After completing its third lunar orbit decrease, India’s Chandrayaan-3 spacecraft has gotten closer to the moon. As a result, the spacecraft’s orbit around the Moon has progressively changed from a highly elliptical one (174 km x 1437 km) to a nearly circular one (150 km x 177 km). The distance between the object’s closest and furthest points from the moon, known as the perilune and apollune, respectively, in an elliptical orbit, is extremely different. Perilune and apolune differ in a nearly circular orbit by a very little amount.
The next step for ISRO is to maneuver the spaceship into a circular orbit 100 km above the lunar surface. The orbit circularization phase is what ISRO refers to at this point. When this orbit is attained, the spacecraft will always be 100 km above the moon for its entire orbit.
Commands to activate the engines and move the craft farther from the earth (orbit-raising operations) were given while it was circling the planet. In those situations, the engine was started to move the craft forward and give it higher velocities. By firing the engines in the opposite direction from normal, or “opposite,” firing, or “retro-firing,” the craft’s velocity is decreased and its orbit is lowered.