ISROs ambitious Chandrayaan 4 sample return mission to Moon

In September 2024, the Union Cabinet chaired by Prime Minister Narendra Modi formally approved the Chandrayaan 4 mission by ISRO with a budget of Rs 2,104 crore. ISRO is aiming for an ambitious mission to return samples from the lunar surface. ISRO will have to develop technological capabilities that it currently lacks for the mission, including docking spacecraft in lunar orbit, lifting off from the surface of the Moon, and a robotic arm for collecting lunar samples. The target landing zone is close to that of the Chandrayaan 3 mission, and may even be in the alternate landing zone.

ISRO plans to use five elements for the mission, including a Reentry Module, a Transfer Module, an Ascender Module, a Descender Module and a Propulsion Module. ISRO cannot deploy all the elements of the mission on a single rocket, and will do so with a pair of LVM3 rockets, the most powerful launch vehicle in India’s operational fleet. Two stacks of the mission will dock in space before making the hop to the Moon, using the economical route taken by the Chandrayaan, Chandrayaan 2 and Chandrayaan 3 missions, that saved on fuel during the trip from the Earth to the Moon.

The Chandrayaan 4 mission will execute a soft, controlled landing on the lunar surface, and then collect and isolate samples using two mechanisms, a scoop as well as a drill. While the drill will access material from deeper depths, at two metres, the scoop will pick up the material close to the surface. Both of these samples will be isolated from each other in the Ascender Module. The Ascender Module will then liftoff from the surface of the Moon, and dock with the Reentry Module. A robotic arm will then transfer the samples from the Ascender Module to the Reentry Module.

The scoop on the left and the drill on the right, both for retrieving samples. (Image Credit: Aditya Madanapalle/News9). 

The Reentry Module will then make the return trip to Earth, down to the surface using parachutes to shed velocity during the descent. The Reentry Module is designed to protect the material inside from the rough ride through the atmosphere. The planned landing zone is expected to have unique thermo-physical properties with material ejected from the formation of the distant Tycho crater. ISRO plans to operate the lander for one lunar day, indicating that it will not be carrying a radioactive heat source, and will not be surviving the lunar night where temperatures can drop to -180°C.

ISRO will be demonstrating a number of novel capabilities during the course of the mission, including docking in an elliptical orbit around the Earth, lunar sample collection and containerisation, ascending from the surface of the Moon to lunar orbit, docking and undocking in lunar orbit, transferring samples from one module to another, and demonstrate Earth return and atmospheric re-entry at the end of the mission. The process of sample collection is expected to take place within two days on the lunar surface.

Throughout the mission, ISRO has to ensure that the samples are not contaminated, and are totally isolated from the environment. The collected samples will subsequently be analysed by the sophisticated laboratories on Earth. ISRO plans to develop the Chandrayaan 4 mission in an accelerated timeframe. ISRO will be relying on private industry partners for providing the various components of the mission, as well as multiple space agencies around the world to use ground stations, and ensure maximal returns from the payloads on board. This is because the ground stations on India cannot maintain line-of-sight with the spacecraft while it orbits the Earth, and such infrastructure sharing agreements allow all spacefaring nations to keep the costs of their missions low.

ISRO aims to return about three kilograms of lunar sample from the region. The analysis on Earth will help test various theories on the formation and evolution of the Moon. The samples can open a valuable window into the processes at work during the infancy of the Solar System. ISRO aims to launch the Chandrayaan 4 mission in 2027. The Chandrayaan 4 mission will demonstrate in-principle, all the technologies necessary for the ambitious crewed mission to the Moon, that ISRO plans to achieve by 2040. India aims to eventually set up its own base on the Moon by 2047.