On-orbit Performance Prediction

The data collected at the XRCF cannot be directly applied to prediction of in-orbit performance because several significant effects influence the ground data which will be different in orbit. The source at XRCF is not located at an infinite distance from the ACIS, the XRCF source has a finite size which is resolved by the HRMA in measurements near the optical axis, the gravitational effects of loading on the HRMA structure cannot be perfectly removed by the HRMA mounting fixture, and the ACIS operating temperature differs slightly from the expected in-orbit values. Thus we must use the data collected at XRCF and the sub-assembly results to refine and validate a model of the HRMA/ACIS response.

The preceeding sections describe the status of the testing and validation of the model. Then, given raytrace models of the HRMA which are appropriate to zero-gravity and infinite source distance, we apply our ACIS models to obtain predictions of the in-orbit performance.

For this report (January, 1999) we have not received the exact ray-trace results for the XRCF tests. Approximate SAOSAC ray files exist, which incorporate finite-distance XRCF effects and on-orbits predictions, but we still lack ray files with the effect of finite-source-size. We will in future reports obtain the ray-traces and produce user-friendly summaries of the expected HRMA/ACIS performance.