India becomes the fourth country to land on the moon – 8/23/2023 – Science

The Chandrayaan-3 mission managed to land successfully on the surface of the Moon this Wednesday (22). The successful landing makes India the fourth country to accomplish the feat, after Russia (then Soviet Union), United States and China. This is in addition to being the first to make a descent to the lunar south pole, a more challenging region for landings than the equatorial belt.

It was the second attempt by the Indians, after the Chandrayaan-2, launched in 2019, which had a lunar orbiter (still in operation), and a landing module containing a rover. During the final approach for the landing, on September 6 of that year, the module crashed into the lunar soil – after which it was diagnosed as a software failure in the operation of the descent engines.

Almost four years later, Chandrayaan-3 is an improved version of the Vikram lander and Pragyan rover used in that attempt. Launched last July 14, this time it did not have an orbiter, but a simple propulsion module for orbital maneuvers.

The path to the Moon was essentially the same on both occasions, with an insertion into Earth’s orbit, followed by maneuvers to gradually enlarge the apogee (the point of maximum distance from Earth), until capture by lunar gravity. From there, the reverse maneuver followed, with the propulsion module gradually circularizing Chandrayaan-3’s orbit around the Moon, with an average altitude of almost 160 km, which was reached last Wednesday (16).

After that, the propulsion module was ejected and Vikram’s four engines were in charge of adjusting the trajectory to a pre-landing orbit (precisely what failed last Saturday with the Russian mission Luna-25), with perilunium (closest point from the lunar surface) of 25 km and Apollonium (farthest point) of 134 km.

It is precisely from the low altitude of 25 km that Vikram began the final procedure of descent to the surface, aiming at a region close to the lunar south pole.

With the success of the landing, Chandrayaan-3 (the name simply means “lunar ship” in Sanskrit) starts to fulfill two additional objectives: to carry out observations and experiments with the instruments on board the Vikram descent module (“value”) and to demonstrate the capabilities of the small rover Pragyan (“wisdom”).

The shelf life for both is about 14 days — the time it takes for the diurnal phase of the lunar day to last. Both were not designed to survive the cold that befalls the natural satellite at night.