The back-end electronics for the Imaging X-ray Polarimetry Explorer telescope

The Imaging X-Ray Polarimetry Explorer (IXPE) is the next NASA small explorer mission, due to be launched on May 2021. It will perform polarization measures of soft X-ray photons (similar to 2 8keV), together with imaging, spectroscopy, and timing. The core of the detector units is the Gas Pixel Detector (GPD) with dedicated back-end electronics (BEE). We designed the latter with a radiation-tolerant FPGA for data acquisition and processing, event sequencing, and on-line data compression. Two custom digital serial interfaces implement the communication of the units with a central on-board computer: Command and Control Interface and Science Data Interface. This BEE exploits the auto-trigger capability of the GPD and can process its output of 300 photons per second with 30% of system dead time. We designed comprehensive test-equipment to emulate the on-board computer. It is based on a commercial FPGA on a VME-board together with dedicated software for control and data collection.