SPACE OPTICS: Thermal sieve isolates collimator from cooled test optics

摘要

Testing advanced space optics (which virtually all receive collimated light) before launch often requires cryogenic vacuum testing to simulate the space environment. Because apertures for some of these systems can be quite large (like the 6.5 m aperture of the James Webb Space Telescope's primary mirror), any reduction in complexity of the test setup helps cut costs. Such a test setup needs to provide collimated light; the conventional way to do this in noncryogenic test is to include a collimator in the vacuum chamber. However, this is not ideal for cryogenic testing, as thermal radiation from the collimator is a problem unless the collimator is kept at the same low temperature as the test optics. Custom collimators designed to work at a precise cryogenic temperature are costly.