Authors: Roman Project Science Team at NASA Goddard Space Flight Center
Released: 2025-09-05
Updated: n/a
Primary Reference(s): Schlieder et al., 2024; Louie et al. (in prep.)
Please cite this Data Release Page URL when referring to these data products.
Roman's Wide Field Instrument (WFI) underwent its second thermal vacuum (TVAC) test in a space-like environment at BAE Systems, Inc. between March and May 2024 (Schlieder et al., 2024). As part of this TVAC2 campaign, the WFI Bright Star Saturation test was conducted to characterize how WFI Sensor Chip Assemblies (SCAs) respond to saturation from a wide range of bright, in-focus point sources, similar to those expected during Roman's science surveys. A telescope simulator was used to project nine simulated point sources with magnitudes ranging from ~4 to ~18 mag through the F146 filter, onto a grid of locations on SCAs 4 and 11. A comprehensive description of the test and subsequent analyses will be provided in Louie et al. (in preparation). For user reference, we provide a summary PDF under the "Resources" section below, which includes an overview of the test and selected quicklook analysis results.
The TVAC2 WFI Bright Star Saturation Test began with a series of three Initial dark exposures, during which the element wheel was intended to be in the DARK position - an opaque mask used to block incoming light and isolate detector and instrument thermal background signals. These darks are typically used to correct the subsequent illuminated exposures for background contributions. However, upon reviewing the data, we discovered that the F146 filter was positioned instead of the DARK element. As a result, some SCAs were exposed to stray light leaking from optical fibers in the telescope simulator.
To address this, we substitute Final dark exposures collected after all illuminated exposures had been completed in the Bright Star test. A total of 18 Final dark exposures were taken with the DARK element in place over a period of approximately 1 hour. We opted to use the last 3 dark exposures in this sequence for analysis because investigation revealed persistence from the simulated bright star exposures had decayed back down to the background level.
Here we release a select subset of raw data from the Bright Star Saturation Test. This includes exposures from SCA11 for two simulated point sources, one at approximately magnitude 7 and another at approximately magnitude 17, and the Final dark exposures described above.
The full Bright Star Test dataset, including the full set of post-illumination Final darks for persistence analysis, will be released at a later date. For more information on Roman WFI persistence performance, please visit the Roman WFI Performance webpage under the "Focal Plane System" tab.
Brief descriptions of the released data and additional resources can be found below.