Abstract
Full aperture testing of large cryogenic optical systems has been impractical due to the difficulty of operating a large collimator at cryogenic temperatures. The Thermal Sieve solves this problem by acting as a thermal barrier between an ambient temperature collimator and the cryogenic system under test. The Thermal Sieve uses a set of thermally controlled baffles with array of holes that are lined up to pass the light from the collimator without degrading the wavefront, while attenuating the thermal background by nearly 4 orders of magnitude. This paper provides the theory behind the Thermal Sieve system, evaluates the optimization for its optical and thermal performance, and presents the design and analysis for a specific system.
Highlights
The aperture sizes of space optical systems have been increased to achieve higher resolution and more light collecting capability
Since space optical systems are very difficult to be repaired while they are operating in space, the final performance test in a space-like environment is essential for a successful space optical system development
A new conceptual testing configuration to test a cryogenic optical system inside a vacuum chamber was introduced with the Thermal Sieve
Summary
The aperture sizes of space optical systems have been increased to achieve higher resolution and more light collecting capability. For a space optical system, the whole system is tested inside a cryogenic vacuum chamber which simulates the actual operating environment. For the cryogenic thermal control inside the vacuum chamber, the heat transfer to the optical system under test needs to be minimized. One obvious solution may be a collimator operating at the same temperature as the space optical system, so that they are at a thermal equilibrium Making such a customized cryogenic collimator working at a particular cryogenic A new optical testing configuration utilizing Thermal Sieve (TS), a.k.a. cryogenic thermal mask, was developed and introduced [4] It provides effective thermal decoupling between a cryogenic optical system under test and a collimator operating at an ambient temperature, while passing the test beam without significant degradation in its wavefront.
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