Context: Indian Space Research Organisation (ISRO) has announced that India is set to launch its first X-Ray Polarimeter Satellite (XPoSat), aiming to investigate the polarisation of intense X-Ray sources. 

Significance

• It is India’s first and the world’s second polarimetry mission.

• The other such major mission is NASA’s Imaging X-ray Polarimetry Explorer (IXPE) that was launched in 2021. 

X-Ray Polarimeter Satellite (XPoSat) Mission

• Space-based X-Ray astronomy: It has been established in India, focusing predominantly on imaging, time-domain studies, and spectroscopy, the upcoming XPoSat mission marks a major value addition.

• Observation: The XPoSat spacecraft is designated for observation from Low Earth Orbit (non-sun synchronous orbit of ~650 km altitude, low inclination of approximately six degree), carrying two scientific payloads.

• Spatial and Temporal Studies: With these two payloads, the XPoSat mission is capable of simultaneous studies of temporal, spectral, and polarization features of the bright X-Ray sources.

• Mission Objective: 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.

• Observe the X-Ray sources: The payloads onboard XPoSat will observe the X-Ray sources during the spacecraft’s transit through the Earth’s shadow, i.e., during the eclipse period.

• Primary Payloads: The primary payload of XPoSat, POLIX (Polarimeter Instrument in X-rays), is designed to measure polarimetry parameters —specifically the degree and angle of polarization — in the medium X-ray energy range of 8-30 keV photons originating from astronomical sources.

• The POLIX payload was developed by the Raman Research Institute (RRI), Bengaluru, with support from various ISRO centres.

• Secondary payload: The secondary payload is the XSPECT (X-ray Spectroscopy and Timing) payload, which will provide spectroscopic information within the energy range of 0.8-15 keV.

• The XSPECT payload was developed by the U.R. Rao Satellite Centre (URSC), ISRO.

• The XPoSat will be launched by the Polar Satellite Launch Vehicle (PSLV), from the Satish Dhawan Space Center in Sriharikota.