BENGALURU: One of the four major hurdles to the mission is preventing the damage to lander Vikram due to lunar dust. This dust is likely to rise when the lander is setting on the moon from the distance of 30 metres.ISRO has designed Vikram in such a way that the lunar dust does not form plumes and settles on the top of the lander. “Moon dust is a major concern for any moon landing mission,” ISRO Chairman, K Sivan had said. However ISRO has devised a way of overcoming this hurdle.
HOW IT HAPPENS
In the past, four thrusters at four corners would be used for landing, and during that moment, dust rises and covers the entire lander.To prevent the blanket of dust settling on the spacecraft, the lander will stop the use of four corner engines and will only settle on one single central thruster. “This will happen after the lander reaches an altitude of 30 metre, from where the central engine will fire,” he said.
The plume coming from one engine will hit the ground and the “dust will go flat outwards and settle away from the lander. It won’t come up. The criticality is because of the possibility of dust being reduced because of the use of the central engine,” he said.
WHY THESE FOUR BURNERS AT ALL?
However, these four engines have a role of their own, and are crucial in the earlier stages — a day following the lander-orbiter separation, on September 3. The engines will be necessary for burns between two rotations. On September 4 again, the four burners will be needed to achieve a lesser altitude from 100x100 km to 100x35 km orbit, and is essential to make the descent to the lunar surface easy.
Following the descent, the pictures of the moon’s surface will also be available right then. “When the lander comes down to a point where it is normal to the surface of the moon, pictures will be available after that,” Sivan assured.Pictures will also be taken by the rover after it rolls out. However, clear pictures of lander and rover will be available only five-and-a-half hours after the landing, he said.
ANOTHER MAJOR HURDLE: THE LANDER TOPPLING
ISRO’s chosen point on the south pole of the moon, between craters Manzinus C and Simpelius N also plays a crucial role in the success of the mission.For the lander Vikram to safely land on the lunar surface, it cannot settle on an inclined surface, lest it topples. The space agency has estimated the slope of landing to be less than 12 degree. Anything beyond can make the lander topple, apprehends the ISRO chief. A similar debacle will be in store if one leg settles on the boulder.
LEARNING FROM ISRAEL
Sivan stressed the need to make the mission more autonomous. “This is one of the lessons from Israel’s failure of its Beresheet mission to soft-land on the moon earlier this year.We should not have ground control in descending stage,” he said, explaining that instead of the lander being remotely controlled from earth-based stations, the lander should have sensors guiding the landing. As part of this, the Indian space agency has learnt about ‘sensors characterisation’,he added.