This mission is not only India's first dedicated polarimetry mission but also the world's second, following Nasa's Imaging X-ray Polarimetry Explorer (IXPE) launched in 2021

India is poised to ring in 2024 with a roaring launch of the Polar Satellite Launch Vehicle carrying the country's first X-Ray Polarimeter Satellite (XPoSat) on January 1, 2024.

The Indian Space Research Organisation (Isro) has announced that the XPoSat mission will lift off at 9:10 am using a Polar Satellite Launch Vehicle (PSLV), marking a significant milestone in India's space exploration journey.

The XPoSat mission is designed to investigate the polarisation of intense X-ray sources, a scientific endeavour that will place India at the forefront of space-based polarimetry.

This mission is not only India's first dedicated polarimetry mission but also the world's second, following Nasa's Imaging X-ray Polarimetry Explorer (IXPE) launched in 2021.

XPoSat aims to study the 50 brightest known sources in the universe, including pulsars, black hole X-ray binaries, active galactic nuclei, neutron stars, and non-thermal supernova remnants. The satellite will be placed in a circular low Earth orbit of 500–700 km, with a mission lifespan of at least five years.

The primary payload, POLIX (Polarimeter Instrument in X-rays), will measure the degree and angle of polarization in the medium X-ray energy range of 8-30 keV photons of astronomical origin. Complementing POLIX, the XSPECT (X-ray Spectroscopy and Timing) payload will provide spectroscopic information in the energy range of 0.8-15 keV.

Developed by the Raman Research Institute (RRI) in collaboration with U R Rao Satellite Centre (URSC), these instruments are expected to offer new insights into the physics of celestial objects. By measuring the polarisation of X-rays, scientists can infer critical information about the geometry and emission mechanisms of these distant sources.

The XPoSat mission is anticipated to break new ground in our understanding of the universe. It will add two crucial dimensions—degree and angle of polarization—to the existing spectroscopic and timing data, potentially resolving ambiguities in current theoretical models of astronomical emissions.