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Due to the poor CTE of the backside CCD in ACIS-2C, an extended pixel island is being extracted from the raw data. Events are still detected on a 3x3 pixel island using the rules described above; however, an extra pixel is extracted from all sides to hopefully aid in the analysis. Events are written to the event list as a 25 pulse height vector in the order illustrated below:
This was done so that software that was written to only look for 3x3 pixel islands can still get that information without any change to the code.
Events are still not detected at the frame and node boundaries; however the spacing is now bigger. There is now a two pixel boundary around each quadrant, so one should expect to see a 4 pixel gap in images at quadrant boundaries.