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Proceedings Paper

The Hubble Space Telescope attitude observer anomaly
Author(s): Morgan M. Van Arsdall; Patrick R. Ramsey; Scott R. Swain
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Paper Abstract

In mid-2004, the Hubble Space Telescope (HST) began experiencing occasional losses of lock during Fine Guidance Sensor (FGS) guide star acquisitions, threatening a potential loss of science. These failures were associated with an increasing disparity between the FGS-derived estimates of gyro bias calculated in orbit day and those calculated in orbit night. Early efforts to mitigate the operational effects of this Attitude Observer Anomaly (AOA) succeeded; however, the magnitude of the anomaly continued to increase at a linear rate and operational problems resumed in mid-2005. Continued analysis led to an additional on-orbit mitigation strategy that succeeded in reducing the AOA signature. Before the investigation could be completed, HST began operations under the life-extending Two Gyro Science mode. This eliminated both the operational effects of and the visibility into the AOA phenomenon. Possible causes of the anomaly at the vehicle system level included component hardware failures, flight software errors in control law processing, distortion of the telescope optical path, and deformation of vehicle structure. Although the mechanism of the AOA was not definitively identified, the Anomaly Review Board (ARB) chartered to investigate the anomaly concluded that the most likely root cause lies within one of HST's 6 rate-integrating gyroscopes. This paper provides a summary of the initial paths of investigation, the analysis and testing performed to attempt to isolate the source, and a review of the findings of the ARB. The possibility of future operational impacts and available methods of on-orbit mitigation are also addressed.

Paper Details

Date Published: 30 June 2006
PDF: 12 pages
Proc. SPIE 6270, Observatory Operations: Strategies, Processes, and Systems, 62701K (30 June 2006); doi: 10.1117/12.672457
Show Author Affiliations
Morgan M. Van Arsdall, Lockheed Martin Technical Operations (United States)
Patrick R. Ramsey, Lockheed Martin Technical Operations (United States)
Scott R. Swain, Lockheed Martin Technical Operations (United States)

Published in SPIE Proceedings Vol. 6270:
Observatory Operations: Strategies, Processes, and Systems
David R. Silva; Rodger E. Doxsey, Editor(s)

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