ISRO stated that the disengagement of at least one contact -- in both the main and redundant paths -- of a connector led to the failure of NVS-02.
More than a year after the loss of India's strategic navigation satellite NVS-02, the Indian Space Research Organisation (ISRO) on Wednesday officially disclosed the causes behind the mission failure.
However, the space agency did not elaborate on the proximate cause of the malfunction.
ISRO stated that the disengagement of at least one contact -- in both the main and redundant paths -- of a connector led to the failure of NVS-02.
NVS-02 Mission Failure Explained
ISRO said an apex committee constituted to review the incident concluded that 'the most likely cause for the observation is the disengagement of at least one contact (in each of the main and redundant paths) of the connector'.
Following an extensive analysis of simulation data, the committee determined that the satellite could not be raised to its intended orbit because the drive signal failed to reach the pyro valve in the oxidiser line of the engine.
Yet ISRO has not explained how the contacts in both the primary and redundant paths became disengaged.
Connector Disengagement Root Cause
Key Points
- ISRO confirmed connector contact disengagement in both main and redundant paths caused NVS-02 mission failure and satellite loss.
- Pyro valve failed to open as oxidiser signal never reached engine, leaving satellite stranded in transfer orbit.
- Launched January 2025 aboard GSLV-F15, NVS-02 remained inoperable despite successful placement into Geosynchronous Transfer Orbit.
- Mission cost about Rs 600 crore, with redundancy compromised because both power lines used same connector.
- ISRO implemented corrective measures, successfully tested in CMS-03 mission, strengthening redundancy and reliability for future launches.
Pyro Valve Oxidiser Signal Failed
On January 29, 2025, NVS-02 was successfully placed into Geosynchronous Transfer Orbit (GTO) but later became inoperable when a pyro valve failed to open, blocking the flow of oxidiser.
The satellite was launched aboard the Geosynchronous Satellite Launch Vehicle (GSLV-F15).
Weighing 2,250 kg, NVS-02 remained stranded in GTO after the valve malfunction prevented oxidiser from feeding the engine, making it impossible to fire the liquid apogee motor (LAM) and raise the spacecraft to its designated Geostationary Orbit.
Even at the time, speculation had pointed to a faulty electrical connector as a possible cause.
Retired ISRO officials described the incident as an unprecedented failure for the agency, which has successfully orbited numerous Earth observation and communication satellites.
Notably, NVS-02 was carried on the 100th rocket launched from the Sriharikota spaceport.
ISRO Redundancy System Under Review
In February last year, industry experts and former senior ISRO officials, speaking on condition of anonymity, suggested that the valve may not have received power.
One probable explanation, they said, was that the power supply connector had not been properly connected after final tests, though the reasons were unclear.
With the total mission cost estimated at around Rs 600 crore -- split roughly equally between the rocket and the satellite -- critical systems were expected to have built-in redundancies.
In the case of NVS-02, there was reportedly full redundancy in the valve, electronics, and power supplies.
However, experts noted that both the main and redundant power lines passed through the same connector, undermining the concept of full redundancy.
Ideally, they argued, independent connectors should have been used.
They also stressed that critical systems in rockets and satellites should have two or three fully independent redundancies, preferably with components sourced from different vendors to minimise the risk of batch failures.
A retired senior ISRO official explained that the agency typically follows a two-way redundancy policy in system configurations, and in some highly critical operations -- such as heat shield separation -- even employs four-way redundancy.
In 2017, the IRNSS-1H satellite -- intended as a replacement for IRNSS-1A -- failed when the heat shield of the Polar Satellite Launch Vehicle did not open, leaving the satellite trapped inside the rocket.
ISRO said the committee reviewing the NVS-02 failure has issued recommendations to strengthen redundancy and reliability in pyro system operations for future missions.
'In line with these recommendations, all corrective actions were successfully implemented in the CMS-03 spacecraft launched on November 2, 2025, by LVM-3 M5.
'The pyro systems performed satisfactorily, placing the satellite in its intended orbit.
'These recommendations will be followed for all future missions, as applicable,' ISRO said.
Venkatachari Jagannathan can be reached at venkatacharijagannathan@gmail.com
Feature Presentation: Ashish Narsale/Rediff
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