Time Series Analysis of ACS/WFC Bias Striping

The Wide Field Channel of the Advanced Camera for Surveys (ACS/WFC) on the Hubble Space Telescope (HST) exhibits instrumental noise in the form of a striped pattern on 0-second exposure bias images. This noise was noticed after Servicing Mission 4 (SM4), where the CCD Electronics Box Replacement was installed (CEB-R). The CEB-R contains an Application-Specific Integrated Circuit (ASIC) which imparts a low frequency noise which appears to have direct correlation with the striping pattern. This pattern was characterized for mitigation in science exposures shortly after its discovery (Grogin et al. 2011, STScI Instrument Science Report ACS-2011-05). We applied the same analysis to determine if this noise has evolved over time. We fit a model to the potential evolution of the bias striping to judge if a new mitigating algorithm needs to be applied to the ACS/WFC calibration pipeline for science images. We isolated the striping noise in 2230 images to compare the stripe intensity for each year over ten years (2011 - 2020). This analysis displayed no significant change in the striping noise since it was first discovered in 2010.