News Excerpt:

After achieving the objectives of all experiments onboard, the PSLV Orbital Experimental Module (POEM - 3) is likely to enter the Earth’s atmosphere and burn up within the next 75 days.

About POEM - 3:

• It is a space platform that uses the spent PS4 stage of the PSLV-C58 vehicle that launched XPoSat on January 1, 2024.
• POEM-3 flew with nine Payloads from Vikram Sarabhai Space Centre (VSSC), PRL, Academia, and Space start-ups inducted through IN-SPACe.
• ARKA200 (Xenon Based Electric Propulsion) and RUDRA (HAN-based Green Propellant Thruster) from Bellatrix.
• LEAP-TD (Satellite Bus with VHF/UHF Downlink & UHF Uplink – Tested using IIST ground station) from Dhruva Space.
• Payload Data, collected regularly for Women Engineered Satellite (WeSAT’s - Solar irradiance and UV Index study) from LBS Institute of Technology for Women.
• BeliefSat0 (Amateur Radio satellite) from KJ Somayia Institute of Technology
• RSEM (Radiation Shielding experiment) from TakeMe2Space
• DEX (interplanetary Dust particle experiment) from PRL.
• 100 W Fuel Cell Power System (FCPS) and Si-C based High Power Li-Ion (10AH/32V) Battery from VSSC.
• POEM-3 was lowered to a 350 km circular orbit to minimize the orbit decay time after the experiment's completion.
• With the orbital decay and re-entry of POEM-3, the PSLV-C58 XPoSat mission will leave zero space debris.

What is POEM?

• It is a platform that helps perform in-orbit experiments using the final stage of ISRO’s rocket, the Polar Satellite Launch Vehicle (PSLV).
  • The PSLV is a four-stage rocket where the first three spent stages fall back into the ocean, and the final stage (PS4) — after launching the satellite into orbit — ends up as space junk.
• In the PSLV-C53 mission undertaken in 2022, the spent final stage was utilized as a “stabilized platform” to perform experiments.
  • It was the first time the PS4 stage orbited the earth as a stabilized platform.
• To cut down on space debris, ISRO has been taking steps such as lowering the orbit of defunct satellites and the last stages of the rockets and removing excess fuel.
  • It ensures that the mission leaves no debris.
• So far, on three POEM platforms, ISRO has flown a total of 21 experiments.

How does ISRO keep POEM ‘alive and stable’ in orbit?

• POEM has a dedicated Navigation Guidance and Control (NGC) system for altitude stabilization, which stands for controlling the orientation of any aerospace vehicle within permitted limits.
• The NGC acts as the platform’s brain to stabilize it with specified accuracy.
• POEM derives its power from solar panels mounted around the PS4 tank and a Li-Ion battery.
• It navigates using four sun sensors, a magnetometer, gyros & NavIC.
• It carries dedicated control thrusters using Helium gas storage.
• It is also enabled with a telecommand feature.

Has ISRO repurposed and used PS4 rocket junk earlier?

• ISRO first demonstrated the capability of using PS4 as an orbital platform in 2019 with the PSLV-C44 mission that injected Microsat-R and Kalamsat-V2 satellites into their designated orbits.
• Kalamsat-V2, a student payload, was the first to use PS4 as an orbital platform.
• The fourth stage in that mission was kept alive as an orbital platform for space-based experiments.
• The fourth stage had Li-Ion batteries in that mission, and solar panels were added in later missions.
• The repurposing and upgrading of the fourth stage of the PSLV rocket involved stabilization of the orbital platform.

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