Chandra X-RAY Observatory enter safe mode

Prelims level : Science & Technology – Space Technology Mains level :
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  • The Chandra X-ray Observatory, which has been observing the universe in high-energy light since 1999, entered a protective “safe mode”. The cause of the safe mode transition (possibly involving a gyroscope) is under investigation.


  • • During the safe mode, the observatory is put into a safe configuration, critical hardware is swapped to back-up units, the spacecraft points so that the solar panels get maximum sunlight, and the mirrors point away from the Sun.
  • Analysis of available data indicates the transition to safe mode was normal behaviour for such an event. All systems functioned as expected and the scientific instruments are safe.
  • Gyroscopes help spacecraft maintain proper orientation. If a faulty gyroscope is to blame for Chandra’s current plight, the observatory would be in good company: A gyroscope failure knocked NASA’s iconic Hubble Space Telescope into safe mode last week.

Safe mode:

  • • Safe mode is an operating mode of a modern spacecraft during which all non-essential systems are shut down and only essential functions such as thermal management, radio reception and attitude control are active.
  • Safe mode is entered automatically upon the detection of a predefined operating condition or event that may indicate loss of control or damage to the spacecraft. Usually the trigger event is a system failure or detection of operating conditions considered dangerously out of the normal range.
  • Cosmic rays penetrating spacecraft electrical systems can create false signals or commands and thus cause a trigger event.
  • While in safe mode the preservation of the spacecraft is the highest priority. Typically, all non-essential systems, such as science instruments, are shut down. The spacecraft attempts to maintain orientation with respect to the Sun for illumination of solar panels and for thermal management.


  • • The Chandra X-ray Observatory previously known as the Advanced X-ray Astrophysics Facility is a Flagship-class space observatory launched by NASA on July 23, 1999.
  • Chandra is one of the Great Observatories, along with the Hubble Space Telescope, Compton Gamma Ray Observatory (1991–2000), and the Spitzer Space Telescope.
  • The telescope is named after the Nobel Prize-winning Indian-American astrophysicist Subrahmanyan Chandrasekhar.
  • Its mission is similar to that of ESA’s XMM-Newton spacecraft, also launched in 1999.
  • Chandra is sensitive to X-ray sources 100 times fainter than any previous X-ray telescope, enabled by the high angular resolution of its mirrors.
  • Since the Earth’s atmosphere absorbs the vast majority of X-rays, they are not detectable from Earth-based telescopes therefore space-based telescopes are required to make these observations.
  • Chandra focuses on the powerful X-ray emissions from violent cosmic phenomena such as supernovae and black holes.
  • • It is well beyond the original design lifetime of 5 years. In 2001, NASA extended its lifetime to 10 years. It is now well into its extended mission and is expected to continue carrying out forefront science for many years to come.
  • It continues to work towards resuming science operations of the Hubble Space Telescope. On October 5, Hubble entered safe mode after one of the three gyroscopes (gyros) being used to point and steady the telescope failed.
  • Gyroscopes help spacecraft maintain proper orientation.
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