The Indian Space Research Organisation (Isro) on Monday successfully separated the lunar lander, Vikram, from the Chandrayaan-2 orbiter. This was a major milestone in the mission.
The separation was done at 1:15pm on Monday.
The lander will travel towards the lunar surface, leaving the orbiter, which will remain in orbit for one year, to continue to revolve around the Moon.
On Sunday, Isro had successfully carried out Chandrayaan-2's fifth and final orbit manoeuvre to refine its circular path around the Moon.
Chandrayaan-2 consists of an orbiter, a lander and a rover. The 1.5-tonne lander carries the 27-kg rover. The mission of the lander is to soft-land on the lunar South Pole and to safely deploy the rover. The lander and the rover have a mission life of a single lunar day, or 14 days on the Earth.
The rover, Pragyan, has two devices to probe the elemental composition of lunar soil near its landing site and derive the elemental abundance there.
Chandrayaan-2's 384,000-km journey started on July 22 after the GSLV MkIII-M1 vehicle lifted off from Isro's spaceport at Sriharikota, near Chennai.
ISRO (@isro) September 2, 2019
Now, Isro will conduct a small manoeuvre for about three seconds to ensure that all the lander's systems are running normally.
On September 4, Isro will conduct the real manoeuvre for the lander for about six seconds. After checking the systems for three days, on September 7, at 1.40 am, the lander will begin propulsion, and at 1.55 am, it will land.
"It will be a terrifying moment as it is something Isro has not done before," said Isro Chairman K Sivan. He noted that globally, the success rate of a soft landing on the Moon is around 37 per cent. However, Isro is confident of landing smoothly as it has learnt from the mistakes of others and conducted enough tests and simulations.
Isro will employ throttlable control over the engine's thrusters, which is being attempted for the first time. One of the major challenges would be dust: Chandrayaan-2 will shield itself from the sharp, jagged-edged dust blowing up from the surface of the Moon during the landing with a few operational tweaks in the spacecraft. Just 13 metres before the landing, all the engines, except the one at the centre, will be switched off to avoid dust getting into the lander. The centre engine will only push the dust horizontally, thereby keeping the spacecraft risk-free in this regard.
The rover will then be rolled out to the surface of the Moon in nearly four hours, as it will move at a speed of 1 cm per minute. It will stay within 500 metres of the lander during its one-lunar-day mission.
The lander and rover have been tested extensively to survive the lunar night for the 14-Earth-day duration from September 7.
The lander and rover will carry out experiments to find water on the lunar surface and map for chemicals and topography. Isro has said that extensive mapping of the lunar surface to study variations in surface composition is essential to trace back the origin and evolution of the Moon.
The findings of these experiments will be helpful not only for India's future missions, but also for other missions, including NASA's, said Sivan, who added that past missions, including China's, were carried out close to the Equator.
The first data from the rover, Pragyan, will come through about 5.8 hours after landing.
While the battery will be exhausted after 14 days, if other systems are intact, once the next lunar day begins, the rover and lander could recharge their power systems and resume their work. However, Sivan said, "We cannot assure you that it will happen."