India's NavIC navigation system faces a precarious moment after the failure of a critical satellite, raising questions about the reliability of the nation's homegrown alternative to GPS.

NavIC, or Navigation with Indian Constellation, has dropped below the minimum operational threshold following the atomic clock failure on IRNSS-1F. Launched in March 2016, this satellite reached the end of its 10-year design life on 10 March 2026. Although it continues to orbit and transmit one-way broadcast messages, it can no longer contribute to positioning calculations.

A navigation system requires at least four satellites to determine a user's location accurately on Earth. With IRNSS-1F offline, India now relies on just three functional satellites for Position, Navigation, and Timing (PNT) services.

The surviving trio consists of IRNSS-1B, launched in April 2014; IRNSS-1L, launched in April 2018; and NVS-01, the first second-generation satellite sent into orbit in May 2023. IRNSS-1B has already exceeded its own 10-year lifespan and operates on extended time.

NVS-01 stands out as the healthiest, equipped with India's first indigenous rubidium atomic clock. This marks a shift away from reliance on imported timekeeping hardware, which plagued earlier missions.

Atomic clocks form the core of any satellite navigation system. They measure time by monitoring the precise vibrations of atoms, enabling receivers to calculate signal travel time from satellite to user.

Even a billionth-of-a-second error in timing can displace a position fix by hundreds of metres. Without a functioning clock, a satellite becomes useless for navigation.

NavIC's troubles stem from a history of setbacks. Of the 11 satellites launched by July 2025, only four were delivering full PNT services at that point. Four others managed one-way broadcasts after losing navigation capability, one was decommissioned, and two failed to reach proper orbits.

The IRNSS-1F clock failure on 13 March 2026 reduced the PNT count from four to three. NavIC aims for a seven-satellite constellation to cover India and a 1,500 km region around it, but it remains far short.

Replacement efforts hit a snag with NVS-02, launched in January 2025. A minor electrical fault prevented its orbit-raising engine from firing, stranding it in an elliptical orbit where it cannot provide services.

ISRO applied lessons from this mishap to CMS-03, launched successfully in November 2025 into its intended orbit. Yet NVS-03, slated for a late 2025 launch, has not yet lifted off, indicating schedule slippage.

In July 2025, Union Minister of State for Science and Technology Dr Jitendra Singh informed the Lok Sabha that NVS-03 would fly by year's end, followed by NVS-04 six months later. These delays leave NavIC vulnerable.

The next-generation NVS satellites offer improvements, including L1 band support. This allows compatible smartphones to use NavIC via software updates alone, without additional hardware.

On the ground, NavIC already powers real-time tracking for about 8,700 trains, with ambitions to reach 12,000. It also aids disaster alerts, marine navigation, and vehicle tracking.

With only three satellites operational, these applications face risks. IRNSS-1B's ageing status adds urgency, as its failure could drop NavIC to just two PNT providers.

India's push for self-reliance in navigation persists despite the hurdles. Indigenous atomic clocks in NVS-01 signal progress, and upcoming launches promise to rebuild the constellation.

Restoring full functionality demands swift action on NVS-03 and beyond. Until then, NavIC's capacity hangs in the balance, underscoring the challenges of sustaining a regional navigation powerhouse.

Agencies