In the wake of the successful launches of Chandrayaan-3 Moon lander and Aditya-L1 ventures, the Indian Space Research Organisation (ISRO) is gearing up for a mission that promises to advance scientific understanding in the field of Astronomy.
The upcoming mission, known as XPoSat (X-ray Polarimeter Satellite), is India’s inaugural dedicated polarimetry mission designed to investigate the intricate dynamics of bright astronomical X-ray sources under extreme conditions.
XPoSat will be placed into a low Earth orbit and carry two scientific payloads designed to explore this challenging domain.
The primary payload, POLIX (Polarimeter Instrument in X-rays), is tasked with measuring the polarimetry parameters, specifically the degree and angle of polarization, within the medium X-ray energy range of 8-30 keV for astronomical X-ray photons. Additionally, the XSPECT (X-ray Spectroscopy and Timing) payload will provide valuable spectroscopic data within the energy range of 0.8-15 keV.
An ISRO official confirmed, “XPoSat is ready for launch,” indicating that the mission is poised to proceed.
Astronomical sources such as black holes, neutron stars, active galactic nuclei, and pulsar wind nebulae exhibit complex physical processes governing their X-ray emissions. The understanding of these emissions has been a challenge for scientists.
While previous space-based observatories have contributed significant spectroscopic and timing data, fully comprehending the nature of these emissions remains a complex puzzle for astronomers. Polarimetry measurements, which include parameters such as the degree and angle of polarization, add an additional dimension to understanding these emissions.
By combining polarimetric observations with spectroscopic measurements, the XPoSat mission aims to address critical questions and disentangle the complexities of astronomical emission processes. This mission represents a significant leap forward in India’s scientific endeavors in the field of X-ray astronomy.
POLIX, the X-ray Polarimeter for astronomical observations, is equipped with a collimator, scatterer, and four X-ray proportional counter detectors. These detectors are strategically positioned around the scatterer, composed of low atomic mass material to induce anisotropic Thomson scattering of incoming polarized X-rays. The collimator restricts the field of view to 3 degrees by 3 degrees, ensuring that only one bright source is within the field of view during most observations.
POLIX is expected to observe around 40 bright astronomical sources from various categories over the planned five-year lifetime of the XPoSat mission. It marks a pioneering effort as the first payload in the medium X-ray energy band dedicated to polarimetry measurements.
XSPECT, the X-ray Spectroscopy and Timing payload, complements POLIX by providing high-resolution spectroscopy and timing data in the soft X-ray range. XSPECT’s capacity for long-term monitoring of spectral state changes, variations in line flux and profile, and simultaneous observation of soft X-ray emission across the energy range of 0.8-15 keV is poised to provide invaluable insights into various types of X-ray sources.
This includes X-ray pulsars, black hole binaries, low-magnetic field neutron stars in low-mass X-ray binaries (LMXBs), active galactic nuclei (AGNs), and Magnetars.
The XPoSat mission represents a remarkable milestone in India’s pursuit of cutting-edge astronomical research, further establishing its presence on the global scientific stage.
