The Indian Space Research Organisation (ISRO) is likely to launch the country’s first polarimetry mission by December 28, senior scientists from the space agency said on Sunday.

“India is set to launch its first X-Ray Polarimeter Satellite (XPoSat), aiming to investigate the polarization of intense X-Ray sources. While space-based X-Ray astronomy has been established in India, focusing predominantly on imaging, time-domain studies, and spectroscopy, this upcoming mission marks a major value-addition,” Isro said in a statement.

XPoSat is India’s first and the world’s second space mission to measure the polarisation of light. Polarimetry is a powerful tool that allows astronomers to infer information about celestial objects, from passing comets to distant galaxies. Isro scientists explained that the mission is unique and crucial because it will help them understand and measure emissions from various astronomical sources—black holes, neutron stars, active galactic nuclei, pulsar wind nebulae— that are otherwise challenging to study.

Such emissions are mostly tracked by studying the chemical make-up (using a spectroscope) and the time it takes them to travel a distance.

The space agency in its latest mission document explained that the XPoSat spacecraft is designated for observation from low earth orbit—non-Sun synchronous orbit of around 650km altitude, low inclination of around six degrees—carrying two scientific payloads.

“...With these two payloads, the XPoSat mission is capable of simultaneous studies of temporal, spectral, and polarization features of the bright x-ray sources. The mission objectives include—measurement of x-ray polarization in the energy band of 8-30 keV emanated from x-ray sources; long-term spectral and temporal studies of cosmic x-ray sources in the energy band of 0.8-15 keV. The mission life is expected to be around five years. The payloads onboard XPoSat will observe the x-ray sources during its transit through the Earth’s shadow—during the eclipse period,” the space agency said.

The POLIX payload is developed by the Raman Research Institute (RRI), Bengaluru, with support from Isro centres, while the XSPECT payload is developed by Isro’s UR Rao Satellite Centre (URSC)