ISRO launches XPoSat; here is what it is expected to do

The Indian Space Research Organisation (ISRO) successfully launched the X-ray Polarimeter Satellite (XPoSat) to study celestial objects on January 1, 2024.

The XPoSat was launched by ISRO’s PSLV-C58 Mission, which is the 60th mission of PSLV (Polar Satellite Launch Vehicle).

“PSLV-C58 vehicle placed the satellite precisely into the intended orbit of 650 km with 6-degree inclination,” ISRO wrote on X, formerly Twitter. The space agency added that XPoSat’s health is normal. It also has begun generating power.

The satellite carries two payloads:

• POLIX (Polarimeter Instrument in X-rays) built by Raman Research Institute
• XSPECT (X-ray Spectroscopy and Timing) by Space Astronomy Group of U R Rao Satellite Centre

POLIX will measure the degree and angle of polarisation in the medium X-ray energy range of 8-30 kilo electron volt (keV) photons originating from astronomical sources. Polarisation refers to the direction of travel of an electromagnetic wave vector’s tip. It can be vertical (up and down), horizontal (left to right), or circular (rotating in a constant plane left or right), according to NASA.

It can be used to study the origin of cosmic rays in the universe, the nature of black holes, and the role of black holes in the evolution of galaxies, among others.

“POLIX’s primary objective is to observe bright astronomical sources across various categories during the planned 5-year lifetime of the XPoSat mission,” ISRO said on its website.

XSPECT will offer fast timing and excellent spectroscopic resolution in soft X-rays in the range of 0.8-15 keV. It can distinguish between two wavelengths emitted by objects.

This instrument, according to ISRO, is designed to observe a variety of sources. These include X-ray pulsars (rotating neutron stars that emit pulses of radiation at regular intervals), black hole binaries, low-magnetic field neutron stars, active galactic nuclei (a small region at the centre of some galaxies), and magnetars (young and highly magnetized neutron stars).

Scientists are yet to understand the emissions mechanisms from various astronomical sources such as blackhole, neutron stars, active galactic nuclei, pulsar wind nebulae, and the like. These originate from complex physical processes and are challenging to understand, the space agency noted.

The polarimetry measurements can provide information on the degree of polarisation and the angle of polarisation, which can help scientists better understand the emission processes from astronomical sources.

“Apart from its capability of timing and spectroscopy-based observations, the insights derived from X-ray polarisation measurements, especially on celestial objects like black holes, neutron stars, and active galactic nuclei, hold the potential to significantly improve our understanding of their physics,” ISRO said in its website.

Additionally, it added, the mission could play a pivotal role in building expertise in X-ray polarimetry in India.

Further, PSLV will carry out the PSLV Orbital Experimental Module (POEM) activity to conduct in-orbit scientific experiments using the spent PS4 stage (the uppermost stage of PSLV) as an orbital platform. It carried 10 payloads built by private companies, colleges, and ISRO.