The manoeuvre has provided critical data for future lunar missions
The Indian Space Research Organisation (ISRO) executed a groundbreaking operation on December 4, 2023, successfully manoeuvring the Chandrayaan-3 mission's Propulsion Module (PM) from Lunar Orbit to Earth orbit. This feat is a first of its kind and marks a key milestone in space exploration and technology.
 
Launched on July 14, 2023, aboard the LVM3-M4 vehicle from the Satish Dhawan Space Centre (SDSC-SHAR), Chandrayaan-3 aimed to demonstrate a soft lunar landing near the moon's south polar region and perform experiments using its Vikram lander and Pragyan rover.
 
The mission achieved its primary objectives, with the Vikram lander successfully touching down on August 23, followed by the deployment of the Pragyan rover. The scientific instruments onboard operated for one lunar day, fulfilling the mission's objectives.
 
The primary function of the Propulsion Module (PM) in the Chandrayaan-3 mission was to facilitate the transportation of the lander from its initial position in Geostationary Transfer Orbit (GTO) to its intended destination in a lunar polar circular orbit. This task involved executing a series of complex manoeuvres to navigate the lander through space and accurately position it in orbit around the Moon.
 
The successful completion of this role by the PM was a critical step in the mission, enabling the lander to reach its target location for the subsequent phases of the Chandrayaan-3 mission.
 
Post-lander separation, the PM continued its journey, equipped with the Spectro-polarimetry of Habitable Planet Earth (SHAPE) payload, an instrument dedicated to observing Earth.
 
Re-Orbiting to Earth, A Strategic Decision: After completing its initial tasks, the PM, with over 100 kg of remaining fuel, was re-orbited to Earth. This decision was driven by two primary objectives; Firstly, the re-orbiting was essential for the continued operation of the Spectro-polarimetry of Habitable Planet Earth (SHAPE) payload. This strategic move aimed to extend the operational life of SHAPE, enabling prolonged Earth observation from a more suitable orbit.
 
Secondly, the manoeuvre provided critical data for future lunar missions. This information is particularly valuable in the context of planning and executing trajectories for upcoming missions, including those that might involve lunar sample return, thereby playing a pivotal role in advancing lunar exploration.
 
The success lies within the process of re-orbiting consisting of meticulously planned operations aligning with an intended outcome.
 
While the process of re-orbiting was being executed, ISRO paid close attention to the trajectory of the PM to ensure it did not pose any risk to the multitude of satellites orbiting Earth. This involved careful planning and continuous monitoring to avoid any potential collisions or interference with these satellites. Such precautions are crucial given the crowded nature of certain Earth orbits, especially the Geosynchronous Equatorial Orbit (GEO) belt.
 
A substantial element of the Chandrayaan-3 mission involved the development of a specialized analysis tool by the UR Rao Satellite Centre, part of ISRO's flight dynamics team. This tool, innovatively designed from fundamental principles, played a vital role in the mission, particularly in validating the complex manoeuvres required for the return journey of the Chandrayaan-3 Propulsion Module (PM) from the Moon to Earth orbit.
 
Its development represents a major advancement in space mission planning and execution, with the creation of sophisticated tools for navigating and managing intricate space missions.
 
The successful re-orbiting of the Propulsion Module to Earth orbit by the Chandrayaan-3 mission reflects India's advancing capabilities in space technology. Additionally, this achievement sets a solid foundation for upcoming lunar exploration endeavours and potential lunar sample return missions. This achievement brings us one step closer to understanding and exploring our lunar neighbour.