ISRO’s XPoSat Mission: Study About Black Holes

The X-ray Polarimeter Satellite (XPoSat) is a space observatory built by the Indian Space Research Organisation (ISRO). It was launched on January 1, 2024, and is expected to operate for at least five years. XPoSat’s mission is to study the polarization of X-rays from bright celestial sources in the medium frequency band. It will also study the dynamics of bright astronomical X-ray sources in extreme conditions.

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What is XPoSat?

XPoSat, the X-ray Polarimeter Satellite, is India’s inaugural mission dedicated to analyzing the polarization of X-rays from bright celestial sources in the medium-frequency band. Equipped with two payloads, the Indian X-ray Polarimeter (POLIX) and X-ray Spectroscopy and Timing (XSPECT), developed by the Raman Research Institute and UR Rao Satellite Centre in Bengaluru, it operates in a low Earth orbit (~650 km, low inclination of ~6 degrees). With an estimated mission life of around five years, XPoSat observes polarized X-ray emissions, particularly during the eclipse periods when magnetars or neutron stars transit through Earth’s shadow.

X-ray Polarimeter Satellite (XPoSat)

The X-ray Polarimeter Satellite (XPoSat) is a space observatory manufactured by the Indian Space Research Organisation (ISRO). It was launched on January 1, 2024, and is expected to operate for at least five years.

XPoSat is ISRO’s first dedicated mission to study the polarization of X-rays from bright celestial sources in the medium frequency band. The spacecraft will carry two scientific payloads in a low earth orbit. The payloads include the Indian X-ray Polarimeter (POLIX) and X-ray Spectroscopy and Timing (XSPECT).

XPoSat’s configuration is modified from the IMS-2 bus platform. X-ray polarization is a crucial diagnostic tool for examining the radiation mechanism and geometry of celestial sources. XPoSat carries two scientific payloads in a low Earth orbit:

1. POLIX: Indian X-ray Polarimeter
2. XSPECT: X-ray Spectroscopy and Timing

XPoSat will carry out long-term spectral and temporal studies of cosmic X-ray sources. It will also carry out polarization and spectroscopic measurements of X-ray emissions from cosmic sources.

XPoSat Mission Launch Date

The Indian Space Research Organisation (ISRO) launched the X-ray Polarimeter Satellite (XPoSat) on January 1, 2024 at 9:10 AM IST. The launch took place from the Satish Dhawan Space Centre in Sriharikota. The launch was precise, with a deviation of only 3 kilometers.

XPoSat is the world’s second satellite-based mission dedicated to making X-ray polarimetry measurements. The mission will study black holes and colossal stars.

XPoSat Mission Budget

The X-ray Polarimeter Satellite (XPoSat) cost around ₹250 crore (approximately $30 million). The XPoSat is India’s first dedicated polarimetry mission to study the dynamics of bright astronomical X-ray sources. The XPoSat is expected to last more than five years, compared to the two-year life span of the NASA IXPE, which is on a similar mission.

XPoSat Mission Purpose

This mission aims to achieve the following objectives:

• Measure X-ray polarization within the 8-30keV energy range from approximately 50 cosmic sources using the POLIX payload through Thomson Scattering.
• Conduct extensive spectral and temporal studies of cosmic X-ray sources in the 0.8-15keV energy band with the XSPECT payload.
• Perform polarimetric and spectroscopic measurements of X-ray emissions from cosmic sources using the POLIX and XSPECT payloads, respectively, within a shared energy band.

Polarisation of X-rays

• X-rays are composed of electric and magnetic waves in constant motion, with polarised X-rays exhibiting organized vibrations in the same direction.
• When X-rays from magnetars or black holes interact with materials in the Universe, scattering changes the direction of the electric component, resulting in polarisation perpendicular to the original and scattered photon plane.
• Polarisation measurements, both angular and in degree, offer insights into the nature and processes of X-ray-emitting sources.

XPoSat vs. Global X-ray Missions

• Global X-ray polarisation missions are limited, with balloon-based experiments like HX-POL and XL-Calibur by NASA being short-duration.
• AstroSat, India’s previous space mission, focused on timing and broadband spectroscopy of X-ray sources but lacked polarisation studies.
• XPoSat’s POLIX payload fills the gap with its dedicated X-ray polarisation observations in the medium energy band (8-30 keV), complementing NASA’s Imaging X-ray Polarimetry Explorer (IXPE) that operates in the soft X-ray band (2-8 keV).
• XPoSat offers an extended observational energy band compared to IXPE, enhancing the understanding of X-ray polarisation in cosmic sources.

XPoSat Mission Significance

• XPoSat is India’s first mission dedicated to analyzing X-ray polarization from celestial sources in the medium energy band (8-30 keV).
• Two payloads, POLIX and XSPECT, developed by Raman Research Institute and UR Rao Satellite Centre, are integral to XPoSat.
• Operates in a low Earth orbit (~650 km, low inclination of ~6 degrees) and targets polarized X-rays from sources like magnetars and black holes.
• Unique focus on the medium energy band makes XPoSat a game-changer in X-ray polarization measurements.
• Observations include both persistent (known) and transient sources (pulsars, active galactic nuclei).
• X-rays in space become polarized due to factors like strong magnetic fields and interactions near black holes.
• Scientists utilize polarized X-rays to probe the nature of radiations and understand the intricate processes behind their generation.

XPoSat Mission UPSC

XPoSat, India’s inaugural X-ray Polarimeter Satellite, launched on January 1, 2024, and operated by ISRO, aims to study X-ray polarization from bright celestial sources in the medium-frequency band (8-30 keV). It carries two payloads, POLIX and XSPECT, conducting spectral studies and polarimetric measurements in a low Earth orbit (~650 km). XPoSat’s unique focus and advanced instruments make it a game-changer in X-ray polarization studies, contributing valuable insights into cosmic X-ray sources’ nature and processes.

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