Solar observatory almost fully recovered.

SOHO is back in business. More than 4 months after ground controllers lost contact with the Solar and Heliospheric Observatory on June 24 and the craft spun out of control, all 12 of the satellite's instruments have been switched on and nearly all detectors are functioning.

The process of restoring power to instruments began Oct. 5, 2 weeks after controllers were able to point the craft back in its proper direction and place it in its proper orbit (SN: 8/8/98, p. 91). On Nov. 4, a device that analyzes the sun's ultraviolet light became the last of the 12 instruments to resume operation, says Bernard Fleck, the European Space Agency's SOHO project scientist, who is based at NASA's Goddard Space Flight Center in Greenbelt, Md.

Scientists had feared that some of the detectors, which were exposed to temperatures as low as -120oC and as high as 110 [degrees] C during the time that the craft was without power, would not survive.

One of three detectors that image the sun's outer atmosphere, or corona, and one of two detectors that measure the solar wind are not functioning properly, says Joseph B. Gurman, NASA's SOHO project scientist at Goddard. He notes, however, that the exposure to high temperatures has improved by 60 percent the sensitivity of solid-state detectors on SOHO's extreme-ultraviolet-imaging telescope.