Life-Test Investigation and Status of the NIRISS Dual Wheel Cryogenic Mechanism for JWST
Abstract
The Dual Wheel (DW) mechanism has been developed for cryogenic operation within the Fine Guidance Sensor (FGS) to fly on the James Webb Space Telescope (JWST), and has been more recently adapted to provide an updated selection of infra-red filters and grisms to enable imaging and slitless spectroscopy functions. During the flight qualification process for the mechanism, life-test goals were not met, with both wheel mechanisms achieving a significant portion of intended life, and notably the filter wheel completing a greater portion than the pupil wheel. An investigation was initiated in 2010 to determine the root cause of the life-test unit failure and to determine ways to extend mechanism life. With the reconfiguration of FGS to accommodate the Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument, which evolved in parallel with the investigation, there is now a heavier reliance placed on the dual wheel, so the extension of the mechanism lifetime has become of elevated criticality to the JWST and Canadian science teams. Root causes, conclusions and status of ongoing activities for the flight hardware are described, including design enhancement and ongoing validation of the improved stepper motor gear head.
- Publication:
-
15th European Space Mechanisms and Tribology Symposium
- Pub Date:
- September 2013
- Bibcode:
- 2013ESASP.718E..39G