The spacecraft responsible for delivering the Chandrayaan-3 lander to the moon has successfully returned to Earth orbit, showcasing essential technologies for a prospective Indian lunar sample return mission. The Indian Space Research Organisation (ISRO) made the announcement on December 4, revealing that the propulsion module for the Chandrayaan-3 mission is now positioned in a high Earth orbit. Notably, ISRO had not previously disclosed plans to bring the propulsion module back to Earth orbit.
Initially weighing 2,145 kilograms, the propulsion module, a modified version of ISROs I-3K satellite bus, played a crucial role in transporting the Chandrayaan-3 lander from an initial elliptical Earth orbit to a low lunar orbit. Following its launch on July 14, the module underwent a series of maneuvers, including raising the apogee of the orbit, translunar injection burn, and lunar orbit insertion burn. The module then achieved a nearly circular orbit around 150 kilometers above the moon before the lander separated on August 17.
While the lander successfully touched down on the moon on August 23, the propulsion module continued to operate in orbit, employing an instrument named Spectro-polarimetry of Habitable Planet Earth (SHAPE) to observe the Earth. After the lander separation, ISRO provided limited information about the propulsion module activities.
According to ISROs statement, the decision to bring the propulsion module back to Earth orbit was based on the realization that there was an excess of more than 100 kilograms of propellant remaining on the spacecraft. The maneuvers to return the module to Earth orbit commenced on October 9, raising the high point of its orbit around the moon from 150 to 5,112 kilometers.
Subsequent maneuvers included a transearth injection on October 13, involving four close approaches to the moon before leaving its sphere of influence on November 10. The spacecraft then entered a high orbit around Earth, reaching its first perigee on November 22 at an altitude of 154,000 kilometers.
ISRO explained that these maneuvers allowed SHAPE to continue observations closer to Earth, emphasizing their role in gathering additional information for future lunar missions and demonstrating mission operation strategies for a sample return mission.
Although ISRO has not formally announced plans for a lunar sample return mission, discussions about the potential of such a mission have taken place. The next lunar mission on ISROs agenda is the Lunar Polar Exploration Mission (LUPEX), a joint effort with the Japanese space agency JAXA, expected to launch no earlier than 2026. The return of the propulsion module to Earth orbit marks a significant step in advancing technologies for lunar exploration and potential sample return missions.
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