PSLV Orbital Experiment Module (POEM) also known as PSLV Stage 4 Orbital Platform (PS4-OP) is an orbital micro-gravity test bed based on spent fourth stage of the Indian Space Research Organisation's PSLV rocket.
POEM-1.
In June 2022, the PSLV-C53/DS-EO campaign had its PS4-OP referred as PSLV Orbital Experiment Module (POEM) and it was first PSLV fourth stage based orbital platform to be actively stabilized using eight Helium based cold gas thrusters after the primary mission and stage passivization. POEM-1 (COSPAR ID:2022-072E, SATCAT no.:52939) had additional sensors and navigational aids (4 Sun sensors, Magnetometer, MRGPD and NavIC). It generated about 150 watts of power using non-deployable, fixed solar cells wrapped around PS4 tank. Six non-separable payloads facilitated by NSIL and IN-SPACe were hosted aboard.
POEM-2.
In April 2023, on PSLV-C55/TeLEOS-2 campaign, seven non separable payloads were hosted by POEM. POEM-2 had flexible solar arrays wrapped around PS4 propellant tank that generated about 500 watts of power upon deployment. POEM-2 was again 3-axis stabilized by eight Helium based 1N cold gas thrusters (OPACS) developed by LPSC that utilize left-over PS4 pressurant. Expected mission life of POEM-2 (COSPAR ID:2023-057A, SATCAT no.:56308) was of one month. Payloads hosted on POEM-2 are:
POEM-3.
On PSLV-C58/XPoSat campaign, POEM-3 hosted ten payloads weighing ~145 kg cumulatively. PSLV fourth stage was lowered to 350 km orbit at 9.6° inclination after deploying XPoSat to reach the POEM-3 operational orbit. POEM-3 will nominally be operational for a period of one month. For power generation and storage it will again have flexible solar panels in conjunction with 50Ah Li-ion battery and will be three-axis stabilized.It re-entered earths atmosphere on March 21 2024,three months after launch. Payloads hosted on POEM-3 (COSPAR ID:2024-001A, SATCAT no.:58694) are following, seven of them facilitated by IN-SPACe and three are by ISRO,
POEM-4.
POEM-4 (COSPAR ID: 2024-253C, SATCAT no.62461) was launched on 30 December 2024 on PSLV-C60/SpaDeX campaign. It hosted 24 non-separable payloads weighing nearly 120 kg. Ten of these were chosen by IN-SPACe from a variety of non-governmental entities which include startups and universities, while the remaining fourteen are from ISRO. It completed 1000 orbits around earth on 4th March 2025 and had completed most scientific objectives by then.
Following completion of mission objectives, POEM-4 was de-orbited by engine restarts to reduce it's orbit to a nearly circular orbit at 350 km altitude with 55.2 inclination. The PS4 was then passivated as it's orbit decayed to a 174 x 165 km. Tracked by ISRO radar, POEM-4 made a controlled re-entery into the atmosphere and impacted in the Indian Ocean, off the coast of Australia at about 02:33 UTC (08:03 IST) on April 04, 2025.
Future payloads.
List of payloads proposed to be hosted aboard POEM on a future flight.