BENGALURU: The Indian Space Research Organisation (ISRO) performed the penultimate orbit-lowering manoeuvre on the Chandrayaan-2 orbiter on Friday evening.
The fourth lunar-bound orbit manoeuvre beginning at 6.18 pm fired the onboard propulsion system of the orbiter for 1,155 seconds to bring the spacecraft down to an orbital altitude of 124 km x 164 km.
The orbiter is carrying the lander Vikram, which in turn is carrying the robotic rover Pragyan, which is scheduled to conduct lunar surface explorations after India makes its first-ever touchdown on the moon’s surface near its south pole.
The next Lunar bound orbit manoeuvre, which will be the fifth and final one on the orbiter, is scheduled on Sunday (September 1), between 6 pm and 7 pm. That manoeuvre will bring down the orbital altitude down to 100 Km X 100 Km from the lunar surface in a pole-to-pole orbit around the moon.
On September 2, the ISRO scientists’ attention will shift to the lander Vikram, which will separate from the orbiter on that day.
On September 3, a three-second de-orbit manoeuvre will be conducted by the ISRO scientists to check if all systems are normal. Finally, on September 4, the actual de-orbit manoeuvre will be performed for about 6.5 secs to put the lander Vikram in an orbit of 35km perilune (closest to lunar surface) and 97 km apolune (farthest from lunar surface).
For three days after September 4, the scientists will carry out all checks on the orbiting lander. On September 7, at the scheduled time of 1.40 am, the powered descent of the lander Vikram will begin -- a process which ISRO chairman has described as the “most terrifying” of the entire Rs 976 crore mission.
Vikram will land near the lunar South pole on a high plain between two craters, Manzinus C and Simpelius N, to record India as the first country ever to land near the lunar south pole.
The historic event will be witnessed live by Prime Minister Narendra Modi from ISRO Telemetry, Tracking and Command (ISTRAC) facility in Bengaluru.
After a successful landing, the rover Pragyan will emerge from Vikram and begin its exploration within 500 metres for a period of one lunar day (14 earth days), while the static Vikram and the orbiter will continue relaying scientific data back to the Deep Space Network (DSN) situated 35 Km from Bengaluru off Mysore Road.