From Space.com :
Sun-Watching SOHO Spacecraft Experiencing Serious Technical Problems
The possible interruption of regular daily images sent by NASA's
troubled SOHO spacecraft would be a "terrible loss" that would set
space weather forecasting back 20 years, a top forecaster said today.
The craft's primary antenna was not moving properly as of 3:30 p.m. ET
Thursday, though engineers reported minor progress in unsticking the
antenna and shifting it one small step. The problem is with the motor
or drive unit.
The high-gain antenna, used for downloading images and data, has been
acting up for two weeks and has been stuck for nearly a week. Joe
Kunches, lead forecaster at the NOAA Space Environment Center, just
learned about it today.
"When I heard of this problem it sent a sort of chill down my spine,"
Kunches said in a telephone interview. The agency's customers include
NASA and power companies and satellite operators around the world.
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(While there are other spacecraft that could be used for flare
detection and solar wind analysis, like GOES-8, TRACE, and ACE, SOHO
is the only one that has the instruments to image CME's as they
happen. SOHO is also the only spacecraft that has instruments to
image the sun in the extreme UV range. Those UV pictures are very
important for the analysis of flare and sunspot activity, and for the
detection of coronal holes, although the YOKOH soft X-ray satellite
could be used for coronal hole detection. In short, the lost of SOHO
would have a major impact.)