XPoSat: What to know about ISRO’s maiden satellite to study black holes

The ISRO ushered in the New Year on Monday by launching its first X-Ray Polarimeter Satellite (XPoSat) that will help study celestial objects like black holes. The agency’s trusted PSLV-C58 rocket lifted off with the XPoSat, along with 10 other satellites, at 9.10 am from the first launch pad at the spaceport in Sriharikota. 


XPoSat is the first dedicated scientific satellite from ISRO to carry out research in space-based polarisation measurements of X-ray emission from celestial sources. The primary aim is to learn about the polarisation of intense X-ray sources in space. 

XPoSat has two payloads, POLIX (Polarimeter Instrument in X-Rays) and XSPECT (X-ray Spectroscopy and Timing).  

POLIX will help measure polarisation of X-rays in the energy band 8-30keV emanating from about 50 potential cosmic sources through Thomson Scattering, according to the ISRO. The X-Ray polarisation serves as a crucial diagnostic tool for examining the radiation mechanism and geometry of celestial sources. 

Another objective of the mission is to carry out polarisation and spectroscopic measurements of X-ray emissions from cosmic sources. The Mission life is about 5 years. 

The primary payload POLIX for ISRO’s X-ray Polarimeter Satellite mission | ISRO

The 44.4-meter-tall PSLV rocket would first deploy the primary satellite into a 650 km Low Earth Orbit around 21 minutes after lift-off and later the scientists would bring the satellite to a lower altitude of about 350 km by restarting the fourth stage of the vehicle, for conducting the PSLV Orbital Experimental Module-3 (POEM-3) experiment.

Significance of mission 

According to the ISRO, the mission will bring substantial benefits to the Astronomy community globally. Apart from its capability of timing and spectroscopy-based observations, the insights derived from X-ray polarisation measurements on celestial objects like black holes, neutron stars, and active galactic nuclei, hold the potential to significantly improve the understanding of their physics. It will also help build expertise in X-ray polarimetry in India.

Besides ISRO, NASA also conducted a similar study two years ago on the remnants of remnants of supernova explosions, the particle streams emitted by black holes and other cosmic events. 

Other payloads

The payloads are Radiation Shielding Experiment Module by TakeMe2Space, Women Engineered Satellite by LBS Institute of Technology for Women, BeliefSat (an amateur radio satellite) built by K J Somaiya Institute of Technology, Green Impulse Transmitter by Inspecity Space Labs Pvt Ltd, LEATTD — Launching Expeditions for Aspiring Technologies Technology Demonstrator by Dhruva Space Pvt Ltd, RUDRA 0.3HPGP and ARKA 200 developed by Bellatrix Aerospace Pvt Ltd, Dust Experiment (DEX) built by PRL, ISRO and Fuel Cell Power System and Si based High Energy cell built by Vikram Sarabhai Space Centre.