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PSLV Orbital Experiment Module
Satellite bus derived out of launch vehicle upper stage

PSLV Orbital Experiment Platform (POEM) also known as PSLV Stage 4 Orbital Platform (PS4-OP) is an orbital micro-gravity test bed based on spent fourth stage of PSLV. By adding modular subsystems for power generation, communication and stabilization like photovoltaic cells, Telemetry and Telecommand (TT&C) package, attitude control system, data storage etc to the PSLV fourth stage, it can function as a satellite bus. This augmented stage can then host payloads for up to six months while in orbit, making it useful for qualifying components, gaining space heritage and conduct experiments in micro-gravity conditions. Usually the fourth stage of PSLV is discarded after deployment of satellite and remains in orbit for a significant duration in a passive state as a piece of space debris.

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Objective

POEM or PS4-OP was conceived by VSSC/ISRO to help Indian academia and start-ups by providing a low cost platform with essential subsystems to support their payloads hence lowering the barriers of reaching orbit. POEM off-loads the burden of designing, qualifying, procuring a satellite bus, setting up a ground station etc. which reduces the development time and costs associated with using space-grade components thus allowing entities to just focus on payload.456

History

PSLV fourth stage or PS4 has often been used to carry non-separable payloads like AAM on PSLV-C8,7 Rubin 9.1/Rubin 9.2 on PSLV-C148 and mRESINS on PSLV-C219 etc. but such payloads could be supported only for a very short duration as PS4 lacked the capacity to generate power and maintain attitude stability. So it was proposed to augment PS4 with modular subsystems to convert it into a long duration orbital platform after completion of primary mission.101112

In 2017 as an early demonstration on PSLV-C37/Cartosat-2D13 and PSLV-C38/Cartosat-2E campaigns,14 PS4 was kept operational and monitored for over ten orbits after completion of its primary mission of deploying spacecraft.1516 Fourth stage on PSLV-C38 hosted IDEA (Ionization Density and Electric field Analyzer) as a non-separable payload by Space Physics Laboratory of VSSC,1718 two other non-separable payloads were mAMP and 'Earth Pointing Platform'.19

In January 2019, PSLV-C44/Microsat-R became the first campaign where PS4 functioned as an independent orbital platform for short duration as the provisions for on-board power generation capacity were not yet made.20 It hosted a 1U cubesat called KalamSAT-V2 as a non-separable payload by Space Kidz India based on Interorbital Systems kit.212223 Later in April, the fourth stage on PSLV-C45/EMISAT24 had its own power generation capacity as it was augmented with an array of fixed solar cells wrapped around the propellant tank of PS4 generating about 200 watts of power.252627 Three payloads hosted on PS4-OP were, Advanced Retarding Potential Analyzer for Ionospheric Studies (ARIS 101F) by IIST,28 experimental AIS payload by ISRO and AISAT by Satellize.29 To function as an orbital platform, fourth stage was put in spin-stabilized mode using its RCS thrusters.30 PS4-OP on this campaign had mission life of 3 months and AISAT payload onboard was operational for almost a year.3132 According to ISRO, the PS4-OP can transmit commands and data to sustain the payloads and regulate its location in three different orientations.33

After these initial testing campaigns, ISRO issued an Announcement of Opportunity in June 2019 to carry out in-orbit scientific experiments on PS4 orbital platform.34 And in following years POEM-1 aboard PSLV-C53/DS-EO campaign in June 202235 and POEM-2 aboard PSLV-C55/TeLEOS-2 campaign in April 2023 were launched.36 Both of these orbital platforms had mature configurations utilizing 3-axis stabilization and on-board power generation capacity.3738

In July 2023, Indian National Space Promotion and Authorisation Centre (IN-SPACe) issued an announcement of opportunity inviting payloads to be hosted aboard upcoming POEM campaigns tentatively scheduled between November 2023 and June 2024.39

On 1 January 2024, POEM-3 was launched along with XpoSat on PSLV-C58 hosting ten payloads. The stage was lowered from a 650 km (circular) injection orbit of XpoSAT to a 350 km circular orbit for POEM-3 operations.40 POEM-3 re-entered atmosphere on 21 March 2024 over the Pacific Ocean after having accomplished its objectives by February and thus leaving behind no space-debris from the launch.4142

