Polar Orbital Experiment Module : ISRO’s New Mission Sets Precedent for Public-Private Alliance : Daily Current Affairs

Relevance: GS-3: Science and Technology- developments and their applications and effects in everyday life indigenization of technology and developing new technology.

Key Phrases: PSLV-C53, First Official Public-Private Collaboration, Polar Orbital Experiment Module (POEM), New Space India Ltd, Stabilised Platform, IN-SPACe, Navigation Guidance and Control

Why in News?

  • Indian Space Research Organisation’s (ISRO) Polar Satellite Launch Vehicle (PSLV)-C53 was launched with three satellites in its primary payload.
  • It is the first official public-private collaboration for a space launch in India.

Key Highlights:

  • The three satellites from Singapore were launched as part of a contract signed by ISRO through its commercial arm New Space India Ltd.
  • The PSLV-C53 rocket also carried two instruments belonging to private Indian space startups, Digantara and Dhruva Space, which were a part of the mission’s secondary payload and part of its Polar Orbital Experiment Module (POEM).
  • While the primary payload refers to the main satellites launched in a mission, secondary payloads include additional satellites that fly with a mission alongside the primary payload, to maximize utilization of space infrastructure.

What is POEM?

  • The PSLV Orbital Experimental Module is a platform that will 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 will be utilised as a “stabilised platform” to perform experiments.
  • It is the first time that the PS4 stage would orbit the earth as a stabilised platform.
  • POEM is carrying six payloads, including two from Indian space start-ups Digantara and Dhruva Space.

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

  • According to ISRO, POEM has a dedicated Navigation Guidance and Control (NGC) system for altitude 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.
  • It will navigate using four sun sensors, a magnetometer, gyros & NavIC and is enabled with a telecommand feature.
  • It carries dedicated control thrusters using Helium gas storage.

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.
  • It 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.

What is IN-SPACe?

  • Indian National Space Promotion and Authorisation Centre (IN–SPACe or INSPACe) is a single-window autonomous agency under the Department of Space of the Government of India.
  • The Centre acts as a facilitator and regulator of space activities in India.
  • It can authorize a non-government entity to use ISRO’s infrastructure and resources, including ISRO’s launch facilities.
  • It helps in streamlining the process, clarify regulatory hurdles and facilitate contact for public-private partnerships in space.

Do you know about Geosynchronous Satellite Launch Vehicle (GSLV)?

  • (GSLV) is an expendable space launch vehicle designed, developed, and operated by the Indian Space Research Organisation to launch satellites and other space objects into Geosynchronous Transfer Orbits.
  • GSLV is 49.13 m tall and tallest among all other vehicles of ISRO.
  • It is a three-stage vehicle with a lift-off mass of 420 tonnes.

Stages in GSLV:

  • The first stage comprises a solid booster with 138-tonne propellant and four liquid strap-on motors, with 40-tonne propellant.
  • The second stage is a liquid engine carrying 40-tonne of liquid propellant.
  • The third stage is the indigenously built Cryogenic Upper Stage carrying 15-tonne of cryogenic propellants.
  • GSLV rockets using the Russian Cryogenic Stage are designated as the GSLV Mk I while versions using the indigenous Cryogenic Upper Stage are designated the GSLV Mk II.
  • All GSLV launches have been conducted from the Satish Dhawan Space Centre in Sriharikota.

Difference between PSLV and GSLV:

  • GSLV has the capability to put a heavier payload in the orbit than the Polar Satellite Launch Vehicle (PSLV).
  • PSLV can carry satellites up to a total weight of 2000 kg into space and reach up to an altitude of 600-900 km while GSLV can carry weight up to 5,000 kg and reach up to 36,000 km.
  • PSLV is designed mainly to deliver earth observation or remote sensing satellites, whereas, GSLV has been designed for launching communication satellites.
  • GSLV delivers satellites into a higher elliptical orbit, Geosynchronous Transfer Orbit (GTO) and Geosynchronous Earth Orbit (GEO).

Types of Earth orbit:

  1. Geosynchronous Orbit (GSO) & Geostationary Orbit (GEO):
    • Objects in GSO have an orbital speed that matches the Earth’s rotation, yielding a consistent position over a single longitude.
    • GEO is a kind of GSO. It matches the planet’s rotation, but GEO objects only orbit Earth’s equator, and from the ground perspective, they appear in a fixed position in the sky. GSO and GEO are used for telecommunications and Earth observation.
  2. Polar Orbit:
    • Within 30 degrees of the Earth’s poles, the polar orbit is used for satellites providing reconnaissance, weather tracking, measuring atmospheric conditions, and long-term Earth observation.
  3. Sun-Synchronous Orbit (SSO):
    • It is a type of polar orbit.
    • SSO objects are synchronous with the sun, such that they pass over an Earth region at the same local time every day.
  4. Highly Elliptical Orbit (HEO):
    • An HEO is elliptical, with one end nearer the Earth and the other more distant.
    • Satellites in HEO are suited for communications, satellite radio, remote sensing and other applications.


  • The PSLV C53 mission has achieved a new milestone by launching two payloads of Indian Start-ups in Space.
  • The inclusion of the two laid the ground for more public-private partnerships, to be facilitated by the Indian National Space Promotion and Authorization Center (IN-SPACe)

Source: Live-Mint

Mains Question:

Q. What is PSLV Orbital Experimental Module (POEM)? Briefly describe its features and significance of the PSLV-C53 mission.(250 words).