Mission analysis, design and operations plan of India’s first polarimetry satellite: X-ray Polarimetry Satellite (XPoSat)

Abstract

X-ray Polarimeter Satellite (XPoSat) is India’s first landmark mission dedicated to X-ray polarimetry, with the aim of measuring and studying X-rays emitted by bright astronomical objects such as black hole X-ray binaries, pulsar wind nebulae, and accretion-powered pulsars. Polar Satellite Launch Vehicle-C58 (PSLV-C58) launched the XPoSat mission on 1st January 2024, equipped with two significant, scientific instruments: XSPECT (X-ray Spectroscopy and Timing) and POLIX (POLarimeter Instrument in X-rays). With the launch of XPoSat, a new and important fourth dimension of polarization has been added. POLIX became the first in the world to provide measurements of polarization in 8–30 kilo electron Volt (keV) energy band. XSPECT is a spectroscopy payload responsible for providing timing and spectral information in 0.8–15 keV energy band of X-ray emissions from about 54 potential identified cosmic X-ray sources. Astronomical sources emitting X-rays are sites of strong gravity, and strong magnetic fields and have a variety of geometries for scattering, which are expected to give rise to polarization signatures in these sources. This article provides a comprehensive overview from mission specifications to mission design, mission planning, mission analysis, and mission operations aspects of spacecraft configuration, operations, and on-orbit operations of XPoSat mission with the science brought by the first-time flown payload in high energy bands, which will allow astronomers to explore materials under intense magnetic and gravitational fields. The challenges involved in planning and executing the mission operations with critical scenarios have also been highlighted.