What is XPoSat, India’s first polarimetry mission?

Introduction: 

According to ISRO, XPoSat (X-ray Polarimeter Satellite) is India’s first dedicated polarimetry mission to study various dynamics of bright astronomical X-ray sources in extreme conditions.

The Indian Space Research Organisation (ISRO) has joined hands with the esteemed Raman Research Institute (RRI) in Bengaluru, an independent research institution, to embark on an awe-inspiring endeavor - the creation of the remarkable X-Ray Polarimeter Satellite (XPoSat). This groundbreaking satellite, eagerly anticipated, is poised for its upcoming launch later this year.

Just a short while ago, the esteemed chairman of ISRO, Mr. S. Somanath, delivered an impassioned plea to all scientific institutions across India. His earnest request was for these esteemed establishments to actively seek out gifted young minds and guide them in harnessing the transformative power of the data obtained from space missions centered around scientific exploration. With great pride, he made a special mention of the monumental XPoSat project in this context, underlining its immense significance.

What is the XPoSat Mission?

ISRO has described XPoSat as a pioneering venture aimed at unraveling the intricate dynamics of luminous astronomical X-ray sources thriving amidst extreme conditions. This momentous mission holds the distinction of being India's very first, and only the world's second, polarimetry expedition with a focus on studying the multifaceted aspects of these captivating celestial phenomena. It finds itself in the esteemed company of NASA's Imaging X-ray Polarimetry Explorer (IXPE), a significant mission that took flight in 2021.

IXPE boasts an impressive ensemble of three cutting-edge space telescopes, each elegantly equipped with a lightweight X-ray mirror and a detector unit. These remarkable instruments are poised to capture and scrutinize polarized X-rays emanating from neutron stars and supermassive black holes. By meticulously measuring the polarization properties of these X-rays, we gain the ability to decipher their origins, unravel the intricate geometry at play, and delve into the enigmatic inner workings of the radiant sources themselves.

How are X-Rays witnessed in space?

As eloquently outlined on NASA's official website, X-rays possess significantly higher energy and remarkably shorter wavelengths, measuring between 0.03 and 3 nanometers. In fact, some X-rays are so minuscule that they are no larger than a single atom of numerous elements. The wavelength of radiation emitted by an object is determined by its physical temperature. The hotter the object, the shorter the wavelength of peak emission. X-rays, therefore, emanate from celestial entities with scorching temperatures reaching millions of degrees Celsius, such as pulsars, galactic supernova remnants, and black holes.

In a captivating video provided by NASA on the subject of IXPE, it is elucidated that X-rays, akin to all forms of light, comprise moving electric and magnetic waves. Typically, the peaks and valleys of these waves exhibit random orientations. However, polarized light offers a remarkable distinction, as it manifests with two distinct types of waves vibrating in unison, aligned in the same direction. To offer an everyday analogy, the video highlights that fishermen employ polarized lenses to mitigate the blinding glare of sunlight when navigating near water bodies.

The captivating field of polarimetry delves into the meticulous measurement of the angle of rotation experienced by the plane of polarized light. This occurs as the light traverses certain transparent materials, confining the vibrations of its electromagnetic waves to a singular plane. Britannica aptly defines this intriguing scientific domain, shedding light on the intricate nuances of polarized light's interaction with various mediums.

ISRO's website further expands on the subject matter, elucidating that the emission mechanisms observed in diverse astronomical sources, including black holes, neutron stars, active galactic nuclei, and pulsar wind nebulae, arise from complex and enigmatic physical processes. Understanding these mechanisms poses a significant challenge. Even space-based observatories, while invaluable in their contributions, cannot provide comprehensive insights into the exact nature of emissions from such sources. Hence, the development of innovative devices capable of measuring specific properties becomes a crucial endeavor, offering a pathway to unraveling these cosmic mysteries.

What are XPoSat's payloads?

The spacecraft is meticulously designed to accommodate two remarkable scientific payloads, all set to embark on a captivating journey within a low Earth orbit. The primary payload, aptly named POLIX (Polarimeter Instrument in X-rays), assumes a central role in the mission by diligently measuring the crucial parameters of polarimetry—the degree and angle of polarization.

The development of this exceptional payload is a collaborative effort between the esteemed Raman Research Institute (RRI) and ISRO's U R Rao Satellite Centre (URSC), both based in the vibrant city of Bengaluru. With great anticipation, POLIX aims to observe approximately 40 vivid astronomical sources spanning diverse categories over the course of the XPoSat mission's planned lifetime, estimated to be around 5 years. Notably, this extraordinary payload represents a pioneering achievement as the first of its kind to specialize in medium X-ray energy band polarimetry measurements—a testament to the cutting-edge advancements achieved by the XPoSat mission.

In addition to POLIX, the spacecraft is also equipped with the remarkable XSPECT (X-ray Spectroscopy and Timing) payload, offering invaluable insights into the absorption and emission of light by celestial objects. XSPECT's spectroscopic capabilities unlock a wealth of information as it meticulously observes various fascinating sources, including X-ray pulsars, black hole binaries, and low-magnetic field neutron stars. With its multifaceted observation capabilities, XSPECT stands as a crucial instrument in broadening our understanding of the captivating cosmic phenomena that grace our universe.

Source: IE