India shoots to the moon with Chandrayaan-3 lunar lander

India is gearing up to launch a lunar lander on July 14. If the mission succeeds, India will become the fourth country to land on the moon after the US, the former Soviet Union and China. The 6-billion-rupee (US$73-million) project, called Chandrayaan-3, is the second attempt by the Indian Space Research Organization (ISRO) to safely land a craft on the Moon.

Chandrayaan-3 will send a lander and a rover from the Sriharikota space base on India’s east coast to a base near the moon’s south pole. After the craft lands, ISRO scientists plan to send a rover to study the moon’s properties. If successful, the mission would be the first to land near the South Pole; Previous lunar missions had landed at lower latitudes.

ISRO says the moon’s south pole is of special interest because parts of it are permanently in shadow, increasing the possibility of sampling lunar ice for the first time. Also, large craters near the Moon’s south pole may contain traces of early solar system composition.

„The South Pole has a different geography from the surrounding area [US] „The Apollo missions, and therefore Chandrayaan-3, will provide a close-up view of an entirely new part of the Moon,” says Mark Norman, a planetary geochemist at the Australian National University in Canberra.

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

Moon Voyages of India

Chandrayaan-3 follows the successful launch of Chandrayaan-1 in 2008, and the somewhat successful Chandrayaan-2 in 2019. The second mission successfully launched a lunar orbiter with eight operational instruments, but the lander carrying the rover crashed into the moon. In the final moments of its descent in September 2019.

ISRO chief Sridhara Somanath recently said that the crash was caused by a software bug.

India’s third moon mission will focus on landing on the moon. The three-stage rocket will place Chandrayaan-3 in an elliptical orbit approximately 170 kilometers at a distance of 36,500 km. The two-ton propulsion module will then bring the lander-rover complex into a circular orbit about 100 km above the lunar surface. The 1.75-tonne lander, named Vikram, carries a 26-kg, six-wheeled robotic rover called Pragyan, designed to orbit the moon in the equivalent of about 14 Earth days.

ISRO engineers and scientists say they have made changes to the Chandrayaan-3 mission’s software and hardware, especially for the lander thrusters, in the wake of problems with Chandrayaan-2. ISRO has developed an improved soft landing sequence and the lander has four thruster engines instead of five, stronger legs and larger solar panels, and will carry more fuel.

ISRO has not made public the report investigating the Chandrayaan-2 failure. But a retired ISRO engineer said the reason was insufficient 'throttling’ – a gradual reduction in speed – by the engines required during the lunar landing.

Lunar Science

The propulsion module will act as a communication relay satellite, and the Orbiter of Chandrayaan-2 will be used as a backup relay. The propulsion module includes an instrument, the Spectro-Polarimetry of Habitable Planet Earth (SHAP), to collect data on the polarization of light reflected by Earth so researchers can look for other planets with similar signatures.

The lander will be equipped with instruments to measure the density of ions and electrons near the moon’s surface and how this changes over time; measure the surface temperature of the Moon; Scan for earthquakes; and explore the dynamics of the lunar system.

Similar measurements were made by the American Apollo and Chinese Chang’e missions when they landed near the Moon’s equator, but this was the first analysis of the environment at a pole. Thermal conductivity is particularly useful for characterizing the grain size and packing of the regolith — the surface layer of loose rubble — and the landing site, Norman says. Such data cannot be obtained from orbit. „Anytime you study a new piece, there’s always the chance to find something unexpected,” he says.

Although the scientific goals are relatively modest, „this mission is considered an important step towards future operations on the lunar surface, both human and robotic,” says Thomas Hrocensky 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 suggest that landing and long-term survival on the moon remains an enormous challenge, with a few failures.”

Hrozensky says that if India lands on the moon, „it will have important technological and geopolitical dimensions, without dramatic impact on basic scientific knowledge”.

„Landing on the moon continues to be a very valuable political goal for some countries.”