Resolving the Dark Current Anomaly in the Nancy Grace Roman Space Telescope Focal Plane

The Nancy Grace Roman Space Telescope project is NASA's next flagship a strophysics mission t o s tudy dark energy, dark matter, and exoplanets along with the innumerable topics that will be enabled by the infrared survey telescope's Wide Field Instrument and Coronagraph Instrument. The Wide Field Instrument contains a focal plane of 18 newly developed Teledyne H4RG-10 HgCdTe detectors. The focal plane along with Roman's ASIC for Control And Digitization of Imagers for Astronomy (ACADIA) and the focal plane electronics that power them comprise the focal plane system. Roman's focal plane completed its first s ystem l evel thermal vacuum test at NASA Goddard in 2022, when an increase in dark current compared to component level testing was observed for several detectors. Roman chartered an anomaly review board (ARB) and in collaboration with Teledyne undertook a testing program to help identify possible root cause and select from Roman's spare inventory suitable replacement detectors for devices that had significantly d egraded. A p ossible root c ause was determined by the ARB along with recommendations for how to prevent further degradation. Three detectors were replaced in Roman's focal plane, and results from the following focal plane system thermal vacuum test, implementing recommendations from the ARB, demonstrate improved dark current performance. We summarize the initial observation of the detector anomaly, present the detector testing strategy to find s uitable spares and provide evidence of root cause, share the general findings of the ARB, and show new data showing the improved dark current performance.