ISRO’s SSLV launch textbook, but satellites delivered in unstable orbit. ISRO is yet to declare the mission as a failure and will update after analysis. The Centre had allocated Rs 169 crore for the development of the project. The vehicle's Velocity Trimming Module (VTM) uses MON3 fuel (comprising of mixed oxides of nitrogen (3% Nitric Oxide) with a freezing-point at −15 °C

SHAR: While the Small Satellite Launch Vehicle (SSLV) lifted off smoothly from the first launch pad at the Satish Dhawan Space Centre in Sriharikota, the mission did not reach its intended destination on Sunday and the Indian Space Research Organisation (ISRO) said that the satellites are no longer usable.

The Velocity Trimming Module (VTM), which inserts the satellite into their desired orbits, is being cited as the cause of failure as it did not fire in the terminal stage. The VTM was to fire up for 30 seconds but it was barely ignited for one second. 

ISRO Chairman also confirmed the issue was with a logic to identify a sensor failure and then resort to a salvage option by the mission computers, which means that the system has a deficiency and the need to correct the sensor isolation principle for the next developmental flight.

The Indian space agency, while declaring that all stages performed well, had initially hinted at data loss and did not straight away declare the mission a success.

“SSLV-D1 placed the satellites into 356 km x 76 km elliptical orbit instead of 356 km circular orbit. Satellites are no longer usable. Issue is reasonably identified. Failure of a logic to identify a sensor failure and go for a salvage action,” ISRO said in a statement.

ISRO had in the morning said that the "Maiden flight of SSLV is completed. All stages performed as expected. Data loss is observed during the terminal stage. It is being analysed. Will be updated soon.”

An unstable orbit means that the satellite’s performance will be affected and there are chances that it could collide with others or in the worst-case scenario, crash back on the planet.

This marks the loss of two big satellites, the Earth Observation Satellite (EOS-02) and the AzadiSAT, a CubeSat developed by 750 girl students to mark the 75th year of India's Independence. The satellites likely ended up over the Pacific between Australia and New Zealand, as per experts.

ISRO will set up a committee to review the failure. “A committee would analyse and recommend. With the implementation of the recommendations, ISRO will come back soon with SSLV-D2,” ISRO said.

The future of SSLV, ISRO's answer to the small satellite launch market, also looks grim, as the inaugural flight has not given the desired result. Developed at Rs 169 crore, the launch vehicle was pegged to be ready for flight in just 72 hours and could carry satellites up to 500 kilograms into space.

This is the second loss for ISRO in the span of just one year, which has had a perfect track record of launching satellites and missions into not just Low Earth orbit (LEO), but also in deep space. The unstable delivery comes just months after the successful launch of the PSLV-C53 mission that deployed the Earth Observation Satellite.

ISRO had hit upon another loss in 2021 when its GSLV-F10 mission was lost minutes after lift-off. ISRO lost the mission just 297.3 seconds after lift-off to a "technical anomaly", which it later said was due to a deviation in performance of the Cryogenic Upper Stage (CUS) of the launch vehicle. Subsequent to lift-off the build-up of pressure in the propellant (Liquid Hydrogen or LH2) tank during the flight was not normal leading to a lower tank pressure at the time of ignition of the engine. This led to an insufficient flow of Liquid Hydrogen into the engine thrust chamber and the reduction in LH2 tank pressure was due to a leak in the respective Vent and Relief Valve (VRV), which is used for relieving the excess tank pressure during flight.