India's ISRO joins an elite club of space agencies which use a very complex and technical device, a Rubidium atomic clock in their GPS satellites. Only 4 other national space agencies use this atomic clock - USA's NASA, EU's ESA, China's CNSA and Russia's ROSCOSMOS

India made a significant jump towards self-dependency after the successful launch and deployment of its NVS-1 NavIC satellite. While technologically, every component on board the NVS-1 NavIC satellite is an engineering marvel in and of itself, one component that really stands out is the Rubidium Atomic Clock that has been placed on board the satellite. So rare and difficult is this clock to make, that only 5 countries so far have used it for their space missions.

The atomic clock that has been used in the NVS-1 NavIC satellite is a highly technical piece of engineering. Although it is a clock and will be used to keep track of time, the sophistication and accuracy with which it works have made it indispensable for most space missions. And yet, India’s ISRO is only the fifth space agency ever to employ it.

What makes our Rubidium Atomic Clock even more special, is that it was indigenously developed and was created by the Space Applications Centre in Ahmedabad. The inclusion of this clock is significant, as it is a sophisticated technology possessed by only a select few countries, highlighting India’s technical capabilities in this field.

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How Does A Rubidium Atomic Clock Work?

To put it very simply, a Rubidium Atomic Clock works just like most other atomic clocks, namely the Caesium standard. However, because it is more portable and easier to handle, Rubidium clocks are what astrophysicists and engineers working with space travel love to work with.

Basically, an atomic clock is driven partly by quartz, and partly by a precisely collected and layered collection of atoms, that helps the quartz resonate at a very specific frequency. The more accurate the frequency of the quartz, the more accurate will the clock be. Most watches rocking a quartz movement are guaranteed accurate to around 15 seconds a month or so, meaning for every month it runs, it will gain or lose its accuracy by about 15 seconds and needs to reset.

How Accurate Is A Rubidium Atomic Clock?

Rubidium Atomic Clocks on the other hand, will keep accurate time for several days without input from GPS. It will go off by a microsecond in every 10 years, or so. And, just in case you forgot, 1 second has 10,00,000 microseconds. For a Rubidium Atomic Clocks to go off by one complete second, the clock will have to keep on ticking for 20 million years. That’s how accurate it is.

What Use Does The NavIC Satellite Have For It?

Most satellites that need to support geo-positioning functions, like the NVS-1 NavIC, need to have an accurate sense of time, without depending on any external inputs. Most digital watches, the ones on your computers and smartphones, often rely on GPS to get rid any of variances or inaccuracies that may come up. However, satellites in space, for obvious reasons, cannot use GPS to correct themselves. GPS requires precise clocks to provide astounding positional accuracy. Atomic clocks in GPS satellites keep time to within three nanoseconds i.e. three-billionths of a second. Position accuracy depends on the receiver.

Deep space missions, such as interplanetary probes and missions to asteroids or comets, require highly accurate timekeeping over long durations. Rubidium atomic clocks provide the necessary stability and precision for tracking and coordinating these missions, aiding in the collection of valuable scientific data.

For that matter, even basic GPS satellites, like the NVS-1 NavIC, contains multiple atomic clocks that contribute very precise time data to the GPS signals. GPS receivers decode these signals, effectively synchronizing each receiver to the atomic clocks.

Which Countries Have Used Rubidium Atomic Clock For Their Space Missions?

Several countries have recognized the value of rubidium atomic clocks in space exploration. India joins the following countries that have utilised this technology in their space missions:

1. United States for their Deep Space Atomic Clock or DSAC, which is a miniature, ultra-stable Rubidium Atomic Clock designed for deep space missions. It was successfully tested on board the Orbital Test Bed satellite in 2019.

2. European Space Agency or the ESA which has incorporated several Rubidium Atomic Clocks into its navigation systems, the European Galileo satellite constellation.

3. China and its Beidou navigation satellite system, which provides navigation services primarily for the Asia-Pacific region.

4. Russia and its GLONASS navigation system.