ISRO’s Successful Re-Entry of POEM-4 Module

On April 4, 2025, the upper stage of the PSLV-C60 mission, known as the PSLV Orbital Experimental Module (POEM-4), successfully re-entered the Earth’s atmosphere. This event occurred at 2.33 UTC, or 8.03 a.m. IST, over the Indian Ocean. The re-entry marked achievement for the Indian Space Research Organisation (ISRO) in managing space debris and ensuring the sustainability of outer space operations.

Launch and Mission Overview

The PSLV-C60 mission was launched on December 30, 2024. It carried twin SPADEX satellites into a 475 km orbit. The PSLV’s upper stage, POEM-4, was configured to operate in a similar orbit. During its operational phase, POEM-4 hosted 24 payloads, including 14 from ISRO and 10 from various Non-Governmental Entities (NGEs). All payloads performed as expected, providing valuable scientific data.

Tracking and Re-Entry Prediction

ISRO monitored POEM-4’s orbit continuously using its Radar Facilities and collaborated with the United States Space Command (USSPACECOM). The tracking data was essential for predicting the re-entry trajectory. As the mission progressed, POEM-4’s orbit decayed to 174 km by 165 km, leading to the prediction of its re-entry on April 4, 2025.

De-Orbiting and Passivation

Prior to re-entry, POEM-4 was de-orbited through controlled engine restarts. This manoeuvre adjusted its orbit to a nearly circular path at an altitude of 350 km with a 55.2-degree inclination. To mitigate risks associated with space debris, ISRO passivated the upper stage by venting leftover fuel, thus preventing accidental break-up during re-entry.

Monitoring the Re-Entry Event

The re-entry event was closely monitored by ISRO’s System for Safe and Sustainable Space Operations Management (IS4OM). Regular updates were provided throughout the re-entry process. The successful re-entry of POEM-4 is a testament to ISRO’s commitment to reducing space debris and supporting its Debris Free Space Mission (DFSM).

Significance of the Mission

The safe re-entry of POEM-4 puts stress on ISRO’s leadership in sustainable space practices. It marks the agency’s focus on environmental responsibility in outer space. The mission contributes to ongoing efforts to maintain a safe operational environment for future space activities.

Questions for UPSC:

1. Examine the significance of managing space debris for future space missions.
2. Critically discuss the role of ISRO in the context of international space collaboration and sustainability.
3. Estimate the impact of satellite payloads on scientific research and technological advancements.
4. Analyse the importance of tracking systems in ensuring the safety of space operations.

Answer Hints:

1. Examine the significance of managing space debris for future space missions.

1. Space debris poses collision risks to operational satellites and spacecraft, jeopardizing missions.
2. Effective debris management ensures long-term sustainability of outer space activities.
3. Mitigating debris helps maintain a safe environment for future exploration and commercial ventures.
4. International guidelines and cooperation are essential for establishing best practices in debris management.
5. Technological innovations in debris removal can enhance space mission safety and efficiency.

2. Critically discuss the role of ISRO in the context of international space collaboration and sustainability.

1. ISRO actively collaborates with global space agencies for knowledge sharing and technology exchange.
2. The agency’s successful missions promote international partnerships in scientific research and exploration.
3. ISRO’s commitment to sustainability aligns with global efforts to minimize space debris and ensure safe operations.
4. Through initiatives like the Debris Free Space Mission, ISRO demonstrates leadership in responsible space practices.
5. ISRO’s contributions enhance India’s standing in the global space community and encourage collaborative projects.

3. Estimate the impact of satellite payloads on scientific research and technological advancements.

1. Satellite payloads provide critical data for various fields, including environmental monitoring and weather forecasting.
2. They enable advancements in communication technologies, improving connectivity and access to information.
3. Scientific research conducted via satellite payloads leads to innovations in areas such as remote sensing and Earth observation.
4. Payloads contribute to national security through surveillance and reconnaissance capabilities.
5. Collaboration between governmental and non-governmental entities enhances the diversity and scope of research outcomes.

4. Analyse the importance of tracking systems in ensuring the safety of space operations.

1. Tracking systems provide real-time data on satellite positions, essential for collision avoidance.
2. They facilitate the prediction of re-entry trajectories, ensuring safe disposal of defunct satellites.
3. Collaboration between agencies like ISRO and USSPACECOM enhances tracking accuracy and reliability.
4. Effective tracking helps in managing space traffic, reducing the risk of accidents in congested orbits.
5. Advanced tracking technologies contribute to the development of future space missions and operational safety protocols.