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                          Figure 1: ACIS Block Diagram

A block diagram of the instrument is shown in Figure 1. ACIS includes a focal plane detector assembly, a detector control and processing system, a digital processing system, and a thermal control system which will house the CCD focal plane ( Figure 2) and provide for maintaining the focal plane temperature at or below -100 degrees centigrade. The detector assembly will also maintain the alignment of the focal plane to the AXAF-I X-ray mirror assembly and aspect system to provide the capability of obtaining sub-arc second aspect determination during all of the ACIS observations. The detector control and processing assembly will provide the biases and three phase clocking signals required to operate the CCD detectors, as well as synchronizing processing functions of the front-end amplification and digital to analog conversion of the CCD-pixel charge output signal. The digital processing system will perform the data compression, spacecraft interfacing (data and command control), housekeeping, and instrument control functions, in addition to providing for a software management system. A power system will be provided to interface to the spacecraft power system and manage the power requirements of the ACIS subsystems.

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