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Updated: Jul 18, 2019 23:31 IST

Three days after the launch of India’s second mission to the moon was aborted 56 minutes from take-off due to a technical snag, the Indian Space Research Organsation (Isro) announced that the glitch has been corrected and Chandrayaan 2 is ready for launch on July 22 at 2.43pm.

The new launch timing, however, will leave no margin for error due to a shorter window period, according to a senior official from the space agency who asked not to be named.

“July 15 was ideal for the launch of the Chandryaan-2 mission as there was a 10-minute window period, which gave us room for adjustments in the complex mission. Now, all the launch windows are just of one minute, so everything has to be right and the satellite has to be launched precisely at the planned time,” he said.

The July 22 launch will be just two days after the world celebrates the 50th anniversary of the Apollo 11 landing on the moon and Neil Armstrong becoming the first man to walk its surface on July 20, 1969.

The mission was to be launched on July 15 at 2.51am, but was aborted when a technical snag was detected during the fuelling of the cryogenic stage of the rocket. “The Chandrayaan 2 launch was called off due to a technical snag noticed at around one hour before launch. An expert committee was constituted to analyse the issue and suggest remedial action. The expert committee identified the root cause of the technical snag and all corrective actions are implemented. Thereafter, the system performance is normal,” a statement from the space organisation said.

Scientists had earlier indicated that a more suitable window would be available on July 29-30 during the new moon, but Isro concluded that the July 22 window was adequate for the spacecraft.

No changes in path were suggested by the committee and Chandrayaan 2 will be injected in a 170 x 40,400km elliptical orbit around the Earth. The orbit will be raised till it enters the moon’s sphere of influence. After this the orbiter will travel around the moon in a 100x100km orbit before the lander and rover will attempt a soft landing near the South Pole between two craters, Manzinus C and Simpelius N on day 54.

“Launching the mission next month would have required a change in the inclination of the spacecraft. This would have required more fuel, reducing the payload capacity,” said former Isro scientist familiar with the developments.

Higher fuel consumption was one of the reasons the launch of the Chandrayaan 2 mission was delayed from the March-April window to the July window. The Apollo 11 mission landed on the surface of the moon in four-and-a-half days. The Indian mission chose a slower but more fuel-efficient route. “There are several ways to reach the moon, the trajectory chosen for Chandrayaan 2 uses the Earth and moon’s gravity to create a slingshot-like path, reducing the fuel consumption,” said the former Isro official quoted in the first instance.

Helium leak

Although Isro officials said that the proceedings of the committee were confidential, officials outside Isro who work closely with the space agency have said that there was a helium leak in the cryogenic stage of the GSLV Mark III launch vehicle. This was because a malfunction in a nipple joint valve used in cryogenic engines that use liquid oxygen and hydrogen as fuel. Helium, being the only gas with a boiling point less than Hydrogen, is used to maintain pressure in the propellant tank, to keep it from collapsing and preventing the formation of bubbles

The Chandrayaan 2 mission will be the first operational flight of the GSLV Mark III launch vehicle, which uses oxygen liquified at -183 degrees Celsius and Hydrogen at -253 degrees Celsius in the cryogenic upper stage. The first stage of GSLV Mark III uses two solid fuel rocket boosters for lift-off and the second core stage uses two liquid fuel engines.

On July 15, the launch vehicle detected an anomaly on its own during the fuelling procedure. “The 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 told HT after the launch was aborted.

Scientific mission

If all goes well, the landing of Chandrayaan 2 will make India the fourth country after the US, the erstwhile USSR, and China to land on the moon. It will also be the first mission to land on the moon’s south pole.

India’s first mission to the moon (Chandrayaan 1 in 2008) dropped an impactor near the Shackleton crater on the south pole of the moon, on the birth anniversary of India’s first prime minister Jawaharlal Nehru. The place where the imoactor was dropped is named Jawahar Point. The probe discovered evidence of water in the lunar atmosphere, soil and rocks.

The Chandrayaan 2 lander and the rover will attempt to observe the water ice in the shadowy areas inside the crater. Scientists are also hoping to find cold traps preserving the history of the solar system.