Charge Transfer Inefficiency in the Hubble Space Telescope since Servicing Mission 4

摘要

We update a physically-motivated model of radiation damage in the HubbleSpace Telescope Advanced Camera for Surveys/Wide Field Channel, using data upto mid 2010. We find that Charge Transfer Inefficiency increased dramaticallybefore shuttle Servicing Mission 4, with ~1.3 charge traps now present perpixel. During detector readout, charge traps spuriously drag electrons behindall astronomical sources, degrading image quality in a way that affects objectphotometry, astrometry and morphology. Our detector readout model is robust tochanges in operating temperature and background level, and can be used toiteratively remove the trailing by pushing electrons back to where they belong.The result is data taken in mid-2010 that recovers the quality of imagingobtained within the first six months of orbital operations.