Characterizing persistence in the IR detector within the Wide Field Camera 3 instrument on the Hubble Space Telescope

摘要

Like essentially all IR arrays, the IR detector in the Wide Field Camera 3 (WFC3) instrument on-board Hubble SpaceTelescope (HST) exhibits afterimages, known as persistence, following exposures to light levels that approach orexceed saturation of individual pixels of the detector. The nature of the persistence in the HgCdTe WFC3/IR detector isdistinctly non-linear in that the amount of persistence is not simply proportional to the exposure level. Instead, theamount of persistence is small until the exposure reaches about half saturation at which point it rises fairly rapidly untilthe exposure reaches about twice saturation and then it increases gradually with increasing saturation. The persistenceshows typical power law decay with time over the periods of time that are relevant to HST observations. Given thefrequent usage of the WFC3/IR detector on HST, it is not possible to completely avoid the effects of persistence inobservations obtained with HST by introducing time gaps between IR observations. Therefore, we have developed aparameterized persistence model that we are using to estimate the amount of persistence in all WRC3/IR images. Theseestimates are available for all existing WFC3/IR images through the Mikulski Archive at STScI (MAST) to help HSTusers remove persistence from their images. Here we discuss the characterization of persistence in the WFC3 detector inorbit, the fraction of observations that are affected by persistence, and the effectiveness of the tools we have developedto reduce the effects of persistence in WFC3 images.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.