The Indian Space Research Organisation (ISRO) has achieved a remarkable feat by successfully returning the Propulsion Module (PM) of the Chandrayaan-3 spacecraft to Earth’s orbit. Originally intended for lunar operations, the PM exceeded its lunar mission objectives, showcasing India’s capability to not only launch objects to the Moon but also retrieve them. This accomplishment follows the lunar hop by Vikram, the lander of Chandrayaan-3, demonstrating ISRO’s capacity to restart engines on the Moon and operate equipment beyond initial expectations.
According to ISRO’s official release, the PM of Chandrayaan-3 was moved from an orbit around the Moon to an orbit around Earth, marking a unique experiment. The primary objective of Chandrayaan-3 was to demonstrate a soft landing near the lunar south polar region and conduct experiments using the instruments onboard the lander Vikram and the rover Pragyaan. Launched on July 14, 2023, the spacecraft made history when Vikram Lander successfully touched down on the Moon on August 23, deploying the Pragyan rover to explore the uncharted lunar south pole.
The scientific instruments on the lander and rover operated continuously for one lunar day, meeting the defined mission life objectives. However, the Propulsion Module, responsible for ferrying the Lander module from Geosynchronous Transfer Orbit (GTO) to the final lunar polar circular orbit and separating the Lander, still had over 100 kg of fuel available after a month of lunar operations. This surplus fuel prompted the decision to utilize it for additional information gathering and mission operation strategies, demonstrating the feasibility of future lunar missions.
To achieve this, ISRO opted to re-orbit the PM to a suitable Earth orbit, considering safety measures to prevent collisions with the Moon’s surface or entering Earth’s Geostationary Orbit (GEO) belt. The optimal Earth return trajectory was designed for October 2023. The PM underwent maneuvers to raise the apolune altitude, increasing the orbit period, and later targeting an Earth orbit of 1.8 lakh x 3.8 lakh km.
On October 13, 2023, the trans-earth injection (TEI) maneuver was successfully performed, and the PM completed four moon fly-bys before departing the Moon’s Sphere of Influence (SOI) on November 10. Currently, the PM is orbiting Earth, and its trajectory includes variable perigee and apogee altitudes, with no threats to operational Earth-orbiting satellites.
The SHAPE (Spectro-Polarimetry of the HABITABLE Planet Earth) payload onboard the PM is being operated during Earth’s field of view, and a special operation was conducted during a solar eclipse on October 28, 2023. The SHAPE payload operations will continue, contributing to Earth observation.
ISRO’s flight dynamics team developed an analysis tool for this operation, validated through the return maneuvers. The outcomes include trajectory and maneuver planning for Moon-to-Earth return, software module development for such maneuvers, and the execution of a gravity-assisted flyby. Importantly, the return maneuvers prevent uncontrolled crashing on the Moon’s surface, aligning with the requirement of no debris creation.
This successful operation reflects India’s advancements in space exploration and contributes valuable insights for future lunar missions and beyond.
