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1 Introduction

NASA's Advanced X-Ray Astrophysics Facility (AXAF) is scheduled for launch in September, 1998. The AXAF telescope employs Wolter type I grazing optics and has two focal plane instruments, the microchannel plate High Resolution Camera (HRC) and a CCD based instrument, the AXAF CCD Imaging Spectrometer (ACIS). AXAF also has two grating instruments, the High Energy Transmission Grating (HETG) and the Low Energy Transmission Grating (LETG). [1,2] The ACIS instrument consists of two separate detector arrays, ACIS-I and ACIS-S. ACIS-I is a 2x2 array of CCDs intended for imaging. ACIS-S is a 1x6 array of CCDs intended for use with the HETG to do spectroscopy.[3]

The scientific objectives of the program demand thorough calibration of each CCD placed in the ACIS-I and the ACIS-S. As complete characterization of a single device heavily taxes personnel and laboratory resources, calibration of each of the more than thirty flight quality CCDs becomes infeasible. In response to these constraints, we have developed screening techniques that allow us to determine which CCDs deserve a complete calibration.

In this paper, we describe the measurements that comprise the screening protocol, including determination of device-level performance parameters and the spectral resolution in the .3 - 6 keV band. In addition to discussing the motivation for the acceptance criteria, we summarize the screening results and present representative performance data.