Areas of the CCD with high integrated X-ray dose, such as the east and west limbs, are observed to lose sensitivity for visible photons. The reason for this is still unknown. Thus, the aspect sensor images recorded before 14-Nov-92 when the entrance filter failed contain ``ghost images'' of the X-ray sun. The darkness of the ghosts fades with time to some degree.
For most uses of aspect images the ghosts have no effect. For quantitative studies with aspect images they may become important. Primitive flat-fielding routines are available. Hugh Hudson is the expert to consult.