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Proceedings Paper

FUSE in-orbit attitude control with two reaction wheels and no gyroscopes
Author(s): Jeffrey W. Kruk; Brian F. Class; Dan Rovner; Jason Westphal; Thomas B. Ake; H. Warren Moos; Bryce A. Roberts; Landis Fisher
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Paper Abstract

The Far Ultraviolet Spectroscopic Explorer is a NASA Origins mission launched in June 1999 to obtain high-resolution spectra of astronomical sources at far-ultraviolet wavelengths. The science objectives require the satellite to provide inertial pointing at arbitrary positions on the sky with sub-arcsecond accuracy and stability. The requirements were met using a combination of ring-laser gyroscopes, three-axis magnetometers, and a fine error sensor for attitude knowledge, and reaction wheels for attitude control. Magnetic torquer bars are used for momentum management of the reaction wheels, and coarse sun sensors for safe mode pointing. The gyroscopes are packaged as two coaligned inertial reference units of three orthogonal gyroscopes each. There are four reaction wheels: three oriented along orthogonal axes, the fourth skewed at equal angles (54.7°) with respect to the others. Early in the mission the gyroscopes began showing signs of aging more rapidly than expected, and one failed after two years of operation. In addition, two of the orthogonal wheels failed in late 2001. The flight software has been modified to employ the torquer bars in conjunction with the two remaining wheels to provide fine pointing control. Additional new flight software is under development to provide attitude control if both gyroscopes fail on one or more axes. Simulations indicate that the pointing requirements will still be met, though with some decrease in observing efficiency. We will describe the new attitude control system, compare performance characteristics before and after the reaction wheel failures, and present predicted performance without gyroscopes.

Paper Details

Date Published: 24 February 2003
PDF: 12 pages
Proc. SPIE 4854, Future EUV/UV and Visible Space Astrophysics Missions and Instrumentation, (24 February 2003); doi: 10.1117/12.459948
Show Author Affiliations
Jeffrey W. Kruk, Johns Hopkins Univ. (United States)
Brian F. Class, Orbital Sciences Corp. (United States)
Dan Rovner, Orbital Sciences Corp. (United States)
Jason Westphal, Orbital Sciences Corp. (United States)
Thomas B. Ake, Johns Hopkins Univ. (United States)
H. Warren Moos, Johns Hopkins Univ. (United States)
Bryce A. Roberts, Johns Hopkins Univ. (United States)
Landis Fisher, Johns Hopkins Univ. (United States)

Published in SPIE Proceedings Vol. 4854:
Future EUV/UV and Visible Space Astrophysics Missions and Instrumentation
J. Chris Blades; Oswald H. W. Siegmund, Editor(s)

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