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The maintainer uses ACIS Diagnostic Modes to acquire information when trying to determine causes for abnormal conditions and determine side-effects within the instrument. When diagnosing problems, the maintainer may want to change the system as little as possible from the state it is in when a problem first arises. In order to support this type of operation, ACIS provides diagnostic options to each of its main science modes, allowing selective changes to the operation of the instrument. This allows the maintainer to perform the diagnostic operations while changing the setup as little as possible.
A maintainer executes a diagnostic mode in the same fashion as any other Science Run, by sending the desired parameter block, starting the run, and stopping the run when sufficient telemetry has been generated.
Each of the ACIS Science Modes support a "Raw Mode" option, which instructs ACIS to telemeter the raw, unprocessed pixel data produced by the CCDs. This mode produces large amounts of telemetry (1.5Mbytes - 9Mbytes), but allows the maintainer to bypass the event detection algorithms and see all of the pixel information.
By providing "Raw Mode" for all clocking options, the maintainer can effectively evaluate any un-intended coupling between the CCD clocking and the raw pixel data.
Each of the ACIS Science Modes support the ability to clock the CCD's Serial Output Shift Registers in the reverse direction. This allows the maintainer to see the effects of the clocking on the analog systems.
Timed-Exposure Mode provides separate CCD video chain histograms of the pixel pulse-heights from the respective output-nodes. This provides the maintainer an overall picture of the output-node performance, while using little telemetry, relative to the Raw Modes.
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