FUSE Mission Status Report

Mission Status Report #22      Star Date: October 22, 1999

NOTE: Mission Status Reports on the web page will continue roughly once a week, as events unfold.

-- Bill Blair

A graphic view of the FUSE on orbit (left) and the Satellite Control Center at JHU (right).

(Click either image to see larger version.)

UPRM Ground Station Back to Operational

Time flies when you're having fun. I can't believe it has been 11 days since my last report!

We are all extremely relieved to have our ground station antenna at the University of Puerto Rico back in service and working dependably again. It came back into service just a couple of days after my last report and has been working well since then. It appears to have been a combination of s/w and h/w problems that caused our difficulties, and a complete understanding of what happened has been hard to reconstruct. However, it is working again now, and that's the most important thing for operations! (And by the way, thank goodness hurricane Jose has decided to turn to the north...)

It has been a good week for FUSE operations. Several important tests have run successfully and we have seen a steady stream of science observations intermingled and executed as planned. The test data are still being analyzed, but are beginning to confirm some of our suspicions about the mirror focus and alignment difficulties we have been having. You may recall FUSE operates with four separate telescope mirrors, each of which must be focussed and aligned with respect to the others. We have clear evidence now that at least some of the time when we make a "focus" motion (that is, just a movement up or down to change the mirror focus position), a "tilt" of one or more of the mirrors is also introduced. Hence, if the mirrors were close to aligned before the focus movement, they can become unaligned afterwards. We have also seen some evidence that the mirrors can change their relative positions when we move between objects on the sky. Further measurements to characterize the systematics of these mirror motions are now our highest priority for the ongoing checkout activities. Between tests, we obtain science data with whatever mirrors are aligned at that time, and we are getting some good data!

The FUSE Science team was in town last Thursday and Friday for a team meeting. In general, they left with the impression that we have had some problems but that we are attacking those problems in a proper and systematic way. They also got a look at some of our early science observations and were very excited about the data even though we are not yet focussed and aligned. Since then, we have had even more science results coming in and working their way out to the investigators. We expect to have a very nice set of initial results to present at the American Astronomical Society meeting in Atlanta in January 2000!

Reported by: Bill Blair, Chief of Mission Planning

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