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Updated: Sep 07, 2019 23:54 IST

At 1.53am in the wee hours of Saturday, less than two minutes before the Vikram lander was to touch down on the moon, scientists from the Indian Space Research Organisation (ISRO) lost communication with it. The lander was just 2.1 km away from making history by being the world’s first space mission to soft-land near the lunar South Pole.

If ISRO scientists fail to re-establish communication, the Chandrayaan 2 mission will lose two of the three components, namely its lander, Vikram, and rover, Pragyan, housed inside the lander and which cannot communicate directly with the ground station. Had it landed, the rover was expected to carry out experiments on the lunar surface for one lunar day (14 Earth days).

The orbiter will, however, continue to revolve around the moon and collect significant scientific information on the lunar terrain, elements present on the moon, and the exosphere, the thin layer of atmosphere around the moon.

The lander of the Chandrayaan-2 moon mission was attempting a “soft,” or controlled, landing near the South Pole of the moon where scientists believe there could be water ice. It had begun its powered descent at 1.38am, and reduced its velocity from 1,640 metres per second to 140 metres per second in 10 minutes. In the last few minutes, when the lander was decreasing its altitude to the lunar surface, communications snapped.

The last 15 minutes of the mission, in which the lander attempts to guide itself with the help of its own propulsion system, had been described by Sivan earlier as “15 minutes of terror”.

“Vikram lander descent was as planned and normal performance was observed up to an altitude of 2.1 km. Subsequently, communication from the lander to ground stations was lost,” said a visibly distraught ISRO Chairman K Sivan, shortly after. “The data is being analysed,” he said at the control centre at the ISRO’s Telemetry, Tracking and Command Network (ISTRAC) in Bengaluru.

“The success criteria was defined for each and every phase of the mission and till date 90 to 95% of the mission objectives have been accomplished and will continue contribute to Lunar science , notwithstanding the loss of communication with the Lander.” ISRO later said in a statement.

In 2009, ISRO lost communication with its first mission to the moon 10 months into the two-year life of Chandrayaan 1. Despite that, it is said to have completed over 90% of its mission objectives and went down in history as the mission that conclusively confirmed the presence of water on the moon.

The first mission ended after overheating of systems led to a communications breakdown due to an imported faulty part of the power supply system. Following this, India began to indigenously develop this part.

Just as Chandrayaan 1 paved the way for the second moon mission,data from the Chandrayaan 2 orbiter will add to scientific knowledge and aid future missions.

The landing site of the Chandrayaan 2 lander-rover was chosen based on the mapping of water done by the payloads aboard its predecessor that showed the mission was most likely to find water near the south polar region.

The second mission, which was approved in 2008, was launched on July 22.

Learning from the first mission

The Indian impact probe, which crashed on November 14, 2008 at 89.76 degrees South near the Shackleton crater, put India’s flag on the moon. It also detected water molecules during the fall and in the sub-surface soil at the crash site. This prompted NASA spectrometer (mini-SAR) and M3 (Moon Mineralogy Mapper) to look for and map the water.

“From this we learned that there is a higher concentration of water near the South Pole, which is the reason the current landing site was chosen,” a scientist who was part of the Chandrayaan 1 team had said on condition of anonymity.

An extremely precise trans-lunar injection and the lunar orbit insertion, with the moon and the spacecraft moving at high speeds, were needed to ensure that Chandrayaan 2 ended up at a 90 degree inclination. This was a “unique requirement” for Chandrayaan 2 lander, ISRO chairperson K Sivan had said.

“This complex manoeuvre was tried by India during the Chandrayaan 1 mission and it gave us the technical capability of acquiring a polar orbit,” said M Annadurai, former director of the UR Rao Satellite Centre and the project director of the Chandrayaan 1 mission.

After the power system of Chandrayaan 1 failed, India decided to develop the technology indigenously.

“The Chandrayaan 1 carried on-board several instruments and in order to maintain the weight, the power system had to be optimised. There was a quality issue with the imported DC-DC converters, which led to the heating of the systems and eventual snapping of the communications,” Annadurai explained.

To ensure quality, all systems were indigenously developed for India’s mission to Mars, launched in November 2013. “The hardware for Mangalyaan was essentially the same, but everything was indigenously made. It is still in orbit. Even for Chandrayaan 2, everything has been indigenously developed,” he said.

Renewed interest

Chandrayaan 1’s discovery of water renewed interest in studying the moon.

“There was always a debate about whether there is water on moon. Having water would mean astronauts will be able to stay on the moon longer than the few hours that they did during the Apollo missions. This also means moon might be used as a pit stop for missions farther into the space,” said Annadurai.

“The discovery of water on the moon led many countries to reconsider going to the moon, starting another race to the moon,” he said.

During the 1960s-70s, the United States and the erstwhile Soviet Union attempted as many as two to four lunar missions a year. All the six Apollo missions that landed on the moon took place within four years. No man has landed on the moon since.

NASA sent six orbiters and one impactor to the moon between the 1990s and 2000s. With Chandrayaan 1 finding water molecules, the world’s interest in the moon was piqued again.

China sent two landers and Israel attempted a landing on the moon after 2008. NASA also announced this year that a peopled lunar mission to the South Pole will be attempted in 2024.