In this picture released by ISRO, the Geosynchronous Satellite Launch Vehicle Mark III (GSLV Mk 3) or 'Bahubali' is seen at the second launch pad ahead of the launch of Chandrayaan-2, in Sriharikota. The space mission, which aims to place a robotic rover on the moon, is set to be launched on 15 July 2019.  (Photo: PTI)
In this picture released by ISRO, the Geosynchronous Satellite Launch Vehicle Mark III (GSLV Mk 3) or 'Bahubali' is seen at the second launch pad ahead of the launch of Chandrayaan-2, in Sriharikota. The space mission, which aims to place a robotic rover on the moon, is set to be launched on 15 July 2019. (Photo: PTI)

Chandrayaan-2: How ‘Lander Vikram’ will touchdown on the moon?

  • Once the lander softly lands on the moon, ‘Pragyaan’ will roll out and start exploring the moon’s surface
  • Six-wheeled Pragyaan will explore the moon for 14 earth days, equal to one lunar day

New Delhi: As India gears up to expand its footprint in space with Chandrayaan-2 set for launch early morning on Monday, it will face its toughest challenge, when its home-built Lander Vikram would attempt to land on the moon’s surface covered with craters, rocks and dust.

Chandrayaan-1 launched in October 2008 was equipped with only an orbiter and an impactor. The orbiter continued to revolve around the moon for an year, but the ‘impactor’ was just dropped from Chandrayaan-1 and impacted onto the lunar surface.

“That was a free fall, but this time, the landing has to be controlled. Huge velocity would be required when the Lander gets released from the Orbiter. Deboosting will be extremely challenging and then ensuring that Lander lands softly and rover comes out," said Ajay Lele, senior fellow at the Institute for Defence Studies and Analyses (IDSA), New Delhi.

“But the first challenge would be when the spacecraft would try to enter the moon’s orbit from the earth’s orbit," said Lele.

The orbital location of the moon is constantly changing, so the intersection of Chandrayaan-2 and the moon’s path would have to be accurately predicted. When the moon approaches the Apogee of Chandrayaan-2, which is its farthest point from the earth, the on-board thrusters would fire precisely and reduce its velocity for lunar capture and entry into the lunar orbit.

The space agency has identified a site between the two craters marked Manzinus C and Simpelius N near the Moon’s South Pole for the landing. The onboard Navigation, Guidance and Control (NGC) system and propulsion system of the module will have to work in unison autonomously and automatically for a successful landing.

The firing of on-board engines close to the lunar surface could even lead to backward flow of hot gases and dust. And, the lunar dust carries a negative charge, so it sticks to most surfaces and disrupts the deployment mechanisms and functioning of the solar panels and engines, providing a hostile environment.

Once the lander softly lands on the moon, the six-wheeled ‘Pragyaan’ will roll out and start exploring the moon’s surface for the next 14 earth days, equal to one lunar day. The AI-powered rover will study the physical, thermal properties of the lunar surface and its mineral composition.

“Scientists would have to overcome the communication gap. Both the Rover and Lander will not be able to communicate with the earth, so the connection established with the orbiter would only allow them to relay signals to the earth (which is at a distance of nearly 3.8 lakh km from the moon)," said Lele.

At such far distance, the radio signals used for communication are weak with heavy background noise and need to be picked up by large antennas. So, it will be critical to ensure that the landscape features do not result in a communication shadow area.

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