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Mission Status Report #85      Star Date: Apr. 22, 2005

Steady as She Goes

Caption: FUSE Satellite Control Center, during recovery operations in March 2005. (Photo by Bill Blair, FUSE project, JHU.)

(Click image above to see larger version.)

The FUSE satellite has made slow but steady progress toward the return to science operations over the last few weeks, after the period of hiatus caused by a reaction wheel failure in December 2004. (See this earlier Status report.) Sometimes we have taken the proverbial "two steps forward, one step back," but we are making forward progress!

Since the last report, there have been several significant events. We have been delivering Mission Planning Schedules (timelines of events and pointings) and have gotten considerable experience with the revised control system. We have been purposely staying close to (within 5 degrees of) the south orbital pole, which is the safest orientation right now. However, this pole moves, and so we get experience slewing (moving from one place to another on the sky) in a safe and stable orientation. Testing in this mode has uncovered some minor glitches, but more importantly has provided insight into how to make the control system operate better. Changes have been developed, and are in testing for upload soon, that will make our new pointing system more robust against disturbances. This is good news!

The downside of staying so close to the orbit pole is that only limited targets are available for observation at any given time. However, two weeks ago we actually observed some previously unobserved targets as our view passed through the Large Magellanic Cloud, a neighboring galaxy to the Milky Way. So we have actually done some "new science" since coming back on-line in limited operations mode.

Some days it seems like progress is painfully slow, but I have to remind myself from time to time that what we are doing here really has no precedent. No one has ever operated a finely pointed astronomical satellite with only one operational reaction wheel, let alone with aging and failing gyroscopes as well. Balancing a 3000 pound (1365 Kg) satellite on the earth's magnetic field and pushing it around the sky is a very tricky and complicated business. It is not surprising when things don't go entirely according to plan, but we are learning as we go.

At the moment, for safety reasons, we have the satellite parked in one if its safe modes that will allow the new software patches to be uploaded as soon as they are available. We feel we have learned about as much as we can from the current software, and we need to get the updates in place so we can take the next step.

Continued thanks to all of the FUSE Sciences Operations team, including our partners on the Mission Operations Team from Honeywell Technology Solutions, Inc., and our colleagues at Orbital Sciences Corporation, for their tremendous effort so far, and for their ongoing efforts as we improve the new control system.

Reported by: Bill Blair, FUSE Chief of Observatory Operations

Last Update: April 22, 2005

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