ROSAT: Rest in Peace

Astronomers bid a bittersweet farewell today to a pathbreaking satellite. After defying death countless times during its 8-year career, the Röntgen Satellite (ROSAT) lost its last working instrument yesterday, leaving the spacecraft sightless and drifting. "It's like losing an old friend," says astronomer Nick White of the Goddard Space Flight Center in Greenbelt, Maryland.

When the orbiting x-ray telescope was launched in 1990, researchers anticipated it would scan the skies for pulsars, supernova remnants, and other radiation-emitting objects for just a few years. But the craft's sturdy German engineering--and countless clever resuscitation efforts by ground controllers--enabled ROSAT to become the longest lived x-ray observer ever. It detected more than 150,000 x-ray sources, 20 times more than were known when it was launched. Among its head-turning accomplishments were the discovery of a surprisingly close neutron star and some of the most distant galaxy clusters ever found. "ROSAT has provided us with much more scientific data than we ever hoped for," eulogized Goddard astronomer Robert Petre.

But astronomers knew ROSAT's days were numbered in September, when the sun burned out a key detector during a failed effort to keep the craft alive for another year. It lingered on long enough for scientists make one last observation of a few important objects, including a supernova that was ROSAT's very first target in 1990. "People were disappointed that they couldn't squeeze another year's worth of data out of it," says White. But he and other astronomers won't be grieving long: NASA is planning to launch a new, state-of-the-art x-ray observatory--the Advanced X-ray Astrophysics Facility--in April 1999.