Well one thing they also do is that pretty much any desired image is taken multiple times/multiple exposures, and multiple offset positions in close succession to remove exactly such artifacts. The images are then stacked, etc.
So this allows removal of effects that do not correlate with what is physically should be in the image, but is an artifact of the sensor, image system, etc:
-- sensor artifacts: dead pixels, flat field irregularity, pixel response variations, electronic noise
-- imaging system issues: optical problems, lens/mirror defects
-- and then exactly what's being discussed here: cosmic rays, transient objects (satellite tracks!)
So this allows removal of effects that do not correlate with what is physically should be in the image, but is an artifact of the sensor, image system, etc:
-- sensor artifacts: dead pixels, flat field irregularity, pixel response variations, electronic noise
-- imaging system issues: optical problems, lens/mirror defects
-- and then exactly what's being discussed here: cosmic rays, transient objects (satellite tracks!)