  Soon after launch, the Advanced CCD Imaging Spectrometer (ACIS), one of the
focal plane instruments on the Chandra X-ray Observatory, suffered radiation
damage from exposure to soft protons during passages through the Earth's
radiation belts. The ACIS team is continuing to study the properties of the
damage with an emphasis on developing techniques to mitigate charge transfer
inefficiency (CTI) and spectral resolution degradation. A post-facto CTI
corrector has been developed which can effectively recover much of the lost
resolution. Any further improvements in performance will require knowledge of
the location and amount of sacrificial charge - charge deposited along the
readout path of an event which fills electron traps and changes CTI. We report
on efforts by the ACIS Instrument team to characterize which charge traps cause
performance degradation and the properties of the sacrificial charge seen
on-orbit. We also report on attempts to correct X-ray pulseheights for the
presence of sacrificial charge.
