Towards the calibration of the HETGS effective area

The High-Energy Transmission Grating far AXAF was tested with the AXAF High Resolution Mirror Assembly during December 1996 through April 1991 at NASA's MSFC X-Ray Calibration Facility. This first-use of the HETG confirms sub-assembly measurements and demonstrates the power of this AXAF grating spectrometer. This paper discusses calibration goals, summarizes the pre-XRCF performance predictions, describes the XRCF data taken, and outlines the general approach to their analysis-concentrating on the the HETG contribution to the HETGS effective area. Very preliminary examples of the analysis of the XRCF data are presented. At a crude level (approximate to 30%) the data are in agreement With sub-assembly predictions. Future detailed analysis will result in a definitive instrument calibration.