ISRO launches X-Ray Polarimeter Satellite, will study X Ray emission from celestial sources

Sriharikota: The Indian Space Research Organisation (ISRO) has successfully launched the X-ray Polarimeter Satellite on the very first day of the New Year, in continuation of its stellar space odyssey from the previous year.

The satellite that was launched from Sriharikota spaceport on Monday at 9.10 am, as scheduled, among others, would offer insights into space-based polarisation measurements of X-ray emission from various celestial sources.

ISRO’s PSLV-C58 XPoSat Mission | “Lift-off normal. XPoSat satellite is launched successfully. The POEM-3 is being scripted. XPoSat health is normal. Power generation has commenced.” tweets ISRO pic.twitter.com/CZBEHseTZD

— ANI (@ANI) January 1, 2024

ISRO’s PSLV-C58 Mission is to launch XPOSAT Satellite into an Eastward low inclination orbit. After injection of XPOSAT, the PS4 stage will be re-started twice to reduce the orbit into 350 km circular orbit to maintain in 3-axis stabilized mode for Orbital Platform (OP) experiments. The PSLV Orbital Experimental Module-3 (POEM-3) experiment will be executed meeting the objective of 10 identified payloads, supplied by ISRO and IN-SPACe.

The 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.

According to ISRO The XPOSAT satellite has two payloads:
POLIX: This will measure the polarimetry parameters (degree and angle of polarization) in medium X-ray energy range of 8-30 keV photons of astronomical origin. The payload is being developed by Ramam Research Institute (RRI), Bangalore in collaboration with U R Rao Satellite Centre (URSC). The instrument is made of a collimator, a scatterer and four X-ray proportional counter detectors that surrounds the scatterer. The scatterer is made of low atomic mass material which causes anisotropic Thomson scattering of incoming polarised X-rays. The collimator restricts the field of view to 3 degree x 3 degree so as to have only one bright source in the field of view for most observations. POLIX is expected to observer about 40 bright astronomical sources of different categories during the planned lifetime of XPoSat mission of about 5 years. This is the first payload in the medium X-ray energy band dedicated for polarimetry measurements.

XSPECT: Will give spectroscopic information in the energy range of 0.8-15 keV. An X-ray SPECtroscopy and Timing payload onboard XPoSat, which can provide fast timing and good spectroscopic resolution in soft X-rays. Taking advantage of the long duration observations required by POLIX to measure X-ray polarization, XSPECT can provide long-term monitoring of spectral state changes in continuum emission, changes in their line flux and profile, simultaneous long term temporal monitoring of soft X-ray emission in the X-ray energy range 0.8-15 keV. An array of Swept Charge Devices (SCDs) provide an effective area >30 cm2 at 6 keV with energy resolution better than 200 eV at 6 keV. Passive collimators are used to reduce the background by narrowing the field of view of XSPECT. XSPECT would observe several types of sources viz X-ray pulsars, blackhole binaries, low-magnetic field neutron star (NS) in LMXBs, AGNs and Magnetars.

The objective of the mission is to measure polarisation of X-rays in the energy band 8-30keV emanating from about 50 potential cosmic sources through Thomson Scattering by POLIX payload. To carry out long term spectral and temporal studies of cosmic X-ray sources in the energy band 0.8-15keV by XSPECT payload. To carry out polarisation and spectroscopic measurements of X-ray emissions from cosmic sources by POLIX and XSPECT payloads respectively in the common energy band.

The emission mechanism from various astronomical sources such as blackhole, neutron stars, active galactic nuclei, pulsar wind nebulae etc. originates from complex physical processes and are challenging to understand. The exact nature of the emission from such sources still poses deeper challenges to astronomers. The polarimetry measurements add two more dimension to understanding, the degree of polarization and the angle of polarization and thus is a diagnostic tool to understand the emission processes from astronomical sources.

In a stellar display of prowess, India soared to new heights in 2023 with the successful soft landing of Chandrayaan-3 on the south pole of moon and the launch of Aditya-L1, India’s first solar mission.

The primary objective of the Chandrayaan-3, the country’s first successful lunar landing mission, was to demonstrate a soft landing near the lunar south polar region and perform experiments using the instruments onboard the lander ‘Vikram’ and rover ‘Pragyaan’.
On August 23, Vikram Lander made its historic touchdown on the Moon and subsequently, the Pragyan rover was deployed to survey the uncharted lunar south pole.

These milestones not only secured India’s standing in the global space economy but also fueled the engines for the private space sector in India.
Among other feats India now aims for are the Gaganyaan Mission, setting up ‘Bharatiya Antariksha Station’ by 2035, and sending the first Indian to the Moon by 2040.