All images, warps and stacks, have mask images which indicate image flags for each individual pixels. Below is a table that indicates the meaning for each flag. These flags are applicable for both, the warp and stack images.
Mask values which represent features of the detector
|Flag name||hexadecimal value||Description|
|FLAT||0x0002||Pixel doesn't flat-field properly|
|DARK||0x0004||Pixel doesn't dark-subtract properly|
|BLANK||0x0008||Pixel doesn't contain valid data|
|CTE||0x0010||Pixel has poor Charge Transfer Effici|
|SAT||0x0020||Pixel is saturated or non-linear|