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PSLV Orbital Experimental Module (POEM)

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  • Published
    2nd Jul, 2022


ISRO has recently launched three Singaporean satellites in precise orbit through the PSLV Orbital Experimental Module or ‘POEM’.

What is POEM?

  • The PSLV Orbital Experimental Module is a platform that aims to help perform in-orbit experiments using the final, and otherwise discarded, stage of ISRO’s workhorse 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.
    • However, in PSLV-C53 mission, the spent final stage has been utilised as a “stabilised platform” to perform experiments.
  • POEM is carrying six payloads, including two from Indian space start-ups Digantara and Dhruva Space.


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

Has ISRO repurposed and used PS4 rocket junk earlier?

  • The Indian space agency first demonstrated the capability of using PS4 as an orbital platform in 2019 with the PSLV-C44 mission.
    • In that mission, they injected Microsat-R and Kalamsat-V2 satellites into their designated orbits. 
  • The fourth stage in that mission was kept alive as an orbital platform for space-based experiments.
    • The fourth stage (PS4) of the vehicle was moved to a higher circular orbit of 453 km after two restarts of the stage, to establish an orbital platform for carrying out experiments.
    • Kalamsat-V2, a student payload, first to use PS4 as an orbital platform, was taken to its designated orbit about 1 hour and 40 minutes after lift-off.
  • While in that mission, the fourth stage had Li-Ion batteries, solar panels are an addition this time. 
  • The latest repurposing and upgrade of the fourth stage of the PSLV rocket involves stabilization of the orbital platform.

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