EDITORIAL
India is set to launch its first X-Ray Polarimeter Satellite (XPoSat), aiming to investigate the polarisation of intense X-Ray sources. The mission is likely to take place by the end of this year from SHAR Range. ISRO is expected to use its reliable launch vehicle PSLV for the mission.
ISRO said on Thursday that 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.
The astronomy community is particularly enthused about the prospect of a systematic exploration into the polarization of X-Rays emitted by astronomical sources. This research, supplementing traditional time and frequency domain studies, introduces a novel dimension to X-Ray astronomy, generating anticipation and excitement within the scientific community.
The XPoSat spacecraft is designated for observation from Low Earth Orbit (non-sun synchronous orbit of 650 km altitude, low inclination of 6 degree), 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 five years. The payloads onboard XPoSat will observe the X-Ray sources during its transit through the earth’s shadow, i.e., during the eclipse period.
At this juncture, in order to appreciate the importance of this mission, it is apt to take a retrospective look of the evolution of astronomical instrumentation and gradual unfurling of the mysteries in the cosmos.
Apart from imaging, studying the fluctuations of light from a source, and spectroscopy, there emerged another tool for observational astronomy. To be precise, X-Ray polarisation serves as a crucial diagnostic tool for examining the radiation mechanism and geometry of celestial sources.
Analysing X-Ray polarisation signatures enables measurements of the mass and spin of accreting black holes, comprehension of the source’s geometric arrangement and local properties, exploration of accretion flow, outflow, and jets, investigation into the nature of X-Ray scattering and reflection mediums, estimation of strong magnetic fields, and revelation of the radiation zone and particle acceleration processes in pulsars, among other applications.
