Observatory design for the imaging X-Ray Polarimetry Explorer (IXPE) mission

The goal of the Imaging X-Ray Polarimetry Explorer (IXPE) Mission is 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 uniquely probes astrophysical anisotropies - ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin - that are not otherwise measurable. IXPE will conduct X-ray polarimetry for multiple categories of cosmic X-ray sources that are likely to be polarized such as neutron stars, stellar-mass black holes, supernova remnants and active galactic nuclei. The IXPE Observatory consists of Spacecraft and Payload modules built up in parallel to form the Observatory during system integration and test. The Payload includes three polarization-sensitive, X-ray detectors, each paired with its corresponding grazing incidence mirror module assembly (MMA). A deployable boom provides the correct separation (focal length) between the detector units (DU) and MMAs. These Payload elements are supported by the IXPE Spacecraft which is derived from the BCP-100 small Spacecraft architecture. This paper summarizes the IXPE mission science objectives, describes the Observatory implementation concept including the payload and spacecraft elements and summarizes the expected concept of operations.