Caption: Graphic showing how FUSE might look on-orbit. The telescopes are looking toward the upper right in this picture, and only two of the four telescope doors are visible from this angle. The blue rectangles represent the solar panels, which connect to the spacecraft at the bottom. (Figure courtesy NASA and the FUSE project.)

The FUSE spacecraft experienced a significant anomaly May 8, 2007, involving the skew reaction wheel. After nearly a week of troubleshooting and manual station keeping to keep the satellite in a power positive configuration, we attempted to restart the errant wheel yesterday afternoon.

The good news is, it worked! The wheel was spun up to about 4200 rpm and held there for some 10 hours. The bad news is that it is very difficult to maintain the satellite in a power-positive attitude with the wheel spinning this fast. (Sort of like riding a bucking bronco and trying to point it at the sun.) Late last evening, we put FUSE into it's normal "nadir-pointing" safe mode to recharge the battery fully while we study the performance data from yesterday's successful restart.

I want to express my thanks to the many people who are putting in long hours to keep FUSE safe during this difficult period, and who are helping us troubleshoot the problem.

We request the continued patience of the community while we perform further tests to understand the wheel's performance and adjust our plans accordingly. 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.

For background on reaction wheels, see this report from an earlier wheel problem on FUSE from Jan. 2005.

Reported by: Bill Blair, FUSE Chief of Observatory Operations

Last Update: May 15, 2007

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