NVS-03 Launched with Its Pyro Valves Open: How ISRO Avoided a Repeat of the NVS-02 Failure
ISRO's GSLV-F18 rocket lifted off from the Second Launch Pad at Sriharikota at 23:51 IST on 30 October 2026. It placed the NVS-03 navigation satellite (about 2,250 kg) into a Geosynchronous Transfer Orbit (GTO), the first, oval-shaped orbit from which a satellite climbs to its final position.
ISRO's Chairman explained that the satellite flew with three pyro valves already open. Pyro valves are one-time valves that open a fuel or oxidiser line with a tiny explosive charge. Satellites normally fly with them closed and open them in space.
The reason: in January 2025, the earlier satellite NVS-02 reached its transfer orbit but got stuck there. An electrical signal never reached the pyro valve on its oxidiser line, so its main engine could not fire. A national committee headed by former ISRO Chairman A.S. Kiran Kumar studied the problem, including vibration and shock tests.
The rocket's aim was very precise: the planned lowest point of the orbit (perigee) was 170.36 km and the achieved figure was 170.31 km. The satellite then began firing its own engine to climb towards its geostationary slot at 111.75° East.
NVS-03 carries a mix of Indian-made and imported atomic clocks, and broadcasts a new civilian L1 signal along with the older L5 and S-band signals.
NVS-03 restores NavIC, India's own navigation system, to its minimum working strength of four satellites. ISRO plans to launch NVS-04 and NVS-05 within about the next 10 months.
Pyrotechnic (Pyro) Valves and Spacecraft Propulsion Systems
A pyrotechnic valve, or pyro valve, is a valve on a spacecraft that is opened (or closed) only once, by firing a tiny explosive charge. It sits in the pipes that carry fuel, oxidiser or gas to a satellite's engines. Until it is fired, it seals the pipe completely, with no leakage at all. Once fired, it cannot be reset. Pyro valves are small parts, but if one fails, a satellite worth hundreds of crores can be lost.
NVS-02 was lost because one pyro valve on its oxidiser line never received its firing signal. For NVS-03, ISRO removed that risk by keeping three pyro valves open from the start, relying on latch valves to keep the propellants in place during launch. Understanding what pyro and latch valves do explains both the old failure and this new approach.
NavIC (IRNSS): India's Regional Navigation Satellite System
NavIC (Navigation with Indian Constellation) is India's own satellite navigation system, like the American GPS but covering only India and the region around it. Its official name is the Indian Regional Navigation Satellite System (IRNSS). It tells users their exact position and time using signals from Indian satellites placed high above the equator. A receiver needs signals from at least four satellites to work out a position.
NavIC had fallen below four working satellites, so it could not give reliable positions on its own. NVS-03 restores the minimum working set of four and adds the phone-friendly L1 signal, while NVS-04 and NVS-05 are needed to bring the system back to full strength.
GSLV (Geosynchronous Satellite Launch Vehicle) Programme
The Geosynchronous Satellite Launch Vehicle (GSLV) is ISRO's three-stage rocket for carrying satellites of about 2 to 2.5 tonnes into a Geosynchronous Transfer Orbit. Its third stage is a cryogenic stage, which burns super-cold liquid hydrogen with liquid oxygen. The GSLV has launched all the NVS navigation satellites so far.
The GSLV's job ends once it drops the satellite into the transfer orbit, which it did very precisely in this mission. From there, the satellite's own propulsion system, including its pyro valves and Liquid Apogee Motor, must take over to reach the final orbit. This handover point is exactly where NVS-02 failed in 2025.
- GSLV-F18 / NVS-03 launch: 23:51 IST, 30 October 2026, Second Launch Pad, Sriharikota
- GSLV-F18 is the 20th flight of the GSLV
- NVS-03 mass: about 2,250 kg; target slot: 111.75° East
- Perigee achieved: 170.31 km (target 170.36 km)
- Three pyro valves kept open at launch to avoid a repeat of the NVS-02 failure
- NVS-02: launched 29 January 2025 on GSLV-F15; stuck in GTO because the oxidiser-line pyro valve did not get its firing signal
- NVS-02 inquiry headed by former ISRO Chairman A.S. Kiran Kumar; findings made public in February 2026
- NavIC: minimum 4 working satellites restored; full design is 7 satellites
- NavIC coverage: India plus about 1,500 km around it
- NVS-03 signals: L1, L5 and S-band; carries indigenous and imported atomic clocks
- NVS-04 and NVS-05 planned within about 10 months