First flight of SSLV ends in failure: What exactly went wrong with the ISRO mission?


The maiden lift-off of the SSLV ended in failure after the two satellites — EOS-02 and AzaadiSAT — were placed in an elliptical orbit instead of a circular one, rendering them ‘no longer usable’. ISRO, has attributed the problem to a sensor issue and vowed to come back ‘soon with SSLV-D2’

First flight of SSLV ends in failure: What exactly went wrong with the ISRO mission?

ISRO’s Small Satellite Launch Vehicle during its launch from the Satish Dhawan Space Centre, in Sriharikota. PTI

The Indian Space Research Organisation (ISRO) maiden’s small satellite launch vehicle (SSLV), carrying earth observation satellite EOS-02 and co-passenger students satellite AzaadiSAT, didn’t go as planned on Sunday.

The mission went awry as the SSLV-D1 placed the satellites in an elliptical orbit instead of a circular one, rendering them “no longer usable”, as ISRO later said in a statement.

In its statement, ISRO said, “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 caused the deviation.”


We examine what went wrong with the satellite launch.

The launch

At 9.18 am on Sunday, ISRO’s maiden small satellite launch vehicle (SSLV) lifted off from Sriharikota.

The mission by the space agency was aimed at garnering a larger pie in the small launch vehicles market, as it could place the satellites into Low Earth Orbit.

As per a report published in The Wire, the problem appeared to be the SSLV’s terminal stage, called the velocity trimming module (VTM). According to the launch profile, the VTM was supposed to have burnt for 20 seconds at 653 seconds after launch. However, it burnt for only 0.1 seconds, denying the rocket of the requisite altitude boost.

The two satellites on board the rocket – the primary EOS-2 Earth-observing satellite and the secondary AzaadiSAT student satellite – separated from the vehicle after the VTM burn. This means they are likely to have missed their intended orbital trajectories as well, and entered an elliptical orbit instead.

The space agency on Sunday while providing updates about the launch had tweeted around 11.43 am that “All the stages performed normal. Both the satellites were injected. But, the orbit achieved was less than expected, which makes it unstable.”


At 2.48 pm, ISRO had said it had identified the mission to be a failure as well as the cause of failure.

Later, ISRO’s chairperson S Somanath said in a video statement: “The vehicle took off majestically with the burning of the first stage and the subsequent S2 and S3 performed very well. The performance was very good in the mission and finally when it reached the orbit at an altitude of 356 km, the satellites were separated. However, we subsequently noticed an anomaly in the placement of the satellites in the orbit.”

The chairperson further explained that when a satellite is placed in such an orbit, the satellites cannot maintain course for a long time and fall off. “The satellites have already come down from that orbit and they are no longer usable,” said Somanath.

According to the ISRO, “failure of logic to identify a sensor failure and go for salvage action caused the deviation. A committee would analyse and recommend. With the implementation of the recommendations, ISRO will come back soon with SSLV-D2”.

Not its first failure

This isn’t the first time that ISRO has faced a setback on its mission launch.

The Polar Satellite Vehicle Launch (PSLV), now considered as ISRO’s trusted workhorses, was not successful in its first flight way back on 20 September 20 1993.

ISRO first tasted defeat back on 10 August 1979, when the country’s first experimental flight of SLV-3 carrying Rohini Technology Payload could not place the satellite into its intended orbit.

ISRO witnessed of its biggest setbacks on 7 September 2019 when the Chandrayaan 2 orbiter crashed on the lunar surface instead of gently landing and was destroyed together with the rover. Prime Minister Narendra Modi, who was present at the space agency to witness the historic mission, had later condoled with the ISRO staff, saying what they had achieved was no small feat.

Later in August 2021, the launch of GISAT-1, an earth observations satellite onboard GSLV Mk 2 rocket, had failed barely 350 seconds after its launch from India’s spaceport. According to ISRO’s initial analysis on launch day, it was caused due to “a technical anomaly in the cryogenic stage”.

With inputs from agencies

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