FUSE Mission Status Report

Mission Status Report #27      Star Date: December 20, 1999

NOTE: Mission Status Reports on the web page will be updated as new information warrants.

-- Bill Blair

A star field in the Large Magellanic Cloud, as viewed by Hubble Space Telescope. (Click image to see larger version, or GO HERE for more information.)

FUSE Goes over the Million Mark!

FUSE operations have continued smoothly over the last couple of weeks, concentrating on a spectrograph focus program and requested science observations. The focus data are still being analyzed, but we expect to see our first improvement in spectral resolution as a result of these tests and their implementation. The fact that we were able to carry out these tests successfully is an indication that we are getting pretty good at "managing" the alignment of the four telescope mirrors, so that data are obtained in the most efficient mode possible.

The FUSE satellite reached a milestone during this period, going over 1 million seconds of acquired science data! It has taken a bit longer than expected to reach this milestone, but we are picking up steam! With 31 million seconds in a year and an operating efficiency near 1/3rd (which we expect to be able to achieve), we should be able to get about 10 million seconds of science data before the REAL turn of the millennium on January 1, 2001! (Note editorial opinion, not necessarily held by everyone on the FUSE team!)

Much of the last week was spent observing stars in the nearby galaxy known as the Large Magellanic Cloud (see photo above). At about 170,000 light years distant, this galaxy is near enough to permit observations of individual stars with FUSE, while still being a separate star system, with different chemical abundances and a different star formation history from our own galaxy, the Milky Way. We have many science programs to do in this galaxy and got a good start on them this last week! That FUSE can observe such stars at high spectral resolution in far ultraviolet light is a testament to its excellent sensitivity, and is a demonstration of one of the primary capabilities needed to do the overall FUSE science program.

Looking to the future, we are taking a day this week to reboot the FUSE instrument computer and load new code that will permit much more autonomy to the satellite for repairing any radiation-induced problems in the computer memory. These radiation problems, known as "single event upsets" or SEUs, usually only affect one out of the two FUSE detectors, but can take anywhere from 12 to 24 hours to "fix" from the ground, depending on when we have ground station contacts with the satellite. The new code will allow FUSE to detect when these SEUs occur and fix them itself almost immediately.

Over the holiday period we will observe some very faint extragalactic targets which require very long exposures. This will ease the burden on the Mission Planning and Operations teams, allowing them to enjoy the holiday period as well. The entire science and operations team has worked incredibly hard over the last six months!

Finally, FUSE will take a small break right around the "Y2K" boundary to ensure a smooth transition. While all systems have been checked for Y2K compliance, it seems only prudent to place ourselves in a benign operating stature for an added bit of safety.

Just a reminder: The FUSE Science team will be presenting initial science results in Atlanta at the American Astronomical Society meeting, Jan. 11-15, 2000! Over two dozen papers will be presented at that time.

And now for a holiday present: Want to see a few example FUSE spectra? CLICK HERE!

Reported by: Bill Blair, Chief of Mission Planning

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