In a remarkable start to the year, the Indian Space Research Organisation (ISRO) has achieved yet another milestone by successfully launching the X-ray Polarimeter Satellite (XPOSAT). This significant launch, part of ISRO’s PSLV-C58 Mission, aims to explore and understand space-based polarisation of X-ray emissions originating from a variety of celestial sources.
Mission Overview
The XPOSAT satellite was launched at 9.10 am from Sriharikota spaceport on Monday. Its primary mission objective is to delve into the dynamics of bright astronomical X-ray sources, offering insights into these celestial phenomena that occur in extreme conditions.
During the PSLV-C58 Mission, the XPOSAT Satellite will be placed into an Eastward low inclination orbit. Subsequently, the PS4 stage will undergo two restarts to adjust the orbit into a 350 km circular orbit, ensuring a stable 3-axis mode for Orbital Platform (OP) experiments. This mission includes the PSLV Orbital Experimental Module-3 (POEM-3) experiment, aiming to accommodate and execute ten identified payloads contributed by ISRO and IN-SPACe.
XPOSAT: India’s Maiden Polarimetry Mission
XPOSAT represents India’s inaugural dedicated polarimetry mission, aiming to study the complex dynamics of bright astronomical X-ray sources in space. It carries two significant payloads designed to meet its objectives:
POLIX: Developed collaboratively by the Raman Research Institute (RRI), Bangalore, and U R Rao Satellite Centre (URSC), POLIX operates within the medium X-ray energy range of 8-30 keV photons. Its primary role is to measure polarimetry parameters (degree and angle of polarization) from various astronomical sources. Comprising a collimator, scatterer, and four X-ray proportional counter detectors, POLIX aims to observe around 40 bright astronomical sources throughout its projected mission duration of approximately 5 years.
XSPECT: Functioning within the energy range of 0.8-15 keV, XSPECT provides spectroscopic information and enables fast timing with high-quality spectroscopic resolution in soft X-rays. It complements POLIX by facilitating long-term monitoring of spectral state changes, line flux variations, and temporal monitoring of soft X-ray emissions. Equipped with Swept Charge Devices (SCDs) and passive collimators, XSPECT targets various sources, including X-ray pulsars, black hole binaries, low-magnetic field neutron stars, active galactic nuclei (AGNs), and Magnetars.
Mission Objectives and Significance
The primary objectives of the mission encompass measuring X-ray polarisation in the 8-30keV energy band from approximately 50 cosmic sources using the POLIX payload. Additionally, XSPECT will conduct prolonged spectral and temporal studies of cosmic X-ray sources within the 0.8-15keV energy band.
The emission mechanisms of various astronomical sources, including black holes, neutron stars, active galactic nuclei, and pulsar wind nebulae, are intricate and challenging to comprehend. Polarimetry measurements provide astronomers with essential dimensions of polarization degree and angle, serving as vital diagnostic tools to decode these complex emission processes.
ISRO’s successful launch of the X-ray Polarimeter Satellite represents a significant leap in space research and exploration. With this achievement, India has now become the second country in the world, after the United States, to deploy a dedicated astronomy observatory specifically focused on studying black holes and neutron stars.
Looking ahead, the agency is pursuing endeavors like the Gaganyaan Mission, envisioning the establishment of the ‘Bharatiya Antariksha Station’ by 2035, and aiming for the first Indian lunar landing by 2040.