Chandrayaan-2 all set to enter Moon’s orbit on Tuesday

The moment of reckoning is finally here for India’s boldest lunar mission, Chandrayaan-2. On August 20, Tuesday, almost a week after it left the Earth’s orbit, the spacecraft will be inserted into a lunar orbit ahead of an unprecedented soft-landing.

The insertion is tentatively scheduled between 8.30 and 9.30 am on Tuesday, as Indian Space Research Organisation (Isro) chairman K Sivan informs. Though a ‘challenging’ manoeuvre, Isro is all prepared. The spacecraft, asserts Sivan, is functioning according to plan.

The spacecraft’s sound health should give Isro a massive shot of confidence as it fires Chandrayaan-2’s liquid engine to activate the orbit-insertion move. But this will just be the beginning of a complex set of manoeuvres that will follow.

The mission composite integrating an orbiter, the lander Vikram and rover Pragyan will be progressively lowered through four orbit manoeuvres. Once the spacecraft reaches the orbit of about 100 km from the lunar surface, Vikram will separate from the orbiter on September 2.

The lander will undertake two more orbit manoeuvres before Isro initiates the most critical task of soft-landing the spacecraft near the lunar South Pole on September 7. After the July 22 launch of Chandrayaan-2 aboard the GSLV Mk-III Mk1 vehicle from Sriharikota, this would be a game-changing finale.

On August 14, the mission had entered the Lunar Transfer Trajectory (a defined path between Earth and Moon) after five Earth orbit-raising manoeuvres.

The spacecraft’s health is now being tracked continuously from the Mission Operations Complex (MOX) at Isro Telemetry, Tracking and Command Network (ISTRAC) in Bengaluru. The Indian Deep Space Network (IDSN) antennas at Byalalu are also part of the monitoring system.

Chandrayaan-2 will earn its stamp of success once its footprints are on the lunar surface. But this task would be anything but simple. The descent of the lander Vikram itself would have to endure “15 minutes of terror” as Sivan had said at the launch.

Once the descent begins, Vikram would drop to an altitude of about 7.5 km from the Moon’s surface in under 11 minutes. The speed of descent will be reduced progressively, but at less than 100 m from the surface, Vikram would pause to hover and study the surface to ascertain if it is fit to land.

The imagery captured by the lander’s onboard cameras will be relayed to the orbiter and terrestrial control centres.

Only after an analysis of the data shows that the chosen area is fit to land and flat enough for rover Pragyan to roll out, will the soft-landing manoeuvre be initiated.

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