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NASA gently nudges sleeping space 'scopes Chandra, Hubble out of gyro-induced stupor

X-ray probe could be awake by end of this week

NASA's rough month is improving somewhat: the American space agency is spinning up a spare gyroscope to bring the orbiting Chandra X-Ray Observatory back online by the end of the week, and it reckons it can wake the Hubble Space Telescope soon.

Chandra automatically and unexpectedly entered “safe mode” late last week, sending its mission specialists on a hunt for the cause. In safe mode, science experiments are suspended, primary hardware hands its tasks over to backup systems, and the satellite orients itself to get maximum sunlight on its solar panels.

One possible reason identified last week was a glitch in a gyroscope that confused the machine and forced it to enter safe mode as a precaution to prevent any damage. And that's turned out to be the case. In a October 15 update, NASA said:

The safe mode was caused by a glitch in one of Chandra's gyroscopes resulting in a 3-second period of bad data that in turn led the on-board computer to calculate an incorrect value for the spacecraft momentum. The erroneous momentum indication then triggered the safe mode.

NASA's eggheads have decided that the guilty gyroscope will be put in reserve, and another brought online.

“Once configured with a series of pre-tested flight software patches, the team will return Chandra to science operations which are expected to commence by the end of this week,” the agency's officials announced.


NASA's Chandra probe suddenly becomes an EX-ray space telescope (for now, anyway)


As The Register noted last week, Chandra has performed sterling work in its 19 years, including snapping the first images of a shockwave from a supernova, picturing galaxies in the process of merging, revealing different types of black holes, and playing a key role in preparing the route for the New Horizons probe flyby of Pluto and other Kuiper belt objects.

There are also hopeful noises coming out of NASA's Hubble team. On Saturday, NASA posted an update that detailed the problems suffered by a backup gyro brought online after Hubble also unexpectedly dived into safe mode on October 5.

NASA said the issue confronting the anomaly review board is that the gyro it brought into service in the orbiting probe is reporting rotation rates “orders of magnitude higher than they actually are.”

Tests “showed that the gyro is properly tracking Hubble’s movement, but the rates reported are consistently higher than the true rates,” the update continued. In other words, the gyro speeds up or slows down when it should, but is reporting the wrong absolute values for its rotation.

If the Hubble team can implement solutions from the ground to compensate for the problem, the space 'scope will return to three-gyro operations – if not, one of the gyros now in service will be parked and the telescope will be put into single-gyro mode.

NASA said Hubble would still be able to provide science “well into the 2020s.” ®

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