The Hubble Space Telescope, NASA’s jewel of the skies, is temporarily out of service. On Friday, the telescope stood down from observing and put itself into “safe mode” after one of its gyroscopes, which keep it aimed at objects of scientific interest, died.
NASA has appointed a review board to investigate the gyroscope problem. The telescope carries a total of six gyroscopes, but only three are needed to run the telescope. The others serve as backups.
During Hubble’s early years the gyroscopes died often, and replacing them was one of the main tasks of servicing missions. During the last and final servicing mission, in May 2009, astronauts installed six new gyroscopes. Two have since died, leaving a backup and three working gyroscopes, one of which expired on Friday.
But when ground controllers tried to bring the backup gyroscope online, it behaved erratically, sending garbled messages back to the ground, said Ken Sembach, director of the Space Telescope Science Institute in Baltimore, which operates the telescope.
The instrument may simply need to be rebooted, Dr. Sembach said in a brief telephone interview on Monday. But, he added, “We don’t want to start flipping switches until we understand what’s happening.”
Dr. Sembach said that the review board would need at least a few days to reach any conclusion. Hubble can operate with just two gyroscopes if necessary, as it did from 2005 to 2009 while waiting for astronauts to come fix it. Even one gyroscope will do in a pinch.
The flow of heavenly cosmic postcards has stopped for now, but Dr. Sembach said that Hubble still has years of good science ahead of it.