CHENNAI: Two days after the July 22 launch, the Indian Space Research Organisation (ISRO) on Wednesday afternoon successfully raised Chandrayaan-2’s acutely elliptical orbit around the earth to 230 km (closest point to earth) by 45,162 km (farthest point from earth) in its first orbit-raising operation.
After four more such orbit-raising operations, ISRO is scheduled to enter the mission’s Moon orbiting phase on August 20 before landing near the Lunar south pole on September 7.
In the days to come, ISRO is scheduled to perform four more such earth orbit-raising operations, increasing the orbit to 233.2 km by 1,43, 953 km in its fourth operation on August 6 before sending the spacecraft hurtling towards the moon orbit, in what is called the Trans Lunar Insertion.
The GSLV MkIII M1 rocket launcher on July 22 afternoon released the spacecraft in an orbit of 170 km by 45,475 km around the earth.
These orbit-raising procedures are carried out for the spacecraft to gain the velocity and the momentum required to make it to the Moon, 3.84 lakh km away from the earth.
In simple terms, ISRO scientist explains that these earth orbits are akin to a slinger rotating his slingshot several times around his body to gain adequate momentum before releasing it at a high velocity to strike a target at a distance.
After every rotation, the slinger relaxes his hold for the slingshot to get slightly longer before beginning the next high-speed rotation, which is exactly what the ISRO does during earth orbit-raising operations.
During the orbit-raising operations, ISRO scientists fire the on-board propulsion system for the spacecraft to expand its orbit.
On Wednesday, ISRO scientists fired these thrusters onboard Chandrayaan-2 spacecraft for a period of 57 seconds to achieve a much higher perigee (the shortest distance from the earth during its elliptical orbit) of 230 km from its launch perigee of 170 km. However, the apogee (farthest distance from earth) was marginally reduced from 45,475 km to 45,162 km.
But in the next four orbit-raising operations, the apogee will be significantly increased in repeated succession.
In the early hours of July 26, ISRO is scheduled to increase Chandrayaan-2’s earth orbit to 262.9 km x 54,848 km; on July 29, to 281.6 km x 71,341 km; on August 2, to 262.1 km x 89,743 km; and on August 6, to 233.2 km x 1,43,953 km.
Trans Lunar insertion will be attempted on August 14 when the orbit will be increased to 278.4 km x 4,12,505 Km when the spacecraft will be released towards the moon orbit.
July 26, 2019, between 1 am and 2 am to 262.9 Km x 54,848 km
July 29, 2019, between 3 pm and 4 pm to 281.6 Km x 71,341 Km
August 2, 2019, between 2 pm and 3 pm to 262.1 Km x 89,743 Km
August 6, 2019 between 2pm and 3pm to 233.2 Km x 1,43,953 Km
Trans Lunar insertion will be attempted on August 14 at 03:00 - 04:00...278.4 km x 4,12,505 Km.