16381

This is a continuation and modification of Program 15761 and is to be executed this cycle for internal CTE. There are two epochs of observations comma one set in November-December 2020 and the other in May-June 2021. The charge transfer efficiency (CTE) of the ACS CCD detectors declines as damage due to on-orbit radiation exposure accumulates. This degradation will be monitored twice a cycle to determine the useful lifetime of the CCDs (prior to 2015 comma cycles were only monitored once a year). All the data for this program is acquired using internal targets (LED) only comma so all of the exposures should be taken during Earth occultation time (but not during SAA passages). This program emulates the majority of the ACS pre-flight ground calibration and post-launch SMOV testing (program 8948) comma so that results from each epoch can be directly compared. Extended pixel edge response (EPER) data will be collected over a range of six signal levelsdoublePoint 182 comma 430 comma 1620 comma 3400 comma 7100 comma and 42 comma 000 electrons. The data will be 0.5-sec darks post-flashed to the given levels. The post-flash LED will be used at low and high current comma and readout will use gain (CCDGAIN=2). Both parallel and serial CTE measurements can be made with the data. Both CCDAMP=AD and CCDAMP=BC will be monitored to test for CTE amplifier dependence. Shutter problems encountered during the first epoch of Program 15761 led to additional S-C exposures and containers being required to properly manage shutter behavior for EPER observations.