ISRO Successfully Places Chandrayaan-3’s Propulsion Module in Earth’s Orbit

The Indian Space Research Organisation (ISRO) has announced that the Propulsion Module (PM) of Chandrayaan-3 has been relocated from an orbit around the Moon to an orbit around Earth. This operation is being described as a unique experiment.

The primary objective of the Chandrayaan-3 mission was to demonstrate a soft landing near the lunar south polar region and conduct experiments using the instruments on the ‘Vikram’ lander and the ‘Pragyan’ rover. The spacecraft was launched on July 14, 2023, from the Satish Dhawan Space Centre.

On August 23, the Vikram lander successfully touched down on the Moon and the Pragyan rover was deployed. The scientific instruments on both the lander and rover were operated continuously for one lunar day, as planned.

ISRO has stated that the mission objectives of Chandrayaan-3 have been completely achieved. The main objective of the Propulsion Module was to transport the lander module from the Geostationary Transfer Orbit (GTO) to the final lunar polar circular orbit and then separate the lander.

Initially, the plan was to operate the payload for approximately three months during the mission life of the PM. However, due to precise orbit injection and optimal earth or lunar burn maneuvers, over 100 kg of fuel remained in the PM after one month of operations in the lunar orbit.

ISRO decided to use the remaining fuel in the PM to gather additional information for future lunar missions and demonstrate mission operation strategies for a sample return mission. To continue the SHAPE payload for earth observation, the PM was re-orbited to a suitable earth orbit. This mission plan was developed to avoid collisions and ensure the safety of the GEO spacecraft.

On October 9, 2023, the first maneuver was performed to raise the apolune altitude to 5,112 km from 150 km, increasing the orbit period from 2.1 hours to 7.2 hours. The second maneuver was revised to target an Earth orbit of 1.8 lakh x 3.8 lakh km, considering the estimate of available propellant. The Trans-Earth injection (TEI) maneuver was performed on October 13, 2023.

The PM made four Moon fly-bys before departing the sphere of influence (SOI) of the Moon on November 10. Currently, the PM is orbiting Earth and has crossed its first perigee on November 22. The orbit period is nearly 13 days with a 27-degree inclination. ISRO has stated that there is no threat of close approach with any operational Earth-orbiting satellites.

The SHAPE payload is being operated whenever Earth is in its field of view. Additionally, a special operation of the SHAPE payload was conducted on October 28, 2023, during a solar eclipse. The operations of the SHAPE payload will continue as planned.

ISRO’s flight dynamics team has developed an analysis tool specifically for this operation. The team has validated the tool through the return maneuvers carried out for the Chandrayaan-3 PM. The main outcomes of these maneuvers include the planning and execution of trajectory and maneuvers to return from the Moon to Earth, the development and validation of a software module for such maneuvers, the planning and execution of a gravity-assisted fly-by, and the avoidance of uncontrolled crashing onto the Moon’s surface, thus meeting the requirements of no debris creation.

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