Mission Status Report #105 Star Date: May 31, 2007
FUSE Recovery Progressing Well!
Caption: The FUSE satellite floats in front of an infrared image of the Carina Nebula, a region of intense star formation, taken with the Spitzer Space Telescope. Many hot stars within this nebula, including the enigmatic Eta Carina itself, have been the subject of intense study with FUSE observations. Joint observations at several wavelengths using facilities from ground-based telescopes to NASA space telescopes are needed to fully understand complex processes such as star formation. (Figure courtesy NASA and the FUSE project.)
The FUSE spacecraft experienced a significant anomaly May 8, 2007, involving the skew reaction wheel. However, today I have some terrific news!
The last week has provided not only significant progress on the recovery, but real hope that a return to operations may be possible in the near future. Late on Thursday, May 24, 2007, we were able to get the skew wheel spinning again. Using revised procedures, we were also able to keep the spacecraft stable enough to remain power positive, and thus keep the wheel spinning. I am happy to report that, as of late today, the wheel has been spinning for a full week!
Analysis of the telemetry during this period has shown continued improvement in the performance of the wheel over time. The first 24 hours after this restart was a mixed bag, with periods of steady performance and periods with excess drag. However, letting the wheel run solidly for a week has shown a trend toward reduced friction, and a marked decrease in friction spikes (that is, very short periods of increased friction) as time has progressed. Assuming this trend continues, it appears the wheel is in the process of "healing" itself.
There is significant work still to be done. As a conservative measure, we may decide to just keep the wheel spinning in one direction and avoid low wheel speeds and "zero crossings" as much as possible. Hence, our planning tools and operational procedures need to be adjusted to make this happen. Alternatively, as we transition back into an operational state and get experience, we may decide we can live with rapid transitions from positive to negative wheel speed (and vice versa) while minimizing the time near zero wheel speed. Time (and experience) will tell. Either way, the improvements over the last week are dramatic and very encouraging, and we are hopeful that a return to operations may be just around the corner.
I want to express my continued thanks to the many people who are putting in long hours to keep FUSE safe during this difficult period, and who are now helping to bring us back into an operational state.
More information will be provided here, electronically to the FUSE users mailing list, and through the NASA project scientist's office at NASA/Goddard as the information becomes available.
Reported by: Bill Blair, FUSE Chief of Observatory Operations
Last Update: May 31, 2007
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