Chairman K Sivan said that using deorbiting manoeuvres, the space agency would rotate the lander to the opposite side and burn 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 deorbiting manoeuvre, the agency will once again rotate the lander to the opposite side and conduct a small burn of the engines to further bring down the orbit.
The lander will then make a powered descent to the Moon's surface in the unexplored south pole on September 7.
Sivan said that 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.
"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 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 mission 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 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."