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27 August 2010 Tunable filter imager for JWST: etalon opto-mechanical design and test results
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The Tunable Filter Imager of the James Webb Space Telescope will be based on blocking filters and a tunable Fabry- Perot etalon with an average resolution of about 100. It will operate in two wavelength bands from 1.6 μm to 2.5 μm and from 3.1 μm to 4.9 μm at a cryogenic temperature of about 35K. It will respectively be used to study the First Light and re-ionization of the universe by surveying Lyman-alpha sources and to provide an in-depth study of proto-planetary systems as well as giant planets of nearby stars. The Tunable Filter Imager (TFI) is designed to image a sky field of view of 2.2' by 2.2' (magnified to 4.6 deg. x 4.6 deg. at the etalon). Its tunable etalon has an aperture of 56 mm. It operates at low orders 1 and 3 for the two wavelength bands which reduces the number of blocking filters to a number of eight. The etalon gap tuning between 2.5 μm and 5.5 μm is provided by piezoelectric actuators and will be servo controlled by using capacitive displacement sensors. In this paper, we present the etalon's opto-mechanical design that allows us to achieve the stringent requirements in terms of resolution over a wide infrared wavelength band, and operation at low gap at cryogenic temperature. Cryogenic test results will be shared as well.
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D. Touahri, P. Cameron, C. Evans, C. Haley, Z. Osman, A. Scott, and N. Rowlands "Tunable filter imager for JWST: etalon opto-mechanical design and test results", Proc. SPIE 7808, Infrared Remote Sensing and Instrumentation XVIII, 78081K (27 August 2010);


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