On 30 December 2024, POEM-4 was launched with 24 non-separable payloads as part of the PSLV-C60/SpaDeX mission.4344 The PS4 stage was restarted twice to lower the orbit from 470 km to 350 km circular orbit for POEM-4 operations.45

Platform capabilities

Specifications and capabilities of PSLV fourth stage based orbital platform which may improve over time.464748

  • Mission life: Up to six months depending on left-over Helium pressurant in fourth stage.
  • Maximum mass of payload: 30 kg
  • Maximum size: About 3U, depends on spare area available for a particular mission and mounting location.
  • Maximum power of payload: 200 to 500 watts
  • Power bus: 28 Volts
  • Maximum data rate: 1 Mbps
  • Pointing accuracy:
    • During sunlit period: within ±1°
    • During eclipse: ±5°
    • Slew rate within 0.5° per second during stabilized regime.
  • Data storage: 1GB
  • TT&C: S-band
  • Downlink at ISRO ground station
  • Suitable for experiments requiring large Inertia and structure.

Missions

Further information: List of PSLV Orbital Experiment Module Flights

As of February 2025, the POEM module has been used on Four missions;

  1. PSLV-C53/POEM-1
  2. PSLV-C55/POEM-2
  3. PSLV-C58/POEM-3
  4. PSLV-C60/POEM-4

See also

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References

  1. "Payloads". www.isro.gov.in. Archived from the original on 24 July 2023. Retrieved 24 July 2023. https://www.isro.gov.in/Payloads.html ↩

  2. "Opportunities for science experiments in the fourth stage of India's PSLV" (PDF). 21 February 2019. Archived (PDF) from the original on 9 October 2022. http://www.unoosa.org/documents/pdf/copuos/stsc/2019/tech-55E.pdf ↩

  3. "Announcement of Opportunity (AO) for Orbital platform: an avenue for in-orbit scientific experiments" (PDF). 15 June 2019. Archived from the original (PDF) on 6 August 2020. Retrieved 23 February 2020. https://web.archive.org/web/20200806072033/https://www.isro.gov.in/sites/default/files/orbital_platform-_ao.pdf ↩

  4. "Opportunities for science experiments in the fourth stage of India's PSLV" (PDF). 21 February 2019. Archived (PDF) from the original on 9 October 2022. http://www.unoosa.org/documents/pdf/copuos/stsc/2019/tech-55E.pdf ↩

  5. "Announcement of Opportunity (AO) for Orbital platform: an avenue for in-orbit scientific experiments" (PDF). 15 June 2019. Archived from the original (PDF) on 6 August 2020. Retrieved 23 February 2020. https://web.archive.org/web/20200806072033/https://www.isro.gov.in/sites/default/files/orbital_platform-_ao.pdf ↩

  6. "IN-SPACe Announcement of Opportunity for hosting of payloads on POEM Page - IN-SPACe". www.inspace.gov.in. Archived from the original on 26 July 2023. Retrieved 25 July 2023. https://www.inspace.gov.in/inspace?id=inspace_hosting_payloads_on_poem_page ↩

  7. "PSLV C8 / AGILE brochure" (PDF). Archived from the original (PDF) on 23 February 2020. Retrieved 23 February 2020. https://web.archive.org/web/20200223011646/https://www.isro.gov.in/sites/default/files/flipping_book/PSLV-C8/files/assets/common/downloads/publication.pdf ↩

  8. "PSLV C14/Oceansat-2 brochure" (PDF). Archived from the original (PDF) on 6 August 2020. Retrieved 23 February 2020. https://web.archive.org/web/20200806094152/https://www.isro.gov.in/sites/default/files/flipping_book/PSLV-C14/files/assets/common/downloads/publication.pdf ↩

  9. "Space-India July 2012 to August 2013" (PDF). Archived from the original (PDF) on 6 August 2020. Retrieved 23 February 2020. https://web.archive.org/web/20200806152719/https://www.dos.gov.in/sites/default/files/flipping_book/Space%20India%20July%2012-Aug%2013/files/assets/common/downloads/Space%20India%20July%2012-Aug%2013.pdf ↩

