The possible interruption of regular daily images sent by the 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.
SOHO was built by the European Space Agency and is a joint project with NASA.
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.
Strong storms can be deadly to spacewalking astronauts. The crew of the International Space Station, while inside, is generally not endangered, but they do have a special protective area they can go to in a severe storm.
A peak of solar activity occurred during 2001 and 2003. Sunspots and solar flares are now on the decline, but scientists say significant activity can occur at any time.
"It would be a terrible loss for us if it proves to be a loss," Kunches said. "We've grown over the years to rely on it."
SOHO (Solar and Heliospheric Observatory) launched in 1995. No other combination of satellites can gather the range of data it provides, he said.
20-year setback
"It's hard to overstate the importance of that data," Kunches said. "I'm hopeful they'll be really resourceful and keep it coming in some fashion." If not, he added, space weather forecasting "would be set back about 20 years."
Other satellites, including NOAA's GOES-12, collect real-time solar data. But none compete with SOHO. Particularly important, Kunches said, is the probe's Large Angle and Spectrometric COronagraph (LASCO) instrument, one of 11 on SOHO. LASCO blocks light from the Sun's bright disk in order to photograph the visibly fainter yet powerful bursts of particles that are spat out.
"If LASCO can't supply data [daily], we really don't have any other alternative," Kunches said.
Minor movement
SOHO engineers have been trying to unstick the antenna for six days. At 3:30 p.m. ET Thursday, SOHO Deputy Project manager Paal Brekke told SPACE.com that they had just succeeded in moving it slightly. It's not clear what that means, he said. But it is possible that the antenna can be moved, step-by-step, into a more favorable position that would cut the possible downtime from one month out of three to about 18 days every three months.
Work continues and more may be learned by Friday.
If the antenna is not shifted significantly, its ability to transmit images will cease "in the next couple of days," said SOHO Project Scientist Bernhard Fleck. The craft travels on an elliptical orbit and its antenna must be moved periodically to keep it pointing Earthward.
After about a month of hibernation, the craft's orbit would bring it back into a position in which some orbital gymnastics might be employed -- the spacecraft would be flipped upside down -- to point the antenna toward Earth, and the business of space weather forecasting would return again, for a time at least, to the 21st Century.
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