Mission Status Report #24 Star Date: November 12, 1999
NOTE: Mission Status Reports on the web page will continue roughly once a week.
A graphic view of the FUSE on orbit (left) and one of the four FUSE Mirrors (right).
(Click either image to see larger version.)
FUSE Mirror Alignments Being Characterized
FUSE operations have continued smoothly over the last week. A checkout program involving the tweaking of various thermal control parameters completed last weekend, and science observations of an Active Galactic Nucleus and a nearby white dwarf star were accomplished successfully. The four optical channels of the telescope are aligned at an approximate level, increasing the frequency of data gathering with light from all four mirrors.
As has been the case off and on over the last several weeks, we continue with detailed and systematic checkout tests that are characterizing the small relative motions we are seeing between our four primary mirrors. (See photo above, or click here for more information about the FUSE mirrors.) The extent of these motions is exceedingly small. We see the star images from the four separate mirrors move by a relative amount roughly equivalent to the width of a human hair, and yet this is enough to be significant! (Interestingly, the actual relative motions of the mirrors themselves is roughly 50 times smaller still!) The tests are producing good data and we are well on our way toward understanding this problem.
Preliminary analysis of these test data indicates that certain orientations of the satellite with respect to the sun and the earth are much more susceptible to mirror motions than others. This suggests an immediate operational fix: avoid those orientations as much as possible, and much of the problem will go away! While it will take some time to quantify these results at the level needed to take corrective action during observations, we can already see the direction we need to head to successfully address this problem.
As mentioned last week, we have a period coming up next week where normal operations will be put on hold for a few days due to the upcoming Leonid meteor shower. Interestingly, one of the big concerns is NOT from direct damage by a micrometeroid collision itself, but from possible electrical surges that might be produced from such an impact. FUSE will point in a benign direction during the storm and turn off many of it's high voltage electrical systems as a precaution.
Reported by: Bill Blair, Chief of Mission Planning
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