For 22 days now, it's been a much darker world for scientists who study the sun.
Since June 24, when communication with a key research satellite broke down, disappointed scientists have been scrambling to find other ways to glean information about solar activity - information that sometimes affects day-to-day life on Earth.
The Solar and Heliospheric Observatory (SOHO), which made continuous observations about the sun since December 1995, helped physicists predict powerful explosions in the sun's atmosphere. These explosions send high-energy particles toward Earth capable of damaging communications satellites, interfering with power lines, and irradiating astronauts in space.
"It's a huge loss that we just don't know how to replace," says Ernie Hildner, who directs the space environment center in Boulder, Colo., for the National Oceanic and Atmospheric Administration.
Some scientists have not given up hope that the $1.2 billion satellite can be saved. Since losing contact with SOHO during a routine maintenance operation, engineers have used large antennas daily to try to reestablish contact.
Bill Worrall, the US spaceflight operations manager at Goddard Space Flight Center in Greenbelt, Md., says SOHO should rotate so that its solar panels can recharge as they again begin facing the sun. Maximum sun exposure should occur in mid-September, scientists calculate.
A review panel with the National Aeronautics and Space Administration and the European Space Agency is expected this week to reveal what went wrong on June 24. Sources say new computer software may have contributed to the communication failure.
Solar forecasters primarily used a SOHO instrument visualizing faint emissions from particles leaving the solar atmosphere. This information has saved the electric power industry $30 million a year, says Dr. Hildner.
In addition, physicists around the world have relied on SOHO's 12 instruments to collect data that they say have vastly improved their understanding of the sun's dynamic processes. Using SOHO's data, they have discovered the existence of solar quakes and rivers of gaseous molecules beneath sunspots.
MEANWHILE, to fill in gaps left by SOHO's absence, scientists are coordinating ground-based and remaining space-based observatories. But these cannot fully compensate for SOHO, says Jack Harvey of the National Space Observatory in Tucson, Ariz. The remaining satellites do not have SOHO's versatility, and ground-based observatories must watch the sun through Earth's atmosphere, making for sometimes-murky results.
Scientists at Stanford University in Palo Alto, Calif., say they'll propose building a satellite to replace a SOHO instrument that measured oscillations at the sun's surface. The new satellite could also carry unused instruments originally built for use on SOHO, says Stanford's Phil Sherrer, head of the project. If funded, the new spacecraft could be launched in three years, in time for scientists to watch the sun's most active period of the current 11-year solar cycle, says Dr. Sherrer.
If SOHO is irretrievably lost, scientists will have to wait for the next solar cycle to see the solar maximum as well as they expected to with SOHO. "It's really hard to work so hard, knowing all these secrets will be revealed, and all of a sudden it's not there," says Barbara Thompson, an astrophysicist at Goddard.