More than a year after NVS-02 failed to reach its planned orbit, the Indian Space Research Organisation (ISRO) clearly explained what went wrong and the corrective steps taken to prevent such issues in future missions. This helped many Indians understand what happened to this important navigation satellite.
NVS-02 was launched aboard the GSLV-F15 rocket from Sriharikota at 6:23 a.m. on January 29, 2025. It was ISRO’s first launch of the year, the 17th GSLV flight and the 11th Mk2 mission. The launch phase was flawless. About 19 minutes after liftoff, the satellite was placed into a Geostationary Transfer Orbit (GTO), measuring about 170 km at perigee and 37,785 km at apogee, with an inclination of 20.8 degrees. GTO is a temporary orbit that helps a satellite gradually move to its final geosynchronous position.
After separation, the spacecraft deployed its solar panels and stabilised itself. These systems worked normally. The next step was orbit raising moving into a circular Geosynchronous Orbit (GSO), where the satellite would rotate with Earth and remain fixed over one location. However, this crucial step failed.
ISRO confirmed that orbit-raising manoeuvres could not be carried out because the valves allowing oxidiser to flow into the main engine did not open. Without an oxidiser, the engine could not fire, and without thrust, the satellite could not reach its final slot.
As a result, NVS-02 remains in GTO. Other onboard systems power, communication and controls are functioning normally. The spacecraft is healthy, but since it could not reach geosynchronous orbit, it cannot deliver reliable navigation services as planned. The main mission objective was not achieved.
ISRO formed a Failure Analysis Committee headed by former Chairman A. S. Kiran Kumar to investigate the pyro valve failure. A pyro valve is a small but critical device that opens using a tiny explosive charge to release fuel or oxidiser inside the engine. If it does not open, the engine cannot operate.
“The investigation found that the ignition signal did not reach the pyro valve in the oxidiser line. The issue was traced to an electrical connection linked to the pyro valves in both the primary and backup systems. In simple terms, a small electrical contact became loose. Because of this, the ignition signal could not activate either valve. Even the backup system failed, as the loose contact affected both,” explained space analyst Girish Linganna.
As per this analyst, fuel system connectors link wires, valves and fuel lines inside the spacecraft. The loose contact within these connectors prevented the signal from reaching the valves. As a result, the oxidiser could not flow, the engine could not start, and orbit raising could not take place.
NVS-02, weighing 2,250 kg, is the second satellite in the NVS series. Like NVS-01, it transmits navigation signals in L1, L5 and S bands and carries a C-band ranging payload that helps ground stations measure its exact distance and maintain high accuracy. The satellite was designed to provide two services — Standard Positioning Service (SPS) and Restricted Service (RS). SPS is for the general public, including mobile phones, vehicle navigation systems, ships and aircraft. It offers position accuracy better than 20 metres (2σ) and timing accuracy better than 40 nanoseconds (2σ) in the main service area.
The term 2σ (two sigma) means the accuracy is reliable about 95 per cent of the time. In simple words, if the system promises 20 metres accuracy at 2σ, then in about 95 per cent of cases the error will remain within 20 metres.
Restricted Service is meant only for authorised users such as the military and strategic agencies. It uses encrypted signals that cannot be accessed or tampered with publicly. RS provides higher accuracy, stronger reliability and protection against jamming or spoofing. SPS serves civilians, while RS supports defence and strategic operations.
“While NVS-02 was a setback, ISRO demonstrated its resilience soon after. On November 2, 2025, CMS-03 (GSAT-7R) was launched aboard the LVM-3 M5, India’s most powerful rocket. The mission was a major boost for the Indian Navy and successfully validated the improved dual-connector fix in the pyro system. The flawless performance proved that ISRO does not merely face failures, it studies them, strengthens its systems and evolves with every mission,” remarked Linganna.
