WASHINGTON -- NASA could have avoided a March 21 mishap that damaged a $40 million science satellite with better maintenance and training, an agency investigation board reported Friday.
The High Energy Solar Spectroscopic Imager (HESSI) was damaged during preflight verification tests because of a malfunction in the vibration-test system at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.
The spacecraft was to have been shaken with a force of 2 Gs -- the equivalent of two times the force of gravity. Instead, it was shaken to 20 Gs, which damaged the satellite.
The reason was a misalignment between two pieces of the test stand due to a broken support bearing, investigators found.
That led to an abnormally high level of static friction, which caused the computer controlling the test to compensate and induce too large a shock into HESSI
"It's similar to what happens when you are trying to close a sticky wooden window that [is] just a little out of kilter in the frame," said Denny Kross, engineering systems chief at the Marshall Space Flight Center in Huntsville, Alabama.
"As soon as the window starts to stick, your brain says 'push down harder.' And if you are not careful, you can push down so hard that, when the window does break free, it slams down onto the bottom of the window sill," he said.
The accident could have been prevented had a scheduled maintenance program requiring periodic inspections of the vibration stand been in place, the board found.
The teams doing the testing also should have been trained to look for potential performance problems in pre-test data.
JPL is adding new steps and procedures to avoid similar incidents, Kross said.
HESSI, meanwhile, will be repaired and rebuilt at the University of California, Berkeley, and will be returned to JPL for continued testing. A launch date is uncertain.
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