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T. B. Ake (JHU/CSC), B. F. Class (OSC), B. A. Roberts, J. W. Kruk, W. P. Blair, H. W. Moos (JHU), FUSE Operations Team
The Far Ultraviolet Spectroscopic Explorer (FUSE) satellite was at the peak of its scientific productivity when attitude control hardware problems began to surface two years after launch. On November 25 and December 10, 2001, FUSE lost use of two of its four reaction wheels required for slewing and pointing control. The pitch and yaw wheels despun due to excessive friction between the rotors and wheel housings. The remaining roll and skew wheels were inadequate for three-axis control. Since then, several innovative techniques have been developed using the magnetic torquer bars (MTBs), which were installed for momentum management, for attitude control. The first flight software update, made within 10 days of the December failure, constrained the skew wheel to control pitch and directed yaw torque requests to the wheel unloading routine, causing the software to respond as if addition momentum needed to be removed by the MTBs. This achieved enough pointing stability to allow work to proceed on developing a new control law fully integrating the MTBs in the control loop. This software was loaded on January 25, 2002 and immediately reestablished fine pointing capability. The concepts and development of this system are unique in astronomical space observatories and demonstrates the feasibility of using the geomagnetic field for pointing control without the use of reaction wheels for near-earth orbit astronomy missions.
This work is supported by NASA Contract NAS5-32985 to the Johns Hopkins University.
If you would like more information about this abstract, please follow the link to http://fuse.pha.jhu.edu. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.
The author(s) of this abstract have provided an email address for comments about the abstract: ake@pha.jhu.edu
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.