Chandra X-ray Observatory Dynamic Background Aspect Camera Assembly Flight Software Patch

A real-time procedure was successfully executed on 5/18/23 to uplink a flight software patch that updates the Aspect Camera Assembly (ACA) Processor Electronics Assembly (PEA) to enable on-board dark current subtraction using a dynamically generated dark current map. This substantially improves the ability of the ACA to track faint stars as Chandra continues warming. This complex patch is the culmination of six years of effort including a very comprehensive program of design analysis and ground testing. In addition, in order to develop and test the patch a high-fidelity hardware emulator of the ACA CCD and readout electronics was built and a full-featured software development toolkit for Forth was written.  The updated ACA flight software is running as planned.

Chandra components
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