Ground calibration of the x-ray mirror assembly for the X-Ray Imaging and Spectroscopy Mission (XRISM) II: imaging performance and stray light

The X-Ray Imaging and Spectroscopy Mission (XRISM) is an x-ray astronomy satellite being developed in collaboration between NASA, JAXA, and ESA, and is scheduled for launch in Japanese fiscal year 2022. The x-ray mirror assembly (XMA) for XRISM has been developed at NASA’s Goddard Space Flight Center (GSFC). Two units were fabricated, one each for a micro-calorimeter array (Resolve) and a CCD array (Xtend). The ground calibration and performance verification measurements for XRISM XMA were taken at the 100-m x-ray beamline at NASA/GSFC. X-ray images at the focal plane were taken by scanning across the entire mirror aperture with a 15 mm×15 mm pencil beam. These measurements were performed at seven different energies including 1.5 keV (Al Kα), 4.5 keV (Ti Kα), 6.4 keV (Fe Kα), 8.0 keV (Cu Kα), 9.4 keV (Pt Lα), 11.1 keV (Pt Lβ), 17.5 keV (Mo Kα). A method for background subtraction was developed using a back-illuminated CCD camera with a 30 mm×30 mm (i.e. 17′×17′) array at the focal plane. Results from the measurements on the imaging performance show a small energy dependence in the angular resolution. We will also present the results of the stray light measurements.