The Imaging X-ray Polarimetry Explorer (IXPE) and New Directions for the Future

Abstract

An observatory dedicated to X-ray polarimetry has been operational since 9 December 2021. The Imaging X-ray Polarimetry Explorer (IXPE), a collaboration between NASA and ASI, features three X-ray telescopes equipped with detectors sensitive to linear polarization set to 120°. This marks the first instance of a three-telescope SMEX mission. Upon reaching orbit, an extending boom was deployed, extending the optics and detector to a focal length of 4 m. IXPE targets each celestial source through dithering observations. This method is essential for supporting on-ground calibrations by averaging the detector’s response across a section of its sensitive plane. The spacecraft supplies power, enables attitude determination for subsequent on-ground attitude reconstruction, and issues control commands. After two years of observation, IXPE has detected significant linear polarization from nearly all classes of celestial sources emitting X-rays. This paper outlines the IXPE mission’s achievements after two years of operation in orbit. In addition, we report developments for future high-throughput X-ray optics that will have much smaller dead-times by using a new generation of Applied Specific Integrated Circuits (ASIC), and may provide 3D reconstruction of photo-electron tracks.