Atomic Clock Failure on NavIC Satellite
Context:
The Indian Space Research Organisation (ISRO) recently announced that the onboard atomic clock of the IRNSS-1F satellite stopped functioning.
This occurred just days after the satellite completed its designed 10-year mission life on March 10, 2026.
Atomic clocks are key for satellites being able to provide positioning data used for applications such as navigation of vehicles, mapping and surveying, and even planning large constructions with accuracy.
What is an Atomic Clock?
An atomic clock is the beating heart of any navigation satellite.
It acts as a highly precise frequency standard that measures time by tracking the natural, ultra-stable electromagnetic resonances (vibrations) of atoms, most commonly Rubidium.
Satellite positioning works by calculating the exact time it takes for a signal to travel from the satellite to a receiver.
Even a tiny timing error—just a billionth of a second—can throw off positioning calculations by several meters, making precise atomic clocks indispensable for accurate GPS-like services
Impact on the NavIC System:
Navigation with Indian Constellation (NavIC)—formerly known as IRNSS—was designed with a constellation of seven satellites (three geostationary and four geosynchronous) operating 24x7 to provide accurate positioning, navigation, and timing (PNT) services over India and surrounding regions.
Due to the atomic clock failure, IRNSS-1F can no longer provide precise PNT services, though it will be repurposed to continue providing one-way broadcast messaging services.
This setback leaves the NavIC constellation with only three fully functional satellites for navigation (IRNSS-1B, IRNSS-1L, and NVS-01).
The loss is critical because a satellite navigation system requires a minimum of four functional satellites simultaneously to calculate an accurate position on the ground.
Advancements in new satellites:
The most important change to the new- generation NavIC satellite was an indigenously developed atomic clock developed by ISRO.
The newer generation satellites also have a longer mission life: 12 years.
Importantly, they send signals in a third frequency, L1, besides the two (L5 and S) in existing satellites.
As GPS commonly uses L1, this improves interoperability with other positioning systems.
L1 also helps in using NavIC data in wearable devices.