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Proceedings Paper

A contamination control cover for the Mid Infrared Instrument of the James Webb Space Telescope
Author(s): Adrian M. Glauser; Ulrich Langer; Alex Zehnder; Manuel Güdel
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Paper Abstract

During its cold mission phase at 7 Κ the Mid Infrared Instrument (MIRI) is the coldest spot on the James Webb Space Telescope (JWST) and will act consequently as a cryopump of the instrument's environment. Since the absorption of outgassing molecules from the spacecraft (mainly water and hydrocarbons) on optical surfaces would lead to a significant degradation of the optical performance of MIRI, a Contamination Control Cover (CCC) has been introduced. This cover is placed in the entrance optical path of MIRI right after the picko. mirror (POM) and will be closed during the instrument's cool down phase and at MIRI's operational temperature each time the POM is heated up for decontamination. The CCC will be used further as an optical shutter for dark sky calibration and for the protection against latency images which might emerge from coronagraphic filter changes. Therefore, the CCC has been designed to be multi operational with approximately 3000 life cycles. A contact-free labyrinth seal allows the required reduction of molecular flow towards the instrument and avoids the possibility of any freezing. The CCC is operational between 300 Κ and 7 Κ and is actuated by two redundant stepper motors. In this paper we describe the design of the CCC and the results of the qualification campaign. Further a dedicated measurement of its molecular conductance at various temperatures is presented.

Paper Details

Date Published: 23 July 2008
PDF: 8 pages
Proc. SPIE 7018, Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation, 70184L (23 July 2008); doi: 10.1117/12.789467
Show Author Affiliations
Adrian M. Glauser, Paul Scherrer Institut (Switzerland)
Ulrich Langer, RUAG Aerospace (Switzerland)
Alex Zehnder, Paul Scherrer Institut (Switzerland)
Manuel Güdel, Paul Scherrer Institut (Switzerland)
Institute of Astronomy, ETH Hönggerberg (Switzerland)

Published in SPIE Proceedings Vol. 7018:
Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation
Eli Atad-Ettedgui; Dietrich Lemke, Editor(s)

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