AHMEDABAD: In a few hours from now, when India's third lunar mission, Chandrayaan-3, will make a historic landing on the south pole of the Moon, several scientists at Isro-Space Applications Centre (SAC) and Physical Research Laboratory (PRL), recall how the landing sites were chosen.Live updates: Chandrayaan-3 missionThe landing site selection for Chandrayaan-3 was based on a rigorous analysis of various datasets from previous lunar missions, such as Chandrayaan-1, Chandrayaan-2, Selene, and US-led Lunar Reconnaissance Orbiter (LRO) mission.The criteria included topography, slope, illumination, and hazard avoidance.

A team of scientists from the Isro and other institutions used a moving window technique to search for hazard-free areas of 4km x 2.4km within the latitude range of 60° to 70° south on the near side of the Moon.They selected 20 sites for further characterization using medium-resolution data from US's LRO's Lunar Orbiter Laser Altimeter (LOLA), Selene, and LRO's Narrow Angle Cameras (NACs).

Out of these 20 sites, eight were chosen for detailed characterization using high-resolution data from OHRC, a camera onboard Chandrayaan-2 orbiter.

The OHRC acquired stereo images of the eight sites at better than 32cm pixel resolution, which were used to generate digital elevation model, recalls a paper published by a team of scientists from the High Resolution Data Processing Division, Amitabh, K Suresh, Ajay K Prashar and Abdullah Suhail.