This paper documents and investigates the optical performance of metal mirrors at cryogenic temperatures.It also reviews the telescope system level optical performance for several telescope systems designed and fabricated at SSG.These include data on the LAIRTS Telescope (Large Aperture Infrared Telescope Sensor), the CLAES Telescope (Cryogenic Limb Array Etalon Spectrometer), and the SPIRIT II Telescope (Spatial Infrared Rocketborne Interferometer Telescope).A brief discussion of the design and fabrication of these mirrors is included along with a summary of the driving design performance constraints on cryogenic infrared optics.A review of the test techniques and cryogenic test facilities is given. Interferometric testing is the primary tool used to test these mirrors and systems. This section of the paper also discusses the data analysis methods utilized to determine the cryogenic optical performance of these mirrors.
This paper documents the development of the SPIRIT III telescope from the design through its test activities at SSG, Inc. The SPIRIT III Instrument is the primary infrared instrument on the Mid-Course Space Experiment (MSX). The telescope is an all reflective optical system consisting of twelve mirrors. It represents the largest high straylight rejection, cryogenic telescope built by SSG to date. The nominal collecting aperture is 14 inches. It was designed and built to integrate with a multi-color radiometer and a Michelson interferometer built by the Space Dynamics Laboratory at Utah State University. Key performance features are discussed and measured test data is presented. These include: an internal scan mirror assembly, low scatter mirrors and baffle assemblies, cryogenic optical performance and contamination control. The structural/thermal trade-off issues of a satellite-based cryogenic instrument are presented along with a review of the test techniques and test equipment utilized at SSG to qualify the SPIRIT III telescope. OPTICAL DESIGNThe SPIRIT III telescope configuration is shown in block diagram form in Figure 1.0. The telescope consists of three optics modules -an afocal high straylight rejection optics module, the radiometer optics module, and the AFOCAt HI6H STRML1GHT REJECTION RADIOMETER interferometer optics module. The afocal optics operate at 4:1 magnification and image the 14.5 inch diameter entrance aperture to the Lyot stop which is located on the scan mirror assembly. The entrance aperture is located in the baffle assembly approximately 32 inches from the primary mirror. The afocal optics are: a concave off-axis parabolic primary, a convex off-axis hyperbolic secondary, a concave off-axis parabolic tertiary, and a fold flat. The first field stop is located between the secondary and tertiary. It is at this first field stop where the telescope splits the 0-81 94-0938-31931$4.00 SPIE Vol. 1765 Cryogenic Optical Systems and instruments V (1992) /41 Figure 1.0. Spirit III telescope block diagram Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/24/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx
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