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Updated: Jul 23, 2019 08:55 IST

Exactly a week ago, the Chandrayaan-2 launch was called off 56 minutes and 24 seconds before the scheduled lift-off due to a technical snag, sending ripples of disappointment through the nation.

Within 24 hours, scientists from the Indian Space Research Organisation (Isro) analysed the situation, figured out the glitch and repaired it, said the space agency’s chief and people with knowledge of developments.

Over the next 1.5 days, the expert committee overseeing the correction of the “technical snag” conducted mandatory tests to ensure that the vehicle was ready for launch just a week later.

“Immediately after the technical snag was observed in an intelligent way a week ago, the entire team swung into action. The work done over the next 24 hours was mind boggling. The vehicle was quickly brought back to normal – the root cause of the technical snag was identified and corrected within the 24 hours,” said Isro chairperson K Sivan.

He lauded the work of the scientists, who ensured a successful launch on Monday at 02:43 pm from the Satish Dhawan Space Centre in Andhra Pradesh’s Sriharikota.

“The mammoth task was possible only because of the hard work of the entire team that worked continuously, forgetting about their families so that the snag could be fixed properly. The expert committee has also been on the job for the last seven days. I salute all the people who made it happen successfully,” he said as scientists around him appeared relieved and cheerful after a successful launch.

Prime Minister Narendra Modi also lauded the scientists who had fixed the snag. “You found the technical glitch with alacrity and took steps to solve it. And now, within a week you achieved success in the launch. You deserve a special congratulations for this,” Modi said.

With less than an hour to go on July 15, the inbuilt system in the launch vehicle -- the GSLV Mark III, which is India’s most-powerful rocket -- had detected the anomaly on their own.

“This system performed precisely in the way it was designed to and we managed to save the nearly ₹1,000 crore mission in time. We were lucky that the mission did not enter the automatic launch sequence else all would have been lost,” an Isro official had said on condition of anonymity .

Officially, Isro maintained the “technical snag” was an internal issue and the committee proceedings a “secret”, a former Isro scientist with knowledge of the developments said that the launch had to be called off because of a helium leak that was caused by malfunctioning valve.

The GSLV Mark III uses cryogenic fuel, which refers to liquified oxygen and hydrogen. In such cryogenic engines, helium is used to maintain pressure in the propellant tank and ensure a steady flow of the fuel without formation of bubbles. A Helium leak had led to an explosion that destroyed Space X’s Falcon 9 mission in 2016.

The expert committee also recommended some changes in the path of the spacecraft to ensure that it landed on the intended date September 7 at 02:58 am. This was necessary so that scientific payloads could perform experiments during the full lunar day equivalent to about 14 Earth days. The Chandrayaan-2 spacecraft will spend six additional days in Earth’s orbit and 15 fewer days around the Moon before it lands on the day that was originally planned.

“Now, having injected the spacecraft in the intended orbit around the Earth, the scientists will perform 15 very crucial maneouvers over the next one-and-a-half months bringing it in place around the moon. Then, the D-day will come when we will experience 15 minutes of terror while ensuring a successful landing on the moon’s South Pole,” said Dr Sivan.