In the late hours of Sunday (around 11:00 pm Indian Standard Time), the Indian Space Agency pushed its Chandrayaan-3 spacecraft closer to the Lunar surface. This is part of a gradual process that will eventually lead the craft to the Lunar soft landing that is scheduled for August 23.
Since undergoing the Lunar orbit insertion in the evening hours of Saturday and starting to circle the moon, this is the first time that the craft’s Lunar orbit is being reduced. Since Saturday, the craft has been in a 164 km x 18074 km orbit around the moon. With the engine firing done on Sunday night, the craft’s orbit has been lowered to 170 km x 4313 km.
“The spacecraft successfully underwent a planned orbit reduction manoeuvre. The retro-firing of engines brought it closer to the Moon’s surface, now to 170 km x 4313 km. The next operation to further reduce the orbit is scheduled for August 9, 2023, between 13:00 and 14:00 Hrs. IST.” ISRO said in a tweet.
The journey so far
Chandrayaan-3 was launched on July 14 from India’s spaceport, Satish Dhawan Space Centre, Sriharikota. Sixteen minutes from lift-off, the craft was placed in a highly elliptical orbit around the Earth. Thereafter, by performing five engine burns on as many occasions, the craft gradually raised its orbit and slingshot itself further away from Earth, while continuing to remain in Earth’s orbit.
On the intervening night of July 31 and August 1, Chandrayaan-3 performed its Trans-Lunar injection burn. By this long-duration firing of its engines, the craft was pushed out of Earth’s gravitational influence and hurled towards Lunar gravitational influence. “By firing its engines for the TLI, the craft gained departure velocity and set course from the earth orbit towards a location in the vicinity of the moon,” Dr Mylswamy Annadurai, former Director of ISRO’s UR Rao Satellite Centre, had told WION.
The journey that lay ahead
ISRO has said that the craft’s next operation would be the second reduction of orbit around the moon. It is scheduled for August 9, around 1-2 pm IST. Just like ISRO slingshot the craft away from earth by performing multiple engine firings, a similar process would be carried out for the reverse effect. Engine retro firings would be done to bring the craft closer to the lunar surface and eventually into a circular orbit around the moon.
Thereafter, the craft would be brought to 100×30 km orbit, and then a process of Rough braking, Attitude hold, Fine braking, and velocity reduction would be carried out, in the run-up to the lunar landing. ISRO has planned the Lunar landing at 5:47 pm Indian Standard Time, on August 23.
Objectives of Chandrayaan-3
India’s 3rd Lunar spacecraft comprises a propulsion module, lander and rover. The combined mass of them is 3.9 tonnes. The key goal of the craft is to perform a lunar soft-landing and perform in-situ analysis near 70 degrees latitude of the Lunar surface. The mission is expected to last 14 earth days or one lunar day, during which the six-wheeled rover and the lander will perform their respective experiments.