Orbital verification of the CXO high-resolution mirror assembly alignment and vignetting

Prior to launch, the High Resolution Mirror Assembly (HRMA) of the Chandra X-ray Observatory underwent extensive ground testing at the X-ray Calibration Facility (XRCF) at the Marshall Space Flight Center in Huntsville, Alabama. The resulting data were used to validate a high fidelity raytrace model for the HRMA performance. Further observations made during the post-launch Orbital Activation and Calibration period allow the on-orbit condition of the X-ray optics to be assessed. Based on these ground-based and on-orbit data, we examine the alignment of the X-ray optics based on the off-axis point spread function. We discuss how single-reflection ghost data obtained at XRCF can be used to better constrain the HRMA optical axis data. We examine the vignetting and the single-reflection ghost suppression properties of the telescope. Slight imperfections in alignment lead to a small azimuthal dependence of the off- axis effective area; the morphology of off-axis images also shows an additional small azimuthal dependence varying as 1/2 the position angle.