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Mission Status Report #108      Star Date: July 16, 2007

The Pendulum of Fate Swings Again...

Caption: The FUSE satellite is seen superimposed on an optical image of the nearby galaxy known as the Large Magellanic Cloud, a satellite galaxy of the Milky Way. At a distance of only 170,000 light years, the Large Magellanic Cloud is of intense in this galaxy have been observed with FUSE since 1999. (Graphic courtesy NASA and Lauren Fowler, the JHU FUSE project.)

(Click image above to see larger version.)

It has been an up-and-down year for the FUSE satellite. After an exceptional winter and spring of operations, an unexpected anomaly occurred on May 8, 2007, involving the skew reaction wheel, the last of what were originally four reaction wheels on the satellite. After one month of troubleshooting and rewriting control software, science operations were recovered on June 12, 2007, and for one month, all was back to normal. (See the Status Report Archive for earlier reports.)

On last Thursday evening, July 12, 2007, fate dealt us another blow as the excess friction problem on the skew wheel returned with a vengeance. The wheel was operating perfectly up to the time of the reoccurrence of the anomaly. Since that time, we have been primarily concerned with the health and safety of the spacecraft. This week will be spent assessing the anomaly and making every reasonable attempt to recover motion in the errant wheel.

If the wheel can be restarted, we will assess its ability to perform science operations again and proceed from there. In the event that the wheel cannot be restarted, this will mean the end of science operations with FUSE. We have pulled many rabbits out of the hat over the years, but a "no-wheels" mode will not be one of them. We see no viable way to point the spacecraft at the level required for science without at least one reaction wheel.

Keep your fingers crossed. I will post further news as conditions warrant.

Reported by: Bill Blair, FUSE Chief of Observatory Operations

Last Update: July 16, 2007

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