India aims for the Moon with the Chandrayaan-3 lunar lander

India is preparing to launch a spacecraft that will take a lander to the moon on July 14. If the mission is successful, India will become only the fourth country to carry out a controlled lunar landing, after the United States, the former Soviet Union and China. The 6 billion rupee ($73 million) mission, dubbed Chandrayaan-3, is the Indian Space Research Organization (ISRO)’s second attempt to land an aircraft safely on the Moon.

Chandrayaan-3 will send a lander and rover from the Sriharikota spaceport off the east coast of India to a site near the moon’s south pole. After the craft lands, ISRO scientists plan to deploy the rover to study the properties of the Moon. If successful, the mission will be the first to land near the south pole; previous lunar missions have landed at lower latitudes.

ISRO says the lunar south pole is of particular interest because parts of it remain permanently in shadow, raising the possibility of sampling lunar ice for the first time. Additionally, large craters near the lunar south pole may hold clues to the composition of the early Solar System.

The south pole region has a very different geology from the region around the [US] The Apollo missions, so Chandrayaan-3 will provide a close-up view of an entirely new region of the Moon, says planetary geochemist Marc Norman of the Australian National University in Canberra.

A successful landing could also be an important step towards future Indian Moon missions and is seen as a demonstration of India’s growing geopolitical ambitions.

Lunar missions in India

Chandrayaan-3 follows the successful lunar orbiter Chandrayaan-1, which launched in 2008, and the partially successful Chandrayaan-2, which launched in 2019. The second mission successfully launched a lunar orbiter with eight functioning instruments, but the lander carrying the rover crashed into the Moon during the final moments of its descent in September 2019.

ISRO President Sreedhara Somanath recently said the crash was due to a software glitch.

India’s third lunar mission will focus on the moon landing. A three-stage rocket will place Chandrayaan-3 in an elliptical parking orbit approximately 170 kilometers by 36,500 km. A two-ton propulsion module will then carry the landerrover complex into a circular orbit about 100 km above the surface of the Moon. The 1.75-ton lander, called Vikram, contains a 26-kilogram, six-wheeled robotic rover called Pragyan, designed to circle the Moon for the equivalent of about 14 days on Earth.

ISRO engineers and scientists say they have made changes to the Chandrayaan-3 mission’s software and hardware, particularly to the lander’s thrusters, in the wake of the problems with Chandrayaan-2. ISRO has developed better soft landing sequences and the lander has four thrusters instead of five, sturdier legs and bigger solar arrays, and will carry more fuel.

ISRO has not publicly released a report analyzing the failure of Chandrayaan-2. But a retired ISRO engineer said the cause was insufficient step-down by the engines, a crucial requirement during lunar descent.

Science of the moon

The propulsion module will serve as a communications repeater satellite and the Chandrayaan-2 orbiter will be used as a backup repeater. The propulsion module has an instrument, Spectro-polarimetry of HAbitable Planet Earth (SHAPE), to collect data on the polarization of light reflected from Earth so researchers can look for other planets with similar signatures.

The lander will be equipped with instruments that will measure the density of ions and electrons near the surface of the Moon and how this changes over time; measure the temperature of the surface of the Moon; look for lunar earthquakes; and investigate the dynamics of the lunar system.

Similar measurements were made by the US Apollo and Chinese Change missions as they landed closer to the Moon’s equator, but this will be the first analysis of the environment at one of the poles. Thermal conductivity in particular depends on the grain size and packing of the regolith, the surface layer of loose rubble, and so will be useful in characterizing the landing site, Norman says. Such data cannot be obtained from orbit. And whenever you study a new area, there’s always a chance you’ll discover something unexpected, he says.

While the science goals may be relatively modest, the mission is seen as a critical step towards future lunar surface operations, both manned and robotic, says Tomas Hrozensky of the European Space Policy Institute in Vienna. He says Chandrayaan-3 will help achieve the goal of establishing a long-term human presence on the Moon and other planets. Recent examples, with some failures, suggest that landing and a long-term presence on the Moon remains an immense challenge.

If successful, India’s moon landing will have important technological and geopolitical dimensions, likely without a dramatic impact on fundamental scientific knowledge, Hrozensky says.

The moon landing continues to be a highly prized political goal for some nations.