BI-(5x5) island

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:

p₂₀ p₂₁ p₂₂ p₂₃ p₂₄

p₁₈ p₆ p₇ p₈ p₁₉

p₁₆ p₄ p₀ p₅ p₁₇

p₁₄ p₁ p₂ p₃ p₁₅

p₉ p₁₀ p₁₁ p₁₂ p₁₃

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.