XPOSAT (Syllabus: GS Paper 3 – Sci and Tech)

Context: Indian Space Research Organisation (ISRO) put its first polarimetry mission X-ray Polarimeter Satellite (XPoSat) in a precise circular orbit of 650 km.

X-ray Polarimeter Satellite (XPoSat)

• About: It is India’s maiden mission dedicated to analysing the polarisation of X-rays emanating from bright celestial sources in the medium frequency band.
• Objectives: Measuring X-Ray polarization in the energy band of 8-30 keV from X-Ray sources and conducting long-term spectral and temporal studies of cosmic X-Ray sources in the energy band of 0.8-15 keV.
• Observation Period: Approximately five years, with the payloads observing X-Ray sources during the spacecraft's transit through Earth's shadow, specifically during the eclipse period.
• Primary and Secondary Payloads of XPoSat:
• POLIX: It is the world’s first instrument designed to operate in the medium X-ray of 8 to 30 kilo electron Volt (keV) energy band. 

oIt comprises a collimator, which is the key component to filter light originating from bright sources in the field of view.

• XSPECT: It is designed to conduct fast timing and high spectroscopic resolution in a soft X-ray energy band (0.8-15 keV).

oIt will observe a variety of sources like X-ray pulsars, black hole binaries, low-magnetic field neutron stars, active galactic nuclei or AGNs (a compact region at the centre of a galaxy that emits a significant amount of energy across the electromagnetic spectrum) and magnetars.

What is the polarisation of X-rays?

• X-rays comprise electric and magnetic waves that are constantly in motion. Being sinusoidal waves, they do not follow a patterned direction of motion. 
• Whereas, a polarised X-ray is both organised and has two waves vibrating in the same direction.
• Polarisation measurements: Angular and Degree of polarisation – are believed to provide clues about the bright X-ray emitting sources the nature of these radiations and the complex process they undergo.