NavIC (IRNSS): Concept, Importance of Atomic Clocks, Challenges & Global Navigation Systems

What is NavIC (IRNSS)?

NavIC (Navigation with Indian Constellation) is India’s indigenous regional navigation satellite system, developed by the Indian Space Research Organisation (ISRO) to provide accurate positioning services independent of foreign systems like GPS.
The system is designed to cover India and an area extending up to about 1500 km beyond its borders, ensuring strategic autonomy in navigation services for both civilian and military purposes.
NavIC consists of a constellation of 7 core satellites, positioned in a combination of:
- Geostationary Orbit (GEO) – fixed relative to Earth
- Geosynchronous Orbit (GSO) – inclined orbit covering India more effectively
Unlike global systems that focus on worldwide coverage, NavIC is optimized for regional precision, making it more reliable in:
- Dense urban environments
- Forest regions
- Mountainous terrain
The system provides an accuracy of around 10 meters, which is sufficient for applications like navigation, disaster management, tracking, and defense operations.
However, since its inception, NavIC has faced technical constraints, particularly related to atomic clock failures and aging satellites, which have impacted its long-term reliability.

Atomic clocks are the core component of any satellite navigation system, as the entire positioning mechanism depends on extremely precise time measurement.
Each satellite continuously transmits signals containing the exact time at which the signal was sent, and a receiver calculates its distance from the satellite based on the time taken by the signal to reach it.
This process is known as Trilateration, where signals from at least four satellites are used to determine the user’s exact position on Earth.
Even a nanosecond-level error in time measurement can lead to meters of error in position, which can severely affect navigation accuracy.
Therefore, atomic clocks ensure:
- Ultra-high precision timing
- Accurate distance calculation
- Reliable positioning services
In the case of IRNSS-1F, the failure of the atomic clock rendered the satellite incapable of providing precise navigation data, significantly reducing its operational utility.

Several satellites in the NavIC constellation are now approaching or exceeding their designed lifespan of around 10 years, which raises concerns about system continuity.
IRNSS-1A has already become non-functional due to the failure of all its atomic clocks, highlighting a recurring technical issue.
Satellites like IRNSS-1B and IRNSS-1C have also reached the end of their operational life, leading to a gradual decline in system performance.
The recent failure of the atomic clock in IRNSS-1F has further reduced the number of satellites capable of delivering accurate positioning data.
As a result :
- The overall accuracy of NavIC is affected
- Coverage becomes less reliable
- Redundancy in the system is reduced

NVS-02 is part of the second-generation NavIC satellites, launched in January 2025 using the GSLV-F15 rocket, with the aim of replacing aging satellites and enhancing system capability.
After launch, the satellite was placed in a transfer orbit, from where it was supposed to move to its final orbit using its onboard propulsion system.
However, due to a technical malfunction, the satellite’s engine failed to ignite.
Investigations revealed that :
- The pyro valve in the oxidizer line did not receive the activation signal
- As a result, fuel flow to the engine could not be initiated
This prevented the satellite from reaching its designated orbit, making it partially or completely ineffective.
This failure is particularly concerning because it follows earlier setbacks like the IRNSS-1H mission failure (2017), indicating recurring challenges in replacement missions.

One of the most critical challenges is the frequent failure of atomic clocks, which directly impacts the accuracy and reliability of the navigation system.
The aging satellite constellation is another major issue, as many satellites are nearing the end of their operational life without timely replacements.
Delays and failures in launching replacement satellites weaken the system’s robustness and continuity.
The limited adoption of NavIC-enabled receivers and devices has restricted its widespread use, especially compared to GPS, which is globally integrated into smartphones and applications.
NavIC also suffers from limited coverage, as it is a regional system, whereas global competitors offer worldwide services.
Additionally, the system faces competition from well-established global navigation systems, which are more mature, reliable, and widely adopted.

There are four major global navigation satellite systems (GNSS):
- Global Positioning System - GPS (USA) – the most widely used system globally
- GLONASS (Russia) – Russia’s independent navigation system
- Galileo (European Union) – provides high-precision civilian services
- BeiDou (China) – rapidly expanding with global coverage
These systems typically consist of 20–30 satellites placed in Medium Earth Orbit (MEO), enabling global coverage.
In contrast, NavIC is a regional navigation system, designed for high accuracy within a limited geographical area rather than global reach.
Japan’s QZSS (Quasi-Zenith Satellite System) is another regional system that complements GPS, similar to how NavIC serves India.

ISRO is working on developing indigenous atomic clocks, which will reduce dependence on foreign technology and improve reliability.
New-generation satellites include support for the L1 frequency band, making NavIC compatible with standard smartphones and increasing its usability.
The design life of satellites has been extended from 10 years to 12 years, ensuring better long-term stability.
Efforts are being made to enhance interoperability with global systems, allowing NavIC to work alongside GPS and others for improved accuracy.

India aims to achieve complete independence in navigation services, reducing reliance on foreign systems like GPS, especially in critical situations such as conflicts.
NavIC plays a key role in national security, enabling secure and reliable navigation for defense operations.
It also has significant economic potential in sectors like :
- Transportation and logistics
- Aviation and maritime navigation
- Drone technology
- Smart city infrastructure
To achieve these goals, India needs to :
- Expand its satellite constellation
- Improve technological reliability
- Encourage private sector participation
- Promote wider adoption of NavIC-enabled devices