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

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 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 will likely have missed their intended orbital trajectories and entered an elliptical orbit instead.

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

At 2.48 pm, ISRO said it had identified the mission as a failure and 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 excellent during the mission, and finally, when it reached orbit at an altitude of 356 km, the satellites were separated. However, we subsequently noticed an anomaly in the placement of the satellites in orbit.”

The chairperson further explained that when a satellite is placed in such an orbit, the satellite 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 analyze 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 ISRO has faced a setback on its mission launch.

The Polar Satellite Vehicle Launch (PSLV), now considered ISRO’s trusted workhorse, was unsuccessful in its first flight on 20 September 20, 1993.

ISRO first tasted defeat 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 its most significant 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, 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.”

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