Chandrayaan-2, India’s second mission to the moon, is all set to be launched on July 15, at 02.51 hours. It will take close to 50 days for the spacecraft to land on the moon on September 6 or 7.
Why does it take so long to reach the moon?
The spacecraft, which has three components — the orbiter, the lander and the rover, has to travel a distance of 3.84 lakh km before reaching the moon’s orbit. For a launch vehicle to cover this distance, which is the GSLV Mark III in this case, it follows several steps.
According to K Sivan, Chairman, Indian Space Research Organisation (ISRO), the launch strategy is similar to that of Chandrayaan-1, which was launched in 2008 and was the first to discover water on the moon.
After the launch from Sriharikota on July 15, it will take 16 days for Chandrayaan 2 to reach the earth’s orbit using the rocket’s propulsion system. To reach the moon’s orbit, Chandrayaan 2 will perform a series of Trans Lunar Injection (TLI) burns. These are meant to increase the spacecraft’s velocity to change its orbit from circular low Earth orbit to reach the vicinity of moon.
This process will take six days as the moon’s location is continuously changing due to orbital motion.
Once Chandrayaan 2 reaches the moon’s orbit, it will revolve around the moon for 27 days to de-orbit the lander on its surface. From the moon’s orbit at 100 km, it will take four days for the lander and rover combo to reduce the distance to 30 km.
It will take 15 minutes for the lander, named Vikram, to soft land on the moon from a distance of 30 km. Sivan describes these 15 minutes as the “most terrifying moment”. It is important for ISRO since this is the very first time the organisation has attempted such a complex mission. If the soft landing is successful, India will be the fourth country to land on the moon. (With Chandrayaan 1, the organisation tried a crash landing and placed an orbiter in the moon's orbit)
However Sivan is confident about the success. “We have left no stones unturned and have done testing at molecular level. We have full confidence and that is why we are going ahead with the mission,” he added.
After the landing on the moon’s South Pole, the rover will be separated from the lander. “This will take four hours. The rover will move at the speed of 1 cm per second,” Sivan added.
“By the time it lands on the moon’s surface, it will be September 6th or 7th, as we might have to do minor adjustments,” he said. The duration of mission is 15 earth days or one lunar day. However the orbiter will revolve around the moon for a one year period.
What will each of the three components do?
The orbiter will map the major elements present on the lunar surface including water, and will send a 3-D map for the study of lunar minerals and geology. The lander will study moon-quakes near landing side, lunar thermal properties and plasma. The rover will analyse the composition of elements in the moon.
Desi message on the moon
Science apart, Chandrayaan 2 will leave an imprint of the Asoka Chakra and ISRO symbol on the moon. Sivan explained that one side of the rover wheel has Asoka chakra and other has ISRO symbol that will be imprinted on the moon as it rover moves on the moon's surface.
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