Ghost Image
This is a crosstalk between channels affect. A bright point source in one channel causes a ghost image in another channel that is not viewing the source. The worst case is a source in channel 3 causing a ghost in channel 4 of 0.04% of the channel 3 intensity (according to Hora et al). SSC will provide an estimate of the level.
To create our test ghost images we took a 256 x 256 pixel section from a corner of one of the 512x512 original fields added in a background, and multiplied by 0.01% for bands 1-3, and 0.04% for band 4.