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ISRO has executed a unique experiment by relocating the Chandrayaan-3’s Propulsion Module (PM) from lunar orbit to Earth’s orbit. Originally designed to transport the Lander module and operate the Spectro-polarimetry of Habitable Planet Earth (SHAPE) payload, the PM had an excess of fuel after its lunar orbit operations. To gather additional information for future lunar missions and showcase mission operation strategies for a sample return mission, ISRO decided to re-orbit the PM to a suitable Earth orbit.
The mission plan prioritized collision avoidance, ensuring the PM wouldn’t crash onto the Moon’s surface or enter Earth’s GEO belt. The optimal Earth return trajectory was designed for October 2023. The first maneuver on October 9 raised the apolune altitude, and a Trans-Earth Injection (TEI) maneuver on October 13 set the PM on an Earth orbit trajectory. The PM, now orbiting Earth, underwent four Moon fly-bys before departing the Moon’s Sphere of Influence on November 10.
The SHAPE payload is being operated whenever Earth is in its field of view, including a special operation during a Solar Eclipse on October 28. The UR Rao Satellite Centre/ISRO’s flight dynamics team developed an analysis tool for this operation, validated through return maneuvers for the Chandrayaan-3 PM.
Chandrayaan-3’s primary mission was to demonstrate a soft landing near the lunar south polar region and conduct experiments using the instruments on Vikram and Pragyaan. Launched on July 14, 2023, the mission’s objectives were achieved, with Vikram Lander making a historic touchdown on the Moon on August 23. The Chandrayaan-3 comprised an indigenous Lander module, Propulsion module, and Rover, successfully demonstrating new technologies for interplanetary missions.
The return maneuvers for the PM have yielded valuable outcomes, including the planning and execution of trajectory maneuvers for Moon-to-Earth return, development and validation of software modules for such maneuvers, and planning and execution of gravity-assisted flybys across celestial bodies, providing insights for future missions.
