Atomic Clock


  • Recently, India has been willing to join an exclusive group of four other countries — the US, the UK, Japan, and South Korea — to have their atomic clocks.

About the Atomic Clock

  • It is a type of clock that uses the vibrations of atoms to measure time with extraordinary precision.
  • They are the most accurate timekeeping devices in the world, with the ability to measure billionths of a second.


  • Most modern clocks keep time using a quartz crystal oscillator.
  • These devices take advantage of the fact that quartz crystals vibrate at a precise frequency when voltage is applied to them.
  • However, by space navigation standards, quartz crystal clocks aren’t very stable.
  • After only an hour, even the best-performing quartz oscillators can be off by a nanosecond (one billionth of a second), and after six weeks, they may be off by a full millisecond.
  • Atomic clocks combine a quartz crystal oscillator with an ensemble of atoms to achieve greater stability.
  • NASA’s Deep Space Atomic Clock will be off by less than a nanosecond after four days and less than a microsecond (one-millionth of a second) after 10 years.

Atomic Clocks in Space Navigation

  • To determine a spacecraft’s distance from Earth, navigators send a signal to the spacecraft, which then returns it to Earth.
  • The time the signal requires to make that two-way journey reveals the spacecraft’s distance from Earth because the signal travels at a known speed (the speed of light).

Atomic Clocks in India:

  • India’s NAVIC satellite navigation system works on Indian atomic clocks.
  • ISRO and the National Physical Laboratory (NPL) have signed an MoU under which the latter will help authenticate precise timings for the space agency, and also end its dependence on the US-built GPS.