Plug Pulled on FUSE

After an eight-year run that gave astronomers a completely new perspective on the universe, NASA said it terminated its Far Ultraviolet Spectroscopic Explorer mission Thursday. The satellite, known as FUSE, became inoperable in July when it lost its ability to point accurately and steadily at areas of interest.

"For all intents and purposes, FUSE is dead," said Bill Blair, FUSE chief of observatory operations, on the satellite's Web site, adding that it will take years for astronomers to comb through the mountain of data generated by the mission.

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 interest to astronomers. About 200 individual stars in this galaxy have been observed with FUSE since 1999. (Graphic courtesy NASA and Lauren Fowler, the JHU FUSE project)

"FUSE will be up there tumbling around for a long time (roughly 30 years by some estimates)," Blair wrote. Because the solar panels will occasionally point toward the sun for brief periods, the mission team had to put the satelite into a configuration where it couldn't "wake up" accidentally and tricked the power system into thinking it was fully charged so the batteries, usually reenergized by the solar panels, can't overcharge and cause a problem.

The other main concern was to make sure that FUSE stays "quiet," and doesn't turn on its radio transmitter, which would possibly cause interference with future satellites using the same radio frequency. So the mission team put FUSE's computers in standby mode and the transmitter was turned off.

"FUSE accomplished all of its mission goals and more," said Alan Stern, associate administrator for the Science Mission Directorate at NASA. "FUSE vastly increased our understanding of our galaxy's evolution and many exotic phenomena and left a strong legacy on which to build the next generation of investigations and missions."

Launched in 1999, FUSE helped scientists answer important questions about the conditions in the universe immediately following the Big Bang, how chemicals disperse throughout galaxies, and the composition of interstellar gas clouds that form stars and solar systems.

"FUSE helped pioneer low-cost, principal investigator-led astronomy missions," said Jon Morse, director of NASA's Astrophysics Div.

FUSE's achievements include:

Showing that enough water has escaped from Mars to form a vast ocean 100-feet deep,
Discovering far more deuterium, a form of hydrogen, in the Milky Way galaxy than astronomers had expected,
Detecting an atmosphere of very hot gas surrounding the Milky Way,
Showing that about 10 percent of matter in the local universe consists of million-degree gas floating between the galaxies.

FUSE was a joint mission of NASA, the Canadian Space Agency and the French Space Agency. The Johns Hopkins University built the telescope and managed the mission. The University of Colorado, Boulder, built FUSE's spectrograph and the University of California, Berkeley, made the detectors.

"FUSE collected quality science data for eight years, longer than its five-year goal. By any measure, FUSE was a success," said George Sonneborn, FUSE project scientist at NASA's Goddard Space Flight Center, Greenbelt, Md.

NASA will continue its ultraviolet (UV) study of the universe in 2008 by installing a new UV spectrograph on the Hubble Space Telescope and repairing another that failed in August 2004.

For more information, visit: http://fuse.pha.jhu.edu