Imaging X-Ray Polarimetry Explorer (IXPE) - One Year On-Orbit

The Imaging X-Ray Polarimetry Explorer (IXPE) is designed to expand understanding of high-energy astrophysical processes and sources, in support of NASA's first science objective in Astrophysics: “Discover how the universe works.” Polarization measurements and imaging are key capabilities of the IXPE observatory. IXPE, an international collaboration between NASA and the Italian Space Agency (ASI), is a NASA Small Explorer designed as a 2-year mission. It launches to a circular LEO orbit at an altitude of 600 km and an inclination of ~0 degrees on a Falcon 9 launch vehicle. The payload uses a single science operational mode to capture the X-ray data from the science targets. The mission design follows a simple observing paradigm: pointed viewing of known X-ray sources (with known locations in the sky) over multiple orbits (not necessarily consecutive orbits) until the observation is complete. IXPE's payload is a set of three identical, imaging, X-ray polarimetry telescopes mounted on a common optical bench and co-aligned with the pointing axis of the spacecraft. The BCP-Small spacecraft provides the necessary resources to support and operate the payload elements and enable continuous science data collection. The Observatory communicates with ground stations via S-band link. The ground system consists of three major elements: the ground stations for data receipt and command upload to the Observatory; the Mission Operation Center (MOC); and Science Operations Center (SOC). Launch occurred on 9 December 2021. The IXPE Observatory has been collecting science data from cosmic X-ray sources since 11 January 2022. These include extreme astronomical objects, such as stellar-mass and supermassive black holes, magnetars, Blazars, neutron stars, and pulsars. This paper summarizes the IXPE mission, describes the Observatory, ground system, and commissioning and overviews recent science results.