Joint AXAF high-resolution mirror assembly and AXAF CCD Imaging Spectrometer calibration at the MSFC X-Ray Calibration Facility

Abstract

The flight AXAF CCD Imaging Spectrometer (ACIS) and the High-Resolution Mirror Assembly (HRMA) telescope were extensively calibrated at NASA MSFC's X-Ray Calibration Facility (XRCF). We present result based on HRMA/ACIS characteristics that were obtained with the following tests: (a) Point-Spread Function (PSF) tests measuring the core and wings of the PSF on-axis and at several off-axis positions, at the point of ideal focus. (b) Effective-Area (EA) test measuring the total effective collecting area over the PSF at many energies. We investigate the dependence of the effective area and energy response of ACIS/HRMA as a function of several ACIS parameters. (c) Count-rate- linearity (pile-up) test measuring the effect of increasing the mean incident rat of photons per pixel on the PSF, and EA, source centroid, and photon detection. The goal of the calibration is to provide accurate estimates of the in-orbit performance of the ACIS/HRMA instrument and to enable translation of in-orbit measurements to absolute values of the incident x-ray flux and physical models of the source emission.