GUWAHATI: The Propulsion Module (PM) of Chandrayaan-3, India's lunar mission, has been manoeuvred from its lunar orbit to a successful orbit around Earth. The Chandrayaan-3 mission, launched on July 14, 2023, achieved its primary objective of demonstrating a soft landing near the lunar south polar region and conducting experiments using the Vikram Lander and Pragyaan Rover.
Following the historic touchdown of Vikram Lander on the Moon on August 23 and the subsequent deployment of the Pragyaan rover, the mission's objectives were fulfilled. The PM, responsible for ferrying the Lander module from Geostationary Transfer Orbit (GTO) to the final lunar polar circular orbit and separating the Lander, also accomplished its primary mission.
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With over 100 kg of fuel still available in the PM after a month of lunar orbit operations, a decision was made to utilise this surplus fuel to gather additional information for future lunar missions. To avoid potential collisions with the Moon's surface or Earth's Geostationary Earth Orbit (GEO) belt, the PM was re-orbited to a suitable Earth orbit.
The re-orbiting plan commenced on October 9, 2023, with the first manoeuvre raising the apolune altitude to 5112 km from 150 km, extending the orbit period. The second manoeuvre, performed on October 13, targeted an Earth orbit of 1.8 lakhs x 3.8 lakhs km. The PM made four Moon fly-bys before departing the Moon's Sphere of Influence (SOI) on November 10, and it is currently orbiting Earth.
The PM's orbit has a period of nearly 13 days with a 27-degree inclination, and there are no threats of close approaches to operational Earth-orbiting satellites based on the current orbit prediction. The SHAPE payload continues to operate whenever Earth is in its field of view, and special operations were conducted during a Solar Eclipse on October 28, 2023.
The successful return manoeuvres of Chandrayaan-3's PM have yielded valuable outcomes for future missions, including trajectory planning, gravity-assisted flybys, and controlled end-of-life scenarios to avoid debris creation. The Indian Space Research Organisation's (ISRO) flight dynamics team developed an analysis tool for this operation, which is undergoing validation through Chandrayaan-3 PM's return manoeuvres.