 "ISRO POEM-4 shows the space agency is on song")
One of the world’s most famous poems about space, planets, and the stars is “Twinkle, Twinkle, Little Star,” written by the English author Jane Taylor and published in 1806 as “The Star”. While many associate the beautiful melody of the poem with composer Mozart, the actual composer of the tune remains unknown. In recent years, the Indian Space Research Organisation (ISRO) has been found working on a different type of poem. This poem could be viewed as a symbol of space innovation.
On December 30, 2024, ISRO successfully launched the PSLV Orbital Experimental Module (POEM-4) during its PSLV C60 mission. The primary purpose of this launch was to test docking technology with two satellites (chaser and target). The PSLV C60 mission has successfully placed these satellites in the intended orbit. The actual docking experiment is expected to take place around January 7, 2025, and the success of the docking aspects of this mission will only be determined then, but POEM-4, part of this mission, has reached its desired altitude and is functioning properly.
POEM is a novel platform developed by ISRO a few years back. PSLV is capable of placing multiple payloads into orbit, and its mission profile consists of four different stages. The fourth stage PS4 is the uppermost stage, which delivers the satellites to a predesignated orbit. After that, this PS4 continues to loiter in space and ends up becoming space debris. Hence, ISRO decided to ensure that PS4 could also be put to some use after the satellites get delivered. The purpose was not to remain complacent only with the success of the primary mission but to utilise the system towards its fullest potential.
Earlier there were attempts to carry non-separable payloads on the last (fourth) stage of PSLV. However, such experimentation could happen only for a limited period of time. There were some basic limitations, like the PS4 lacked the capacity to generate power and maintain attitude stability. Hence, it was thought that there is a need to augment PS4 with some mechanism that could convert it into a long-duration orbital platform after completion of the primary mission.
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More ShortsToday, POEM has emerged as an innovative platform that transforms the fourth stage of the PSLV into an orbital experiment module after the primary mission gets completed. Now it is equipped with important capabilities such as power supply, telemetry, and command support. With this upgraded POEM, it is possible to conduct front-line scientific and technological experiments in space. It ensures the seamless conduct of on-board experiments. And such experimentation could last for around six months. ISRO has found this to be a cost-effective approach to undertake research. It is also providing an opportunity to Indian industry, particularly the start-ups working in the space domain and academia, to utilise the opportunity provided by ISRO for testing various technologies.
During a few launches that took place between 2017 and 2019, ISRO had used the opportunity to experiment on PS4. In one launch, PS4 was kept operational and monitored for over ten orbits after completion of its primary mission. In another launch, few non-separable payloads were sent. Finally, during the January 2019 launch, PS4 functioned as an independent orbital platform. However, since there were no systems available for on-board power generation, the first phase could function only for a short duration.
During launch, after a few months, ISRO ensured that the fourth stage would have its own power generation capacity. The power was generated by wrapping solar cells around the propellant tank of PS4. Thruster was used to allow PS4 to function as an orbital platform. After ensuring that they have the technical expertise to use the PS4 as an experimentation platform, ISRO announced opportunities for the scientific establishment of their orbital platform in-orbit scientific experiments.
The POME-1 mission (PSLV-C53) took place during June 2022 with five payloads, and the POEM-2 mission (PSLV-C55) took place during April 2023 with seven experimental non-separable payloads. Around 2019/2020, India took a call to open up the space sector, and the so-called space start-up movement could be said to have started around the same time. Indian National Space Promotion and Authorisation Centre (IN–SPACe), which is a single-window dealing with space commerce, became a reality by June 2020. Subsequently, IN-SPACe made an announcement for various public and private agencies about the opportunity for hosting their payloads on POEM for upcoming missions during 2023 and 2024.
The POEM-3 mission (PSLV-C58) was launched on January 1, 2024, carrying nine payloads from organisations such as VSSC, PRL, academia, and space start-ups. After the primary launch, during which satellites are deployed into orbits at altitudes between 500 and 700 km, the PS4 stage is lowered to a circular orbit at 350 km. According to ISRO, the PS4 is a three-axis attitude-controlled platform equipped with power generation, telecommand, and telemetry capabilities to support the payloads.
Once positioned in the lower altitude, the PS4 completes several orbits. Typically, the PS4 is designed to survive for a maximum of six months before re-entering the Earth’s atmosphere and burning up due to the extreme temperatures at the boundary of space. Through this controlled re-entry process, ISRO ensures that no debris remains in space after the mission, maintaining space safety and sustainability.
During the recent launch (PSLV-C60) on December 30, 2024, the POEM-4 carried 24 payloads. There are 14 payloads from various research laboratories of ISRO and ten from industry and academia that are selected by IN-SPACe. A brief look at these payloads indicates that agencies are carrying out different types of experiments, which include some from astrobiology and some that are trying to study various aspects of the ionosphere. It is important to study the ionosphere because any disturbances in its character impact our communication systems. Also, there is an experiment on green fuel and a few trials related to robotic arms and debris capture mechanisms. These tests would help ISRO in the long run from the point of view of establishing a space station.
ISRO’s efforts in developing innovative platforms like POEM deserve appreciation. It has found a unique method towards enabling small-scale, cost-effective payloads for scientific experiments. Additionally, ISRO is making significant contributions to space debris mitigation by ensuring that the last stage of their PSLV launches does not remain in low Earth orbit. ISRO is On Song.
The author is Deputy Director General, MP-IDSA, New Delhi. The views expressed in the above piece are personal and solely those of the author. They do not necessarily reflect Firstpost’s views.
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