Charge Transfer Inefficiency in the Hubble Space Telescope since
  Servicing Mission 4
  We update a physically-motivated model of radiation damage in the Hubble
Space Telescope Advanced Camera for Surveys/Wide Field Channel, using data up
to mid 2010. We find that Charge Transfer Inefficiency increased dramatically
before shuttle Servicing Mission 4, with ~1.3 charge traps now present per
pixel. During detector readout, charge traps spuriously drag electrons behind
all astronomical sources, degrading image quality in a way that affects object
photometry, astrometry and morphology. Our detector readout model is robust to
changes in operating temperature and background level, and can be used to
iteratively remove the trailing by pushing electrons back to where they belong.
The result is data taken in mid-2010 that recovers the quality of imaging
obtained within the first six months of orbital operations.
