ISRO’s Chandrayaan-2 will now involve the lander going around the moon, taking a close look at the lunar surface, before descending on the dusty terrain for a battery of tests. The earlier plan was to make a direct landing after the lander carrying a rover separates from the orbiter.
The change in plan, made at the fourth technical review meeting on June 19, entailed major changes to the lander hardware, including addition of a fifth liquid engine and a new leg configuration. This has resulted in further delay of the mission that missed three deadlines. The team hasn’t decided how many times the lander should orbit before landing, but they know the orbit will be elliptical, with the farthest point at 100km and the nearest at 30km. This changed the mission configuration and caused the delay.
As per the earlier plan, the lander was to separate from the orbiter at 100km and descend vertically up to 18km from the moon’s surface. From there, the orientation would change, making the lander go slightly horizontal for about 8.5km and then make a soft landing, a senior member of the Chandrayaan-2 team said.
“The earlier plan gave the lander little time to assess the tough terrain it has to touch as it slows from 6,000kmph to near zero to make a soft landing. The new plan allows the lander a better assessment,” said a senior scientist. The lander will use its micro star sensors to read its own velocity and deploy its four reaction wheels for the landing.
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