India's Lunar Landing Fails, but the Search at the Moon's South Pole Continues

Author: 一毫秒的永恒

If everything had gone to plan, India's Pragyan rover would have emerged from the Vikram lander, as shown, and spent 14 Earth days exploring the Moon | credit: ISRO

In the early hours of September 7, 2019, Beijing time, contact was lost with the Vikram lander aboard Chandrayaan-2, the second lunar probe developed by the Indian Space Research Organisation (ISRO), at an altitude of only 2.1 kilometers above the Moon. India had hoped to make history as the fourth country, after the United States, Russia, and China, to achieve a soft lunar landing and the first to land at the Moon’s south pole. The failure dealt a severe blow to the country’s confidence. The Beresheet lander built by the Israeli nonprofit SpaceIL, introduced in the preceding article, had likewise crashed during its landing attempt.

Indian Prime Minister Narendra Modi had arrived at the Satish Dhawan Space Centre at midnight on September 6, 2019, ready to witness a milestone in India’s space history. At 04:20 Beijing time on September 7, the Vikram lander departed from its planned trajectory. ISRO chairman K. Sivan reluctantly announced that its signal had been lost 2.1 kilometers above the Moon, and silence fell across ISRO’s mission-control center.

Comparison of Vikram's planned and actual trajectories, showing that the lander descended too quickly in its final moments | credit: ISRO

Under the flight plan, Vikram would be traveling at 331 km/h when it reached an altitude of 5 kilometers, slowing to 100 km/h as it descended farther. ISRO’s published data, however, showed that at an altitude of 1.09 kilometers the lander still had a horizontal velocity of 176 km/h and a vertical velocity of 215 km/h. When its signal disappeared, Vikram was horizontally about 1 kilometer off course from the target landing site. Without a control routine to brake the spacecraft, a crash was foreseeable. Exactly what caused the landing failure remained unknown.

Prime Minister Modi speaks with ISRO chairman K. Sivan after witnessing the loss of contact with Vikram at ISRO | credit: ISRO

Despite the failed landing, Modi did not lose heart. “We have achieved a great deal, and I am proud of you,” he said. He later wrote on Twitter, “They gave their best and have always made India proud. These are moments to be courageous, and we will remain hopeful and continue working hard on our space programme!”

Chandrayaan-2 consisted of three main components: an orbiter, the Vikram lander, and the Pragyan rover. It entered lunar orbit on August 20, 2019. On September 2, the lander separated from the orbiter and began its descent toward the Moon. It was designed to operate for 14 Earth days, and its recommended landing site lay between the craters Manzinus C and Simpelius N.

Although Pragyan and Vikram had crashed, the Chandrayaan-2 orbiter would continue a year-long remote study of the Moon. Orbiting approximately 100 kilometers above the lunar surface, it would use 8 scientific instruments and cameras to continue examining the Moon from afar. Its principal instruments included an X-ray spectrometer for measuring the abundance of different elements on the Moon; a solar X-ray monitor for studying high-energy radiation from the Sun; a terrain-mapping camera and a high-resolution orbiter camera for producing detailed maps of the lunar surface; and instruments for observing the Moon’s tenuous atmosphere, or exosphere.

Distribution of surface ice at the Moon's south pole (left) and north pole (right), detected by NASA's Moon Mineralogy Mapper aboard India's Chandrayaan-1 spacecraft | credit: NASA

As the name Chandrayaan-2 suggests, India was no newcomer to lunar exploration. Chandrayaan-1, the country’s first lunar mission, launched on October 22, 2008, and reached lunar orbit a little more than two weeks later. Over a period of more than 2 years, it was to explore the lunar surface and produce complete maps of the Moon’s chemical characteristics and 3D topography. The polar regions were a particular focus because solid water might be present there.

Chandrayaan-2 had some similarities to Chandrayaan-1, but it also carried new technologies that ISRO was testing for future planetary missions, including the next mission to Mars. India announced that Chandrayaan-3 would launch in 2024 and, like Chandrayaan-2, include a rover. After SpaceIL’s Beresheet lander crashed several months earlier, India was striving to become the fourth country to make a soft landing on the lunar surface. Unlike Beresheet, however, the Chandrayaan-2 mission would continue through its lunar orbiter.

The United States, Russia, and China remained the only countries to have achieved a soft landing on the Moon. Only one country had landed successfully on both the near and far sides: China.

Note: Chandrayaan-3 launched at 2:35 p.m. Indian Standard Time on July 14, 2023, and successfully made a soft landing about 619 kilometers from the Moon’s south pole. India thereby became the fourth country, after the Soviet Union, the United States, and China, to soft-land a probe on the lunar surface, and the first to land successfully near the lunar south pole.

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