  10. "Opportunities for science experiments in the fourth stage of India's PSLV" (PDF). 21 February 2019. Archived (PDF) from the original on 9 October 2022. http://www.unoosa.org/documents/pdf/copuos/stsc/2019/tech-55E.pdf ↩

  11. "Announcement of Opportunity (AO) for Orbital platform: an avenue for in-orbit scientific experiments" (PDF). 15 June 2019. Archived from the original (PDF) on 6 August 2020. Retrieved 23 February 2020. https://web.archive.org/web/20200806072033/https://www.isro.gov.in/sites/default/files/orbital_platform-_ao.pdf ↩

  12. Kumar, Chethan. "2 days after Space Station news, Isro calls for "docking experiments" on PSLV stage-4". The Times of India. Archived from the original on 24 August 2019. Retrieved 23 February 2020. https://timesofindia.indiatimes.com/india/2-days-after-space-station-news-isro-calls-for-docking-experiments-on-pslv-stage-4/articleshow/69800354.cms ↩

  13. The launch of PSLV–C37/CARTOSAT – 2 Series Satellite - Live. 15 February 2017. Event occurs at 1 hour 08 minutes 14 seconds. https://www.youtube.com/watch?v=fujsQ5teHJI&t=4094s ↩

  14. "In-situ observations of rocket burn induced modulations of the top side ionosphere using the IDEA payload on-board the unique orbiting experimental platform (PS4) of the Indian Polar Orbiting Satellite Launch Vehicle mission - ISRO". www.isro.gov.in. Archived from the original on 21 September 2022. Retrieved 27 June 2022. https://www.isro.gov.in/situ-observations-of-rocket-burn-induced-modulations-of-top-side-ionosphere-using-idea-payload-board ↩

  15. "Department of Space Annual Report 2017-18" (PDF). Archived (PDF) from the original on 13 February 2018. https://www.isro.gov.in/sites/default/files/article-files/node/9805/annualreport2017-18.pdf ↩

  16. rajasekhar, pathri (20 June 2017). "Isro to lower rocket's altitude". Deccan Chronicle. Archived from the original on 6 August 2020. Retrieved 23 February 2020. https://www.deccanchronicle.com/science/science/200617/isro-to-lower-rockets-altitude.html ↩

  17. "Department of Space Annual Report 2017-18" (PDF). Archived (PDF) from the original on 13 February 2018. https://www.isro.gov.in/sites/default/files/article-files/node/9805/annualreport2017-18.pdf ↩

  18. "In-situ observations of rocket burn induced modulations of the top side ionosphere using the IDEA payload on-board the unique orbiting experimental platform (PS4) of the Indian Polar Orbiting Satellite Launch Vehicle mission - ISRO". www.isro.gov.in. Archived from the original on 21 September 2022. Retrieved 27 June 2022. https://www.isro.gov.in/situ-observations-of-rocket-burn-induced-modulations-of-top-side-ionosphere-using-idea-payload-board ↩

  19. 5th Manohar Parrikar Vidnyan Mahotsav: Talk By ISRO Chairman Dr. S. Somanath. 13 December 2023. Event occurs at 50 min. 36 sec. https://www.youtube.com/watch?v=bwV0S7uEPMg&t=3036s ↩

  20. Rajwi, Tiki (12 January 2019). "PSLV lift-off with added features". The Hindu. ISSN 0971-751X. Archived from the original on 6 August 2020. Retrieved 23 February 2020. https://www.thehindu.com/news/national/kerala/pslv-lift-off-with-added-features/article25981654.ece ↩

  21. "PSLV-C44 - ISRO". isro.gov.in. Archived from the original on 17 January 2019. Retrieved 26 June 2020. https://web.archive.org/web/20190117013408/https://www.isro.gov.in/launcher/pslv-c44 ↩

