The Imaging X-Ray Polarimeter Explorer (IXPE) Mission System Using a Small Satellite

The goal of the Imaging X-Ray Polarimeter Explorer (IXPE) Mission is to expand understanding of high-energy astrophysical processes and sources. IXPE will add two new dimensions to on-orbit x-ray science: polarization measurements and detailed imaging. Polarization uniquely probes physical anisotropies that are not otherwise measurable—ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin. Detailed imaging enables the specific properties of extended X-ray sources to be differentiated. 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 detector arrays paired with three x-ray mirror module assemblies (MMA). A deployable boom provides the correct separation (focal length) between the detector units and MMAs. MSFC provides the X-ray optics and Science Operations Center (SOC) along with mission management and systems engineering. Ball is responsible for the spacecraft, payload mechanical elements and flight metrology system and payload, spacecraft and system I&T along with launch and operations. The MOC is located at CU/LASP. IAPS/INAF and INFN provide the polarization-sensitive detector units (DU) and detectors service unit (DSU) via the Italian Space Agency (ASI). The Observatory communicates with the ASI-contributed Malindi ground station via S-band link. The science team generates and archives IXPE data products at the HEASARC. The IXPE “mission system” is made up of the flight segment, ground segment and launch segment – this paper briefly summarizes the IXPE mission science objectives, overviews the flight segment (the payload, spacecraft, and Observatory implementation concepts), and summarizes the expected operations concept. A SpaceX Falcon 9 launch vehicle was selected in June 2019 to launch the IXPE Observatory. Mission CDR occurred in June 2019 and the IXPE Project is now firmly in the build phase