Discuss the technological challenges NavIC has faced and how the second-generation NVS satellites address them.

NavIC (IRNSS) is India's own regional navigation system. It provides Position, Navigation and Timing (PNT) services over India and about 1,500 km beyond its borders [1]. Its value depends on keeping a complete constellation in orbit, and technology gaps have repeatedly weakened it. The NVS series is designed to close these gaps. GSLV-F18 has now placed its third satellite, NVS-03, in orbit [1].

Technological challenges faced

• Imported atomic clocks: NavIC's accuracy depends on onboard atomic clocks. The first-generation satellites relied on imported clocks, so a failed clock made the satellite useless for navigation and replacements depended on foreign suppliers.
• Ageing first-generation fleet: IRNSS satellites must be replaced on time. NVS-02, for instance, was meant to replace IRNSS-1E [2].
• No L1 signal: The original NavIC broadcast only in the L5 and S bands, which most consumer chipsets do not use. This limited civilian adoption.
• Small regional constellation: With so few satellites, losing even one weakens position fixes across the region.
• Spacecraft reliability: NVS-02 reached its transfer orbit but could not raise its orbit. The drive signal never reached the oxidiser pyro valve because connector contacts came apart in both the main and the backup paths [5].

How NVS satellites respond

• Indigenous clocks: NVS-01 (GSLV-F12, 2023) carried India's first indigenous atomic clock [3]. NVS-02 and NVS-03 carry indigenous clocks alongside procured ones [2][1].
• Indigenous timing electronics: SAC built the Atomic Clock Monitoring Unit in India. It generates the 10.23 MHz onboard master timing reference and saves about ₹3 crore per satellite [4].
• L1 band: The NVS satellites add L1 to the existing L5 and S signals, which widens civilian use [3][1].
• Replenishment: The F12, F15 and F18 launches have replaced ageing satellites one after another [3][2][1].
• Lessons learnt: The Apex Committee's corrective actions were applied on CMS-03 (November 2025), and its pyro systems worked as intended [5].

Persisting gaps

• NVS-03 still carries procured clocks, so India is not yet fully self-reliant in atomic clocks [1].
• A successful launch only reaches a transfer orbit. NVS-03 must still complete its own orbit raising before it can provide service.

Overall, the NVS series addresses NavIC's main weaknesses: clock dependence, limited signals and ageing satellites. Fully indigenous clocks, replacements launched before satellites fail, and wider L1 adoption in devices can turn NavIC into a dependable public service. This would advance Atmanirbhar Bharat and India's strategic autonomy in PNT.