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Mission Status Report #111      Star Date: October 18, 2007

FUSE is Dead...Long Live FUSE!

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.)

Dear FUSE Community,

As discussed in my last status report, the FUSE satellite has terminated science operations and has entered the close-out phase of the project, which will last approximately one year. However, today marked a significant event in this process: the conclusion of actual on-orbit activities with the satellite. That's right. Today we "killed" FUSE.

We couldn't just "turn off" a satellite like FUSE. It involves a whole process of going through various steps to circumvent all of the normal protections that are in place to prevent mistakes from happening. It took most of the day to do the dirty task, but it has been done.

FUSE will be up there tumbling around for a long time (roughly 30 years by some estimates), and the solar panels will occasionally point toward the sun for brief periods. So the trick was to put the satellite into a configuration where a) it can't "wake up" accidentally, and where b) the batteries (charged by the solar panels) cannot and will not overcharge and cause some kind of problem. Hence, power relays to various subsystems, like the reaction wheel assemblies or the science instrument, were opened so they cannot draw power, and the power system was tricked into thinking it is fully charged when it is not, so the battery cannot overcharge.

The other main concern was to make sure that FUSE stays "quiet," that is, does not turn on its radio transmitter, possibly causing interference with future satellites that might use its radio frequency. Toward the end, FUSE's computers (there are several) were commanded into "standby" mode so that they would not process any commands unintentionally, and then the transmitter was turned off. FUSE will be monitored for several days now to make sure that this last command was processed, and that FUSE remains quiet. For all intents and purposes, FUSE is dead.

Or is it? Over the last eight years, FUSE obtained over 130 million seconds (over 4 years!) of on-target observing time! This huge mountain of data will remain available to scientists to mine for years to come. It is this science archive that will form the lasting legacy of the FUSE mission. With no other missions similar to FUSE on the drawing boards at this point, this archive will have to suffice for astronomers for the foreseeable future. Hence, the headline on this page:

FUSE is Dead...Long live FUSE!

I would be remiss if I did not thank all of the FUSE Sciences Operations team, past and present, including our partners on the Mission Operations Team from Honeywell Technology Solutions, Inc., and our colleagues at Orbital Sciences Corporation, as well as the JHU operations staff, for their exceptional efforts in keeping FUSE operating. It's been a fantastic experience.

Reported by: Bill Blair, FUSE Chief of Observatory Operations

Last Update: October 18, 2007

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