A view of the Chandrayaan-2 orbiter spacecraft module orbiting the moon

The Indian Space Research Organisation (ISRO) has finalised the coordinates of three possible landing sites for its third lunar mission – Chandrayaan-3 – expected to be launched later this year. All the probable landing sites are on the moon’s south polar region on the side facing earth, senior scientists from the space agency said on Tuesday.

The criteria for selecting the landing sites for Chandrayaan-3 – a follow-on mission to Chandrayaan-2 which is meant to demonstrate end-to-end capability in safe landing and roving on the lunar surface – included local and global slope, illumination from the sun, radio communication with earth, and crater and boulder sizes, a space scientist said, asking not to be named.

The moon’s southern polar region is of particular interest to scientists because there’s a possibility of finding water ice. Chandrayaan-3, expected to be launched at the end of 2023, will have a lander and a rover.

The Chandrayaan program, also known as the Indian lunar exploration programme, is an ongoing series of outer space mission by Isro. The first moon rocket, Chandrayaan-1, was launched in 2008, and was successfully inserted into the lunar orbit.

Chandrayaan-2 was successfully launched and inserted into lunar orbit in 2019, but its lander crash-landed on the moon’s surface when it deviated from its trajectory while attempting to land on September 6, 2019, due to a software glitch.

The prime landing site for Chandrayaan-3 lies between Manzius U and Boguslawsky M craters on the moon. It also provides flexibility for the lander to land at any place in the 4km x 2.4km area within a distance of 100m from the lander hovering point, according to Isro.

To select suitable sites using coarse and medium resolution data, the local slope should be less than 10 degrees, the global slope should tend towards the equator, more than 90% of the site area should be sunlit for 10-11 days, boulder size should not be more than 2m, and there should be minimum crater and boulder distribution in the area, said a scientist from Isro’s Space Application Centre, who is associated with the mission.

“The site selection started with the analysis of the three shortlisted sites for Chandrayaan-2 landing in the 70-80 degrees latitude range,” he said, seeking anonymity. “These sites were revisited again for Chandrayaan-3 landing sites, but it was found that these sites are not meeting the landing area (4km x 2.4km) requirement.”

Chandrayaan-3 consists of an indigenous lander module, a propulsion module, and a rover. Its objectives include developing and demonstrating new technologies required for interplanetary missions. The lander will have the capability to soft land at a specified lunar site and deploy the rover, which will carry out in-situ chemical analysis of the lunar surface during the course of its mobility.

The lander and the rover will have scientific payloads to carry out experiments on the lunar surface.

Chandrayaan-3 will be launched by Launch Vehicle Mark-3 (LVM-3) rocket from Satish Dhawan Space Centre, Sriharikota. The propulsion module will carry the lander and rover configuration till 100km lunar orbit.

The aim of the mission is to demonstrate safe and soft landing on the lunar surface, and have the rover moving around on the lunar surface to conduct in-situ scientific experiments.

Isro has three big-ticket missions lined up between the end of 2023 and the first quarter of 2024. Aditya-L1, India’s first dedicated scientific mission to study the sun, and Gaganyaan’s uncrewed ‘G1’ mission is targeted to be launched in the last quarter of 2023. This would be followed by the second uncrewed ‘G2’ mission in the second quarter of 2024, before the final human space flight ‘H1’ mission in the fourth quarter of 2024.