The second de-orbiting manoeuvre for Chandrayaan-2's Vikram lunar lander was performed successfully by the Indian Space Research Organisation (Isro) on Wednesday.
According to Isro, the manoeuvre started at 03:42 hours on September 4, 2019, as planned, using the onboard propulsion system. The duration of the manoeuvre was nine seconds.
With this manoeuvre, the required orbit for the Vikram Lander to commence its descent towards the surface of the Moon has been achieved.
The lander is scheduled for a powered descent between 0100-0200 hrs IST on September 7, 2019, which would then be followed by its touchdown between 0130-0230 hrs IST.
After successfully separating India's first Moon lander, Vikram, on Monday, Isro conducted the first de-orbit manoeuvre successfully on Tuesday.
The de-orbit manoeuvre effort is aimed at soft-landing the lander in the South polar region of the Moon, between two craters -- Manzinus C and Simpelius N -- on September 7, 2019.
The powered descent will be carried out in a 15-minute window between 0130 hours and 0230 hours IST on September 7, through which Vikram will touch down on the surface of the Moon.
De-orbiting manoeuvres involve firing the spacecraft's engines to slow down its pace and bring it closer to the Moon's surface.
Through this manoeuvre, the space agency rotated the lander to the opposite side and burned all the five engines for a short while to reduce the distance between the lander and the Moon's surface, before rotating it back to the previous position. In the second manoeuvre, the agency once again rotated the lander to the opposite side and conduct a small burn of the engines to further bring down the orbit.
"The manoeuvre was considered critical because it marks an important phase of the lunar landing process of Chandrayaan-2 and even a minute hurdle during this manoeuvre could have an impact on the whole mission," said Isro Chairman K Sivan.
After Vikram's touchdown, the rover, Pragyan, will roll down from the former to carry out the research for which it was designed. Even after the separation of Vikram, the Orbiter will continue to fly around the Moon.
On July 22, the Rs 978-crore Chandrayaan-2 was launched into space by India's heavy-lift rocket, the Geosynchronous Satellite Launch Vehicle-Mark III (GSLV Mk III), in a textbook-style operation from Isro's spaceport at Sriharikota, near Chennai. Chandrayaan-2's total journey is estimated to be around 384,000 km.
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 Pragyan rover 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."