ISRO to launch XPoSat for studying black holes and neutron stars on January 1

ISRO is targeting the launch of its X-ray Polarimeter Satellite (XPoSat) on January 1. According to reports, the launch is scheduled for 9:10 am IST from Satish Dhawan Space Center in Sriharikota using the Polar Satellite Launch Vehicle (PSLV).

The upcoming mission PSLV-C58, ISRO says, is “India's first dedicated polarimetry mission to study various dynamics of bright astronomical X-ray sources in extreme conditions.” These sources are black holes, neutron stars, active galactic nuclei, and the pulsar wind nebulae whose emission mechanism of X-rays are extremely hard to understand.

The XPoSat consists of two payloads - POLIX and XSPECT - with separate objectives. The first payload, Polarimeter (POLIX) has been jointly developed by the Raman Research Institute and UR Rao Satellite Centre.

"POLIX is expected to observe 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," ISRO said in an official statement.

The second payload XSPECT (X-ray SPECtroscopy and Timing) will help scientists gather 'soft X-rays' in high spectroscopic resolution. "XSPECT would observe several types of sources viz X-ray pulsars, black hole binaries, low-magnetic field neutron star (NS) in LMXBs, AGNs (active galactic nucleus) and Magnetars," ISRO said. 

After injecting the satellite in the desired orbit, the upper stage of the PSLV will be used for other experiments in a 350 km circular orbit. “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,” ISRO said in its brochure. 

The study of the universe in X-rays began in the early 1960s and several satellites have been launched for their study ever since. Notably, all of them are installed in space as the Earth's atmosphere absorbs most of the X-rays. NASA's Chandra X-ray and the NuSTAR observatories are the two major missions currently carrying out X-ray astronomy.

The agency says that studying the universe in X-rays and gamma rays will help scientists shed light on the fundamental physics of our universe, its origin and evolution. 

Apart from XPoSat, which is the primary payload, the PSLV will be carrying 10 other payloads from private companies like Bellatrix and Dhruva Space for experiments in the low-Earth orbit. Another major payload is the 'Women Engineered Satellite' (WESAT) made by the Thiruvananthapuram-based LBS Institute of Technology for Women.