By Fakir Balaji

Bengaluru, Sep 6 (IANS): Excitement is building up in Bengaluru, as India's moon lander ‘Vikram braces for a slow descent and soft-landing near the moon's south pole in the wee hours of Saturday, followed by the rollout of its rover ‘Pragyan for a stroll after dawn.

"A sort of countdown is underway for the grand finale of the Chandrayaan-2 mission for Vikram to touch down between 1:30-2:30 a.m. on Saturday in a maiden attempt and for Pragyan to step out of it 3-4 hours later to roll over the lunar surface," an official of the Indian Space Research Organisation (ISRO) told IANS here on Friday.

Even as the nation gears up for the climax of the mission's 46-day voyage after its launch on July 22 from Sriharikota in Andhra Pradesh off the Bay of Bengal, hundreds of scientists and engineers have been working overtime at the space agency's Telemetry, Tracking and Command Network Centre (Istrac) in this tech hub's northern suburb for guiding Vikram to land gently between two huge craters and settle down before it opens the door for Pragyan to roll out.

"After the second de-orbiting on early Wednesday, the 1,471-kg Vikram has been elliptically spinning around the moon's north and south poles at a distance of 35 km x 101 km since then for the descent after 1:00 am. A command will be given to fire its four motors onboard for the lander's gradual descent motor at reduced velocity (speed). At 400 metres altitude, its sensors will capture the images of the surface hovering over it for 12 seconds for the final descent in 25 seconds and soft landing," the official said.

As Vikram descends from 100 metres altitude, all the four motors will be shut off while the central engine will be on till the touchdown. This is to minimise the rise of dust particles on the impact of Vikram's touchdown.

As there is no air in the moon's atmosphere, electrostatic forces from the lander's motors will emit particles that will settle down after some time.

"As the entire descent of Vikram will be visible on the display panels in the network centre through telemetry signals, we will get confirmation of the landing soon after its touchdown," said the official.

The signals will reach the network centre from Vikram through its orbiter spinning around the moon at 100 km away from its surface and via the space agency's Deep Space Network (DSN) at Bylalu, about 40 km southwest of Bengaluru.

"Commands will be given between 5-6 a.m. to open Vikram's door and roll out the 27 kg Pragyan in slow motion onto the surface, as the dust is expected to settle down in 3-4 hours after the lander's touch down," noted the official.

All going well, pictures of Vikram and Pragyan on the lunar surface near its south pole will reach the network centre by 7:00 a.m. for visual proof of the mission's success in its maiden attempt.

Cameras of Vikram and Pragyan will take the images of both and the region around their location and beam them to the network centre through its orbiter to the DSN for downloading them at the network centre in turn.