Context:  The Indian Space Research Organisation (ISRO) kicked off the new year with the launch of the PSLV-C58 X-ray Polarimeter Satellite (XPoSat) on January 1, 2024.

1. On January 1, 2024, the PSLV-C58 mission achieved success, placing the primary satellite, XPoSat, into the intended orbit of 650 km with a 6-degree inclination
2. The successful launch of XPoSat makes India the second nation globally to send an observatory for studying astronomical Sources, including black holes and neutron stars
3. PSLV Orbital Experimental Module-3 (POEM-3): During the mission, the POEM-3 experiment was executed to meet the objective of deploying 10 other payloads
4. PS4 Stage Operations: After injecting XPoSat into a 650 km, 6-degree orbit, the PS4 stage was lowered to a 350 km, ~9.6-degree orbit by restarting it twice. The PS4 stage serves as a 3-axis stabilized orbital platform for conducting experiments with space-qualify systems
5. Launch of 10 Payloads: The PSLV also launched 10 payloads developed by start-ups, educational institutions, and ISRO centers, including Radiation Shielding Experimental Module (RSEM), Women Engineered Satellite (WESAT), BeliefSat-0 Amateur radio satellite, Green Impulse TrAnsmitter (GITA), LEAP-TD, RUDRA 0.3 HPGP, ARKA-200, Dust Experiment (DEX), ISRO Fuel cell Power System (FCPS), and Si-based High Energy cell

XPoSat

• XPoSat, or X-ray Polarimeter Satellite, is India's pioneering mission in polarimetry designed to study astronomical Sources in extreme conditions.
• It represents the world's second X-ray polarimetry mission after NASA's Imaging X-ray Polarimetry Explorer (IXPE) launched in 2021.
• A collaborative effort between ISRO and the Raman Research Institute (RRI) in Bengaluru, Karnataka.

Scientific Payloads:

• XPoSat carries two primary scientific payloads: Polarimeter Instrument in X-rays (POLIX) and X-ray Spectroscopy and Timing (SPECT).
• POLIX measures polarimetry parameters like degree and angle of polarization in the medium X-ray energy range (8-30 keV) from astronomical Sources.
• SPECT provides timing and spectroscopic information within the energy range of 0.8-15 keV for X-ray photons.

Significance in Astronomical Understanding:

• Polarimetry measurements serve as a valuable diagnostic tool for understanding emission processes from various astronomical Sources.
• Complex emission mechanisms from Sources like black holes, neutron stars, active galactic nuclei, and pulsar wind nebulae pose challenges to current understanding.
• Combining polarimetric observations with spectroscopic and timing data aims to overcome limitations in comprehending these astronomical emission processes.