Indian lunar lander Vikram has begun its journey's most crucial last leg after separating from Chandrayaan 2, which has been going around the Moon ever since it reached the lunar orbit on August 20.
Indian Space Research Organisation (ISRO) engineers successfully achieved the separation of the lander, which carries the lunar rover, Pragyan, in its belly, on Monday at 1:15 pm and is going around the Moon at a nearly circular orbit of 119km x 127km.
The lander will undergo two orbit-lowering manoeuvres (termed Deorbit #1 and Deorbit #2) on Tuesday and Wednesday respectively, an ISRO statement said. The second orbit-lowering exercise is expected to place the lander on an orbit that will be as close as 36km from the lunar surface at the closest and 110km at the farthest.
The lander will be slowed down for the powered descent on September 7 to touch down on the surface of the lunar South Pole where no country has landed so far, according to the statement. Once the lander touches down it will release the rover, Pragyan, which carried a scientific payload for conducting experiments on the lunar surface.
"The health of the orbiter and lander is being monitored from the Mission Operations Complex... All the systems of Chandrayaan 2 orbiter and lander are healthy," ISRO said in a tweet.
Vikram will land on the lunar region that has been little explored until now. Most lunar landings have taken place in the northern hemisphere or in the equatorial region. Pragyan will use a ramp that Vikram will lay to roll down to the lunar surface.
Chandrayaan 2, the composite orbiter carrying Vikram and Pragyan, was launched on July 22 by India's most powerful rocket GSLV Mk3 from the Vikram Sarabhai Space Centre in Sriharikota. Within minutes of the takeoff, the three-stage launcher placed Chandrayaan 2 on an elliptical orbit that at the closest was some175km from the earth's surface. Prime Minister Narendra Modi congratulated ISRO chairman K Sivan and his team on the successful launch of the moon mission.
After a series of earth-side orbit raising manoeuvres, Chandrayan 2 was raised to 221 x 143,585km orbit getting it ready for the translunar journey. The orbiter was catapulted with a final push on its journey of more than 4,00,000 km to the lunar orbit on August 14.
The risky lunar capture was achieved on August 20 when Chandrayaan 2 was slowed down to enable its capture in the lunar orbit. The manoeuvre itself was risky as more than the optimal velocity would have caused the spacecraft to escape the feeble gravitational pull of the Moon and be lost in the void beyond. A lower than the correct velocity would have also caused the spacecraft to miss the lunar orbital intersection.
Until now, ISRO has more or less used the same playbook as the one for Chandrayan 1 that reached the lunar orbit on in November 2003, except for the change in the launcher shortening the journey time. But Chandrayaan 1 carried an impact probe that was caused to crash on the lunar surface from an altitude of about 100km on November 14. In contrast Chandrayaan 2's payload, Vikram will attempt a soft-landing with its rover payload.