How the moon kicked Chandrayaan-3 propulsion module into a new orbit

India's Chandrayaan-3 mission achieved a historic soft landing on the Moon's south pole on August 23, 2023, marking a monumental leap in the nation's space capabilities. While the successful deployment of the Vikram lander and Pragyan rover garnered global attention, a lesser-known but equally significant achievement involved the mission's Propulsion Module (PM). After its primary task of carrying the lander to lunar orbit, ISRO executed an ingenious maneuver, utilizing the Moon's gravitational influence to kick the PM into a new, wider Earth orbit. This unplanned yet strategic move underscores India's growing prowess in advanced orbital mechanics and offers a glimpse into the future of space exploration.

The **background context** for this achievement lies in India's consistent and evolving space program, spearheaded by the Indian Space Research Organisation (ISRO). Established in 1969, ISRO has steadily progressed from launching sounding rockets to developing indigenous satellite launch vehicles (PSLV and GSLV) and undertaking complex interplanetary missions. India's lunar exploration began with Chandrayaan-1 in 2008, which famously discovered water molecules on the Moon. Chandrayaan-2 in 2019 aimed for a soft landing but faced a setback with the lander. Learning from this, Chandrayaan-3 was designed with enhanced robustness and redundancy, culminating in its triumphant success. The Propulsion Module, a crucial component of Chandrayaan-3, was responsible for carrying the lander and rover composite from Earth orbit to a 100 km lunar orbit.

**What happened** was a testament to ISRO's ingenuity. After successfully separating the lander module and placing it on its trajectory for the lunar descent, the Propulsion Module was left with residual fuel. Instead of letting it drift or de-orbit in lunar space, ISRO engineers decided to utilize this remaining fuel and the Moon's powerful gravitational field. Through a series of orbital maneuvers performed between October and November 2023, the PM was precisely guided to perform a 'gravitational assist' maneuver around the Moon. This 'slingshot' effect, where a spacecraft uses the gravity and orbital motion of a celestial body to alter its own speed and trajectory, propelled the PM out of its lunar orbit and into a new, wider Earth orbit. This new orbit is designed to be stable, with a perigee (closest point to Earth) of 1.5 lakh km and an apogee (farthest point from Earth) of 3.8 lakh km, allowing it to continue orbiting Earth for several years while carrying its Spectro-polarimetry of HAbitable Planet Earth (SHAPE) payload.

**Key stakeholders** involved in this remarkable feat primarily include ISRO, the national space agency, which planned, designed, executed, and monitored the entire mission. The scientists, engineers, and technicians at various ISRO centers, such as the U R Rao Satellite Centre (URSC) and Liquid Propulsion Systems Centre (LPSC), were instrumental. The Government of India, particularly the Department of Space (DoS) which functions under the Prime Minister's Office, provides the policy framework and funding. Additionally, various public and private sector industries contribute to manufacturing components and providing services for ISRO missions.

This achievement holds immense **significance for India**. Scientifically, it demonstrates a profound understanding of orbital dynamics and fuel-efficient mission planning, paving the way for more complex and extended deep-space missions. Technologically, it showcases India's capability to execute intricate orbital maneuvers, potentially extending the operational life of spacecraft and managing space debris more effectively. Economically, such advancements enhance India's credibility in the global space market, attracting more international collaborations and commercial launch opportunities through entities like NewSpace India Limited (NSIL). Strategically, it elevates India's standing as a formidable space power, capable of independent and innovative space exploration. This also inspires a new generation of scientists and engineers, fostering a scientific temper, which aligns with the spirit of Article 51A(h) of the Constitution, promoting scientific temper, humanism, and the spirit of inquiry and reform.

Looking at **future implications**, this maneuver sets a precedent for future deep-space missions. The ability to repurpose mission modules and extend their operational life through gravitational assists can significantly reduce the cost and complexity of future endeavors like Mangalyaan-2 (Mars Orbiter Mission-2), Shukrayaan (Venus mission), or even potential sample return missions. It also contributes to the broader global effort in space debris management by demonstrating controlled orbital changes. The Indian Space Policy 2023, which aims to enhance the role of the private sector and boost India's global space economy share, will be further strengthened by such demonstrable capabilities. The policy emphasizes leveraging space assets for national development and promoting scientific research, aligning perfectly with the outcomes of Chandrayaan-3.

In conclusion, the Chandrayaan-3 Propulsion Module's journey into a new Earth orbit, guided by the Moon's gravity, is more than just a technical feat. It's a symbol of India's innovative spirit, strategic foresight, and growing stature in the global arena of space exploration, promising a future where India plays an even more pivotal role in unlocking the mysteries of the cosmos.