Performance expectation versus reality

The AXAF (Advanced X-ray Astrophysics Facility) High Resolution Mirror Assembly (HRMA) now is complete and has been tested at the NASA Marshall Space Flight Center (MSFC) X-ray Calibration Facility (XRCF). The surface and alignment properties of the mirror were thoroughly measured before the X-ray test, which allowed accurate performance predictions to be performed. The preliminary analysis of the measured X-ray image distributions for all energies tested show excellent agreement with predictions made before the beginning of the test. There is a discrepancy between the measured and predicted effective areas; this typically is less than 5%, and is less than 13% for all energies measured. We present evidence that this discrepancy is due to uncertainties in the calibration of the test instrumentation, and therefore can be expected to be reduced when results from further instrument calibration tests now in progress are incorporated into the analysis. We predict that 65-80% (depending upon energy) of the flux from an imaged point source will be contained in a one arc second diameter aperture in flight. We expect the HRMA to more than fulfill the requirements necessary to achieve the AXAF scientific objectives.