XRISM (X-Ray Imaging and Spectroscopy Mission): Ground Calibration of the X-ray Mirror Assemblies and Comparison with Raytracing Simulations

The X-Ray Imaging and Spectroscopy Mission (XRISM) is a joint mission of the Japan Aerospace Exploration Agency (JAXA) and the National Aeronautics and Space Administration (NASA), with the participation of the European Space Agency (ESA). The mission aims to study celestial X-ray objects in the Universe with high-throughput imaging and high-resolution spectroscopy, using its Xtend and Resolve instruments. It was successfully launched from the Tanegashima Space Center, in Japan, in September 2023. The X-ray Mirror Assemblies (XMAs) for both instruments on board the XRISM satellite were built at NASA’s Goddard Space Flight Center and calibrated at the 100-meter X-ray beamline on site. A narrow X-ray pencil beam scanning method was used to calibrate both Resolve and Xtend XMAs, at nine different energies, in order to measure the on-axis and off-axis effective area response, imaging performance, stray light, and performance variation across the aperture. A raytracing simulator (xrtraytrace, available from HEASARC) was developed by the Hitomi and XRISM teams to generate response matrices, and its XRISM model input files were tuned to reproduce the calibration data. Here we give a summary of the ground calibration results obtained from raster and local spot scans. We then present the method used to tune the XMA model calibration files to produce simulated data that are consistent with the calibration measurements. Finally, we show the comparison of the simulated results with the measured effective areas, vignetting curves, and point spread functions, which is essential for XRISM data analysis.