India launched its first navigation satellite in 2013, the Indian Regional Navigation Satellite System (IRNSS-1A). It was soon found that there was a problem in one of the rubidium atomic clocks on board the satellite. And later, the other two atomic clocks also failed.
The European atomic clocks could not be repaired as the design, and the functionality was not native to the ISRO team.
And this was not the only instance of it either, as nine out of the 21 clocks in the IRNSS fleet have failed, says a source to The Times of India.With this setback, India’s plans for regional GPS are hindered, because of repeated failures of the atomic clocks on the satellites.
Owing to this, ISRO has planned to make its atomic clocks, from the design to the build. This will let ISRO have full control over it and take steps to perfect the technology.
SAC has developed an indigenous atomic clock, and this clock is currently undergoing a series of qualification tests. Once it successfully clears all tests, the desi atomic clock will be used in an experimental navigation satellite to test its accuracy and durability in space.
Well, if atomic clocks are hard to make and prone to breakdowns, why do engineers insist on them? Can’t my regular Casio wristwatch do the trick just as well?
Apparently not. Here’s why.
Firstly, regular watches have an error of 10-20 seconds in a month, while atomic clocks have an error of 1 second in 100 million years!
So, a GPS receiver listens and compares the different timing signals from GPS satellites, uses that information to calculate exactly where on earth you are.
And if the clocks on the satellites tend to be even a little off, you will miss the next left turn by 100 meters and lose your way to the office.
Hence, it’s crucial to keep the most accurate clocks on board these satellites. And that’s why engineers insist on these.
So, how does an atomic clock function? In the early days, we looked upon the skies to keep time, but today, we look into the atoms themselves.
Atomic clocks derive their time from Cesium (Cs) or Rubidium (Rb) atoms. These elements have atoms that jump between two atomic states.
When an atom changes from a high-energy state to that of lower energy, the difference in energy is emitted as light. We count the ticking rate or frequency of this light and determine time. It is interesting to note that this difference in energy is always constant.