Blitz Bureau
NEW DELHI: INDIA’S homegrown satellite navigation system, NavIC, is facing a crucial turning point. A series of atomic clock failures aboard its firstgeneration satellites and the recent setback with NVS-02 have left the constellation stretched thin. To safeguard services and ensure strategic autonomy, the Indian Space Research Organisation (ISRO) is now betting on its own indigenously designed rubidium clocks – a technological leap that could end years of dependence on foreign suppliers.
The clock crisis
High-precision atomic clocks are the heart of every navigation satellite, providing the timing accuracy that allows receivers on the ground to pinpoint their location. Each NavIC satellite originally carried three imported rubidium clocks built by Swiss firm SpectraTime. But starting in 2016, the constellation began to falter. IRNSS-1A lost all three of its clocks, rendering the satellite unusable. Over the next two years, more anomalies surfaced – nearly nine out of 24 clocks had failed by 2018. ISRO admitted procurement and design vulnerabilities, echoing similar troubles faced by Europe’s Galileo programme.
The failures meant NavIC had fewer healthy satellites to sustain reliable service, forcing ISRO into urgent replacements. An attempted launch of IRNSS-1H in 2017 failed when its fairing did not separate, adding to the crisis. IRNSS-1I finally restored some capacity in 2018, but the clock issue cast a long shadow.
Indigenous breakthrough
Learning from these setbacks, ISRO’s Space Applications Centre developed the Indian Rubidium Atomic Frequency Standard (iRAFS). After years of qualification, the indigenous clocks were successfully flown aboard NVS01, launched in May 2023. For the first time, India’s own navigation satellite operated on an Indian-built time standard. In-orbit tests confirmed stable performance, and on July 4, 2023, NavIC’s much-awaited L1 civilian service was declared operational – broadening compatibility with smartphones and commercial devices.
ISRO officials say these clocks match international benchmarks, with precision in the order of 10- ¹³ to 10- ¹⁴ and drift of just fractions of a nanosecond per day. The development is widely hailed as a major step towards technological self-reliance.
Fresh setbacks
But progress remains fragile. In January this year, ISRO launched NVS-02, the second second-generation NavIC satellite. Within hours, a propulsion system valve malfunction prevented the main engine from firing. The satellite was stranded in transfer orbit and declared non-functional as a navigation asset.
That left NavIC with only four fully operational satellites—IRNSS-1B, IRNSS-1F, IRNSS-1I and NVS-01— providing Position, Navigation and Timing (PNT) services. Another four older satellites are used only for short messaging. One has been decommissioned. With a minimum of seven satellites required for robust coverage, the system today operates with very little redundancy.
The Government has confirmed that NVS-03 will be launched by the end of 2025, followed by NVS-04 and NVS05 at roughly six-month intervals. All will carry multiple indigenous rubidium clocks, along with extended design life and the new civilian L1 signal.
Strategic mission
ISRO has also steered NavIC System Time to within tens of nanoseconds of UTC, synchronised with the National Physical Laboratory, strengthening its reliability for civilian and military users alike.
The mission is not just technological, it is strategic. NavIC provides India with an independent fallback in case of denied access to GPS or other global constellations during conflicts. Its restricted coverage (about 1,500 km around India) makes it less global than GPS or Galileo, but highly relevant for defence, aviation, maritime, disaster management, and telecom applications.
Analysts warn that with only four healthy navigation satellites, India cannot afford further delays. A single additional failure could compromise geometry and accuracy of signals, undercutting confidence in NavIC-enabled services. The stakes are high: international smartphone makers, including Apple and Qualcomm-powered Android devices, are already enabling NavIC in select handsets. Wider adoption hinges on uninterrupted coverage.
