The Hubble Space Telescope was disabled by the failure of a nine-year-old gyroscope that was originally intended to be replaced after two or three years, the makers of the device said Monday.
Three of the Hubble's six gyros must work for the Hubble to operate -- with Saturday's failure, only two work.
"Our guys provide information to [NASA about] life expectancy," said Joseph Militano, a spokesman for Allied Signal, the company that makes Hubble's gyroscopes. "Those things have fully achieved their life expectancy."
A NASA official who helps oversee the Hubble Telescope mission could not recall a plan to swap out the gyros every two to three years.
He said that NASA operated under a plan to replace the gyros only as needed, he said.
"Our plan, and the plan that we execute, is to repair what's broken and to make periodic upgrades to systems if they improve the productivity of the telescope," said Keith Kalinowski, systems manager for the Hubble project.
Saturday's failure of a gyroscope -- a spinning disk that helps keep the telescope steady enough to focus on any object at which it is aimed -- will leave the Hubble inoperable for at least three weeks, when a planned servicing mission is carried out by a space shuttle repair team.
In fact, the recent failure is one of seven gyroscope failures that have plagued the observatory since its launch in 1990.
Still, Kalinowski said that while the failure is unfortunate, the space agency made no mistakes.
"We view these things as random failures of the units," Kalinowski said. "We're in the business of making the best judgments available to us, and sometimes things don't work out exactly as you would hope."
20/20 hindsight
In hindsight, NASA missed an opportunity in 1997 to head off a series of gyroscope failures that has led the space agency to take the Hubble offline.
During a servicing mission in February 1997, no gyroscopes were replaced by NASA.
Months after, problems began. One gyroscope failed in the spring of 1997, another in 1998, and two in 1999.
During that period, no Hubble repair missions were planned.
But after the first failure of 1999 -- in January -- NASA calculated that the Hubble had only a one-in-two chance of operating without incident before the next scheduled repair mission, then planned for May 2000.
So the repair mission was moved up to October of 1999, when, according to NASA calculations, the chances of a successful operation increased to 7 in 10.
That mission has since been pushed back to December 6 because of wiring problems with the space shuttle fleet.
And then there were two
When originally launched, the Hubble Telescope had a complement of six gyros, though it could operate successfully with three. But within three years the margin of error was gone -- half of the original gyros had stopped operating.
An electrical problem was later identified as affecting the three defunct gyros, plus a still operating fourth one. All four were replaced during a servicing mission in 1993.
That restored to the observatory six operational gyros, which performed without a major problem for three years. NASA apparently had enough confidence in these units to pass up an opportunity to replace any during a second servicing mission in early 1997.
They miscalculated. Since 1997, four more gyroscopes have failed.
Today, the telescope has only two operational gyros, ending the craft's ability to carry out any scientific observation.
According to Kalinowski, of the seven gyros that have failed since the telescope went into service, two gyros broke from electrical problems, one from an external electrical issue, and the final four from a wiring problem.
During the shuttle repair mission in December, all six gyros on Hubble will be replaced with newly manufactured units.
advertisement