  22. Interorbital Systems [@interorbital] (25 January 2019). "Congratulations to ISRO and SpaceKidzIndia on getting their CubeSat into orbit! The students modified their IOS CubeSat kit, complete w/ their own experiments!" (Tweet) – via Twitter. https://x.com/interorbital/status/1088526772109422592 ↩

  23. Singh, Surendra (16 December 2018). "In a first, ISRO will make dead rocket stage "alive" in space for experiments". The Times of India. Archived from the original on 8 November 2020. Retrieved 23 February 2020. https://timesofindia.indiatimes.com/india/in-a-first-isro-will-make-dead-rocket-stage-alive-in-space-for-experiments/articleshow/67067817.cms ↩

  24. "PSLV-C45/EMISAT Mission Press-kit" (PDF). Archived from the original (PDF) on 23 March 2019. Retrieved 23 July 2023. https://web.archive.org/web/20190323093804/https://www.isro.gov.in/sites/default/files/pslv-c45_launch_kitv5.0_fn_23.03.19.pdf ↩

  25. Clark, Stephen. "Indian military satellite, 20 more Planet imaging CubeSats launched by PSLV". Spaceflight Now. Archived from the original on 6 April 2019. Retrieved 23 February 2020. https://spaceflightnow.com/2019/04/01/indian-military-satellite-20-more-planet-imaging-cubesats-aboard-successful-pslv-launch/ ↩

  26. Press briefing by S Somanath (Chairman, ISRO). 22 April 2023. Event occurs at 1 minutes 22 seconds. https://www.youtube.com/watch?v=lGyCpYFS90o&t=81s ↩

  27. "PSLV-C45/EMISAT Mission Curtain Raiser video (English)". www.isro.gov.in. Archived from the original on 26 July 2023. Retrieved 23 July 2023. https://www.isro.gov.in/mission_PSLV_C45_CameraView.html ↩

  28. "Department of Avionics, R. Sudharshan Kaarthik, Ph.D (Assistant Professor)". Archived from the original on 13 February 2020. Retrieved 23 February 2020. https://www.iist.ac.in/avionics/sudharshan.kaarthik ↩

  29. "Exseed Sat-2". Satellize. Archived from the original on 23 February 2020. Retrieved 23 February 2020. https://satellize.com/index.php/exseed-sat-2/ ↩

  30. "Opportunity for Scientific Experiments on PSLV Upper Stage Orbital Platform" (PDF). 16 June 2021. Archived (PDF) from the original on 9 October 2022. https://www.unoosa.org/documents/pdf/psa/hsti/Hyper-Microgravity_Webinar2021/Hyper-Microgravity_Webinar2021/9_RegionalActivities/R._Senan_Hypermicrogravity_ISRO.pdf ↩

  31. "Opportunity for Scientific Experiments on PSLV Upper Stage Orbital Platform" (PDF). 16 June 2021. Archived (PDF) from the original on 9 October 2022. https://www.unoosa.org/documents/pdf/psa/hsti/Hyper-Microgravity_Webinar2021/Hyper-Microgravity_Webinar2021/9_RegionalActivities/R._Senan_Hypermicrogravity_ISRO.pdf ↩

  32. Press briefing by S Somanath (Chairman, ISRO). 22 April 2023. Event occurs at 1 minutes 22 seconds. https://www.youtube.com/watch?v=lGyCpYFS90o&t=81s ↩

  33. Linganna, Girish (3 January 2025). "While POEM-4 Experiments Run, SPADEX Prepares for Docking Day". india.com. Retrieved 3 January 2025. https://www.india.com/news/india/while-poem-4-experiments-run-spadex-prepares-for-docking-day-7510978/ ↩

  34. "Announcement of Opportunity (AO) for Orbital platform: an avenue for in-orbit scientific experiments" (PDF). 15 June 2019. Archived from the original (PDF) on 6 August 2020. Retrieved 23 February 2020. https://web.archive.org/web/20200806072033/https://www.isro.gov.in/sites/default/files/orbital_platform-_ao.pdf ↩

  35. "NSIL's Second Dedicated commercial launch "PSLV-C53/ DS-EO Mission" successfully accomplished on 30th June 2022" (PDF). Archived from the original (PDF) on 18 May 2023. https://web.archive.org/web/20230518082810/https://www.nsilindia.co.in/sites/default/files/Press%20Release%20-%20PSLV%20C-53%20DS-EO%20Mission.pdf ↩

