Recovered SOHO Passes Health Check

NAPLES, ITALY--After 4 months of nail-biting over the fate of one of their most successful research spacecraft ever, solar astronomers are breathing a sigh of relief this week. After spinning out of control last June and being baked and frozen by extreme temperatures, the Solar and Heliospheric Observatory (SOHO) appears to have come through its ordeal unscathed. "It is a miracle," says Bernhard Fleck, the European Space Agency (ESA) project scientist for SOHO at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

A joint project between NASA and the ESA, SOHO was launched in late 1995 and has made groundbreaking observations of the sun's atmosphere and its roiling surface. When the observatory spun out of control following a series of ground control errors, astronomers feared they had lost their chance to watch the sun as it reaches its 11-year maximum in solar activity around 2001. But ground engineers reestablished contact with the spacecraft in August and painstakingly worked to slow its spin and recharge its batteries. SOHO doesn't seem particularly bothered for having spent weeks out of touch with its navigators. "All the data we have seen up to now look very good," says principal investigator Claus Fröhlich of the Physical Meteorological Observatory at Switzerland's Davos World Radiation Center.

To date, seven of SOHO's 12 instruments have been switched on successfully, reports Fleck, who is amazed at how smoothly the recovery has gone. "We haven't observed any adverse effects due to the thermal stress so far," he said.

The interruption of data-taking was a setback for researchers studying the long-term oscillations of the sun. But in spite of the lost time, astronomers who spoke with Science are unanimous in praise for the Goddard recovery team, which has been toiling 7 days a week since June.