LOI of Chandrayaan-2
Almost 30 days after it was launched, the Chandrayaan-2 spacecraft on 20 August 2019 moved into the lunar orbit, and started going around the moon, in preparation for a landing on September 7. Chandrayaan-2, launched from Satish Dhawan Space Centre in Sriharikota on July 22, is India’s first lander mission to the moon. The lunar orbit insertion manoeuvre carried out at about 9 am, for about 30 minutes, precisely injected Chandrayaan-2 in a pre-defined orbit (around the moon), in a perfect way.
- The spacecraft has been injected into an elliptical orbit that is 114 km away from the moon’s surface at its nearest point and 18072 km at its furthest.
- This orbit would be changed through another series of manoeuvres, to let the spacecraft eventually attain a near-circular orbit of 100 km around the moon.
- At this point, the Vikram lander, along with the small Pragyaan rover, is slated to separate from the main composite module and start its incremental descent towards the moon’s surface.
- The separation is scheduled for September 4, following which the lander and rover would position themselves in a lower orbit, while the landing is planned to take place at 0140 am IST on September 7. The main spacecraft module would continue to go around the moon in its orbit for at least one full year.
- Vikram is meant to land in the region around the South Pole of the moon, Chandrayaan-2 needed to attain an orbit that had an inclination of 90 degrees with respect to the lunar equator. In other words, the lunar orbit selected for Chandrayaan-2 had to pass directly overhead the polar regions.
- Today’s manoeuvre, Chandrayaan-2 is now going around the moon in an orbit of 114 km x 18072 km with an inclination of 88 degrees. In due course, this orbit would be brought down to 100km x 100km, and further to 100km x 30km. At that time, the inclination of the orbit would also be 90 degrees.
- After its launch on July 22, the spacecraft had been put in an earth-bound orbit. It went around the earth till August 14, raising its orbit incrementally five times, before beginning its six-day journey towards the moon with higher energy.
- The ambitious Moon mission, which has been a pioneering achievement for India scientists, was launched on the back of the powerful GSLV Mk-III rocket carrying “a billion dreams” from the Satish Dhawan Space Centre at Sriharikota.
- The textbook launch became successful as the spacecraft crossed Earth’s escape velocity in 16 minutes 23 seconds. It had been deposited in an earth orbit by the 640-tonne GSLV Mk-III which, after burning its successive stages, separated itself completely from the spacecraft.
- The orbit at its nearest was 170 km from earth, and 39,120 km at the furthest. The launch went off without any hitch, a week after it was aborted 56 minutes before liftoff due to a technical snag.
Five Earth-raising manoeuvres
- Over the course of 23 days, the heavy spacecraft spent its time circling the Earth’s orbits as scientists performed a series of earth raising manoeuvres before placing it into the Lunar orbit.
- Two days after its ascent into space, Chandrayaan 2, on July 24, had successfully performed its first manoeuvre, two days later, on July 26, it performed its second earth-bound orbit raising manoeuvre.
- On July 29 it performed its third raising manoeuvre after being put in an Earth-bound elliptical orbit. Two more such manoeuvres were performed on August 02 and August 06 before preparing to break free from the Earth and move towards the Moon on August 14.
Chandrayaan-2 to soft-land on Moon on September 7
- Following the Lunar Orbit Insertion (LOI), there would be four more manoeuvres to make the spacecraft enter its final orbit, passing over the lunar poles at a distance of about 100 km from Moon’s surface.
- Subsequently, the Vikram lander would separate from the orbiter on September 2. Two orbit manoeuvres would be performed on the lander before the initiation of powered descent to make a soft landing on the lunar surface on September 7.
- The Chandrayaan 2 mission will try to understand the composition of the Moon by studying the measurements on the near-surface plasma environment and electron density in the lunar ionosphere.
- The mission will also measure the thermophysical property of the lunar surface and seismic activities. Apart from this, Chandrayaan 2 will also study the water molecule distribution using infrared spectroscopy, synthetic aperture radiometry & polarimetry as well as mass spectroscopy techniques.