  36. "India's PSLV launches with two Singaporean satellites – Spaceflight Now". Archived from the original on 6 June 2023. Retrieved 26 July 2023. https://spaceflightnow.com/2023/04/22/indias-pslv-launches-with-two-singaporean-satellites/ ↩

  37. "PSLV-C53/DS-EO mission" (PDF). Archived from the original (PDF) on 5 July 2022. https://web.archive.org/web/20220705162540/https://www.isro.gov.in/sites/default/files/article-files/pslv-c53-ds-eo-mission/pslv-c53-ds-eo-mission-brochure-english/brochure_pslv_c53-ds-eo_mission_english.pdf ↩

  38. "PSLV-C55/TeLEOS-2 mission press kit" (PDF). Archived from the original (PDF) on 28 May 2023. https://web.archive.org/web/20230528023203/https://www.isro.gov.in/media_isro/pdf/Missions/PSLVC55/PSLVC55TeLEOS.pdf ↩

  39. "IN-SPACe Announcement of Opportunity for hosting of payloads on POEM Page - IN-SPACe". www.inspace.gov.in. Archived from the original on 26 July 2023. Retrieved 25 July 2023. https://www.inspace.gov.in/inspace?id=inspace_hosting_payloads_on_poem_page ↩

  40. PTI (1 January 2024). "ISRO Fires Fourth Stage Of PSLV-C58 Twice To Hold Scientific Experiments". NDTV Profit. Retrieved 1 January 2024. https://www.ndtvprofit.com/technology/isro-fires-fourth-stage-of-pslv-c58-twice-to-hold-scientific-experiments ↩

  41. "PSLV accomplishes zero orbital debris mission". www.isro.gov.in. Archived from the original on 25 March 2024. Retrieved 26 March 2024. https://web.archive.org/web/20240325150554/https://www.isro.gov.in/PSLVC58_POEM3_accomplish_zero_orbital_debris_mission.html ↩

  42. "POEM-3 Mission achieves all its Payload objectives". www.isro.gov.in. Retrieved 26 March 2024. https://www.isro.gov.in/POEM-3_Mission_achieves_Payload_objectives.html ↩

  43. "PSLV-C60 SPADEX Mission Press-kit" (PDF). https://www.isro.gov.in/media_isro/pdf/Missions/PSLVC60/PSLVC60-mission-brochure-english.pdf ↩

  44. "POEM-4 in PSLV-C60 / SpaDeX Mission". www.isro.gov.in. Retrieved 9 February 2025. https://www.isro.gov.in/POEM_4_Payloads_spadex.html ↩

  45. C.S, Hemanth (31 December 2024). "ISRO's PSLV-C60 Mission: 10 payload from non-government entities successfully deployed on POEM-4". The Hindu. ISSN 0971-751X. Retrieved 9 February 2025. https://www.thehindu.com/sci-tech/science/pslv-c60-mission-10-payload-from-non-government-entities-successfully-deployed-of-on-poem-4/article69046002.ece ↩

  46. "Opportunity for Scientific Experiments on PSLV Upper Stage Orbital Platform" (PDF). 16 June 2021. Archived (PDF) from the original on 9 October 2022. https://www.unoosa.org/documents/pdf/psa/hsti/Hyper-Microgravity_Webinar2021/Hyper-Microgravity_Webinar2021/9_RegionalActivities/R._Senan_Hypermicrogravity_ISRO.pdf ↩

  47. DAY 1 | PS 5 | SESSION A. 31 January 2022. Event occurs at 8 minutes. https://www.youtube.com/watch?v=J7XKKZMrkB4&t=475s ↩

  48. "IN-SPACe Announcement of Opportunity for hosting of payloads on POEM Page - IN-SPACe". www.inspace.gov.in. Archived from the original on 26 July 2023. Retrieved 25 July 2023. https://www.inspace.gov.in/inspace?id=inspace_hosting_payloads_on_poem_page ↩