IXPE instrument integration, testing and verification

The Imaging X-ray Polarimetry Explorer (IXPE) is a scientific observatory with the purpose of expand observation space adding polarization property to the X-ray sourceƒ_Ts currently measured characteristics. The mission, selected in the context of NASA Small Explorer (SMEX) is a collaboration between NASA and ASI that will provide to observatory the instrumentation of focal plane. IXPE instrument is composed by three photoelectric polarimeter based on the Gap Pixel Detector (GPD) design, integrated by INFN inside detector unit (DU) that comprises all the electrical interfaces required to control and communicate with GPD. The three DUs are interfaced with spacecraft through a de-tector service unit (DSU) that collect scientific and ancillary data and provides a basically data handling and interfaces to manage the three DUs. AIV has been planned to combine calibration of DUs and Instrument integration and veri-fication activities. Due the tight schedule and the scientific and functional requirements to be verified, in IAPS/INAF have been assembled two equipments that work in parallel. The flight model of each DU after the environmental tests campaign was calibrated on-ground using Instrument Calibration Equipment (ICE) and subsequently integrated in the instrument in the AIV-T process on a AIV and Calibration Equipment (ACE), both the facilities managed by Electrical Ground Support Equipment (EGSE) that emulate the spacecraft interfaces of power supply, functional and thermal control and scientific data collection. AIV activities test functionalities and nominal/off-nominal orbits activities of IXPE instrument each time a calibrated DU is connected to DSU flight model completing step by step the full instrument. Here we describe the details of instrumentation and procedures adopted to make possible the full integration and test activities compatibly with calibration of IXPE Instrument.