{'fraction_non_alphanumeric': 0.016489988221436984, 'fraction_numerical': 0.00530035335689046, 'mean_word_length': 5.111510791366906, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Characterizing persistence in the IR detector within the Wide Field Camera 3 instrument on the Hubble Space Telescope

Like essentially all IR arrays, the IR detector in the Wide Field Camera 3 (WFC3) instrument on-board Hubble Space Telescope (HST) exhibits afterimages, known as persistence, following exposures to light levels that approach or exceed saturation of individual pixels of the detector. The nature of the persistence in the HgCdTe WFC3/IR detector is distinctly non-linear in that the amount of persistence is not simply proportional to the exposure level. Instead, the amount of persistence is small until the exposure reaches about half saturation at which point it rises fairly rapidly until the exposure reaches about twice saturation and then it increases gradually with increasing saturation. The persistence shows typical power law decay with time over the periods of time that are relevant to HST observations. Given the frequent usage of the WFC3/IR detector on HST, it is not possible to completely avoid the effects of persistence in observations obtained with HST by introducing time gaps between IR observations. Therefore, we have developed a parameterized persistence model that we are using to estimate the amount of persistence in all WRC3/IR images. These estimates are available for all existing WFC3/IR images through the Mikulski Archive at STScI (MAST) to help HST users remove persistence from their images. Here we discuss the characterization of persistence in the WFC3 detector in orbit, the fraction of observations that are affected by persistence, and the effectiveness of the tools we have developed to reduce the effects of persistence in WFC3 images.