Chandrayaan-2: Lander separation from Orbiter hrs away

Mission completes fifth and final lunar-bound orbit-lowering maneouvre on Sunday

The much-awaited separation of the Lander, Vikram from the Chandrayaan-2 Orbiter is now just hours away. On Sunday, the fifth lunar-bound orbit maneouvre on the spacecraft was successfully performed at 6.21 pm, placing the Orbiter-Lander-Rover composite in an orbit of 119 km X 127 km.

Sunday’s maneouvre lasted 52 seconds, and was achieved using the mission’s onboard propulsion system. “All spacecraft parameters are normal,” declared the Indian Space Research Organisation (Isro).

The Orbiter will now be placed in an orbit of 100 km X 100 km, to relay high resolution imagery of the lunar surface to the Earth stations for well over a year.

The critical Lander separation from the Orbiter has been scheduled between 12.45 pm and 1.45 pm on Monday. The operation will be activated once the spacecraft is in the right orbit, and is expected to be extremely fast, lasting less than a second.

It is critical that the spacecraft is stabilized in a predetermined orbit before the separation commands are relayed from the Earth station. The process itself will be performed using the onboard systems. But this time, the mechanical separation will involve the Lander being delinked from the cylindrical structure currently attached to the Orbiter’s top.

Once the Lander is successfully detached, Isro will perform two de-orbit maneuvers on Vikram to prepare for its sofr-landing in the south polar region of the moon on September 7. The space agency on Sunday released the tentative plan for future operations.

The first de-orbit maneouvre of Vikram will take place between 9 am and 10 am on September 3. The Lander will be lowered to an orbit of 109 km X 120 km. After a second de-orbit maneouvre between 3 am and 4 am on September 4, the Lander-Rover composite will reach an orbit of 36 km X 110 km around the Moon.

Over the next two days, the mission will undergo extremely critical visual analysis of the landing site before embarking on the all-important landing on September 7. The powered descent is now scheduled between 1.30 am and 2.30 am, a process described by the Isro Chairman K Sivan as ’15 terrifying minutes.’