IXPE

IXPE (for Imaging X-ray Polarimetry Explorer) is a NASA Small Explorer Program (SMEX) space X-ray observatory launched in December 2021, intended for a 2-year mission, specifically to observe polarization of X-ray sources, such as active galactic nuclei (AGNs) and magnetars. It has three identical X-ray telescopes, the three to provide redundancy as well as collection area. The sensors are a type of proportional counter (gas ionized by the incident X-rays, producing photoelectrons) with an array of electron sensors allowing the direction of the electrons to be recorded, which reveals information on the photon's polarization.