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NASA tests sunshield for Webb telescope

By Sharon Gill - 20 Sep 2011 13:21:0 GMT
NASA tests sunshield for Webb telescope

NASA is conducting tests on the James Webb Space Telescope's sunshield, which will protect its mirrors and instruments whilst on its mission to observe remote objects in the universe.

The sunshield, which will enable the Telescope to retain its cryogenic operating temperature of minus 387.7 degrees Fahrenheit, comprises five layers made of Kapton.

Kapton is a high-performance plastic with reflective metallic coating, yet is thinner than half the thickness of a sheet of paper. Since each layer could cover a tennis court - bigger than any Kapton manufacturer can supply, more than fifty individual pieces are stitched together like a quilt to produce the required size.

Testing involves the using a high-precision laser radar to measure the layer every few inches at room temperature and pressure, from this a 3D map of the surface is created, which is curved in multiple directions. The 3D map will be compared with computer models to establish if the material performed as predicted and that critical clearances with adjacent hardware are achieved.

The test will be conducted on all five layers, giving engineers an accurate indication of how the entire sunshield will behave once in orbit.

The tests are expected to be completed in two weeks.

Once testing and model analysis have been completed, the full size layers will be sent to Northrop Grumman in Redondo Beach, California to enable engineers to verify the process of how the layers will unfurl in space. The sunshield layers will be folded, similar to a parachute, so they can be safely stowed for launch.

According to Keith Parrish, Webb Sunshield manager at NASA's Goddard Space Flight Centre in Greenbelt, Md, the conclusion of these tests will be the last stage of the sunshield's development program.

In 2010, a scale model of the sunshield was tested in simulated extreme temperatures to confirm that it would enable telescope to cool to the required operating temperature.

A joint project between NASA, the European Space Agency and the Canadian Space Agency, the Webb Telescope is the successor to Hubble. It is the most powerful space telescope ever to be constructed and will be used to explore planets surrounding distant stars and provide images of the first ever galaxies formed.

Top Image: September 2009 artist conception of the James Webb Space Telescope, with the 5 layer sunshield stretched out in space. Credit: © NASA