Big Cosmic Ray Hits
Occasionally a very energetic cosmic ray will produce more than the usual dot or streak. In this image the hit is in the lower right quadrant. Notice the streak leading up to the hit, the halo around the hit, and Mr. Staypuft streaks induced by the hit. This image has been processed with an old flat field and linearity and mask files as well as showing uncorrected pedestal. CALNICA has clipped out the saturated part of the cosmic ray hit.
It is possible to partially mitigate the effects of such a hit by only using those reads of a multiaccum sequence that preceded the hit, but this can limit the exposure time for the region in question. Once the region is saturated, the data cannot be recovered.