Chandrayaan-3 landing: Prayers, anticipation amid feverish excitement

Prayers in temples, mosques, and churches coincided with the countdown for the Chandrayaan-3 lander’s descent as schoolchildren waited for live screenings of its landing across the country while Prime Minister Narendra Modi was expected to watch it from South Africa amid feverish anticipation on Wednesday.

The countdown for the descent began on Tuesday as India aims to become the fourth country globally to successfully land on the moon and the first on the lunar South Pole.

The touchdown of the lander module, Vikram, was planned as soon as the sun rises on the moon around 6pm IST on Wednesday, four years after India’s second lunar mission, Chandrayaan-2, crashed on the surface of the moon in September 2019. Indian Space Research Organisation (Isro) has analysed each contingency and rectified the errors of the last mission. It has strengthened the craft’s hardware and software and prepared for worst-case scenarios via simulations besides preparing a backup plan.

Isro chairman S Somanath on Tuesday said all stages of the mission have gone as per plan and they were confident that Vikram will successfully land on the moon.

Chandrayaan-3’s lander will identify its landing site after all final checks on Wednesday. The site has been increased to an area of 4km x 2.5km from the 500m x 500m that was planned for its predecessor.

Thrusters will start a controlled descent of the spacecraft around 5.45pm. Once the lander module reaches closer to the lunar surface, its speed will gradually reduce. Its legs, which have been engineered to be stronger compared to the Chandrayaan-2 lander, will then extend out. The craft will make a landing around 6.04pm.

The lander’s flaps will open to reveal a ramp for the rover, Pragyaan, to roll out following a successful touchdown. The rover will click pictures of the lunar surface once it is placed on the moon. The lander and rover will also take pictures of each other to ensure communication between them, and Isro’s base station.

The indigenous lander module, propulsion module, and rover on Chandrayaan-3 seek to develop and demonstrate new technologies for interplanetary missions. The propulsion module separated from the craft will carry out independent experiments in the lunar orbit.

The lander has the capability to “soft land” and deploy the rover. The rover will carry out in-situ chemical analysis of the lunar surface during the course of its mobility. Both the lander and the rover are equipped with scientific payloads to carry out experiments.

The experiments were expected to go on for 14 Earth days – one lunar day. The Isro chief on Monday told HT that there is a scope for extended life of the solar-powered equipment if it gets recharged after the next lunar sunrise.

Chandrayaan-2 could not make a soft landing on the moon. Officials said the mission was a “part failure”. But Chandrayaan-2’s orbiter has continued to orbit the moon and provided data that has helped Isro prepare for the latest mission.

A failure analysis report of the mission highlighted that the five engines, which have been downsized to four for the latest mission, used for the reduction of velocity developed a higher thrust than intended.

The lander was to lose most of its velocity at a distance of 400m from the lunar surface and start hovering above the landing spot to ensure a soft vertical descent. But the high velocity led to the crash.

Isro has built a sturdier spacecraft for Chandrayaan-3. It has a higher fuel capacity to reduce the possibility of failure and to give the craft more flexibility to manoeuvre possible errors during landing.

Isro has prepared for the best-case scenario of landing on Wednesday evening. Contingency plans in case the lander module is unable to reach the lunar surface have also been made. Isro aims the landing in the initial period after the lunar sunrise so that the mission gets enough days to complete its experiments. The availability of sunlight is crucial to power the equipment.

Isro has planned the mission in a way that the craft lands at the time of lunar sunrise to allow 14 Earth days for experiments as all modules on the craft are solar-powered. It will attempt the landing again within 24-50 hours if it does not happen on Wednesday. Alternate landing sites will also be considered.

The landing could be deferred for a month until the next lunar sunrise if the descent is deemed risky. The craft will hover in its current orbit of 25km x 134km in that case.