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 x 15 mm pencil beam. These measurements were performed at seven different energies including 1.5 keV (Al K alpha), 4.5 keV (Ti K alpha), 6.4 keV (Fe K alpha), 8.0 keV (Cu K alpha), 9.4 keV (Pt L alpha), 11.1 keV (Pt L beta), 17.5 keV (Mo K alpha). A method for background subtraction was developed using a back-illuminated CCD camera with a 30 mmx30 mm (i.e. 17' x 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.