The Webb telescope and instruments must be cooled below 50K to allow them to see faint infrared emissions from astronomical objects. The Webb design includes a large sunshield to block the heat of the Sun and Earth from reaching the cold section of the Observatory. The sunshield consists of five layers of Kapton with aluminum and doped-silicon coatings to reflect the sun's heat back into space.
Mechanical, thermal, micrometeoroid, and radiation tests to demonstrate the durability of the coatings were successfully completed in April 2006. The manufacturing technology needed to apply the coatings to large continuous rolls of Kapton has also been demonstrated.