So Far, So Good for SOHO

NASA and European Space Agency (ESA) engineers announced today at a press conference that they have not detected permanent damage to the Solar and Heliospheric Observatory (SOHO), which spun out of control and lost power after a series of ground control errors in June. Although they haven't yet tested the scientific instruments, the agencies report that excess cold or heat has not damaged the telemetry, power, or control systems of the $1 billion craft, which finally answered ground controller's calls early last month (ScienceNOW, 10 August). In addition, a NASA/ESA panel investigating the transient loss of the probe released a report at the press conference confirming that human error, not mechanical failure, caused the spacecraft's problems.

"So far the recovery [has been] fairly smooth," says Berhard Flick, ESA deputy project scientist for SOHO at NASA's Goddard Space Flight Center. The next step, he says, is to use electric heaters to continue thawing SOHO's frozen hydrazine propellant. Engineers have thawed the main tank and are now warming the pipes that connect the hydrazine tank to the thrusters outside. Flick says that may take up to 2 weeks, since a quicker thaw could burst the pipes. After testing the mechanism that controls the craft's position, controllers will attempt to stop the spacecraft's slow spin. "Finally we will point the spacecraft with thrusters back to the sun," he says.

Meanwhile, a panel of NASA and ESA scientists confirmed earlier reports that the probe's loss was due to human error (ScienceNOW, 16 July). It blamed overloaded staff and data displays that were "not user-friendly"--a problem that was recognized in 1994 but never solved. The committee recommends that NASA and ESA review their ground control procedures and management structure before the satellite comes back on line.

Serge Koutchmy of the Institut d'Astrophysique de Paris, a SOHO co-investigator, is delighted with the progress made with the satellite. "I have the feeling that the ESA and NASA teams are doing very good work recovering the spacecraft," he says.

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