it cools to cryogenic temperatures. Then the mirror will be polished at room temperatures in the opposite of the surface error values observed, so that when the mirror shape changes in the second cryotest, it will distort into a perfect shape.
Since there are 18 mirror segments, each measuring about 1.5 meters (4.9 ft.) in diameter, they will be tested in batches of six and chilled to cryogenic temperatures four times in a six-week time span.
It takes approximately five days to cool a mirror segment to cryogenic temperatures. All flight mirror tests are expected to be completed in June 2011.
Northrop is the prime contractor, leading a team including Ball Aerospace & Technologies Corp.
Goddard Space Flight Center manages the program.
JWST will give scientists clues about the formation of the universe and the evolution of the solar system, from the first light after the Big Bang to the formation of star systems capable of supporting life on planets like Earth.