Introduction

For a comphrensive guide on identifying ACS image anomalies we refer users to this HLA report, ACS CCD Image Anomalies in the Hubble Legacy Archive. The HLA report provide detailed explanations, as well as visual representations of all the known anomalies present in HRC and WFC images. On this page, we list a summary of the image anomalies and artifacts that have been found in all three ACS channels. 

HRC

  • Bleeding along CCD columns from saturated objects
  • CTE trails
  • Hot and warm pixels
  • Occulting finger
  • Optical ghosts from reflections in the F660N filter (generated by bright stars)
  • Prism issues: red leak / pile-up for blue filters

SBC

  • Broken anode disabiling rows 600 to 605.
  • Three dark spots smaller than 50 microns at positions (334, 977), (578, 964), and (960, 851)

  • Two bright spots at (55, 281) and (645, 102) with fluctuating ratesthat are always less than 3 counts per second

WFC

  • Bad CCD columns 
  • Saturated blobs in darks
  • Bias offset between WFC amplifier quadrants
  • Bias striping due to 1/f noise on the bias reference voltage
  • Bleeding along CCD columns from saturated objects
  • CCD amplifier crosstalk (electronic ghosts)
  • CTE trails
  • Dragon's Breath scattered light from an off-chip star 
  • Flecks 
  • Glint from a star in the WFC interchip gap
  • WFC interchip gap
  • Optical ghosts from reflections in the F660N filter (generated by bright stars)

 

Anomaly Example
This WFC frame exhibits bias offsets between amplifier quadrants, correlated noise imposed by the distortion correction (Moire-like pattern), and glint (scattered light centered on the interchip gap). 

 

LAST UPDATED: 06/17/2019

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