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Development and Acceptance Testing of the Dual Wheel Mechanism for the Tunable Filter Imager Cryogenic Instrument on the JWSTThe James Webb Space Telescope (JWST) will carry four scientific instruments, one of which is the Tunable Filter Imager (TFI), which is an instrument within the Fine Guidance Sensor. The Dual Wheel (DW) mechanism is being designed, built and tested by COM DEV Ltd. under contract from the Canadian Space Agency. The DW mechanism includes a pupil wheel (PW) holding seven coronagraphic masks and two calibration elements and a filter wheel (FW) holding nine blocking filters. The DW mechanism must operate at both room temperature and at 35K. Successful operation at 35K comprises positioning each optical element with the required repeatability, for several thousand occasions over the five year mission. The paper discusses the results of testing geared motors and bearings at the cryogenic temperature. In particular bearing retainer design and PGM-HT material, the effects of temperature gradients across bearings and the problems associated with cooling mechanisms down to cryogenic temperatures. The results of additional bearing tests are described that were employed to investigate an abnormally high initial torque experienced at cryogenic temperatures. The findings of these tests, was that the bearing retainer and the ball/race system could be adversely affected by the large temperature change from room temperature to cryogenic temperature and also the temperature gradient across the bearing. The DW mechanism is now performing successfully at both room temperature and at cryogenic temperature. The life testing of the mechanism is expected to be completed in the first quarter of 2010.
Document ID
20100021939
Document Type
Conference Paper
Authors
Leckie, Martin (COM DEV Ltd. Cambridge, Ontario, Canada)
Ahmad, Zakir (COM DEV Ltd. Cambridge, Ontario, Canada)
Date Acquired
August 29, 2013
Publication Date
May 12, 2010
Publication Information
Publication: Proceedings of the 40th Aerospace Mechanisms Symposium
Subject Category
Space Sciences (General)
Distribution Limits
Public
Copyright
Public Use Permitted.

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IDRelationTitle20100021914Analytic PrimaryProceedings of the 40th Aerospace Mechanisms Symposium